17 ms·

Ventum, Dimond, Cervelo – Why do these triathlon bikes look so weird?

62 points by yread 3y ago

ideasphere 3y ago
Trick question, all tri bikes look weird.
AtlasBarfed 3y ago
First off, while the UCI specs don't apply to triathlon bikes, they still roughly have to. A lot of these bikes have aspects that once were legal by UCI rules at some point (although not sure about the "boom" bikes with no seat tube, but bikes like that were made by trek in the 1990s). The UCI is kind of like the Navy: there's a right way to design a racing bike, a wrong way, and then there's the UCI way. It has conservatism and history to be concerned about (bike racing is pretty old in Europe), keeping costs down for the lower run of even UCI pro teams (the female UCI teams can't even field a TT bike for all their teammates in TTTs), and there are durability concerns so bikes don't break and cause crashes in pelotons and the like, because there are already plenty of crashes. Triathlon isn't a big enough sport to have its own weird cogsets, wheel standards, etc, so they generally have to piggyback off what Shimano/SRAM/Campy make for the protour and general bike public. Now, I will say that my P3C with a disc and a trispoke front looks like an amazingly awesome back back when I did serious triathlons. Before children. Also, CFD will be what CFD is, the wind/fluid dynamics doesn't care about your superficial proclivities.
deleted 3y ago
[deleted]
kazinator 3y ago
These frames have to be exceptionally well engineered and built not to be death traps. Some people will be dumb enough to use these for touring, commuting and whatnot. Imagine you're coming down a long mountain road, hit some crack in the road, and the frame goes crack.
- virtue3 3y ago
  Carbon fiber is extremely durable when it is designed to be stressed in the directions it's designed for. For instance if you eat shit and fall laterally the frame is likely to crack :). When you invest in these kinds of bikes you end up having to get them x-rayed after accidents to verify they aren't having sub-surface cracks and are safe to ride. Aluminum will also stress crack and just fracture. Steel is dramatically more ductile and will most likely deform instead of catastrophically failing.
  - Qwertious 3y ago
    Steel also has lower embodied energy than aluminum, it's rather underrated.
    - __loam 3y ago
      Steel is real!
      - kazinator 3y ago
        Steel has a bad rap because cheap, bicycle-shaped objects sold in the consumer mass market are usually made of steel: both frame and often wheel rims too. Like "Ozark Trail" bikes sold by Walmart, bikes for toddlers and what not. These bikes are massively heavy and susceptible to rust.
    - Lio 3y ago
      That is true but aluminium requires less energy to recycle when you're finished with it. I have bikes made of steel, aluminium and carbon fibre. I don't worry about the longevity of any of them. Hydro-formed aluminium is cheap, relatively light and easy to live with IMHO. Horses for courses. I also think geometry of a frame is far more important than frame material for things like comfort but that's a different story. i.e. how much can the seat post flex.
  - prmoustache 3y ago
    The good thing with carbon is it is relatively easy and cheap to repair compared to alu and steel.
zh3 3y ago
Quite a lot of the design inspiration comes from top riders and their coaches - the level of technical knowledge they have is astonishing. We work with bikes like these, covering them with sensors and loadcells (we've had something like 20 ARM processors on a bike at a time, communicating wirelessly), and while the bike is part of the equation most of the drag comes from the rider's body. So a lot of effort also goes into comfort and fit, in order to get the rider into an aero position that they can hold for a period of time (the most aero position may not be possible to hold for very long) so it rapidly becomes an area-under-the-curve thing. We spend a lot of time in the lab, in wind tunnels and in velodromes sorting it all out (now with AI, vision systems, rider position tracking - it's getting really complicated). Also these bikes are not generally roadworthy - every so often we hear a multi-thousand-dollar 'crack!' indicating another frame has had enough.
- Eric_WVGG 3y ago
  Funny, the last time I read an article about bicycles here, a writer was getting dragged for trying to explain that same point. https://news.ycombinator.com/item?id=39181473 https://news.ycombinator.com/item?id=39181473
  - albinowax_ 3y ago
    There's a pretty big gap between the bikes in this post and the kind of carbon road bike most people ride eg, a Giant Defy
  - plagiarist 3y ago
    The point that the racing bike is more likely to have a failure during use? The difference seems to be suggesting people not have a toy they want vs. only explaining that there is a serious drawback. Occasionally something happens that makes the attitude really stand out. I once saw an actual electrician tell someone their 3D printed light switch cover was an accelerant. He suggested they re-do one to attach on top of a standard flame-retardant cover. There were like half a dozen "nuh-uh" comments from people who felt attacked by that.
  - plorkyeran 3y ago
gadders 3y ago
Easier to hide the secret electric engines when the frames are thick /s
Karellen 3y ago
> The tubes of a traditional bike essentially form two diamond shapes. Huh? I only see one diamond shape. There are two triangle shapes; one from the steering column to the seat post, and one from the seat post to the rear-wheel axle. They make up one diamond, not two. What am I missing?
- pests 3y ago
  I think double refers to the tubes making up the frame being double lined for strength. It took me a bit of searching but it does appear "diamond frame" bikes are a concept which then makes sense. Apparently some mountain biking applications or uses with more stress require a "double diamond frame". That's what I could figure out though. I also don't think they need to be exactly triangles, just as long as the nodes are generally connected via the same edges. Also sometimes the top and bottom bar don't meet at a single point on the steering post so that shape ends with with 4 sides.
  - hermitdev 3y ago
    I'm not sure, either, but the double could also refer to having the two triangular arms to secure the rear wheel instead of a single one.
    - pests 3y ago
      I thought that might be it too but found literally 0 references for it. edit: Also, don't all of the designs have two arms in the back? Even the original "diamond frame" has the same rear tire attachment.
