16 ms·

Aerodynamics of Gravel Bikes

151 points by vinceroni 4y ago

cdot2 4y ago
"Some readers have suggested that the boxy shape of the bag could be improved. However, since the bag sits between the handlebars, a rounded shape was actually less aero when we tested it in the wind tunnel." I would not have guessed that. Could a more efficient shape be made?
- matsemann 4y ago
  Yeah, the round shape is actually not very good. But it's the traditional one, from bicycle frames being welded steel tubes. The circle is still as wide as a square would be, and additionally it creates lots of turbulence. An aero frame is much more tear-shaped.
- usrusr 4y ago
  The boxy shape would likely still be less aero in isolation, but certain parts that in its slipstream might be so un-aerodynamic that the see less drag through more turbulent air than through clean air, and the boxy one provides more turbulence. Or it's the reverse, total drag benefits from the boxy rear and the rounded one was round on the rear as well (or not round at all, just some knotty wrap that approximates "round" very roughly, contrasting with a clean box)
- brandmeyer 4y ago
  The round-bottom shape that sits under clip-on aero bars is very good. https://cyclite.cc/en/products/handle-bar-aero-bag-01 https://cyclite.cc/en/products/handle-bar-aero-bag-01 https://torstenfrank.wordpress.com/2021/12/07/aerodynamik-von-bikepacking-taschen-diese-taschen-machen-dich-schneller/ https://torstenfrank.wordpress.com/2021/12/07/aerodynamik-vo...
digdugdirk 4y ago
This is a great overview of the current state of aerodynamics in cycling. I especially loved the comparisons to what's legal in road cycling and to what the current state of the art is in MotoGP. Also, MotoGP is absolutely worth a deeper look for anyone who found this article interesting. They've recently started taking aerodynamics to another level with front and rear winglets in a way that wasn't done before.
WA 4y ago
Related, this fascinating video, which covers different bag positions, clothings etc.: https://www.youtube.com/watch?v=Ue_Tz7e0DmE https://www.youtube.com/watch?v=Ue_Tz7e0DmE
- Lio 4y ago
  I'd also suggest this Francis Cade video1[1] where they tested various bike packing bags in a wind tunnel. Bar bags of any size or shape are really slow. A much better solution is something like a Tailfin aeropack[2]. 1. https://www.youtube.com/watch?v=WcXh_oqs_Bs https://www.youtube.com/watch?v=WcXh_oqs_Bs 2. https://www.tailfin.cc/ https://www.tailfin.cc/
matsemann 4y ago
A gravel bike is the perfect commuter bike! At least if you're not going electric. Almost as light and fast as a road bike. But a bit more upright riding so it's more comfortable. Wider and more treaded tires means tram lines, pot holes, curbs etc. are less of a problem and can handle rough surfaces and not just asphalt. Mounting points and wider forks allow for mudguards / fenders so rain is no problem. The wider space allows for studded tires during winter. Also easier to mount panniers / luggage carriers to carry stuff home from the stores. While I love my road bike for long rides on the weekend, I use my gravel bike daily. And it also allows me to go places I cannot go with the road bike, without having to go all mountain-bikey. Btw, for road biking we often compare aerodynamics using "wattage per dollar". It can be surprising what then should be the first things to improve.
- deleted 4y ago
  [deleted]
- Steltek 4y ago
  Gravel bikes are good commuters, if you like drop bars. Many commuters prefer flat bars for the more upright riding position, which allows for a better field of view for misbehaving drivers. You still also have the classic problem that higher end bikes lose all the commuter friendly features. Carbon forks and frames often lose mounting points for fenders+rack. The marketing vision of a gravel bike is someone expecting to get muddy and who isn't trying to stuff a laptop into a saddle bag. Durable, maintenance friendly choices like threaded BBs and easy cable routing go away. You're stuck with heavy bikes with poor gear ranges, super low end components, cable brakes, etc.
  - bluecalm 4y ago
    I agree but there are exceptions. My carbon bike (from GT) has bikepacking mounts on both the frame and the fork. Mounting fenders wasn't a problem either. It also has outside cable routing but not a threaded BB. I think Canyon is selling bikepacking gravel bike as well (Grizl). There are choices, you just need to look for them. It's true that these days availability is a problem but it's a problem with everything cycling related.
nedludd 4y ago
These in-depth scientific studies always seem to neglect the weight and aerodynamics of the RIDER. That is surely the biggest factor when it comes to speed and efficiency.
- wffurr 4y ago
  Harder to spend money to improve the rider. Fancy clothing, I guess.
  - someweirdperson 4y ago
    Weight reduction is much cheaper on the rider than the bike in many cases though.
  - Lio 4y ago
    A skinsuit or roadsuit will definitely make you faster on the bike. It's pretty easy to measure the effect with a power meter. Weirdly "aero socks" are both a thing and make a big difference to the point that they are heavily regulated by the UCI. Any cylindrical part of the bike or rider is going to perform badly so if you can encourage the airflow to stay attached around it you reduce the amount of effort required to move you forward, hence aero clothing being a big deal. If you're a serious cyclist then it's pretty easy to spend money on good quality clothing.
    - Melatonic 4y ago
      Always made me wonder if taking the swimmers route instead would provide all the same benefits without the cost and look. Shave your whole upper body and go shirtless and you would be pretty damn aero no? Would a skinsuit really improve upon that? In addition after switching to a Brooks saddle (I tried literally 10s of saddles using the "saddle swap" forum feature on some forums) I now no longer ever want to use padded bike shorts again. Of all the short types the simple padded chamois was my favorite (simple foam - no gel or any other BS) and now I just prefer wearing a pair of synthetic lightweight boxer briefs (no fly) that were designed for hiking originally. There is no padding at all and from day one the brooks was extremely comfortable. It only got more comfortable with time and applies all pressure directly to my sit bones. Every other saddle + padded short (even ones that mostly were on my sit bones) ended up forcing padding into the areas between my sit bones and outside them as my weight compressed the padding. I havent tried their new non leather seats but they seem to operate by a similar tension (a tensioned pliable surface vs a hard plastic shape with padding on top) which results in your weight creating additional space below the sit bones vs filling it with padding.
