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How many tenths of an MPH/KPH from new wheels/tires?

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How many tenths of an MPH/KPH from new wheels/tires?

Old 07-26-17, 11:16 AM
  #101  
Samuraidog
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This has been my experience as well. Placebo effect or not, I feel that the wheels make a significant difference.

Originally Posted by f4rrest View Post
All of my wheel upgrades have been totally worth it.

It's almost like having another bike.
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Old 07-26-17, 11:34 AM
  #102  
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Originally Posted by Abe_Froman View Post
Trust me, it does

Total contact patch area = total weight / pressure. Rim shape can't adjust laws of physics.
I don't think that's true, but even if it is, the Enves still run 30 psi lower which embiggens the contact patch significantly.

Also, it's worth noting that I listed a couple dozen things about those wheels that bring significant value to the rider, and we're only arguing about one of them. I take that to mean you agree with everything else I said about their greatness.
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Old 07-26-17, 11:43 AM
  #103  
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Originally Posted by Seattle Forrest View Post
I don't think that's true, but even if it is, the Enves still run 30 psi lower which embiggens the contact patch significantly.

Also, it's worth noting that I listed a couple dozen things about those wheels that bring significant value to the rider, and we're only arguing about one of them. I take that to mean you agree with everything else I said about their greatness.
No doubt, larger rims creating greater effective tire width -> lower pressure will create a more bigly contact patch.

Regarding the rest of your claims - I'm in no position to dispute lol. I don't have nearly enough experience with fancy rims to attempt to dispute your claims. Though I will say that even cheap rims that are built and tensioned properly, should be plenty durable. I had a stock, cheap, double walled AL wheel last year that kept breaking spokes. Measured tension and noticed it was off significantly...re-dished, re-tensioned it properly, and the last 5,000 miles on them have been without issue, or so much as a blip of truing required.

I imagine though that $2k+ wheels are probably more likely to be built correctly from the get-go though.
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Old 07-26-17, 11:57 AM
  #104  
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Originally Posted by Abe_Froman View Post
Trust me, it does

Total contact patch area = total weight / pressure. Rim shape can't adjust laws of physics.
yep, wider and shorter FLO Cyling - The Contact Patch... Why Wider is Better
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Old 07-26-17, 01:18 PM
  #105  
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Originally Posted by Abe_Froman View Post
Erm. Just as an FYI, PSI is the only thing that affects contact patch size. ...
That and hysteresis of the tread (rubber compound, thickness and case material) and speed of the wheel.
Some tires stand on no PSI and others on less.
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Old 07-26-17, 01:22 PM
  #106  
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Originally Posted by Samuraidog View Post
...Placebo effect or not,...
Very real. New shiney is faster.
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Old 07-26-17, 05:30 PM
  #107  
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It appears I was wrong about how contact patch size works.

There's a first time for everything.
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Old 07-26-17, 06:22 PM
  #108  
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Originally Posted by Doge View Post
That and hysteresis of the tread (rubber compound, thickness and case material) and speed of the wheel.
Some tires stand on no PSI and others on less.
Good point, I hadnt actually considered that. Still, those effects have to be miniscule relative to ~100psi
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Old 07-26-17, 06:59 PM
  #109  
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Originally Posted by Abe_Froman View Post
Good point, I hadnt actually considered that. Still, those effects have to be miniscule relative to ~100psi
They are miniscule in like tires. But tires go from supple silk with glue on tread to molded nylon cases.
Just since we were into the minutia, I thought I'd mention that.
It it a bigger factor, although barely one, in thinner tires.
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Old 07-26-17, 07:10 PM
  #110  
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Originally Posted by Doge View Post
It it a bigger factor, although barely one, in thinner tires.
How much bigger? Do you have any quantitative estimates? Are we talking 1 part in 1,000 or 1 in 10,000,000? I mean for tires with the label on only one side, power will definitely be different when they are both on the right, both on the left, or one on each side, but other than knowing the difference is small, I have no idea what the magnitude is or whether it is in any way worth worrying about. Maybe it is; maybe it isn't.
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Old 07-26-17, 07:52 PM
  #111  
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I think the direct effect (of rubber compound, thickness and case material and speed, and I'd include ply layers and directions) on rolling resistance of the tire is very much greater than whatever indirect effect there is from the difference in contact patch size and shape from those same qualities. If that is indeed more than just theoretical.
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Old 07-26-17, 08:02 PM
  #112  
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Originally Posted by asgelle View Post
How much bigger? Do you have any quantitative estimates? Are we talking 1 part in 1,000 or 1 in 10,000,000? I mean for tires with the label on only one side, power will definitely be different when they are both on the right, both on the left, or one on each side, but other than knowing the difference is small, I have no idea what the magnitude is or whether it is in any way worth worrying about. Maybe it is; maybe it isn't.
Edit - I now see you are asking about the tire width. Pretty much the same 1-3% in contact patch if the tires material and PSI are the same. If the material is also different, more.

