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Why car wheels are so flat these days

438 points by CoffeeOnWrite 4y ago

mikotodomo 4y ago
[dead]
pierrebai 4y ago
One question I've had: why are car brakes inside the wheel at all? Is it only ease of servicing? Putting the brake disks on the shaft before the suspension would make wheels lighter and allow positioning the kingpin much further out. I tried to google for an explanation, but only found hits about brakes problems.
- jcampbell1 4y ago
  It is called inboard brakes. I think there is a chance they make a comeback with electric cars because the braking system can be zero maintenance due to regen and the half shafts are already very strong due to the powerful motors.
11235813213455 4y ago
I thought it'd be about reducing wear. Note that tyres are a massive air pollution contributor https://www.polytechnique-insights.com/en/columns/planet/are-electric-cars-a-truly-sustainable-solution#note-12:~:text=59%25%20of%20PM10%20and%2045%25%20of%20PM2.5%20emis%C2%ADsions https://www.polytechnique-insights.com/en/columns/planet/are...
- bagels 4y ago
  It's talking about the outward facing surface of the wheels, when referencing 'flat', not the tires.
- kube-system 4y ago
  The best thing that improved tire wear is just better tire construction.
- blowski 4y ago
  The BBC's "More or Less" pointed out some of the claims about tyres being a major contributor to air pollution are exaggerated. One of the claims was based on the total amount of wear from tyres as weight, without considering that most of that wear is made of very large particles that remain on the ground.
  - marginalia_nu 4y ago
    Some of the data confirming the hypothesis may be from looking at studded snow tires. They tear up a lot of crap in the air if you use them on roads that aren't covered in ice.
  - 11235813213455 4y ago
    The link I gave has serious sources, and "remains on the ground" is a bit vague, a large amount of air pollution is just dust from the road and elsewhere raised up by cars
Swizec 4y ago
This is a great example of the illusion of explanatory depth [1] You read the title and think "D'oh obviously traction", then you see the first picture in the article and think "Yep, obviously flatter tyres because traction", then you read a little more and think "Wait, what do they mean by flat?", ... ... and then it just keeps going deeper and deeper into this rabbit hole you never considered before and barely even noticed. You realize you didn't know shit. The explanation ends up being steering feedback forces. Now I wonder if we can have deeper wheels again with modern electric motor power steering. [^1] https://thedecisionlab.com/biases/the-illusion-of-explanatory-depth https://thedecisionlab.com/biases/the-illusion-of-explanator... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062901/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062901/
- jasonjayr 4y ago
  > The explanation ends up being steering feedback forces. .... which, is used to communicate traction status back to the driver: > The ability of forces to feed back to the driver meant there was significantly more “feel” for what the tires were doing and where the limits of adhesion were. (from the article)
- fnordpiglet 4y ago
  There’s a section on aerodynamics that explains why for any vehicle but especially EV’s can benefit. They give an example that flat wheels improve a model S coefficient of drag by 12%.
fsckboy 4y ago
in order to figure out what this article is saying, I have to learn a lot of terms, and I don't think it's going to be that astonishing or "aha!" so it doesn't seem worth it. The positive scrub ratio measured along the kingpin axis from the kingpin center... if only I knew what a deep dish wheel was as opposed to a flat wheel...
- lozenge 4y ago
  It's not the width of the tire. Think of the tire like a cylinder - it's how the flat face of the tire tapers to the non flat one.
- skybrian 4y ago
  Study the pictures. They mean how far inward the hub and spokes are indented compared to the tire rims.
  - fsckboy 4y ago
    you need to afix another point in your picture. Imagine a basic wheel mounted on the end of a solid axle. Now imagine that you made the axle shorter and replaced the wheel hub with a cone ("deep-dish") that has the tire mounted on the rim at the wide end of the cone. Did you change anything other than angular momentum (I guess I should say polar moment)? if you want to say, "you can't use a cone like that because there needs to be a hinge on the axle at this point for the wheel to steer-turn" then we've arrived at the reason for the limit on deep dishes? or if it's some other reason, it still doesn't seem that hard to describe. what I'm really saying is, the geometric concepts could be taught more simply without the all terminology. My older brother raced cars that he fixed and modified himself, so I grew up basically in a mechanic's shop. That was a long time ago so it's fine if terminology and concepts have changed, but I have a big head start over the average person and I found the article annoyingly incomprehensible
- ForHackernews 4y ago
  Just watch this video, he explains it all very clearly: https://www.youtube.com/watch?v=MXW0bx_Ooq4 https://www.youtube.com/watch?v=MXW0bx_Ooq4
xkzx 4y ago
The flatness in this case is the outer surface of the aluminium rim. And as a rim enthusiast, I can agree that the modern flatness is less appealing than compared to those in the past.
- 6stringmerc 4y ago
  Deep dish on the old M5 was pretty classy looking, as will the Dodge Charger msg wheels with the curve. It’s too bad the deep dish got all bro-dozer crazy. I do very much enjoy watching “Kid Stance” videos on YouTube if you want to see a really brilliant creative guy make some AMAZING custom kid ride on toys…warning: addictive! https://youtu.be/-JF58phVWn0 https://youtu.be/-JF58phVWn0
userbinator 4y ago
For comparison, here's the front suspension of a 1956 Buick: http://buick.oldcarmanualproject.com/manuals/1956/1956%20Buick%20Shop%20Manual/07-Chassis%20Suspension/b_08%201956%20Buick%20Shop%20Manual%20-%20Chassis%20Suspension-003-003.jpg http://buick.oldcarmanualproject.com/manuals/1956/1956%20Bui... Observe that the kingpin axis is entirely inboard of the tire, almost vertical, and the scrub radius is such that the axis meets the ground inboard of the contact patch of the tire (in other words, it doesn't really "scrub" the tire when turning). What stops the suspension from actually steering is the steering system itself and the hands of the driver holding the wheel. You can visualize that in the picture above or below; if the ground pushes the tire rearwards at the contact patch, which is a few millimeters outboard of where the kingpin axis intersects with the ground, that tire will have a tendency to rotate, which will pull on the steering tie rod and send forces to the steering wheel. What isn't mentioned is that if you're braking, then the wheel on the other side also has the same force applied to it; only the difference between the two forces is what attempts to back-drive the steering system. Note that it is harder with rack-and-pinion to approximate https://en.wikipedia.org/wiki/Ackermann_steering_geometry https://en.wikipedia.org/wiki/Ackermann_steering_geometry which is advantageous for tire wear. Personally, I prefer the smoother and more isolated steering feel of a traditional recirculating-ball system, but then again, I'm not the type of driver who likes fast cornering.
- autotech 4y ago
