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Wider wheels, n=1 test

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Wider wheels, n=1 test

Old 08-08-20, 03:13 PM
  #26  
HTupolev
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Originally Posted by guadzilla View Post
Would a heavier rider shift the break point to the left or the right, compared to a lighter rider?
To the right. Higher load needs more stiffness in a suspension system to create the same amount of vertical interaction. More pressure for the same sag, more force to create a given amount of vertical deflection in the sprung mass. Same reason that suspensions on mountain bikes are tuned stiffer for heavier riders.

Originally Posted by guadzilla View Post
Possible reasons I can think of:
4) Zipp and ENVE are pushing hookless rim manufacture, and current ETRTO guidelines limit hookless rims to a max of 5bar/72.5PSI.

The big issue is that optimal setup is a highly multivariate problem, and the differences that need to be measured to give real answers are very small. It would take a pretty broad study to thoroughly sort things out with good accuracy and precision, and the cycling industry just doesn't have a very large or unified R&D budget.

Pertaining to this graph, another fun question is what the shape of the vibration loss curve actually is. It's probably somewhat sigmoidal, since the vibration losses won't just keep increasing as pressure increases: at some point, the suspension system will be transmitting pretty much everything that a surface can transmit, and further stiffening won't do anything to change that.
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Old 08-08-20, 03:51 PM
  #27  
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Originally Posted by WhyFi View Post
I think that the other thing that needs to be considered, in terms of optimization, is the average Schmoe on the bike is a lot ******g heavier than the guys getting paid to play bikes. To me, that moves the break point considerably - moving from 23/25 at ~100 psi to 28/30 at 65-70 immediately translated to being fresher, less beat up and faster on anything longer than an hour or so.
I do wonder how that holds for the boys like Kittel. Do they select appreciably different equipment from the climbers? If so, this all could have been figured out a while ago.
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Old 08-08-20, 04:43 PM
  #28  
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My hunch is that brands are pushing wider tires because the average customer isn't the light, young racing type.

​​​​If you're reasonably light - 65 to 75kg - and want comfort, you can simply ride 23s or 25s at less pressure. At 90 psi they offer a much more muted ride and I found myself even faster on bad roads with around 80 psi.

​​​But for the average customer, 28mm tires may be needed to be able to use comfortable pressures.

​​​
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Old 08-08-20, 06:03 PM
  #29  
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avg customer type?
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Old 08-08-20, 06:57 PM
  #30  
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Originally Posted by Sy Reene View Post
avg customer type?
I resemble that remark!
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Old 08-08-20, 11:27 PM
  #31  
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Originally Posted by HTupolev View Post
To the right. Higher load needs more stiffness in a suspension system to create the same amount of vertical interaction. More pressure for the same sag, more force to create a given amount of vertical deflection in the sprung mass. Same reason that suspensions on mountain bikes are tuned stiffer for heavier riders.
Sorry, i was sloppy in my question - it should have up/down (not left/right) - ie, for a given pressure, is resistance loss higher or lower for a heavier rider? I agree that the actual deflection would be lower for a heavier rider (same force, greater mass) - but how about the actual energy loss? A heavier rider imposes a greater downward force on the system, which results in a greater counter-force - so i would imagine the resistance loss would be higher. In other words, the curve would shift upwards.

Would you agree with that?

The big issue is that optimal setup is a highly multivariate problem, and the differences that need to be measured to give real answers are very small. It would take a pretty broad study to thoroughly sort things out with good accuracy and precision, and the cycling industry just doesn't have a very large or unified R&D budget.
Yeah, true enough.... but there seems to be a very strong degree of certainty behind this argument and a similar commitment to wider wheels. So they must have some science behind it. And good question about the shape of the curve too.

Originally Posted by Branko D View Post
My hunch is that brands are pushing wider tires because the average customer isn't the light, young racing type.
​​​​If you're reasonably light - 65 to 75kg - and want comfort, you can simply ride 23s or 25s at less pressure. At 90 psi they offer a much more muted ride and I found myself even faster on bad roads with around 80 psi.
​​​But for the average customer, 28mm tires may be needed to be able to use comfortable pressures.
​​​
I agree with this but up to a point. Just as bike brands have racing models and endurance/sportive models, one would expect them to have separate "comfort/balanced riding" and "max speed" wheels - I wouldnt expect the industry to give up speed-maximized wheels entirely, you know?

And in any case, the Silca chart was with 190lb system weight, so not superlight either.

It could be that the industry is betting on all-road being the future - these new wheels are certainly ideal for that. And as generalist wheels to handle all sorts of road conditions, it makes sense too - on rougher roads, the inflection point could be a lot lower.

But does that mean for those of us who do ITTs and triathlons on good roads, an older-gen road wheelset with, say 25c tires run at 85psi, would be faster?