I posted a video https://www.bikeforums.net/19744677-post87.html

Those two tires are the same PSI. The Veloflex is a pretty supple tire.

Both have a different line from a water trail. There were no 15mph, 20mph...50mph tests. Riding in the water and rooter tails/trails (that really matters) is about as much lab stuff as I have.

But I do understand hysteresis. It is a real thing when dealing with any periodic thing (rubber, gasses, magnetic fields).
We are talking contact patch size - not Crr...just clarifying.
So guess - the patch size difference is about what you might expect from 2-3 PSI different at 30mph. The softer tire gets the bigger patch.

Last edited by Doge; 07-26-17 at 08:05 PM.
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Old 07-26-17, 08:04 PM
  #113  
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Originally Posted by wphamilton View Post
I think the direct effect (of rubber compound, thickness and case material and speed, and I'd include ply layers and directions) on rolling resistance of the tire is very much greater than whatever indirect effect there is from the difference in contact patch size and shape from those same qualities. If that is indeed more than just theoretical.
Totally agree.

The argument was on area of patch in different tires of the same PSI at speed.
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Old 07-26-17, 08:25 PM
  #114  
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Originally Posted by wphamilton View Post
I think the direct effect (of rubber compound, thickness and case material and speed, and I'd include ply layers and directions) on rolling resistance of the tire is very much greater than whatever indirect effect there is from the difference in contact patch size and shape from those same qualities. If that is indeed more than just theoretical.
The length of the contact patch is a first order factor in rolling resistance. Rolling resistance is the difference in the force required to compress the front of the contact patch from what is returned at the trailing part in the direction of motion. The longer the contact patch, the greater the component in the direction of travel. It's this geometric factor that gives rise to the decrease in Crr with wider tires ( all things equal etc.). Bicycle Science has a good explanation of this.
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Old 07-26-17, 08:32 PM
  #115  
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Originally Posted by wphamilton View Post
I think the direct effect (of rubber compound, thickness and case material and speed, and I'd include ply layers and directions) on rolling resistance of the tire is very much greater than whatever indirect effect there is from the difference in contact patch size and shape from those same qualities. If that is indeed more than just theoretical.
No, it's certainly real; probably meaningless, but real. I imagine you could roughly measure the effect by seeing how hard you have to push a totally deflated tire with your thumb until it deflects 15% or so.
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Old 07-26-17, 08:42 PM
  #116  
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Originally Posted by Abe_Froman View Post
No, it's certainly real; probably meaningless, but real. I imagine you could roughly measure the effect by seeing how hard you have to push a totally deflated tire with your thumb until it deflects 15% or so.
So in my video with two tires on each other, one flexes much more than the other.

I agree the contact area is the same for both, but the more supple tire is kinda wrapped around the other.

What does that mean?
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Old 07-26-17, 08:51 PM
  #117  
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Originally Posted by Doge View Post
So in my video with two tires on each other, one flexes much more than the other.

I agree the contact area is the same for both, but the more supple tire is kinda wrapped around the other.

What does that mean?
Honestly? Not sure. If I had to guess, I'd say it shows how, for the tire that flexes more, it takes less pressure to deform, and therefore has less rolling resistance.
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Old 07-26-17, 09:20 PM
  #118  
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Originally Posted by Doge View Post
I agree the contact area is the same for both, but the more supple tire is kinda wrapped around the other.
The contact area is the same for both, but only because "contact area" here isn't really the same as "contact patch" for a tire rolling on the ground. For tires rolling on the ground, the stiffer tire will likely have less contact patch, since the stiffness is a bit like having more PSI.