- beckerdo 3y ago
  Consider the possibility that one diamond goes from the steering tube to the right rear axle mount and the second diamond goes from the steering tube to the left rear axle mount.
tokai 3y ago
Because triathletes have extraordinary bad taste. Thank God for UCI keeping real bicycle racing proper.
- InCityDreams 3y ago
  Wooden wheels and no pedally bits?
- rhinoceraptor 3y ago
  Bring back the steel bikes, downtube shifters, no helmets, and the smoking in the peloton!
alkonaut 3y ago
The immediate question is: if they are more efficient, why aren't all disciplines using these? The article doesn't say! It suggests in passing that Triathlon has different rules because it doesn't allow "drafting" (Which I'm guessing is something related to team-riding to reduce air resistance, but the article doesn't explain what it is). Are there any rules prescribing (say) that a tour de France bike must use a normal (double triangle) design? Or is that just used because a traditional frame is optimal for weight rather than aerodynamics?
- strken 3y ago
  The article explicitly says that UCI banned NDD bikes. Given that the Tour de France is a UCI event the answer seems obvious.
  - alkonaut 3y ago
    The question I guess is: are UCI-governed events not using "NDD" bikes only because of regulations on what shape can be used, or is triathlon special in that it favors aerodynamics more than other events? That is: if regulation was dropped, would pro cycling be filled with weird looking CF monocoque designs, or is the traditional design still optimal for some use cases (e.g. for weight and events with team ridning and lots of climbing)?
    - hermitdev 3y ago
      UCI has strict regulations on the geometry, weight and even ancillary equipment (think brakes, gear shifts) of bikes. I vaguely recall the minimum weight being something like 14.9 lbs, but this is likely incorrect. Point is, it's quite possible to make a bike that is lighter than this while still remaining safe for racing. I've heard of some using lead ballast to make weight. One advantage of this, though, is you can choose where to place the weight, such as in the bottom of the frame, near the crank, lowering center of gravity and helping stability a bit. The regs do make for some funny situations though. Take a look at a pro peloton and look for the shortest rider, preferably someone close to 5 feet tall. Their bike will be comically oversized for them. The UCI tends to be a fairly conservative organization that favors tradition over accepting the latest technology and design trends, especially with road racing. You're more likely to see new technology in non road disciplines such as cyclocross or mountain biking. Just see disc brakes only just getting into road racing in the past several years (I've not been following racing closely anymore, so not sure when).
ck2 3y ago
I am small so I always wanted a 650c bike to be 2 inches closer to the ground. That alone has to be faster for wind resistance given everything else the same. If 650c is still legal in races I am surprised even large riders haven't adapted frames to sit lower to the ground.
- mauvehaus 3y ago
  You can only lower the bottomo bracket so much. At some point you start having pedal clearance issues. I've put the end of the crank on my Brompton into the ground pedaling around a corner, and it wasn't like I was deeply leaned into it.
tocs3 3y ago
"NDD bikes were designed to be more aerodynamic by completely eliminating surface area." Not sure nut they do not look like they are eliminating surface area. Not saying they are less aerodynamic. Also, I raced road bikes in the late 80s. I am wondering how much these bikes weigh. Then light weight was what was sought after.
- atoav 3y ago
  Yeah my guess would also be that weight is the reason they fell out of favour. Aerodynamics are important, but weight is also, especially if you are outside and the route isn't perfectly flat.
  - Lio 3y ago
    They fell out of favour because the UCI doesn’t allow them in road TTs. Now that doesn’t matter to pure triathlon bikes (as they’re not governed by the UCI) but it matters to the manufacturers accessing a much smaller sub-market. It also matters to the customers who might want to also race UCI events or resell a bike. Essentially double diamond designs are competitive enough now to make non-double diamond unviable.
- scott_w 3y ago
  To a point, weight is less of a concern in the modern era because aerodynamics dominate at almost all speeds. I’ve always found NDD bikes interesting but I suspect the advantages are overstated given the top pros are moving away from them. LCB and Sam Laidlow both rode “classic” TT-style bikes to win the Ironman WC last year.
  - AtlasBarfed 3y ago
    Yeah at the pro-ish level of triathlon, I think you need stiffness even in 112 mile bike legs. These aliens are doing 25-27mph, if you have the inevitable sway from the lack of the triangle, you'll lose power to the drivetrain. The Pros might get to piggyback on some of the wind tunnel testers here or there for reasonable amounts, and the "NDD" bikes might not really stack up much in the "total system" aero testing. One might think that ultraskinny 18mm tires would be more aero, but 1) they have bad rolling resistance and 2) they actually aren't, at least for a while the pro teams were using 25mm tires because aero testing said it was better + lower rolling resistance. Point is, aero is weird. But I haven't followed the state of the art of the last three or four years. Finally, modern tri bikes shape themselves for onboard nutrition transport and integrated fluids, sometimes in the tubes. They also have storage boxes for the flat kit. Ironman triathletes care a lot about that. The article makes it seem like these are all fresh off the design board, but these have been around for, what 5-7 years now? I was kind of hoping for more designs in the article, but these are basically what was the cutting edge back then. I would hope the 10,000$ price tags would have come down, but I doubt it. And the other laughable thing is the wheels in those bikes. Where are the disc wheels? A disc wheel is often more important than the frame and helmet. It's funny. You spend 200$ for an aero helmet, that's 1/3 of the gain, another $2000 for aero wheels, that's 1/3 of the gain, and then 10,000$ for a frame, and that's the last 1/3 of the gain. BTW. The lotus was my favorite bike ever. https://www.theproscloset.com/blogs/road-bikes/colby-pearces-1995-lotus-sport-110 https://www.theproscloset.com/blogs/road-bikes/colby-pearces...

