4 ms·

"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.

by 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...
  - scott_w 3y ago
    > 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. I suspect they're actually really stiff because of the amount of carbon fibre in the construction. What I also suspect is the aerodynamic gains are being overstated in the real-world, which would explain why the pros are going for more standard bikes. The current brands (Canyon, Specialized, Argon-18, Cube) are probably close enough (or faster) in practice that the sponsor money is a better trade-off. > 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. For performance, I 100% agree. That said, disc wheels from the big brands are expensive enough that $10,000 still doesn't cover it. And they probably don't want to put cheaper Chinese wheels on for image purposes (though owning an Elitewheels disc, I'd suspect they're in the same ballpark for aero performance). > then 10,000$ for a frame, and that's the last 1/3 of the gain. It's probably even less than that (going from one TT frame to another) but, hey, if it looks fast, isn't that the real victory? ;-)
  - Lio 3y ago
    Totally agree on the Lotus. Although I prefer the original 108 design to the 110. Seeing Chris Boardman win on it at the Barcelona Olympics was like seeing something arrive from another planet. It left quite an impression on a young me. I know a bike shop owner with one of the road versions in his private collection. Seeing it up close is... like being near a religious relic. Yep I am a cycling nerd! :D https://en.wikipedia.org/wiki/Lotus_108 https://en.wikipedia.org/wiki/Lotus_108
  - pmontra 3y ago
    Pro teams are going 28 mm or even 30 mm at the front and 32 mm at the back. Some measurements from Tour de France 2023 at [1] One of the reasons why larger tires are better is that the size of the contact patch to the road depends only on the internal pressure of the tire. A 20 mm tire and a 40 mm tire have the same contact patch but their shape is different. The one of narrower tire is aligned back to front so the wheel is less round. The contact patch of the wider tire is aligned right to left, so the wheel is more round and it rolls more easily without dissipating energy in elastic deformations. You'd have to inflate the narrower tire to double pressure to compensate, but then the ride is less comfortable and you can double the pressure only up to a point. That was about rolling resistance, then there is aero. Wind tunnel tests discovered that tires should connect smoothly to the profile of the rim without making the classic shape of everyday bike's wheel: a wide tire in narrow rim. They must have the same width instead and a fatter rim is more aerodynamic than a skinny one. Hence the drive to wider tires. However there is catch. A wider tire adds more mass to wheels and they are the worst place to add mass to because it works against you every time you have to make that wheel spin faster. You add mass to the frame and all the static parts of the bicycle if you really have to. And finally a very large tire (100 mm or 4 inches) is obviously too wide to have a reasonable front surface at high speeds. The sweet spot nowadays seems to be around 30 mm. Note that UCI mandates cyclocross tires to be 33 mm max, and they must work in muddy conditions. Road bikes are at almost those widths. [1] https://escapecollective.com/what-we-learned-by-measuring-tyre-widths-at-the-tour-de-france/ https://escapecollective.com/what-we-learned-by-measuring-ty...
Prcmaker 3y ago
I would suggest they mean to say front-facing surface area, which this bikes would indeed achieve over a standard design bicycle. One post in front of another will likely have a bigger impact on aero than a single deeper post. Could be phrased for better clarity I guess, but in an aerodynamic mindset, I think it's sufficient.
occz 3y ago
>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. The focus on reducing weight has largely stopped in favour of optimizing for aerodynamics, which matters more in all instances except for climbing, essentially. In fact, none of the bicycles in the world tour this year are at the weight limit specified by the UCI - they are all a bit above it for the sake of aerodynamics.
- OJFord 3y ago
  I imagine we're also at the point with these kinds of bikes where whatever marginal weight shaving you might achieve is lost in the noise of variation in rider weight? I'm just speculating really though, I ride a Dawes tourer that's older than I am.
  - michaelt 3y ago
    As I understand it, the major competitions all have a minimum allowable weight for the bike - 6.8 kilograms in UCI competitions - to avoid a costly arms race, or dangerously flimsy bikes. And yes, a recreational rider doing a serious distance will often carry 1.5kg of water, so saving 150g with special lightweight paint or whatever is lost in the noise.
    - bluGill 3y ago
      Most recreational riders should lose 10kg or more according to their doctor. However they will instead pay thousands of $$$ to save 150g.
    - tiltowait 3y ago
      > And yes, a recreational rider doing a serious distance will often carry 1.5kg of water, so saving 150g with special lightweight paint or whatever is lost in the noise. But a lighter bike is still a lighter bike. If everyone is carrying 1.5kg of water, then a 150g lighter bike still has as much of an advantage[1] as it always had. [1] Likely unmeasurable. Yes, there's some sarcasm in my comment, but I hear this type of reasoning all the time, e.g. "people say they want thin phones, then put a case on them anyway, so what's the point?" The point is a thin phone plus a case is still thinner than a thick phone plus a case. Similarly, a light bike plus 1.5kg of water is still lighter than a heavy bike plus 1.5kg of water.
virtue3 3y ago
I used to do tri's 10 years ago. Was sorta into it. Friend was super into it. Tri athletes are super into aerodynamics over weight (weight is still important but aerodynamics are more so IE disk wheel inserts etc etc). The reason being because the more effort you spend on the bike the more gassed you are on the run coming up after. (also see below there's no pelotons in tris/TT) Because of the square law of wind resistance basically bike times haven't gotten faster but run times have because riders are conserving more energy while riding at the same speed because of efficiencies in the bike designs. Also you are never allowed to draft in triathlons and must maintain a certain distance behind the rider in front of you unless you are passing on the side unlike
zokier 3y ago
I was also confused about the talk about surface area, its not clear what they mean by that here, nor how reducing it improves aero. Cross-section maybe? My expectation would be that true surface-area minimization would not result optimal aero, as it would be closer to just having circular tube construction?
- bagels 3y ago
  You would use solid bar, and it would be exceptionally heavy.
- bluGill 3y ago
  Surface area, and cross section are different variables. They are not independent variables, but they refer to different parts of aerodynamics. Surface area is a problem because of fiction of air rubbing on the surface. Cross section is a problem because you push the air aside.