  The equalizing brake force from the other side sounds good until you factor in things like ride height differences from worn suspension or imperfect roads. Those and other transient forces disturb that left to right balance. Weird things like bump steer start happening when left to right measurements are off.
- Gordonjcp 4y ago
  You'd loved DIRAVI like on old Citroën CXes then. Instead of a big spring in the Danfoss valve between the steering column and rack it had a little gearbox with a kind of "dogbone link" joining the two, that got pushed from side to side if there was a difference between the rack position and steering column position to push the valve. Then there was a kind of heart-shaped cam that pushed the steering wheel back to the centre, with a spring pressing against it controlled by hydraulic pressure from a speed sensor on the gearbox. The faster you went the harder it pressed the spring until at 70mph you could barely move the steering wheel but the slightest pressure would steer quite quickly. Until you got used to its incredibly sensitive response (about 1.5 turns lock-to-lock) you tended to drive in zig-zags like you were tacking a dinghy up the road, but once you did get used to it nothing ever felt as precise or comfortable. I've driven some incredibly "sporty" cars, "cost as much as a house" end of the market cars, and none of them got close to the CX for steering feel. The earlier GS and GSA had inboard front disc brakes on the side of the gearbox, allowing them to be massive while also allowing the tall skinny tyres (145SR80, about 150mm wide) to be absolutely centred on the kingpin, boresighted on the middle of the contact patch. They had incredible handling, so sharp and responsive, and the non-powered steering was as light as any modern car at parking speeds.
TekMol 4y ago
Does anybody actually enjoy this type of type of SEO content? Stuffed with filler words to the max. Maybe there is an answer to the title somewhere on the page. But the way it is written, it just stole my time until I gave up after a few paragraphs of filler content. First sentence: Have you ever wondered why designers show sketches of concept cars with massive deep dish wheels, but when those cars actually make it to production the wheels end up being fairly flat? No. I just followed a link "Why car wheels are so flat these days" and was interested in the answer. Compare that to a classic essay "A plan for spam" by Paul Graham: http://paulgraham.com/spam.html http://paulgraham.com/spam.html First sentence: I think it's possible to stop spam, and that content-based filters are the way to do it. That's the type of content I would like to see on HN. If it was 2022 style SEO content, PG's essay would have started with "Have you ever wondered why you get so much spam into your inbox these days and why that spam is so terribly boring, sprinkled with typos and ads, often full of images and links, and what you could do to get rid of it?". Shudder.
- hrbf 4y ago
  Same here. Was interested in the answer but I gave up before getting to a satisfactory conclusion. Way too little information density.
- kccqzy 4y ago
  I think the article is fine. You might just be an impatient reader.
  - Double_a_92 4y ago
    Well it's a random thing thrown at me on HackerNews... I don't care that much about car wheels to invest several minutes into reading about this completely random fact. Either it tells me relatively quickly, or I stop caring.
- solardev 4y ago
  I agree. Took way too long to get to the point.
- 4y ago
roughly 4y ago
If you're any kind of a car person, you owe it to yourself to check out the rest of The Autopian - it's an independent car site founded, owned, and operated by deeply weird car people, and it's absolutely amazing. Here's their writeup on the electric F-150 - keep scrolling on that page, and look at the kind of depth and detail they get into: https://www.theautopian.com/the-2022-ford-lightning-is-just-a-standard-f-150-with-an-electric-powertrain-and-thats-why-its-going-to-change-the-world/ https://www.theautopian.com/the-2022-ford-lightning-is-just-... The site is a gem.
- 1letterunixname 4y ago
  Scotty Kilmer from Houston enters the chat to talk about how new cars are plastic garbage and how their low profile tires look "cool" but are woefully fragile.
  - prottog 4y ago
    He actually moved to Tennessee!
  - jackmott 4y ago
    Well the fragility of low profile wheel/tire packages is true at least
  - dzonga 4y ago
    n that the only car worth buying is '91 Toyota Celica
    - kQq9oHeAz6wLLS 4y ago
      The Celica All-Trac is fantastic
      - mlambie 4y ago
      - 4y ago
vishnugupta 4y ago
Given my OCD this drives me nuts because I can’t look at a wheel to get a sense if it’s low on air pressure anymore. I always get nervous thinking it’s gone flat and needs fixing.
- rob74 4y ago
  The "flat" in this article was referring to the hub side (i.e. where a hubcap would be if there was one), not the surface that meets the road.
rob74 4y ago
I can't really understand the author's (and apparently some designers') fetish about "deep dish" wheels. If a flat wheel allows better technical solutions and even improves aerodynamics, I'm all for flat wheels! Hell, even Formula 1 cars (which used to have the "deepest" wheels ever) use hubcaps since this season (https://the-race.com/formula-1/gary-anderson-how-f1s-new-wheel-covers-can-challenge-teams/ https://the-race.com/formula-1/gary-anderson-how-f1s-new-whe...). Maybe that will make "flat wheels" sexy? We will have to wait and see...
- jerlam 4y ago
  There are a lot of car things that have no functional benefit, but exist because they used to mean something (but not anymore) or are useful at racing speeds but not at normal ones, or are simply traditional. One I find particularly amusing is the Ford Mustang Mach-E, a fully battery-powered vehicle, has the ability to play fake engine noise through the cabin speakers because some drivers think engine noise is a feature of "real cars".
  - 6stringmerc 4y ago
    It’s not even an electric car thing - my Focus ST came from the factory with a little sound pipe thingy from the engine to the cabin to make it feel more racy. When I bought it used it was disconnected, which is fine, because the MBRP 2.5” cat back exhaust already installed is about 3x louder than stock. I’m pretty sure BMW was doing it too when they started going all turbo and losing the song of the NA.
    - GordonS 4y ago
      I drove a BMW x5 a couple of years back, and it piped fake engine noise into the cabin. IIRC, it was a petrol v6/v8, so was quite capable of making it's own sound, so the whole thing was pointless - but worse, the fake engine noise sounded totally fake! Honestly, I felt pretty silly with it enabled!
      - doubled112 4y ago
1letterunixname 4y ago
I have a 1985 VW Vanagon camper. Mechanically, it's a POS with 99.9% NLA parts. It has 16" truck tires. Before that, it had properly weight-rated 14" trailer tires (the owner before had under-spec, unsafe passenger car tires on it.) The 16" are much easier to find and cheaper than the 14". Geometry-wise, the OD isn't excessively different that before because it's a massive, strong "pillow" between surfaces and the OD of rim. It's when you get to the point where you can't hop a curb at low speed without worrying about wrecking the rims that there's a problem with low profile tires. There always exists a high enough speed over a large enough obstacle that will cause mechanical damage to rims. If you want to drive a super car with perfect aerodynamics everyday, don't use driveways with any incline to them, don't get near to curbs, and don't drive anywhere with potholes. The challenge is how much optimization for efficiency vs. durability vs. cost manufacturers want to or are ordered to sacrifice.