62 points by yread 3y ago

Trick question, all tri bikes look weird.

First off, while the UCI specs don't apply to triathlon bikes, they still roughly have to. A lot of these bikes have aspects that once were legal by UCI rules at some point (although not sure about the "boom" bikes with no seat tube, but bikes like that were made by trek in the 1990s). The UCI is kind of like the Navy: there's a right way to design a racing bike, a wrong way, and then there's the UCI way. It has conservatism and history to be concerned about (bike racing is pretty old in Europe), keeping costs down for the lower run of even UCI pro teams (the female UCI teams can't even field a TT bike for all their teammates in TTTs), and there are durability concerns so bikes don't break and cause crashes in pelotons and the like, because there are already plenty of crashes. Triathlon isn't a big enough sport to have its own weird cogsets, wheel standards, etc, so they generally have to piggyback off what Shimano/SRAM/Campy make for the protour and general bike public. Now, I will say that my P3C with a disc and a trispoke front looks like an amazingly awesome back back when I did serious triathlons. Before children. Also, CFD will be what CFD is, the wind/fluid dynamics doesn't care about your superficial proclivities.

deleted 3y ago

[deleted]

kazinator 3y ago

These frames have to be exceptionally well engineered and built not to be death traps. Some people will be dumb enough to use these for touring, commuting and whatnot. Imagine you're coming down a long mountain road, hit some crack in the road, and the frame goes crack.

virtue3 3y ago
Carbon fiber is extremely durable when it is designed to be stressed in the directions it's designed for. For instance if you eat shit and fall laterally the frame is likely to crack :). When you invest in these kinds of bikes you end up having to get them x-rayed after accidents to verify they aren't having sub-surface cracks and are safe to ride. Aluminum will also stress crack and just fracture. Steel is dramatically more ductile and will most likely deform instead of catastrophically failing.
- Qwertious 3y ago
  Steel also has lower embodied energy than aluminum, it's rather underrated.
  - __loam 3y ago
    Steel is real!
    - kazinator 3y ago
      Steel has a bad rap because cheap, bicycle-shaped objects sold in the consumer mass market are usually made of steel: both frame and often wheel rims too. Like "Ozark Trail" bikes sold by Walmart, bikes for toddlers and what not. These bikes are massively heavy and susceptible to rust.
  - Lio 3y ago
    That is true but aluminium requires less energy to recycle when you're finished with it. I have bikes made of steel, aluminium and carbon fibre. I don't worry about the longevity of any of them. Hydro-formed aluminium is cheap, relatively light and easy to live with IMHO. Horses for courses. I also think geometry of a frame is far more important than frame material for things like comfort but that's a different story. i.e. how much can the seat post flex.
- prmoustache 3y ago
  The good thing with carbon is it is relatively easy and cheap to repair compared to alu and steel.