hi 4y ago
> the fastest riders in the 200-mile Unbound average 20 mph (32 km/h) across the Flint Hills of Kansas. Let’s not forget that the most important aspect of averaging 20mph on grave roads: drafting, low body weight and high fitness. If you watch footage of the unbound gravel race they mention, the winners are with a group of riders until the very end. The fastest riders are professionals sponsored by the companies trying to sell you this aero gear. If you want to ride faster ride in a group, find your ideal body weight and spend money on a coach. Only then spend money on bike parts beyond the basic lubricated chain, correct tire psi, etc.
- MezzoDelCammin 4y ago
  Personally, I'd change the order. Coach first, body weight second. If there's one piece of equipment to buy first & ASAP, it'd be a powermeter and something to display the readout on. Riding in a group is of course great, but first You got to have the legs to catch up and then the body weight / metabolism to keep up. Having the core / flexibility to be able to spend hours in somewhat aero position doesn't hurt either. It always makes me laugh to see slightly overweight people on carbon frames. Having a few kilos over myself, I always thought I'd rather spend money / time / effort losing 3-4kg of fat, rather than mulling over how to shave 100g off of the groupset or 300g of wheels weight...
  - noir_lord 4y ago
    > but first You got to have the legs to catch up and then the body weight / metabolism to keep up. Not just keep up, if you are riding in a group you need to be fit enough to take your turn on the front where you aren't draughting (at least if the group you are riding with is your team). The actual team dynamics of professional road racing are fascinating, much like F1 they'll often pick the strongest and expect everyone else to support them.
    - MezzoDelCammin 4y ago
      yeah, I've never really been into group riding / drafting on a competitive level. I'm mostly trying to avoid it, actually (more of a self-supported racing kind of guy). Where I train (Paris, polygone de Vincennes) there are quite a few groups riding together, but not sure they'd switch places. I guess it depends on why You do what You do. In my case, if someone wants to ride behind me, I don't mind (other than that it makes me a bit more careful when passing someone / turning corners). I'm there to work on my power output or cadence, not to get KOMs on Strava segments ;-)
benjaminwootton 4y ago
I bought a cool book yesterday which is all about gravel trails in the UK. I had never heard the term gravel bike until reading it. Silly question but can I do these trails on my full suspension mountain bike, or will I be mercilessly mocked and possibly chased out of town? I already have a mountain bike and a road bike so not keen to add a third!
- protonbob 4y ago
  You will certainly not be. At least in the US, mountain bikes for trails are still the norm.
- namdnay 4y ago
  A mountain bike is fine on a gravel trail, if you can lock the shocks
- unklefolk 4y ago
  > ... can I do these trails on my full suspension mountain bike...? Yes. It will be a bit more work on the pedalling front vs a dedicated gravel bike, but I doubt you will encounter any bike snobbery. I have gravel trails near where I live, and you see all kinds of bikes tackling them.
- lukah 4y ago
  If anything, you might be thankful of a full suspension mountain bike on some of our "gravel" trails in the UK. There's such a wide range from US-style back county roads all the way to bridleways with baby-head sized rocks that you probably wouldn't want to be riding on something typically sold as a gravel bike.
  - Doctor_Fegg 4y ago
    Yes, this. There's actually not that much US-style "gravel" in England and Wales: basically a few Forestry Commission tracks in mid-Wales, Northumberland and places like that. Elsewhere it's single-track bridleways that dominate. Routes like King Alfred's Way, the Pennine Bridleway, the Great North Trail and West Kernow Way are sometimes marketed as gravel routes but they're probably more MTB than anything.
ehnto 4y ago
If you want an astonishgly well put together deep dive on gravel and bikepacking aerodynamics, check out: https://www.cyclingabout.com/fascinating-aerodynamics-bikepacking-bicycle-touring/ https://www.cyclingabout.com/fascinating-aerodynamics-bikepa... I cannot recommend him, his videos or articles enough. He lives on the bike, literally, and he applies an unrivaled dedication and passion to thinking and writing about this stuff while on the road. He has tests, science and real world experience to back him up too.
pharmakom 4y ago
I’m sorry but Jan Heine has unscientific methods and his products are of questionable reliability. You can drop 200usd on his tyres. It’s like hifi nerdy but for rubber.
- bigfudge 4y ago
  I agree the tyres are expensive, but their findings on tyre width and pressure are largely bourne out by more controlled tests. In addition, their rolling distance tests include one factor which most standardised rigs didn’t: the losses from hysteresis when uneven surfaces have to lift/return your mass over a bump. I think soft wide tyres would be even more advantageous than most people realise once real losses on real roads are factored in, and compared at speeds most cyclists go at (i.e most people don’t average 30kph). In fact, even using average trip speeds as the comparator would be daft because that would include downhill sections where riders are actually braking, or don’t really care about rolling resistance because the difference between 50 and 55kph downhill makes no practical difference.
  - ActorNightly 4y ago