by tocs3 3y ago

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...
- scott_w 3y ago
  > 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. I suspect they're actually really stiff because of the amount of carbon fibre in the construction. What I also suspect is the aerodynamic gains are being overstated in the real-world, which would explain why the pros are going for more standard bikes. The current brands (Canyon, Specialized, Argon-18, Cube) are probably close enough (or faster) in practice that the sponsor money is a better trade-off. > 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. For performance, I 100% agree. That said, disc wheels from the big brands are expensive enough that $10,000 still doesn't cover it. And they probably don't want to put cheaper Chinese wheels on for image purposes (though owning an Elitewheels disc, I'd suspect they're in the same ballpark for aero performance). > then 10,000$ for a frame, and that's the last 1/3 of the gain. It's probably even less than that (going from one TT frame to another) but, hey, if it looks fast, isn't that the real victory? ;-)
- Lio 3y ago
  Totally agree on the Lotus. Although I prefer the original 108 design to the 110. Seeing Chris Boardman win on it at the Barcelona Olympics was like seeing something arrive from another planet. It left quite an impression on a young me. I know a bike shop owner with one of the road versions in his private collection. Seeing it up close is... like being near a religious relic. Yep I am a cycling nerd! :D https://en.wikipedia.org/wiki/Lotus_108 https://en.wikipedia.org/wiki/Lotus_108
- pmontra 3y ago
  Pro teams are going 28 mm or even 30 mm at the front and 32 mm at the back. Some measurements from Tour de France 2023 at [1] One of the reasons why larger tires are better is that the size of the contact patch to the road depends only on the internal pressure of the tire. A 20 mm tire and a 40 mm tire have the same contact patch but their shape is different. The one of narrower tire is aligned back to front so the wheel is less round. The contact patch of the wider tire is aligned right to left, so the wheel is more round and it rolls more easily without dissipating energy in elastic deformations. You'd have to inflate the narrower tire to double pressure to compensate, but then the ride is less comfortable and you can double the pressure only up to a point. That was about rolling resistance, then there is aero. Wind tunnel tests discovered that tires should connect smoothly to the profile of the rim without making the classic shape of everyday bike's wheel: a wide tire in narrow rim. They must have the same width instead and a fatter rim is more aerodynamic than a skinny one. Hence the drive to wider tires. However there is catch. A wider tire adds more mass to wheels and they are the worst place to add mass to because it works against you every time you have to make that wheel spin faster. You add mass to the frame and all the static parts of the bicycle if you really have to. And finally a very large tire (100 mm or 4 inches) is obviously too wide to have a reasonable front surface at high speeds. The sweet spot nowadays seems to be around 30 mm. Note that UCI mandates cyclocross tires to be 33 mm max, and they must work in muddy conditions. Road bikes are at almost those widths. [1] https://escapecollective.com/what-we-learned-by-measuring-tyre-widths-at-the-tour-de-france/ https://escapecollective.com/what-we-learned-by-measuring-ty...