zh3 3y ago

Quite a lot of the design inspiration comes from top riders and their coaches - the level of technical knowledge they have is astonishing. We work with bikes like these, covering them with sensors and loadcells (we've had something like 20 ARM processors on a bike at a time, communicating wirelessly), and while the bike is part of the equation most of the drag comes from the rider's body. So a lot of effort also goes into comfort and fit, in order to get the rider into an aero position that they can hold for a period of time (the most aero position may not be possible to hold for very long) so it rapidly becomes an area-under-the-curve thing. We spend a lot of time in the lab, in wind tunnels and in velodromes sorting it all out (now with AI, vision systems, rider position tracking - it's getting really complicated). Also these bikes are not generally roadworthy - every so often we hear a multi-thousand-dollar 'crack!' indicating another frame has had enough.

Eric_WVGG 3y ago
Funny, the last time I read an article about bicycles here, a writer was getting dragged for trying to explain that same point. https://news.ycombinator.com/item?id=39181473 https://news.ycombinator.com/item?id=39181473
- albinowax_ 3y ago
  There's a pretty big gap between the bikes in this post and the kind of carbon road bike most people ride eg, a Giant Defy
- plagiarist 3y ago
  The point that the racing bike is more likely to have a failure during use? The difference seems to be suggesting people not have a toy they want vs. only explaining that there is a serious drawback. Occasionally something happens that makes the attitude really stand out. I once saw an actual electrician tell someone their 3D printed light switch cover was an accelerant. He suggested they re-do one to attach on top of a standard flame-retardant cover. There were like half a dozen "nuh-uh" comments from people who felt attacked by that.
- plorkyeran 3y ago

gadders 3y ago

Easier to hide the secret electric engines when the frames are thick /s

Karellen 3y ago

> The tubes of a traditional bike essentially form two diamond shapes. Huh? I only see one diamond shape. There are two triangle shapes; one from the steering column to the seat post, and one from the seat post to the rear-wheel axle. They make up one diamond, not two. What am I missing?

pests 3y ago
I think double refers to the tubes making up the frame being double lined for strength. It took me a bit of searching but it does appear "diamond frame" bikes are a concept which then makes sense. Apparently some mountain biking applications or uses with more stress require a "double diamond frame". That's what I could figure out though. I also don't think they need to be exactly triangles, just as long as the nodes are generally connected via the same edges. Also sometimes the top and bottom bar don't meet at a single point on the steering post so that shape ends with with 4 sides.
- hermitdev 3y ago
  I'm not sure, either, but the double could also refer to having the two triangular arms to secure the rear wheel instead of a single one.
  - pests 3y ago
    I thought that might be it too but found literally 0 references for it. edit: Also, don't all of the designs have two arms in the back? Even the original "diamond frame" has the same rear tire attachment.
beckerdo 3y ago
Consider the possibility that one diamond goes from the steering tube to the right rear axle mount and the second diamond goes from the steering tube to the left rear axle mount.

tokai 3y ago

Because triathletes have extraordinary bad taste. Thank God for UCI keeping real bicycle racing proper.

InCityDreams 3y ago
Wooden wheels and no pedally bits?
rhinoceraptor 3y ago
Bring back the steel bikes, downtube shifters, no helmets, and the smoking in the peloton!

alkonaut 3y ago

The immediate question is: if they are more efficient, why aren't all disciplines using these? The article doesn't say! It suggests in passing that Triathlon has different rules because it doesn't allow "drafting" (Which I'm guessing is something related to team-riding to reduce air resistance, but the article doesn't explain what it is). Are there any rules prescribing (say) that a tour de France bike must use a normal (double triangle) design? Or is that just used because a traditional frame is optimal for weight rather than aerodynamics?