    The tire width definitely has a break even point where wider tires are significantly less efficient than narrower ones unless you run them at unsafe pressures. More volume in the tire means that at the same pressure, there is more deflection, and deflection hysteresis in the tread, notably the rebounding of the tread behind the contact patch is what causes the rolling resistance in the first place.
    - wiredfool 4y ago
      RH 48mm tires at 25psi are pretty damn good on a single. Likewise my tandem uses 44's at 45psi (front, heavy captain) and the rear 53mm at 40 (light stoker).
    - bigfudge 4y ago
      Totally agree. I do think that people underestimate the width of that point tho. For most people who are not racing the suspension benefits probably outweighs the minimal aero loss, but it’s really hard to measure. I have been on fast group rides on 48mm slicks and although I get funny looks (and am not going to win many races because I’m old and lazy) I genuinely L find it easier to keep up than on 28mm tyres i had previously. Part of that is confidence maneuvering at speed on fairly crappy roads though.
alleycat5000 4y ago
Bicycle Quarterly (magazine by the same folks) is a great read, always such a joy when it arrives in the mail! https://www.bikequarterly.com/ https://www.bikequarterly.com/
bbarn 4y ago
I am an out of shape former racer who has ridden his bike 10 times in the last two years. I have a dad belly and rarely work out at all. I recently did The Rift this summer - a 200km gravel race here in Iceland that people come from all over the world to race. I did it on a carbon cyclocross bike from my racing days with file treads. I felt like the light weight of my bike outweighed just about every gravel fad that's out there right now. I was flying past people on the hills, and while the ride felt very rough on the high speed flats, I was still going fast. If I were in my racing shape of a few years ago I think I would have been in the top 5-10% of racers, largely because nearly everyone was on giant heavy gravel bikes with massive tires loaded for friggin bikepacking from the look of it. My wife has a purpose-built gravel bike, and she commented on just how slow it felt going uphill (she is a former state cyclocross champion). With the exception of the absolute professionals, most people "Racing" these events are just there to finish them, and the pros? It's basically just a road race. Gravel offers no significant challenge in handling your bike, and any reasonable set-up can win if it's light enough and the rider is fit enough. The Aero arms race certainly matters in time trials, but I remain unconvinced there's enough benefit for the actual racing. I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too.
- shagie 4y ago
  > I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too. While this is a "on the paved road" race... you should check out Horribly Hilly Hundreds in Wisconsin - https://www.horriblyhilly.com https://www.horriblyhilly.com
  - gammarator 4y ago
    Yeah, rolling hills are tough…. “Rouleur” is a cyclist type for a reason.
- jackmott42 4y ago
  Why don't you actually do some math, or experiments, rather than just telling us you have doubts? This is all really easy stuff to answer. For instance. 75kg rider + bike. Make the bike 1kg lighter. Go up a 8% grade for 1 kilometers at 300 watts Time saved by 1kg weight reduction? 30 seconds out of 40 minutes. Or suppose we add 300grams to the frame to make it aero, which is typical. If that reduces the CdA by .02 out of .25, you are at about a breakeven point. JUST during the 1km climb. Then you save time on all the flats and non technical downhills. Acceleration is even less affected by bike mass. People forget that bike mass is a tiny % of total system mass (our fat asses). And mass is only one of 4 major components that affect acceleration. I'm happy to run through some acceleration scenarios if you like.
helsinkiandrew 4y ago
> The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider There's lots of things you can do - apart from losing a lot of weight, clothing and helmet design is probably the simplest, there's some good references to things that can be done here: https://link.springer.com/article/10.1007/s12283-017-0234-1#Bib1 https://link.springer.com/article/10.1007/s12283-017-0234-1#... >I don’t always use the aero tuck. I find that it’s not very comfortable for more than a few minutes at a time I cycle on a time trial bike (not on gravel) - which has a higher saddle and longer frame so back and arms can get straight and horizontal. It took a lot of effort to get comfortable physically and mentally in that position (you hands feel a very long way from the brakes) and you do loose quite a bit of control in that position, but I don't see why a slightly higher saddle and arms horizontal but wider with hands at the edge handlebars in line with legs wouldn't be possible.
- prmoustache 4y ago
  The most aero time trial like position need training, especially the muscles in the neck area. Even in the pro racing world some racers do not train enough in that position and lose precious time in time trial because they are unable to keep it straight looking at the road constantly and move the head up and down constantly. The helmets manufacturers actually accounted for that and moved to time trial helmets with a much smaller tail as it spent to much pointing in the air.
- seadan83 4y ago
  Gravel has washboards, pot holes, trenches, lips, fallen trees, overhanging trees/brush, large rocks. I'm thinking a lot about downhill riding too with respect to your comment. For a downhill section on gravel, for a 8% grade descent - safety is perhaps the biggest limiting factor. In some gravel races, it is really debatable whether a hardtail or a gravel bike is better. That is all to say is that stability demands can greatly vary from one section to another on a gravel/mountain race course.
qwertox 4y ago