Prcmaker 3y ago

I would suggest they mean to say front-facing surface area, which this bikes would indeed achieve over a standard design bicycle. One post in front of another will likely have a bigger impact on aero than a single deeper post. Could be phrased for better clarity I guess, but in an aerodynamic mindset, I think it's sufficient.

occz 3y ago

>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. The focus on reducing weight has largely stopped in favour of optimizing for aerodynamics, which matters more in all instances except for climbing, essentially. In fact, none of the bicycles in the world tour this year are at the weight limit specified by the UCI - they are all a bit above it for the sake of aerodynamics.

OJFord 3y ago
I imagine we're also at the point with these kinds of bikes where whatever marginal weight shaving you might achieve is lost in the noise of variation in rider weight? I'm just speculating really though, I ride a Dawes tourer that's older than I am.
- michaelt 3y ago
  As I understand it, the major competitions all have a minimum allowable weight for the bike - 6.8 kilograms in UCI competitions - to avoid a costly arms race, or dangerously flimsy bikes. And yes, a recreational rider doing a serious distance will often carry 1.5kg of water, so saving 150g with special lightweight paint or whatever is lost in the noise.
  - bluGill 3y ago
    Most recreational riders should lose 10kg or more according to their doctor. However they will instead pay thousands of $$$ to save 150g.
  - tiltowait 3y ago
    > And yes, a recreational rider doing a serious distance will often carry 1.5kg of water, so saving 150g with special lightweight paint or whatever is lost in the noise. But a lighter bike is still a lighter bike. If everyone is carrying 1.5kg of water, then a 150g lighter bike still has as much of an advantage[1] as it always had. [1] Likely unmeasurable. Yes, there's some sarcasm in my comment, but I hear this type of reasoning all the time, e.g. "people say they want thin phones, then put a case on them anyway, so what's the point?" The point is a thin phone plus a case is still thinner than a thick phone plus a case. Similarly, a light bike plus 1.5kg of water is still lighter than a heavy bike plus 1.5kg of water.

virtue3 3y ago

I used to do tri's 10 years ago. Was sorta into it. Friend was super into it. Tri athletes are super into aerodynamics over weight (weight is still important but aerodynamics are more so IE disk wheel inserts etc etc). The reason being because the more effort you spend on the bike the more gassed you are on the run coming up after. (also see below there's no pelotons in tris/TT) Because of the square law of wind resistance basically bike times haven't gotten faster but run times have because riders are conserving more energy while riding at the same speed because of efficiencies in the bike designs. Also you are never allowed to draft in triathlons and must maintain a certain distance behind the rider in front of you unless you are passing on the side unlike

zokier 3y ago

I was also confused about the talk about surface area, its not clear what they mean by that here, nor how reducing it improves aero. Cross-section maybe? My expectation would be that true surface-area minimization would not result optimal aero, as it would be closer to just having circular tube construction?

bagels 3y ago
You would use solid bar, and it would be exceptionally heavy.
bluGill 3y ago
Surface area, and cross section are different variables. They are not independent variables, but they refer to different parts of aerodynamics. Surface area is a problem because of fiction of air rubbing on the surface. Cross section is a problem because you push the air aside.