strken 3y ago
The article explicitly says that UCI banned NDD bikes. Given that the Tour de France is a UCI event the answer seems obvious.
- alkonaut 3y ago
  The question I guess is: are UCI-governed events not using "NDD" bikes only because of regulations on what shape can be used, or is triathlon special in that it favors aerodynamics more than other events? That is: if regulation was dropped, would pro cycling be filled with weird looking CF monocoque designs, or is the traditional design still optimal for some use cases (e.g. for weight and events with team ridning and lots of climbing)?
  - hermitdev 3y ago
    UCI has strict regulations on the geometry, weight and even ancillary equipment (think brakes, gear shifts) of bikes. I vaguely recall the minimum weight being something like 14.9 lbs, but this is likely incorrect. Point is, it's quite possible to make a bike that is lighter than this while still remaining safe for racing. I've heard of some using lead ballast to make weight. One advantage of this, though, is you can choose where to place the weight, such as in the bottom of the frame, near the crank, lowering center of gravity and helping stability a bit. The regs do make for some funny situations though. Take a look at a pro peloton and look for the shortest rider, preferably someone close to 5 feet tall. Their bike will be comically oversized for them. The UCI tends to be a fairly conservative organization that favors tradition over accepting the latest technology and design trends, especially with road racing. You're more likely to see new technology in non road disciplines such as cyclocross or mountain biking. Just see disc brakes only just getting into road racing in the past several years (I've not been following racing closely anymore, so not sure when).

ck2 3y ago

I am small so I always wanted a 650c bike to be 2 inches closer to the ground. That alone has to be faster for wind resistance given everything else the same. If 650c is still legal in races I am surprised even large riders haven't adapted frames to sit lower to the ground.

mauvehaus 3y ago
You can only lower the bottomo bracket so much. At some point you start having pedal clearance issues. I've put the end of the crank on my Brompton into the ground pedaling around a corner, and it wasn't like I was deeply leaned into it.

tocs3 3y ago

"NDD bikes were designed to be more aerodynamic by completely eliminating surface area." Not sure nut they do not look like they are eliminating surface area. Not saying they are less aerodynamic. Also, I raced road bikes in the late 80s. I am wondering how much these bikes weigh. Then light weight was what was sought after.

atoav 3y ago
Yeah my guess would also be that weight is the reason they fell out of favour. Aerodynamics are important, but weight is also, especially if you are outside and the route isn't perfectly flat.
- Lio 3y ago
  They fell out of favour because the UCI doesn’t allow them in road TTs. Now that doesn’t matter to pure triathlon bikes (as they’re not governed by the UCI) but it matters to the manufacturers accessing a much smaller sub-market. It also matters to the customers who might want to also race UCI events or resell a bike. Essentially double diamond designs are competitive enough now to make non-double diamond unviable.
scott_w 3y ago
To a point, weight is less of a concern in the modern era because aerodynamics dominate at almost all speeds. I’ve always found NDD bikes interesting but I suspect the advantages are overstated given the top pros are moving away from them. LCB and Sam Laidlow both rode “classic” TT-style bikes to win the Ironman WC last year.
- AtlasBarfed 3y ago
  Yeah at the pro-ish level of triathlon, I think you need stiffness even in 112 mile bike legs. These aliens are doing 25-27mph, if you have the inevitable sway from the lack of the triangle, you'll lose power to the drivetrain. The Pros might get to piggyback on some of the wind tunnel testers here or there for reasonable amounts, and the "NDD" bikes might not really stack up much in the "total system" aero testing. One might think that ultraskinny 18mm tires would be more aero, but 1) they have bad rolling resistance and 2) they actually aren't, at least for a while the pro teams were using 25mm tires because aero testing said it was better + lower rolling resistance. Point is, aero is weird. But I haven't followed the state of the art of the last three or four years. Finally, modern tri bikes shape themselves for onboard nutrition transport and integrated fluids, sometimes in the tubes. They also have storage boxes for the flat kit. Ironman triathletes care a lot about that. The article makes it seem like these are all fresh off the design board, but these have been around for, what 5-7 years now? I was kind of hoping for more designs in the article, but these are basically what was the cutting edge back then. I would hope the 10,000$ price tags would have come down, but I doubt it. And the other laughable thing is the wheels in those bikes. Where are the disc wheels? A disc wheel is often more important than the frame and helmet. It's funny. You spend 200$ for an aero helmet, that's 1/3 of the gain, another $2000 for aero wheels, that's 1/3 of the gain, and then 10,000$ for a frame, and that's the last 1/3 of the gain. BTW. The lotus was my favorite bike ever. https://www.theproscloset.com/blogs/road-bikes/colby-pearces-1995-lotus-sport-110 https://www.theproscloset.com/blogs/road-bikes/colby-pearces...