- throwaway0a5e 4y ago
  The kind of person who doesn't understand that trailer tires have some pretty substantial tradeoffs in car use is not going to be loading their classic van heavily enough and then driving it fast enough to have issues with some random car tires that don't match the OEM weight rating.
Neil44 4y ago
Some cars have a virtual ball joint on the bottom of the hub to get around the ‘the brakes are in the way’ issue. Two separate arms with two more inboard ball joints act the same as one arm with the joint much further out. https://en.m.wikipedia.org/wiki/Dual_ball_joint_suspension https://en.m.wikipedia.org/wiki/Dual_ball_joint_suspension
- LeifCarrotson 4y ago
  That article uses the same words, but I needed to see a drawing to understand how it works. This video was useful: https://youtu.be/I1EiR9Axfwg?t=50 https://youtu.be/I1EiR9Axfwg?t=50
sschueller 4y ago
OT but related to tire pressure. There was this gem [1] posted in reddit the other day and I guess it is partly a failure of UI and inexperience. A junior mechanic tried to fill the tires to "100%". https://i.redd.it/eu73w8earfn91.jpg https://i.redd.it/eu73w8earfn91.jpg Edit: fixed, old reddit. App doesn't make old reddit links. [1] https://old.reddit.com/r/Justrolledintotheshop/comments/xcdvww/one_of_my_employees_told_me_he_couldnt_get_all/ https://old.reddit.com/r/Justrolledintotheshop/comments/xcdv...
- a3w 4y ago
  Yes, but more then that pressure is okay for just standing around, says the reddit thread. Also, why not old.reddit? Are the official consumption ratings not based on this kind of overinflation, removing all seats but the driver's? So everyone is expected to do both these things by the car manufacturer, if that is 'realistic use'. /s
  - ed312 4y ago
    As an i.reddit mobile user, it retains the old iphone/mobile optimized css of reddit. There are actual html buttons with minimal js nonsense and not a to of a useless whitespace. On desktop I'm a fervent old.reddit user and sincerely hope they don't deprecate the, (imo better, more info dense), style.
jimjimjim 4y ago
The Autopian is a great car site. It was set up by some Jalopnik writers (david tracy and jason torchinsky). As well as "normal" car articles they love techy/offbeat/unusual aspects of cars and aren't afraid to publish it.
- Theodores 4y ago
  The Autopian has single-handedly revived my interest in blogs. Great content and thanks for the back story!
yason 4y ago
The timeline of this development exceeds the timeline of my own experiences since the 90's. I've always driven cars with rack and pinion steering while wheels went from something like a typical 185-65x15 to 245-40x18. So, wheels are larger and the profile is much smaller (more rim and less rubber between the car and the road). Higher power warrants bigger brakes and bigger brakes warrants larger rims but for the average car rims have grown way oversized. Many cars have the space to take rims that are 2-3 inches smaller than what comes as standard. My anecdotal and average empirical results is that cars with wide rims and little rubber mostly seem to reduce comfort, increase noise, and make the steering very susceptible to unevenness, slopes and grooves of roads and layers of snow and ice and thus requiring constant steering response from the driver. I've had both kinds and the difference is huge, and exaggerated by bad road conditions that we find on our roads. On my older vehicles with a higher and narrower tyre profile I barely have to steer at all but just keep my hand relaxed on the wheel while the car ploughs pretty much through whatever in a direct line. Of course, I keep the wheel geometry of all my cars well-aligned so they shouldn't wander around.
- lloeki 4y ago
  My car is on 225/40/18, has no floating behaviour, and just the right amount of feedback still to feel what happens on the front wheels, whether it's wheel placement, movement, gripping/slipping... It's an absolute joy to drive, whether on long journeys or spiritedly. > just keep my hand relaxed on the wheel while the car ploughs pretty much through whatever in a direct line I would avoid small potholes still but that's basically my feeling on that car. I did slightly bend a rim once when running through a pothole I did not see, and the car ploughed through as described. I recall reading an article a couple of months ago about steering, feedback, and suspension geometry design. It rang very true to my subjective experience that many car suspensions are designed for "comfort" (vs "sporty"), which results in a lack of relevant direct feedback, which makes the car uneven and floaty, like you're somehow disconnected from the road, and still suffer from bumpiness as you have to rely on indirect cues to compensate, which makes for increased latency and overcorrection. I wish I could find this article again, IIRC it all comes down to one angle/offset, which you can't really fix by tuning geometry because it's basically baked in the suspension design. EDIT: it's related to that one[0], but was more detailed regarding that part: > To make matters worse, the suspension geometry often further compromises steering feel in favor of things like putting less load into tie-rods [0]: https://arstechnica.com/cars/2022/01/new-cars-have-lost-their-steering-feel-heres-why-that-matters/ https://arstechnica.com/cars/2022/01/new-cars-have-lost-thei...
t43562 4y ago
I would have enjoyed this but didn't understand it. I think the main problem is that I didn't understand what they meant by tyres "being flat" so the rest of it was impossible to grok.
- ksd482 4y ago
  The part of the tire that touches the road is flat as opposed to being curved.
  - Traster 4y ago
    I think it's actually not - they mean the side face of the wheel, https://images-stag.jazelc.com/uploads/theautopian-m2en/cherokee_liberty-1536x639.jpg https://images-stag.jazelc.com/uploads/theautopian-m2en/cher... They're talking about the wheels, not the tyres.
  - starkd 4y ago
    The newer tires also have the appearance of being flatter. This may be where the confusion is.
- Traster 4y ago
  They that the face which you put the bolts through is flat. On older cars it was concave.
- larrik 4y ago
  I didn't follow what they meant for a while either. This image helped: https://images-stag.jazelc.com/uploads/theautopian-m2en/cherokee_liberty.jpg https://images-stag.jazelc.com/uploads/theautopian-m2en/cher... It's not the tires that are flat, it's the face of the rims.
  - post-it 4y ago
    Ohh. I thought at first it was talking about round, donut-shaped vs thin, cylindrical tires.
- 4y ago
baxuz 4y ago
I'm usually a huge fan of engineering articles but this one isn't really accessible.
londons_explore 4y ago
TL;DR: Wheels contain the brakes, so they need space inside for the brakes. Just inside the wheel is part of the steering pivot mechanism. Constraints around the optimal design of these systems prevent the classic 'domed' wheel construction.
londons_explore 4y ago