I started biking around three years ago. Lots of biking, like 5000-8000+ km a year. As long as I don't weigh my ideal weight and aren't planning on becoming a machine myself, I have zero interest in spending anything in optimizations which will make my bike a better one. I don't care if it could go faster or be more lightweight, spending 600€ for the bike was enough. The cheapest 30€ Schwalbe tires are good enough; I didn't even have a single flat tire this summer after I learned to avoid driving over blackberry branches. And I really enjoy it. During this summer, with the extreme heat, where I loved the 28°C in the shade of the woods I was thinking about how much I'm going to hate this fall, and now that it's here, I love breathing that cold, fresh air and smelling the humid forest. The only thing I hate is when there's frozen snow on pavement in the winter. The only thing I spend money on for biking is quality clothing appropriate for the seasons and accessories like good smartphone holders or bags.
- chitowneats 4y ago
  I appreciate your approach but the reason people like optimizations is for speed. The thrill of riding fast is what keeps a lot of us coming back.
  - lm28469 4y ago
    Lots of people optimise because they fell in the rabbit hole of optimisation and it became an addiction. Like in every hobbies some people completely lose touch with reality. I've seen videos of people comparing weight of bicycle seats and how to shave like 13 grams of weight of the bike, meanwhile the dude had a dad bod and shaving his torso would have shaved more weight than his $$$ seat
  - qwertox 4y ago
    Don't get me wrong, I also love to go down a forest path at 45 kph to the point where I get scared, but I know that I also have to go up again. But going as fast as possible on a horizontal path is not attractive to me at all. If I want to expend energy, I prefer to ride up a hill where I then can have the fun of riding down, even if I have to pedal 20 minutes up to then go down within a minute or two. But I also recognize that there are those who are already super efficient and want to get the absolutely most out of their gear, even improving it as much as possible, which is really ok by me. I wish I were at that point, but I think I'd first have to go to the gym for that.
Zigurd 4y ago
They milk the topic. This could have been 2 pages at most: Aero bars are dorky, doubly on gravel, but they will make the most difference. Heck, clip a fairing to those aero bars. But nobody uses them because you look like a dork. If you can't get over looking like a dork, and you are susceptible to bike marketing <cough>GCN</cough> you'll spend thousands on an aero frame. And then you'll put a hipster handlebar bag on it.
simonebrunozzi 4y ago
> The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider. I have an idea about that, and I would like to explore it. Not having a mechanical engineering background, what do you think would be the best way to build a prototype, patent it, etc? Is there any engineering firm that would provide such service, let's say in Europe?
SavageBeast 4y ago
I ride a Trek Domane 5 AL which allows spacing for a 48mm tire ( odd for a roadie ) - so I put a 48mm gravel tire on it and started riding it on light gravel. Works very very well. Carbon would be even better but Id still be waiting on it to arrive from the factory alas the aluminum version will have to do. The best bike in the world is the one you have in the garage to ride today.
grzes 4y ago
wondering if i should switch handlebars to narrower one. so currently i have 56 frame with 42 handlebars - thats "factory" setup. i noticed that also 54 frame has this handlebars, only 52 size frame comes with 40. anyone has any experiences how it will affect bike handling? i noticed that there is a trend rising to go with narrower handlebars on gravel bikes
- Melatonic 4y ago
  I personally go with the widest handlebars I can. You might gain some aero from skinny ones which would be worth it if you are racing at a high level but you will lose a significant amount of comfort. Wider bars allow more hand positions and are significantly more comfortable for me especially on long rides. Being able to really get a wide grip occasionally feels great on the shoulders. And on top of that you feel much, much more secure with a nice wide grip on difficult terrain like shitty pothole laden roads.
NegativeLatency 4y ago
The aerodynamics of upright bikes compared to recumbents remind me very much of stock car racing compared to f1. Where one is actively pushing forward in terms of speed and performance and the other is stuck with one type because of how it "should" conform to previous ideas of what a bike looks like.
Melatonic 4y ago
Back in the day I found some vintage "aero" bars that were designed to bolt on to any bicycle made before larger diameter drop bars became the norm. I did not want them, however, specifically for the "aero tuck" - I wanted them to give me more hand positions for long term comfort. While I eventually got rid of them because they took too much space on the flats of the bars due to the way they clamped I always wondered if we could design something like an aero bar but specifically for comfort. It could bolt on to the stem or in a way that still allowed multiple hand positions on the flats. The elbow pads were also a very nice way to get some lower back stretches in and I even ended up mounting a small cyclocross brake at the end of one of the aero handles so I could comfortable adjust speed (rear brake only - front brake in this position might be suicide) while going downhill and tucked. Or hell - maybe even something that had a small fold mechanism so that you could fold away the forearm / elbow pads when not in use!
phlipski 4y ago
The article mentions the upper back fairing of a motoGP racer but then blows off the idea for a cyclist because they might get too hot? I've always wondered why road cyclists don't ditch their frame mounted (and drag inducing) water bottles for a camelback. The original camelback was slim and I can't imagine it added any drag seeing as it sits on the back of the cyclist. Plus it has the advantage of allowing the cyclist to maintain a better cylcing position without having to reach down for a bottle. But then again if roadies were really all that concerned about aero and efficiency they'd switch to recumbent bikes...
- vbarrielle 4y ago
  In pro cycling it's actually forbidden to have aero fairings on your bike. During the Armstrong years there has been a controversy about the placement of his radio on his back during time trials that would incur fairing.