I have been having an existential crisis because the 23mms mounted on my old HED Jet 9s measure a little bit larger than the rim, and i am positive this is the ONLY thing keeping me from winning my AG in 70.3s. But i am afraid of angering The Merckx by going against the "wider = better" trend.
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Old 08-09-20, 06:47 AM
  #32  
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You've mentioned Silca a couple times - have you listened to the CyclingTips podcast with Josh and... I think it was Jan Heine? It was from a few years back, and it's almost an hour long, IIRC, but they talk about the real world testing and some of their findings. It's worth a digging up for a listen, if you haven't already.
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Old 08-09-20, 12:25 PM
  #33  
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Originally Posted by WhyFi View Post
You've mentioned Silca a couple times - have you listened to the CyclingTips podcast with Josh and... I think it was Jan Heine? It was from a few years back, and it's almost an hour long, IIRC, but they talk about the real world testing and some of their findings. It's worth a digging up for a listen, if you haven't already.
Ah cool, thanks for the tip - I will hunt it down.
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Old 08-09-20, 02:17 PM
  #34  
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Originally Posted by guadzilla View Post
I seem to recall seeing in a few places that "wider = lower RR for a given pressure" and "lower pressure = higher RR" (although this is for a perfectly smooth surface - the vibration losses account for the roughness, I guess).

So here is what I was trying to say. If you take a 25mm tire and plot its RR and vibration loss, you get 2 curves - the line in blue showing the RR and the line in green, showing the vibration loss for a given surface. The point at which the sum of the two is minimum is the inflection point. This is the whole Silca graph (https://blog.silca.cc/part-4b-rollin...-and-impedance). Assuming for a second that the "wider = lower RR", then for any given pressure, a wider tire will have a lower RR than a thinner tire. So the RR curve for a 28c tire will look like the line in red. My question for Zipp was whether the vibration loss curvel (for a given surface) changed for a tire width or was it dependent entirely on pressure - their reply was that it was more or less dependent entirely on tire pressure (again, for a given surface).



If so, then the inflection point for a wider tire is going to be fairly close to the inflection point for a narrower tire (given the the RR curve for the 28mm tire and the RR curve for a 25c tire are separated by less than a watt - source: https://www.bicyclerollingresistance...000-comparison) .

If you look at the Silca graph on the link above for optimal inflection point for asphalt, it is around 90-110psi for a 25c tire. Based on this, the inflection point for a 28c tire or even a 32c tire should be well within 5-10psi of the same pressure. So 80-100psi. Where the heck are Zipp and Enve coming up with 60-70psi? Admittedly, using the Silca graph again, this means we are looking at a 2W reduction in efficiency - so it isnt huge. But for a product aimed for maximizing speed where even fraction of watts saved were touted as a Big Thing (that's why we are buying $2k wheelsets, right? For that little marginal gain), it seems weird to move to what appears to be a slower product.

And I havent even gotten into the aero side yet. Scroll down a bit to the section on Rolling Resistance vs Aero on the DT Swiss site (https://www.roadrevolution18.dtswiss.com/endurance/) and you find this chart:



So the wider tire has an aero disadvantage. And that disadvantage is worsened at speed. So above 35kph, you dont really want too wide a tire after all, it seems. Atleast as per DT Swiss and SwissSide.

Yet the narrative from Zipp and Enve is pushing us all to wider tires (which have a very small improvement RR for a given pressure, but a significant reduction in aero at higher speeds) and lower pressures (which appear to be far lower than what would be indicated by Silca's numbers, atleast).

Possible reasons I can think of:
1) Industry is latching on to a new trend to sell more wheels (which is a bit overly simplistic - I dont think the industry would just make stuff up across various companies)
2) Silca's science is correct but the numbers are off, and that in reality, the inflection point is at a lot lower pressures
3) There is another aspect - perhaps rider comfort/fatigue - that we havent considered. But if the wheel brands had factored it in, they would talk about it
Possible reasons I can think of:
#4 Sell hookless (carbon) rims that are only safe at lower pressure,
#5 Convince you to lower pressure to a point where liquid sealant can work reliably. -> Sell the whole tubeless idea.
#6 Indirectly, sell more road tubeless stuff, that doesnt work reliably at normal road pressure.

#7 Make you believe your new $3000 nasa approved carbon frame is a magic carpet ride, that is both stiff and compliant at the same time (lol), when in reality its the tyres doing all the magic.

One real benefit to lower pressure wide tyres:
#1 You can run any stiff as a board alloy frame and feel perfectly comfortable. Get the right tyre and the rolling resistance penalty is minimal or even non existent. Im all for it.
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Old 08-09-20, 02:27 PM
  #35  
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Old 08-09-20, 03:00 PM
  #36  
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Originally Posted by guadzilla View Post
It could be that the industry is betting on all-road being the future - these new wheels are certainly ideal for that. And as generalist wheels to handle all sorts of road conditions, it makes sense too - on rougher roads, the inflection point could be a lot lower.