One day, I believe car design regulations will be amended to allow fully electric braking (ie. no hydraulics, drums, rotors, or pads). At that point, the motor can be moved into the wheel (unsprung mass = bad, but weight savings from not needing an axle or gearbox will outweigh this). Suspension and steering design is then far easier, because there is no axle to need to keep straight. Braking redundancy will be achieved by having motors/brakes on all four wheels, and within each motor 3 independant phase coils with independant controllers, such that there are effectively 12 brakes on a car. Normally the controllers work together for smooth braking, traction control, software differential, etc. But even after 3+ failures braking performance should still be satisfactory for an emergency stop. Obviously braking energy needs to go somewhere. In the happy case, it's regen'ed into a battery. If the battery can't accept it, it gets dumped into dump resistors. If the dump resistors fail, it gets dumped into motor coils (of which there are 12 remember). Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags. So the whole system (except the pedal itself) is 12 way redundant.
- ComputerGuru 4y ago
  > Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags. Replacing airbags (at least individually) is cheap enough. Having your entire engine-equivalent need a replacement just to reduce the sprung weight?
- ben_w 4y ago
  I don't claim any physical engineering skills, but don't you need a mechanical (non electrical) system for parking breaks?
  - hollywood_court 4y ago
    Nope. Many modern vehicles have push button electric parking brakes.
  - KingJulian 4y ago
    I would think so too. Any parking brake has to be a fail-safe type brake which has to function in the absence of electricity. Hence, as you mentioned, purely mechanical.
culopatin 4y ago
I’m going through this experiment myself. I have some et20 (+20mm offset wheels) in a car that had 45mm offset wheels from the factory. Meaning the wheel center is 25mm further out than stock. However, the new wheel is also wider, so is not all on one side. The steering is definitely different, especially because I also have tires that are 3 inches wider than the factory ones. The car is harder to keep straight if the ground is uneven because it wants to pull in all sorts of directions. I also don’t like how at full lock the outer wheel drags on the ground. But at this width the closest I can get is an offset of +35mm, any higher and the wheel touches the control arm, and at 40 it would probably hit the springs. Talking to some track guys seems like they are still faster with a wider track than with lower scrub and told me to not worry about it, but I still have my concerns.
whalesalad 4y ago
I had the opportunity to design my own set of wheels with a friend for my Mustang GT. I put a thread together with photos of the process from start to finish, it was a lot of fun. I don't have the Mustang anymore, but the wheels are stacked in my garage awaiting a future project. https://www.mustang6g.com/forums/threads/arcane-stellar-–-a-fully-forged-motorsport-inspired-monoblock-designed-with-a-friend.104077/ https://www.mustang6g.com/forums/threads/arcane-stellar-–-a-...
- mechanical_bear 4y ago
  What sort of pricing for something like this?
  - whalesalad 4y ago
    Retail for a set like this would be in the $5-6k ballpark, but I am not entirely sure as the market has evolved since then.
    - mechanical_bear 4y ago
      Thanks, gorgeous wheels btw.
- fipar 4y ago
  Those are amazing, thanks for sharing! Also, the color on those wheels makes me think of a 90s Impreza (paint job in blue, please!).
mauvehaus 4y ago
> This is felt as kick-back to the driver and if it’s bad enough can rip the wheel out of your hands. Some of you may have had that experience in the past. It can also break the driver's thumb, if the thumb is on the inside of the rim. If you're driving over rough terrain, you're well advised to keep your thumbs on the outside of the rim. This is true even at low speed. I once had to pull a car up onto a normal-sized curb and did so at low speed. Doing so definitely kicked the wheel.
- pwpw 4y ago
  I was taught to do this in open-wheel racing. Thumbs stick straight up rather than gripping inside the wheel. And on bigger crashes, completely let go of the wheel as quickly as possible.
  - techdmn 4y ago
    My dad taught me that when I was learning to drive. What's the last thing you do before impact? Let go of the wheel.
    - ComputerGuru 4y ago
      And, counter-intuitively, get off the brakes! This returns/angles the nose of the car up, which can be the difference between life or death if colliding head-on into a larger object (like a deer).
tobyhinloopen 4y ago
To get more money repairing rim damage, obviously
- throwaway0a5e 4y ago
  The kind of people who get rims repaired rather than just buying new (no doubt based on some hand-wavy BS about safety from someone who makes a margin on the rims they sell) don't buy new rims.
  - tobyhinloopen 4y ago
    They do buy cars with huge rims with exposed metal that is easily scratched. I was scared to park my new car in close spots. Now I got a Mazda CX5 and it has “just” 19” rims with tires that are wider than the rims.
burlesona 4y ago
What a great article! The world is absolutely full of things that are carefully designed around very real engineering constraints that almost none of us know about or ever notice. I always appreciate when a writer can bring me into a new world that I didn’t know anything about and show me the care and attention to detail that I would otherwise have never seen.
dreamcompiler 4y ago
Related question: Why must brakes be inside the wheels rather than inboard on the axle? Why not weld disks onto the axle inboard of the wheels and put the brakes there? That would make more room inside the wheels. Of course on undriven front wheels it wouldn't work because there is no axle, but in front-wheel-drive cars there is one. The brakes could be inboard of the CV joint, no?
- hoosieree 4y ago
  As others said, accessibility and cooling. But inboard brakes are still popular in some niche areas, like sandrails: https://www.dieselworldmag.com/wp-content/uploads/2017/03/DW-1510-RAIL-13.png https://www.dieselworldmag.com/wp-content/uploads/2017/03/DW... This particular example doesn't even have front brakes.
- tricky 4y ago
  See the inboard brakes on 60's Jaguars - Sure, the unsprung weight and improved handling is nice but they are much harder to maintain because 1. you have to lift the car to see if they are worn and 2. if you have to repair a caliper it is almost easier to drop the entire rear suspension than to try to dig the caliper out while everything is on the car.
- rr888 4y ago
  Because then you'd get a huge amount of torque between the brakes and the wheel, esp through the CV joint it'd be unnecessarily brutal. On the back wheels it could be possible, on the front (where most of the braking is) unlikely.
  - throwaway0a5e 4y ago
    If the CV joint can handle peeling out it can handle brake torque. The link between tire and ground is basically always the weak point.
    - rr888 4y ago
      If the wheel is sliding the torque on the wheel will be lower than if the tires were grippier. I guess the comparison is if braking is high (de)-acceleration than the engine. I'm thinking your idea has a lot of the same stresses as engine braking.
js2 4y ago
I'm reading this article and the whole time I'm thinking, my 1998 Jeep Cherokee XJ has completely flat wheels, and then I get to the very bottom: > [Editor’s Note: Not all designers prefer dished wheels. Some commenters were wondering why the Jeep JK/JL Wrangler, which has an old-school steering box instead of a rack and pinion setup, has such flat wheels. As far as I know, this is largely a styling decision. -DT]. So, it also applies the the XJ limited wheels too: https://i.ibb.co/zfHMNbB/B03-FA738-777-A-40-D6-817-F-C0785-ED4-B89-F.jpg https://i.ibb.co/zfHMNbB/B03-FA738-777-A-40-D6-817-F-C0785-E...