151 points by vinceroni 4y ago

"Some readers have suggested that the boxy shape of the bag could be improved. However, since the bag sits between the handlebars, a rounded shape was actually less aero when we tested it in the wind tunnel." I would not have guessed that. Could a more efficient shape be made?

matsemann 4y ago
Yeah, the round shape is actually not very good. But it's the traditional one, from bicycle frames being welded steel tubes. The circle is still as wide as a square would be, and additionally it creates lots of turbulence. An aero frame is much more tear-shaped.
usrusr 4y ago
The boxy shape would likely still be less aero in isolation, but certain parts that in its slipstream might be so un-aerodynamic that the see less drag through more turbulent air than through clean air, and the boxy one provides more turbulence. Or it's the reverse, total drag benefits from the boxy rear and the rounded one was round on the rear as well (or not round at all, just some knotty wrap that approximates "round" very roughly, contrasting with a clean box)
brandmeyer 4y ago
The round-bottom shape that sits under clip-on aero bars is very good. https://cyclite.cc/en/products/handle-bar-aero-bag-01 https://cyclite.cc/en/products/handle-bar-aero-bag-01 https://torstenfrank.wordpress.com/2021/12/07/aerodynamik-von-bikepacking-taschen-diese-taschen-machen-dich-schneller/ https://torstenfrank.wordpress.com/2021/12/07/aerodynamik-vo...

digdugdirk 4y ago

This is a great overview of the current state of aerodynamics in cycling. I especially loved the comparisons to what's legal in road cycling and to what the current state of the art is in MotoGP. Also, MotoGP is absolutely worth a deeper look for anyone who found this article interesting. They've recently started taking aerodynamics to another level with front and rear winglets in a way that wasn't done before.

WA 4y ago

Related, this fascinating video, which covers different bag positions, clothings etc.: https://www.youtube.com/watch?v=Ue_Tz7e0DmE https://www.youtube.com/watch?v=Ue_Tz7e0DmE

Lio 4y ago
I'd also suggest this Francis Cade video1[1] where they tested various bike packing bags in a wind tunnel. Bar bags of any size or shape are really slow. A much better solution is something like a Tailfin aeropack[2]. 1. https://www.youtube.com/watch?v=WcXh_oqs_Bs https://www.youtube.com/watch?v=WcXh_oqs_Bs 2. https://www.tailfin.cc/ https://www.tailfin.cc/

matsemann 4y ago

A gravel bike is the perfect commuter bike! At least if you're not going electric. Almost as light and fast as a road bike. But a bit more upright riding so it's more comfortable. Wider and more treaded tires means tram lines, pot holes, curbs etc. are less of a problem and can handle rough surfaces and not just asphalt. Mounting points and wider forks allow for mudguards / fenders so rain is no problem. The wider space allows for studded tires during winter. Also easier to mount panniers / luggage carriers to carry stuff home from the stores. While I love my road bike for long rides on the weekend, I use my gravel bike daily. And it also allows me to go places I cannot go with the road bike, without having to go all mountain-bikey. Btw, for road biking we often compare aerodynamics using "wattage per dollar". It can be surprising what then should be the first things to improve.

deleted 4y ago
[deleted]
Steltek 4y ago
Gravel bikes are good commuters, if you like drop bars. Many commuters prefer flat bars for the more upright riding position, which allows for a better field of view for misbehaving drivers. You still also have the classic problem that higher end bikes lose all the commuter friendly features. Carbon forks and frames often lose mounting points for fenders+rack. The marketing vision of a gravel bike is someone expecting to get muddy and who isn't trying to stuff a laptop into a saddle bag. Durable, maintenance friendly choices like threaded BBs and easy cable routing go away. You're stuck with heavy bikes with poor gear ranges, super low end components, cable brakes, etc.
- bluecalm 4y ago
  I agree but there are exceptions. My carbon bike (from GT) has bikepacking mounts on both the frame and the fork. Mounting fenders wasn't a problem either. It also has outside cable routing but not a threaded BB. I think Canyon is selling bikepacking gravel bike as well (Grizl). There are choices, you just need to look for them. It's true that these days availability is a problem but it's a problem with everything cycling related.

nedludd 4y ago

These in-depth scientific studies always seem to neglect the weight and aerodynamics of the RIDER. That is surely the biggest factor when it comes to speed and efficiency.

wffurr 4y ago
Harder to spend money to improve the rider. Fancy clothing, I guess.
- someweirdperson 4y ago
  Weight reduction is much cheaper on the rider than the bike in many cases though.
- Lio 4y ago
  A skinsuit or roadsuit will definitely make you faster on the bike. It's pretty easy to measure the effect with a power meter. Weirdly "aero socks" are both a thing and make a big difference to the point that they are heavily regulated by the UCI. Any cylindrical part of the bike or rider is going to perform badly so if you can encourage the airflow to stay attached around it you reduce the amount of effort required to move you forward, hence aero clothing being a big deal. If you're a serious cyclist then it's pretty easy to spend money on good quality clothing.
  - Melatonic 4y ago
    Always made me wonder if taking the swimmers route instead would provide all the same benefits without the cost and look. Shave your whole upper body and go shirtless and you would be pretty damn aero no? Would a skinsuit really improve upon that? In addition after switching to a Brooks saddle (I tried literally 10s of saddles using the "saddle swap" forum feature on some forums) I now no longer ever want to use padded bike shorts again. Of all the short types the simple padded chamois was my favorite (simple foam - no gel or any other BS) and now I just prefer wearing a pair of synthetic lightweight boxer briefs (no fly) that were designed for hiking originally. There is no padding at all and from day one the brooks was extremely comfortable. It only got more comfortable with time and applies all pressure directly to my sit bones. Every other saddle + padded short (even ones that mostly were on my sit bones) ended up forcing padding into the areas between my sit bones and outside them as my weight compressed the padding. I havent tried their new non leather seats but they seem to operate by a similar tension (a tensioned pliable surface vs a hard plastic shape with padding on top) which results in your weight creating additional space below the sit bones vs filling it with padding.