But does that mean for those of us who do ITTs and triathlons on good roads, an older-gen road wheelset with, say 25c tires run at 85psi, would be faster?
It certainly saves them money: you have one rim for gravel and road racing and endurance and everything. Increases profits over making a hundred variations. Look at Specialized, you had rim Venge, disc Venge, rim Tarmac, disc Tarmac, now you just have the new Tarmac and that's it. You do a big cost cutting exercise and market it as advancement. Maybe I'm just a bit cynical, but whenever I see arguments for wide tires they are focused on how they are faster on gravel/cobbles/pothole rutted roads, which I believe, and which is all fine and well, but I don't see how that helps me at all in a triathlon or (most) road races.

Personally, I had the same dilemma what would be faster, and in the end I got myself a pair of older gen LB wheels which mate to 23mm tires just beautifully and are a bit lighter than the wider all road ones, run them with latex tubes around 80-100 psi and I'm loving it, and my hunch is that it's the fastest setup for the money for triathlon or the odd TT.

The only places where I wish for a wider tires are bits of machine roughened tarmac where they shred the top layer (presumably to avoid roads freezing or something - it's rare, anyway, but does rattle you), and of course on gravel, which I generally, well, avoid on my road bike. ​​​​​
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Old 08-09-20, 03:21 PM
  #37  
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Originally Posted by Racing Dan View Post
Possible reasons I can think of:

#4 Sell hookless (carbon) rims that are only safe at lower pressure,

#5 Convince you to lower pressure to a point where liquid sealant can work reliably. -> Sell the whole tubeless idea.

#6 Indirectly, sell more road tubeless stuff, that doesnt work reliably at normal road pressure.


#7 Make you believe your new $3000 nasa approved carbon frame is a magic carpet ride, that is both stiff and compliant at the same time (lol), when in reality its the tyres doing all the magic.


One real benefit to lower pressure wide tyres:

#1 You can run any stiff as a board alloy frame and feel perfectly comfortable. Get the right tyre and the rolling resistance penalty is minimal or even non existent. Im all for it.

You could be right. I've got wheelsets/bikes with some form of Conti GPs on them from 23s-32s. To be honest, there is a little bit of feel difference between the 23s and the 32s. But not much of a difference. Not like the "OMG" moments that some people are experiencing. That could be because I am a 5'8" 200lb rider riding vintage steel bikes from the 70s/80s. It could be because the rims are 32 or 36H clinchers that might not be as stiff as the current crabon rims. Or, it could be because the saddles I ride are vintage ones like the Selle Turbo and Avocet Touring series. Whatever the reason, I couldn't tell you what size of tire I am riding without looking down at it. But that's just me.
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Old 08-09-20, 04:07 PM
  #38  
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Originally Posted by guadzilla View Post
And I havent even gotten into the aero side yet. Scroll down a bit to the section on Rolling Resistance vs Aero on the DT Swiss site (https://www.roadrevolution18.dtswiss.com/endurance/) and you find this chart: ...
I might have missed it, but did they say what yaw angle or distribution was used to generate the drag curve?
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Old 08-09-20, 11:46 PM
  #39  
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Originally Posted by asgelle View Post
I might have missed it, but did they say what yaw angle or distribution was used to generate the drag curve?
No, they didnt, unfortunately (I am assuming they wanted to keep things a bit more accessible).
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Old 08-16-20, 11:43 AM
  #40  
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So another data point. I decided to take the same steel bike for Saturday's 100km ride. This time, I pumped the 37mm WAM tires to 45psi (I think i snuck in a few more on the rear and got it closer to 50psi, I admit... baby steps!).

There were a few times on the ride - when we were on really smooth tarmac, mainly - that I felt the tires were a bit draggy. But they also rolled over rough asphalt really well, with no bouncing. I had no issues taking my pull out front at 35-40kph. And looking at my speed/power numbers, they seemed more or less in the same ballpark as my regular bike with 28mm WAM wheels. To be clear, I am not stating the power was identical - but it was more or less where I'd expect to be. I never looked at the numbers and go "whoa, i am going too slow for this power". So that gap wasnt huge.

I am still not convinced that this is the optimized setup if i want to squeeze all the speed i can out of my meager watts. But for brisk-not-murderous rides, it works well enough.

The bright side is this makes me feel better about flipping my R5. Going from 28mm tires on the Venge to the 30mm tires on the R5 wasnt a huge jump - but 32mm WAM tires on 32mm rims, and a second pair of 35-40mm tires on a different wheelset would make the Factor an awesome do-it-all bike.
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