438 points by CoffeeOnWrite 4y ago

[dead]

One question I've had: why are car brakes inside the wheel at all? Is it only ease of servicing? Putting the brake disks on the shaft before the suspension would make wheels lighter and allow positioning the kingpin much further out. I tried to google for an explanation, but only found hits about brakes problems.

jcampbell1 4y ago
It is called inboard brakes. I think there is a chance they make a comeback with electric cars because the braking system can be zero maintenance due to regen and the half shafts are already very strong due to the powerful motors.

11235813213455 4y ago

I thought it'd be about reducing wear. Note that tyres are a massive air pollution contributor https://www.polytechnique-insights.com/en/columns/planet/are-electric-cars-a-truly-sustainable-solution#note-12:~:text=59%25%20of%20PM10%20and%2045%25%20of%20PM2.5%20emis%C2%ADsions https://www.polytechnique-insights.com/en/columns/planet/are...

bagels 4y ago
It's talking about the outward facing surface of the wheels, when referencing 'flat', not the tires.
kube-system 4y ago
The best thing that improved tire wear is just better tire construction.
blowski 4y ago
The BBC's "More or Less" pointed out some of the claims about tyres being a major contributor to air pollution are exaggerated. One of the claims was based on the total amount of wear from tyres as weight, without considering that most of that wear is made of very large particles that remain on the ground.
- marginalia_nu 4y ago
  Some of the data confirming the hypothesis may be from looking at studded snow tires. They tear up a lot of crap in the air if you use them on roads that aren't covered in ice.
- 11235813213455 4y ago
  The link I gave has serious sources, and "remains on the ground" is a bit vague, a large amount of air pollution is just dust from the road and elsewhere raised up by cars

Swizec 4y ago

This is a great example of the illusion of explanatory depth [1] You read the title and think "D'oh obviously traction", then you see the first picture in the article and think "Yep, obviously flatter tyres because traction", then you read a little more and think "Wait, what do they mean by flat?", ... ... and then it just keeps going deeper and deeper into this rabbit hole you never considered before and barely even noticed. You realize you didn't know shit. The explanation ends up being steering feedback forces. Now I wonder if we can have deeper wheels again with modern electric motor power steering. [^1] https://thedecisionlab.com/biases/the-illusion-of-explanatory-depth https://thedecisionlab.com/biases/the-illusion-of-explanator... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062901/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062901/

jasonjayr 4y ago
> The explanation ends up being steering feedback forces. .... which, is used to communicate traction status back to the driver: > The ability of forces to feed back to the driver meant there was significantly more “feel” for what the tires were doing and where the limits of adhesion were. (from the article)
fnordpiglet 4y ago
There’s a section on aerodynamics that explains why for any vehicle but especially EV’s can benefit. They give an example that flat wheels improve a model S coefficient of drag by 12%.

fsckboy 4y ago

in order to figure out what this article is saying, I have to learn a lot of terms, and I don't think it's going to be that astonishing or "aha!" so it doesn't seem worth it. The positive scrub ratio measured along the kingpin axis from the kingpin center... if only I knew what a deep dish wheel was as opposed to a flat wheel...

lozenge 4y ago
It's not the width of the tire. Think of the tire like a cylinder - it's how the flat face of the tire tapers to the non flat one.
skybrian 4y ago
Study the pictures. They mean how far inward the hub and spokes are indented compared to the tire rims.
- fsckboy 4y ago
  you need to afix another point in your picture. Imagine a basic wheel mounted on the end of a solid axle. Now imagine that you made the axle shorter and replaced the wheel hub with a cone ("deep-dish") that has the tire mounted on the rim at the wide end of the cone. Did you change anything other than angular momentum (I guess I should say polar moment)? if you want to say, "you can't use a cone like that because there needs to be a hinge on the axle at this point for the wheel to steer-turn" then we've arrived at the reason for the limit on deep dishes? or if it's some other reason, it still doesn't seem that hard to describe. what I'm really saying is, the geometric concepts could be taught more simply without the all terminology. My older brother raced cars that he fixed and modified himself, so I grew up basically in a mechanic's shop. That was a long time ago so it's fine if terminology and concepts have changed, but I have a big head start over the average person and I found the article annoyingly incomprehensible
ForHackernews 4y ago
Just watch this video, he explains it all very clearly: https://www.youtube.com/watch?v=MXW0bx_Ooq4 https://www.youtube.com/watch?v=MXW0bx_Ooq4

xkzx 4y ago

The flatness in this case is the outer surface of the aluminium rim. And as a rim enthusiast, I can agree that the modern flatness is less appealing than compared to those in the past.

6stringmerc 4y ago
Deep dish on the old M5 was pretty classy looking, as will the Dodge Charger msg wheels with the curve. It’s too bad the deep dish got all bro-dozer crazy. I do very much enjoy watching “Kid Stance” videos on YouTube if you want to see a really brilliant creative guy make some AMAZING custom kid ride on toys…warning: addictive! https://youtu.be/-JF58phVWn0 https://youtu.be/-JF58phVWn0

userbinator 4y ago

For comparison, here's the front suspension of a 1956 Buick: http://buick.oldcarmanualproject.com/manuals/1956/1956%20Buick%20Shop%20Manual/07-Chassis%20Suspension/b_08%201956%20Buick%20Shop%20Manual%20-%20Chassis%20Suspension-003-003.jpg http://buick.oldcarmanualproject.com/manuals/1956/1956%20Bui... Observe that the kingpin axis is entirely inboard of the tire, almost vertical, and the scrub radius is such that the axis meets the ground inboard of the contact patch of the tire (in other words, it doesn't really "scrub" the tire when turning). What stops the suspension from actually steering is the steering system itself and the hands of the driver holding the wheel. You can visualize that in the picture above or below; if the ground pushes the tire rearwards at the contact patch, which is a few millimeters outboard of where the kingpin axis intersects with the ground, that tire will have a tendency to rotate, which will pull on the steering tie rod and send forces to the steering wheel. What isn't mentioned is that if you're braking, then the wheel on the other side also has the same force applied to it; only the difference between the two forces is what attempts to back-drive the steering system. Note that it is harder with rack-and-pinion to approximate https://en.wikipedia.org/wiki/Ackermann_steering_geometry https://en.wikipedia.org/wiki/Ackermann_steering_geometry which is advantageous for tire wear. Personally, I prefer the smoother and more isolated steering feel of a traditional recirculating-ball system, but then again, I'm not the type of driver who likes fast cornering.