In your video, the stiffer tire doesn't need that full contact area to distribute the load; it's only as big as it is because that's the area required for the supple tire to distribute the load, and the supple tire is touching the stiffer tire across that whole area.
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Old 07-26-17, 09:29 PM
  #119  
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Originally Posted by HTupolev View Post
The contact area is the same for both, but only because "contact area" here isn't really the same as "contact patch" for a tire rolling on the ground. For tires rolling on the ground, the stiffer tire will likely have less contact patch, since the stiffness is a bit like having more PSI.
I mentioned that in post #112 and https://www.bikeforums.net/19746783-post105.html

Originally Posted by HTupolev View Post
In your video, the stiffer tire doesn't need that full contact area to distribute the load; it's only as big as it is because that's the area required for the supple tire to distribute the load, and the supple tire is touching the stiffer tire across that whole area.
But often - depending on road the patch is wrapping around pebble, a rock in the pavement, or a mini hole.
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Old 07-26-17, 09:44 PM
  #120  
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So how many 1/10ths of a speed is kind of all over the map unless you ride in an indoor velodrome. How many fewer kJ at the end of a ride? How much faster in a sprint?
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Old 07-27-17, 05:52 AM
  #121  
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Originally Posted by asgelle View Post
The length of the contact patch is a first order factor in rolling resistance. Rolling resistance is the difference in the force required to compress the front of the contact patch from what is returned at the trailing part in the direction of motion. The longer the contact patch, the greater the component in the direction of travel. It's this geometric factor that gives rise to the decrease in Crr with wider tires ( all things equal etc.). Bicycle Science has a good explanation of this.
I understand where rolling resistance comes from and how it works.

But you were talking about the change in the contact patch area due to stiffer rubber and the like, and speculating about how much the difference in the contact patch changed rolling resistance. That would be a second order effect on rolling resistance, if it's even been empirically determined to be true. It's not the shape itself, but what happens to the rubber around and near the edges.

To be clear, we aren't talking about tires with different inflation pressures, but other elements causing different deformations.

And I am skeptical of both having more than a trivial change, and that in a tire it would be less resistance thereby, because most tire material qualities that I think of causing a smaller and/or rounder area of contact will cause greater rolling resistance (first order), which would oppose the presumed (theoretical?) improvement due only to the shape. So I question whether that's been empirically proven, or is just theoretical.

Last edited by wphamilton; 07-27-17 at 11:23 AM.
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Old 07-27-17, 05:56 AM
  #122  
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Originally Posted by Abe_Froman View Post
No, it's certainly real; probably meaningless, but real. I imagine you could roughly measure the effect by seeing how hard you have to push a totally deflated tire with your thumb until it deflects 15% or so.
They are talking about two tires with the same pressure, but with different size and/or shapes of the contact area.
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Old 08-06-17, 05:43 PM
  #123  
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Did anyone post this - already? Sorry - not going to look. I saw it today. The OP asked for a few tenths of a MPH.
Here is as good answer to that.
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Old 08-07-17, 12:13 PM
  #124  
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Originally Posted by Doge View Post
Did anyone post this - already? Sorry - not going to look. I saw it today. The OP asked for a few tenths of a MPH.
Here is as good answer to that.
https://www.youtube.com/watch?v=VHsL...B2vmHwhTAXEH3g
That was really good thank you for posting.
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Old 08-07-17, 01:07 PM
  #125  
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Originally Posted by OUGrad05 View Post
That was really good thank you for posting.
You are welcome.
Note - that the aero benefits are always going to be felt more at higher speeds. There was no test here at 18mph. Still I think your few tenths hope was pretty conservative.

The other part not reflected in this video (or any I've seen) is the energy to ride these wheels varies. So while we do measure power at the pedals, we do not see a measurement for stabilizing, turning, recovering from bumps and wind gusts. That energy, although very small is used up in arms, and core muscles (and some legs as less experienced riders balance with legs). On a track, that will be seen less than the road as it is somewhat protected from the wind and the road is predictable. On the road the testing I've done has shown both heavier and deeper section road wheels raise the HR a bit for the same power. So low profile wheel @ 225W has a 3-4 BPM lower HR than a higher profile wheel.
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