hi 4y ago

> the fastest riders in the 200-mile Unbound average 20 mph (32 km/h) across the Flint Hills of Kansas. Let’s not forget that the most important aspect of averaging 20mph on grave roads: drafting, low body weight and high fitness. If you watch footage of the unbound gravel race they mention, the winners are with a group of riders until the very end. The fastest riders are professionals sponsored by the companies trying to sell you this aero gear. If you want to ride faster ride in a group, find your ideal body weight and spend money on a coach. Only then spend money on bike parts beyond the basic lubricated chain, correct tire psi, etc.

MezzoDelCammin 4y ago
Personally, I'd change the order. Coach first, body weight second. If there's one piece of equipment to buy first & ASAP, it'd be a powermeter and something to display the readout on. Riding in a group is of course great, but first You got to have the legs to catch up and then the body weight / metabolism to keep up. Having the core / flexibility to be able to spend hours in somewhat aero position doesn't hurt either. It always makes me laugh to see slightly overweight people on carbon frames. Having a few kilos over myself, I always thought I'd rather spend money / time / effort losing 3-4kg of fat, rather than mulling over how to shave 100g off of the groupset or 300g of wheels weight...
- noir_lord 4y ago
  > but first You got to have the legs to catch up and then the body weight / metabolism to keep up. Not just keep up, if you are riding in a group you need to be fit enough to take your turn on the front where you aren't draughting (at least if the group you are riding with is your team). The actual team dynamics of professional road racing are fascinating, much like F1 they'll often pick the strongest and expect everyone else to support them.
  - MezzoDelCammin 4y ago
    yeah, I've never really been into group riding / drafting on a competitive level. I'm mostly trying to avoid it, actually (more of a self-supported racing kind of guy). Where I train (Paris, polygone de Vincennes) there are quite a few groups riding together, but not sure they'd switch places. I guess it depends on why You do what You do. In my case, if someone wants to ride behind me, I don't mind (other than that it makes me a bit more careful when passing someone / turning corners). I'm there to work on my power output or cadence, not to get KOMs on Strava segments ;-)

benjaminwootton 4y ago

I bought a cool book yesterday which is all about gravel trails in the UK. I had never heard the term gravel bike until reading it. Silly question but can I do these trails on my full suspension mountain bike, or will I be mercilessly mocked and possibly chased out of town? I already have a mountain bike and a road bike so not keen to add a third!

protonbob 4y ago
You will certainly not be. At least in the US, mountain bikes for trails are still the norm.
namdnay 4y ago
A mountain bike is fine on a gravel trail, if you can lock the shocks
unklefolk 4y ago
> ... can I do these trails on my full suspension mountain bike...? Yes. It will be a bit more work on the pedalling front vs a dedicated gravel bike, but I doubt you will encounter any bike snobbery. I have gravel trails near where I live, and you see all kinds of bikes tackling them.
lukah 4y ago
If anything, you might be thankful of a full suspension mountain bike on some of our "gravel" trails in the UK. There's such a wide range from US-style back county roads all the way to bridleways with baby-head sized rocks that you probably wouldn't want to be riding on something typically sold as a gravel bike.
- Doctor_Fegg 4y ago
  Yes, this. There's actually not that much US-style "gravel" in England and Wales: basically a few Forestry Commission tracks in mid-Wales, Northumberland and places like that. Elsewhere it's single-track bridleways that dominate. Routes like King Alfred's Way, the Pennine Bridleway, the Great North Trail and West Kernow Way are sometimes marketed as gravel routes but they're probably more MTB than anything.

ehnto 4y ago

If you want an astonishgly well put together deep dive on gravel and bikepacking aerodynamics, check out: https://www.cyclingabout.com/fascinating-aerodynamics-bikepacking-bicycle-touring/ https://www.cyclingabout.com/fascinating-aerodynamics-bikepa... I cannot recommend him, his videos or articles enough. He lives on the bike, literally, and he applies an unrivaled dedication and passion to thinking and writing about this stuff while on the road. He has tests, science and real world experience to back him up too.

pharmakom 4y ago

I’m sorry but Jan Heine has unscientific methods and his products are of questionable reliability. You can drop 200usd on his tyres. It’s like hifi nerdy but for rubber.