autotech 4y ago
The equalizing brake force from the other side sounds good until you factor in things like ride height differences from worn suspension or imperfect roads. Those and other transient forces disturb that left to right balance. Weird things like bump steer start happening when left to right measurements are off.
Gordonjcp 4y ago
You'd loved DIRAVI like on old Citroën CXes then. Instead of a big spring in the Danfoss valve between the steering column and rack it had a little gearbox with a kind of "dogbone link" joining the two, that got pushed from side to side if there was a difference between the rack position and steering column position to push the valve. Then there was a kind of heart-shaped cam that pushed the steering wheel back to the centre, with a spring pressing against it controlled by hydraulic pressure from a speed sensor on the gearbox. The faster you went the harder it pressed the spring until at 70mph you could barely move the steering wheel but the slightest pressure would steer quite quickly. Until you got used to its incredibly sensitive response (about 1.5 turns lock-to-lock) you tended to drive in zig-zags like you were tacking a dinghy up the road, but once you did get used to it nothing ever felt as precise or comfortable. I've driven some incredibly "sporty" cars, "cost as much as a house" end of the market cars, and none of them got close to the CX for steering feel. The earlier GS and GSA had inboard front disc brakes on the side of the gearbox, allowing them to be massive while also allowing the tall skinny tyres (145SR80, about 150mm wide) to be absolutely centred on the kingpin, boresighted on the middle of the contact patch. They had incredible handling, so sharp and responsive, and the non-powered steering was as light as any modern car at parking speeds.

TekMol 4y ago

Does anybody actually enjoy this type of type of SEO content? Stuffed with filler words to the max. Maybe there is an answer to the title somewhere on the page. But the way it is written, it just stole my time until I gave up after a few paragraphs of filler content. First sentence: Have you ever wondered why designers show sketches of concept cars with massive deep dish wheels, but when those cars actually make it to production the wheels end up being fairly flat? No. I just followed a link "Why car wheels are so flat these days" and was interested in the answer. Compare that to a classic essay "A plan for spam" by Paul Graham: http://paulgraham.com/spam.html http://paulgraham.com/spam.html First sentence: I think it's possible to stop spam, and that content-based filters are the way to do it. That's the type of content I would like to see on HN. If it was 2022 style SEO content, PG's essay would have started with "Have you ever wondered why you get so much spam into your inbox these days and why that spam is so terribly boring, sprinkled with typos and ads, often full of images and links, and what you could do to get rid of it?". Shudder.

hrbf 4y ago
Same here. Was interested in the answer but I gave up before getting to a satisfactory conclusion. Way too little information density.
kccqzy 4y ago
I think the article is fine. You might just be an impatient reader.
- Double_a_92 4y ago
  Well it's a random thing thrown at me on HackerNews... I don't care that much about car wheels to invest several minutes into reading about this completely random fact. Either it tells me relatively quickly, or I stop caring.
solardev 4y ago
I agree. Took way too long to get to the point.
4y ago

roughly 4y ago

If you're any kind of a car person, you owe it to yourself to check out the rest of The Autopian - it's an independent car site founded, owned, and operated by deeply weird car people, and it's absolutely amazing. Here's their writeup on the electric F-150 - keep scrolling on that page, and look at the kind of depth and detail they get into: https://www.theautopian.com/the-2022-ford-lightning-is-just-a-standard-f-150-with-an-electric-powertrain-and-thats-why-its-going-to-change-the-world/ https://www.theautopian.com/the-2022-ford-lightning-is-just-... The site is a gem.

1letterunixname 4y ago
Scotty Kilmer from Houston enters the chat to talk about how new cars are plastic garbage and how their low profile tires look "cool" but are woefully fragile.
- prottog 4y ago
  He actually moved to Tennessee!
- jackmott 4y ago
  Well the fragility of low profile wheel/tire packages is true at least
- dzonga 4y ago
  n that the only car worth buying is '91 Toyota Celica
  - kQq9oHeAz6wLLS 4y ago
    The Celica All-Trac is fantastic
    - mlambie 4y ago
    - 4y ago

vishnugupta 4y ago

Given my OCD this drives me nuts because I can’t look at a wheel to get a sense if it’s low on air pressure anymore. I always get nervous thinking it’s gone flat and needs fixing.

rob74 4y ago
The "flat" in this article was referring to the hub side (i.e. where a hubcap would be if there was one), not the surface that meets the road.

rob74 4y ago

I can't really understand the author's (and apparently some designers') fetish about "deep dish" wheels. If a flat wheel allows better technical solutions and even improves aerodynamics, I'm all for flat wheels! Hell, even Formula 1 cars (which used to have the "deepest" wheels ever) use hubcaps since this season (https://the-race.com/formula-1/gary-anderson-how-f1s-new-wheel-covers-can-challenge-teams/ https://the-race.com/formula-1/gary-anderson-how-f1s-new-whe...). Maybe that will make "flat wheels" sexy? We will have to wait and see...

jerlam 4y ago
There are a lot of car things that have no functional benefit, but exist because they used to mean something (but not anymore) or are useful at racing speeds but not at normal ones, or are simply traditional. One I find particularly amusing is the Ford Mustang Mach-E, a fully battery-powered vehicle, has the ability to play fake engine noise through the cabin speakers because some drivers think engine noise is a feature of "real cars".
- 6stringmerc 4y ago
  It’s not even an electric car thing - my Focus ST came from the factory with a little sound pipe thingy from the engine to the cabin to make it feel more racy. When I bought it used it was disconnected, which is fine, because the MBRP 2.5” cat back exhaust already installed is about 3x louder than stock. I’m pretty sure BMW was doing it too when they started going all turbo and losing the song of the NA.
  - GordonS 4y ago
    I drove a BMW x5 a couple of years back, and it piped fake engine noise into the cabin. IIRC, it was a petrol v6/v8, so was quite capable of making it's own sound, so the whole thing was pointless - but worse, the fake engine noise sounded totally fake! Honestly, I felt pretty silly with it enabled!
    - doubled112 4y ago

1letterunixname 4y ago

I have a 1985 VW Vanagon camper. Mechanically, it's a POS with 99.9% NLA parts. It has 16" truck tires. Before that, it had properly weight-rated 14" trailer tires (the owner before had under-spec, unsafe passenger car tires on it.) The 16" are much easier to find and cheaper than the 14". Geometry-wise, the OD isn't excessively different that before because it's a massive, strong "pillow" between surfaces and the OD of rim. It's when you get to the point where you can't hop a curb at low speed without worrying about wrecking the rims that there's a problem with low profile tires. There always exists a high enough speed over a large enough obstacle that will cause mechanical damage to rims. If you want to drive a super car with perfect aerodynamics everyday, don't use driveways with any incline to them, don't get near to curbs, and don't drive anywhere with potholes. The challenge is how much optimization for efficiency vs. durability vs. cost manufacturers want to or are ordered to sacrifice.

throwaway0a5e 4y ago
The kind of person who doesn't understand that trailer tires have some pretty substantial tradeoffs in car use is not going to be loading their classic van heavily enough and then driving it fast enough to have issues with some random car tires that don't match the OEM weight rating.