bigfudge 4y ago
I agree the tyres are expensive, but their findings on tyre width and pressure are largely bourne out by more controlled tests. In addition, their rolling distance tests include one factor which most standardised rigs didn’t: the losses from hysteresis when uneven surfaces have to lift/return your mass over a bump. I think soft wide tyres would be even more advantageous than most people realise once real losses on real roads are factored in, and compared at speeds most cyclists go at (i.e most people don’t average 30kph). In fact, even using average trip speeds as the comparator would be daft because that would include downhill sections where riders are actually braking, or don’t really care about rolling resistance because the difference between 50 and 55kph downhill makes no practical difference.
- ActorNightly 4y ago
  The tire width definitely has a break even point where wider tires are significantly less efficient than narrower ones unless you run them at unsafe pressures. More volume in the tire means that at the same pressure, there is more deflection, and deflection hysteresis in the tread, notably the rebounding of the tread behind the contact patch is what causes the rolling resistance in the first place.
  - wiredfool 4y ago
    RH 48mm tires at 25psi are pretty damn good on a single. Likewise my tandem uses 44's at 45psi (front, heavy captain) and the rear 53mm at 40 (light stoker).
  - bigfudge 4y ago
    Totally agree. I do think that people underestimate the width of that point tho. For most people who are not racing the suspension benefits probably outweighs the minimal aero loss, but it’s really hard to measure. I have been on fast group rides on 48mm slicks and although I get funny looks (and am not going to win many races because I’m old and lazy) I genuinely L find it easier to keep up than on 28mm tyres i had previously. Part of that is confidence maneuvering at speed on fairly crappy roads though.

alleycat5000 4y ago

Bicycle Quarterly (magazine by the same folks) is a great read, always such a joy when it arrives in the mail! https://www.bikequarterly.com/ https://www.bikequarterly.com/

bbarn 4y ago

I am an out of shape former racer who has ridden his bike 10 times in the last two years. I have a dad belly and rarely work out at all. I recently did The Rift this summer - a 200km gravel race here in Iceland that people come from all over the world to race. I did it on a carbon cyclocross bike from my racing days with file treads. I felt like the light weight of my bike outweighed just about every gravel fad that's out there right now. I was flying past people on the hills, and while the ride felt very rough on the high speed flats, I was still going fast. If I were in my racing shape of a few years ago I think I would have been in the top 5-10% of racers, largely because nearly everyone was on giant heavy gravel bikes with massive tires loaded for friggin bikepacking from the look of it. My wife has a purpose-built gravel bike, and she commented on just how slow it felt going uphill (she is a former state cyclocross champion). With the exception of the absolute professionals, most people "Racing" these events are just there to finish them, and the pros? It's basically just a road race. Gravel offers no significant challenge in handling your bike, and any reasonable set-up can win if it's light enough and the rider is fit enough. The Aero arms race certainly matters in time trials, but I remain unconvinced there's enough benefit for the actual racing. I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too.

shagie 4y ago
> I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too. While this is a "on the paved road" race... you should check out Horribly Hilly Hundreds in Wisconsin - https://www.horriblyhilly.com https://www.horriblyhilly.com
- gammarator 4y ago
  Yeah, rolling hills are tough…. “Rouleur” is a cyclist type for a reason.
jackmott42 4y ago
Why don't you actually do some math, or experiments, rather than just telling us you have doubts? This is all really easy stuff to answer. For instance. 75kg rider + bike. Make the bike 1kg lighter. Go up a 8% grade for 1 kilometers at 300 watts Time saved by 1kg weight reduction? 30 seconds out of 40 minutes. Or suppose we add 300grams to the frame to make it aero, which is typical. If that reduces the CdA by .02 out of .25, you are at about a breakeven point. JUST during the 1km climb. Then you save time on all the flats and non technical downhills. Acceleration is even less affected by bike mass. People forget that bike mass is a tiny % of total system mass (our fat asses). And mass is only one of 4 major components that affect acceleration. I'm happy to run through some acceleration scenarios if you like.

helsinkiandrew 4y ago

> The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider There's lots of things you can do - apart from losing a lot of weight, clothing and helmet design is probably the simplest, there's some good references to things that can be done here: https://link.springer.com/article/10.1007/s12283-017-0234-1#Bib1 https://link.springer.com/article/10.1007/s12283-017-0234-1#... >I don’t always use the aero tuck. I find that it’s not very comfortable for more than a few minutes at a time I cycle on a time trial bike (not on gravel) - which has a higher saddle and longer frame so back and arms can get straight and horizontal. It took a lot of effort to get comfortable physically and mentally in that position (you hands feel a very long way from the brakes) and you do loose quite a bit of control in that position, but I don't see why a slightly higher saddle and arms horizontal but wider with hands at the edge handlebars in line with legs wouldn't be possible.

prmoustache 4y ago
The most aero time trial like position need training, especially the muscles in the neck area. Even in the pro racing world some racers do not train enough in that position and lose precious time in time trial because they are unable to keep it straight looking at the road constantly and move the head up and down constantly. The helmets manufacturers actually accounted for that and moved to time trial helmets with a much smaller tail as it spent to much pointing in the air.
seadan83 4y ago
Gravel has washboards, pot holes, trenches, lips, fallen trees, overhanging trees/brush, large rocks. I'm thinking a lot about downhill riding too with respect to your comment. For a downhill section on gravel, for a 8% grade descent - safety is perhaps the biggest limiting factor. In some gravel races, it is really debatable whether a hardtail or a gravel bike is better. That is all to say is that stability demands can greatly vary from one section to another on a gravel/mountain race course.