Neil44 4y ago

Some cars have a virtual ball joint on the bottom of the hub to get around the ‘the brakes are in the way’ issue. Two separate arms with two more inboard ball joints act the same as one arm with the joint much further out. https://en.m.wikipedia.org/wiki/Dual_ball_joint_suspension https://en.m.wikipedia.org/wiki/Dual_ball_joint_suspension

LeifCarrotson 4y ago
That article uses the same words, but I needed to see a drawing to understand how it works. This video was useful: https://youtu.be/I1EiR9Axfwg?t=50 https://youtu.be/I1EiR9Axfwg?t=50

sschueller 4y ago

OT but related to tire pressure. There was this gem [1] posted in reddit the other day and I guess it is partly a failure of UI and inexperience. A junior mechanic tried to fill the tires to "100%". https://i.redd.it/eu73w8earfn91.jpg https://i.redd.it/eu73w8earfn91.jpg Edit: fixed, old reddit. App doesn't make old reddit links. [1] https://old.reddit.com/r/Justrolledintotheshop/comments/xcdvww/one_of_my_employees_told_me_he_couldnt_get_all/ https://old.reddit.com/r/Justrolledintotheshop/comments/xcdv...

a3w 4y ago
Yes, but more then that pressure is okay for just standing around, says the reddit thread. Also, why not old.reddit? Are the official consumption ratings not based on this kind of overinflation, removing all seats but the driver's? So everyone is expected to do both these things by the car manufacturer, if that is 'realistic use'. /s
- ed312 4y ago
  As an i.reddit mobile user, it retains the old iphone/mobile optimized css of reddit. There are actual html buttons with minimal js nonsense and not a to of a useless whitespace. On desktop I'm a fervent old.reddit user and sincerely hope they don't deprecate the, (imo better, more info dense), style.

jimjimjim 4y ago

The Autopian is a great car site. It was set up by some Jalopnik writers (david tracy and jason torchinsky). As well as "normal" car articles they love techy/offbeat/unusual aspects of cars and aren't afraid to publish it.

Theodores 4y ago
The Autopian has single-handedly revived my interest in blogs. Great content and thanks for the back story!

yason 4y ago

The timeline of this development exceeds the timeline of my own experiences since the 90's. I've always driven cars with rack and pinion steering while wheels went from something like a typical 185-65x15 to 245-40x18. So, wheels are larger and the profile is much smaller (more rim and less rubber between the car and the road). Higher power warrants bigger brakes and bigger brakes warrants larger rims but for the average car rims have grown way oversized. Many cars have the space to take rims that are 2-3 inches smaller than what comes as standard. My anecdotal and average empirical results is that cars with wide rims and little rubber mostly seem to reduce comfort, increase noise, and make the steering very susceptible to unevenness, slopes and grooves of roads and layers of snow and ice and thus requiring constant steering response from the driver. I've had both kinds and the difference is huge, and exaggerated by bad road conditions that we find on our roads. On my older vehicles with a higher and narrower tyre profile I barely have to steer at all but just keep my hand relaxed on the wheel while the car ploughs pretty much through whatever in a direct line. Of course, I keep the wheel geometry of all my cars well-aligned so they shouldn't wander around.

lloeki 4y ago
My car is on 225/40/18, has no floating behaviour, and just the right amount of feedback still to feel what happens on the front wheels, whether it's wheel placement, movement, gripping/slipping... It's an absolute joy to drive, whether on long journeys or spiritedly. > just keep my hand relaxed on the wheel while the car ploughs pretty much through whatever in a direct line I would avoid small potholes still but that's basically my feeling on that car. I did slightly bend a rim once when running through a pothole I did not see, and the car ploughed through as described. I recall reading an article a couple of months ago about steering, feedback, and suspension geometry design. It rang very true to my subjective experience that many car suspensions are designed for "comfort" (vs "sporty"), which results in a lack of relevant direct feedback, which makes the car uneven and floaty, like you're somehow disconnected from the road, and still suffer from bumpiness as you have to rely on indirect cues to compensate, which makes for increased latency and overcorrection. I wish I could find this article again, IIRC it all comes down to one angle/offset, which you can't really fix by tuning geometry because it's basically baked in the suspension design. EDIT: it's related to that one[0], but was more detailed regarding that part: > To make matters worse, the suspension geometry often further compromises steering feel in favor of things like putting less load into tie-rods [0]: https://arstechnica.com/cars/2022/01/new-cars-have-lost-their-steering-feel-heres-why-that-matters/ https://arstechnica.com/cars/2022/01/new-cars-have-lost-thei...

t43562 4y ago

I would have enjoyed this but didn't understand it. I think the main problem is that I didn't understand what they meant by tyres "being flat" so the rest of it was impossible to grok.

ksd482 4y ago
The part of the tire that touches the road is flat as opposed to being curved.
- Traster 4y ago
  I think it's actually not - they mean the side face of the wheel, https://images-stag.jazelc.com/uploads/theautopian-m2en/cherokee_liberty-1536x639.jpg https://images-stag.jazelc.com/uploads/theautopian-m2en/cher... They're talking about the wheels, not the tyres.
- starkd 4y ago
  The newer tires also have the appearance of being flatter. This may be where the confusion is.
Traster 4y ago
They that the face which you put the bolts through is flat. On older cars it was concave.
larrik 4y ago
I didn't follow what they meant for a while either. This image helped: https://images-stag.jazelc.com/uploads/theautopian-m2en/cherokee_liberty.jpg https://images-stag.jazelc.com/uploads/theautopian-m2en/cher... It's not the tires that are flat, it's the face of the rims.
- post-it 4y ago
  Ohh. I thought at first it was talking about round, donut-shaped vs thin, cylindrical tires.
4y ago

baxuz 4y ago

I'm usually a huge fan of engineering articles but this one isn't really accessible.

londons_explore 4y ago

TL;DR: Wheels contain the brakes, so they need space inside for the brakes. Just inside the wheel is part of the steering pivot mechanism. Constraints around the optimal design of these systems prevent the classic 'domed' wheel construction.

londons_explore 4y ago

One day, I believe car design regulations will be amended to allow fully electric braking (ie. no hydraulics, drums, rotors, or pads). At that point, the motor can be moved into the wheel (unsprung mass = bad, but weight savings from not needing an axle or gearbox will outweigh this). Suspension and steering design is then far easier, because there is no axle to need to keep straight. Braking redundancy will be achieved by having motors/brakes on all four wheels, and within each motor 3 independant phase coils with independant controllers, such that there are effectively 12 brakes on a car. Normally the controllers work together for smooth braking, traction control, software differential, etc. But even after 3+ failures braking performance should still be satisfactory for an emergency stop. Obviously braking energy needs to go somewhere. In the happy case, it's regen'ed into a battery. If the battery can't accept it, it gets dumped into dump resistors. If the dump resistors fail, it gets dumped into motor coils (of which there are 12 remember). Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags. So the whole system (except the pedal itself) is 12 way redundant.