qwertox 4y ago

I started biking around three years ago. Lots of biking, like 5000-8000+ km a year. As long as I don't weigh my ideal weight and aren't planning on becoming a machine myself, I have zero interest in spending anything in optimizations which will make my bike a better one. I don't care if it could go faster or be more lightweight, spending 600€ for the bike was enough. The cheapest 30€ Schwalbe tires are good enough; I didn't even have a single flat tire this summer after I learned to avoid driving over blackberry branches. And I really enjoy it. During this summer, with the extreme heat, where I loved the 28°C in the shade of the woods I was thinking about how much I'm going to hate this fall, and now that it's here, I love breathing that cold, fresh air and smelling the humid forest. The only thing I hate is when there's frozen snow on pavement in the winter. The only thing I spend money on for biking is quality clothing appropriate for the seasons and accessories like good smartphone holders or bags.

chitowneats 4y ago
I appreciate your approach but the reason people like optimizations is for speed. The thrill of riding fast is what keeps a lot of us coming back.
- lm28469 4y ago
  Lots of people optimise because they fell in the rabbit hole of optimisation and it became an addiction. Like in every hobbies some people completely lose touch with reality. I've seen videos of people comparing weight of bicycle seats and how to shave like 13 grams of weight of the bike, meanwhile the dude had a dad bod and shaving his torso would have shaved more weight than his $$$ seat
- qwertox 4y ago
  Don't get me wrong, I also love to go down a forest path at 45 kph to the point where I get scared, but I know that I also have to go up again. But going as fast as possible on a horizontal path is not attractive to me at all. If I want to expend energy, I prefer to ride up a hill where I then can have the fun of riding down, even if I have to pedal 20 minutes up to then go down within a minute or two. But I also recognize that there are those who are already super efficient and want to get the absolutely most out of their gear, even improving it as much as possible, which is really ok by me. I wish I were at that point, but I think I'd first have to go to the gym for that.

Zigurd 4y ago

They milk the topic. This could have been 2 pages at most: Aero bars are dorky, doubly on gravel, but they will make the most difference. Heck, clip a fairing to those aero bars. But nobody uses them because you look like a dork. If you can't get over looking like a dork, and you are susceptible to bike marketing <cough>GCN</cough> you'll spend thousands on an aero frame. And then you'll put a hipster handlebar bag on it.

simonebrunozzi 4y ago

> The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider. I have an idea about that, and I would like to explore it. Not having a mechanical engineering background, what do you think would be the best way to build a prototype, patent it, etc? Is there any engineering firm that would provide such service, let's say in Europe?

SavageBeast 4y ago

I ride a Trek Domane 5 AL which allows spacing for a 48mm tire ( odd for a roadie ) - so I put a 48mm gravel tire on it and started riding it on light gravel. Works very very well. Carbon would be even better but Id still be waiting on it to arrive from the factory alas the aluminum version will have to do. The best bike in the world is the one you have in the garage to ride today.

grzes 4y ago

wondering if i should switch handlebars to narrower one. so currently i have 56 frame with 42 handlebars - thats "factory" setup. i noticed that also 54 frame has this handlebars, only 52 size frame comes with 40. anyone has any experiences how it will affect bike handling? i noticed that there is a trend rising to go with narrower handlebars on gravel bikes

Melatonic 4y ago
I personally go with the widest handlebars I can. You might gain some aero from skinny ones which would be worth it if you are racing at a high level but you will lose a significant amount of comfort. Wider bars allow more hand positions and are significantly more comfortable for me especially on long rides. Being able to really get a wide grip occasionally feels great on the shoulders. And on top of that you feel much, much more secure with a nice wide grip on difficult terrain like shitty pothole laden roads.

NegativeLatency 4y ago

The aerodynamics of upright bikes compared to recumbents remind me very much of stock car racing compared to f1. Where one is actively pushing forward in terms of speed and performance and the other is stuck with one type because of how it "should" conform to previous ideas of what a bike looks like.

Melatonic 4y ago

Back in the day I found some vintage "aero" bars that were designed to bolt on to any bicycle made before larger diameter drop bars became the norm. I did not want them, however, specifically for the "aero tuck" - I wanted them to give me more hand positions for long term comfort. While I eventually got rid of them because they took too much space on the flats of the bars due to the way they clamped I always wondered if we could design something like an aero bar but specifically for comfort. It could bolt on to the stem or in a way that still allowed multiple hand positions on the flats. The elbow pads were also a very nice way to get some lower back stretches in and I even ended up mounting a small cyclocross brake at the end of one of the aero handles so I could comfortable adjust speed (rear brake only - front brake in this position might be suicide) while going downhill and tucked. Or hell - maybe even something that had a small fold mechanism so that you could fold away the forearm / elbow pads when not in use!

phlipski 4y ago

The article mentions the upper back fairing of a motoGP racer but then blows off the idea for a cyclist because they might get too hot? I've always wondered why road cyclists don't ditch their frame mounted (and drag inducing) water bottles for a camelback. The original camelback was slim and I can't imagine it added any drag seeing as it sits on the back of the cyclist. Plus it has the advantage of allowing the cyclist to maintain a better cylcing position without having to reach down for a bottle. But then again if roadies were really all that concerned about aero and efficiency they'd switch to recumbent bikes...

vbarrielle 4y ago
In pro cycling it's actually forbidden to have aero fairings on your bike. During the Armstrong years there has been a controversy about the placement of his radio on his back during time trials that would incur fairing.