ComputerGuru 4y ago
> Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags. Replacing airbags (at least individually) is cheap enough. Having your entire engine-equivalent need a replacement just to reduce the sprung weight?
ben_w 4y ago
I don't claim any physical engineering skills, but don't you need a mechanical (non electrical) system for parking breaks?
- hollywood_court 4y ago
  Nope. Many modern vehicles have push button electric parking brakes.
- KingJulian 4y ago
  I would think so too. Any parking brake has to be a fail-safe type brake which has to function in the absence of electricity. Hence, as you mentioned, purely mechanical.

culopatin 4y ago

I’m going through this experiment myself. I have some et20 (+20mm offset wheels) in a car that had 45mm offset wheels from the factory. Meaning the wheel center is 25mm further out than stock. However, the new wheel is also wider, so is not all on one side. The steering is definitely different, especially because I also have tires that are 3 inches wider than the factory ones. The car is harder to keep straight if the ground is uneven because it wants to pull in all sorts of directions. I also don’t like how at full lock the outer wheel drags on the ground. But at this width the closest I can get is an offset of +35mm, any higher and the wheel touches the control arm, and at 40 it would probably hit the springs. Talking to some track guys seems like they are still faster with a wider track than with lower scrub and told me to not worry about it, but I still have my concerns.

whalesalad 4y ago

I had the opportunity to design my own set of wheels with a friend for my Mustang GT. I put a thread together with photos of the process from start to finish, it was a lot of fun. I don't have the Mustang anymore, but the wheels are stacked in my garage awaiting a future project. https://www.mustang6g.com/forums/threads/arcane-stellar-–-a-fully-forged-motorsport-inspired-monoblock-designed-with-a-friend.104077/ https://www.mustang6g.com/forums/threads/arcane-stellar-–-a-...

mechanical_bear 4y ago
What sort of pricing for something like this?
- whalesalad 4y ago
  Retail for a set like this would be in the $5-6k ballpark, but I am not entirely sure as the market has evolved since then.
  - mechanical_bear 4y ago
    Thanks, gorgeous wheels btw.
fipar 4y ago
Those are amazing, thanks for sharing! Also, the color on those wheels makes me think of a 90s Impreza (paint job in blue, please!).

mauvehaus 4y ago

> This is felt as kick-back to the driver and if it’s bad enough can rip the wheel out of your hands. Some of you may have had that experience in the past. It can also break the driver's thumb, if the thumb is on the inside of the rim. If you're driving over rough terrain, you're well advised to keep your thumbs on the outside of the rim. This is true even at low speed. I once had to pull a car up onto a normal-sized curb and did so at low speed. Doing so definitely kicked the wheel.

pwpw 4y ago
I was taught to do this in open-wheel racing. Thumbs stick straight up rather than gripping inside the wheel. And on bigger crashes, completely let go of the wheel as quickly as possible.
- techdmn 4y ago
  My dad taught me that when I was learning to drive. What's the last thing you do before impact? Let go of the wheel.
  - ComputerGuru 4y ago
    And, counter-intuitively, get off the brakes! This returns/angles the nose of the car up, which can be the difference between life or death if colliding head-on into a larger object (like a deer).

tobyhinloopen 4y ago

To get more money repairing rim damage, obviously

throwaway0a5e 4y ago
The kind of people who get rims repaired rather than just buying new (no doubt based on some hand-wavy BS about safety from someone who makes a margin on the rims they sell) don't buy new rims.
- tobyhinloopen 4y ago
  They do buy cars with huge rims with exposed metal that is easily scratched. I was scared to park my new car in close spots. Now I got a Mazda CX5 and it has “just” 19” rims with tires that are wider than the rims.

burlesona 4y ago

What a great article! The world is absolutely full of things that are carefully designed around very real engineering constraints that almost none of us know about or ever notice. I always appreciate when a writer can bring me into a new world that I didn’t know anything about and show me the care and attention to detail that I would otherwise have never seen.

dreamcompiler 4y ago

Related question: Why must brakes be inside the wheels rather than inboard on the axle? Why not weld disks onto the axle inboard of the wheels and put the brakes there? That would make more room inside the wheels. Of course on undriven front wheels it wouldn't work because there is no axle, but in front-wheel-drive cars there is one. The brakes could be inboard of the CV joint, no?

hoosieree 4y ago
As others said, accessibility and cooling. But inboard brakes are still popular in some niche areas, like sandrails: https://www.dieselworldmag.com/wp-content/uploads/2017/03/DW-1510-RAIL-13.png https://www.dieselworldmag.com/wp-content/uploads/2017/03/DW... This particular example doesn't even have front brakes.
tricky 4y ago
See the inboard brakes on 60's Jaguars - Sure, the unsprung weight and improved handling is nice but they are much harder to maintain because 1. you have to lift the car to see if they are worn and 2. if you have to repair a caliper it is almost easier to drop the entire rear suspension than to try to dig the caliper out while everything is on the car.
rr888 4y ago
Because then you'd get a huge amount of torque between the brakes and the wheel, esp through the CV joint it'd be unnecessarily brutal. On the back wheels it could be possible, on the front (where most of the braking is) unlikely.
- throwaway0a5e 4y ago
  If the CV joint can handle peeling out it can handle brake torque. The link between tire and ground is basically always the weak point.
  - rr888 4y ago
    If the wheel is sliding the torque on the wheel will be lower than if the tires were grippier. I guess the comparison is if braking is high (de)-acceleration than the engine. I'm thinking your idea has a lot of the same stresses as engine braking.

js2 4y ago

I'm reading this article and the whole time I'm thinking, my 1998 Jeep Cherokee XJ has completely flat wheels, and then I get to the very bottom: > [Editor’s Note: Not all designers prefer dished wheels. Some commenters were wondering why the Jeep JK/JL Wrangler, which has an old-school steering box instead of a rack and pinion setup, has such flat wheels. As far as I know, this is largely a styling decision. -DT]. So, it also applies the the XJ limited wheels too: https://i.ibb.co/zfHMNbB/B03-FA738-777-A-40-D6-817-F-C0785-ED4-B89-F.jpg https://i.ibb.co/zfHMNbB/B03-FA738-777-A-40-D6-817-F-C0785-E...