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Results are in! 32mm tires (Vittoria) marginally faster than 28mm GP4000

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Results are in! 32mm tires (Vittoria) marginally faster than 28mm GP4000

Old 02-10-18, 02:38 PM
  #26  
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Originally Posted by rm -rf View Post
I've not heard of this method to compare inflation pressures.
But yeah, I run my 25mm GP4000S, measured at 29mm on my wide rims, at 65F / 80R.

The area of a circle goes up by the square of the radius. Treating the inflated tire + rim as a circle:
30.5mm: (30.5/2)^2 *3.14 = 730 sq mm
33.5mm: = 881 sq mm.
That's 881/730, or 20% more volume in the larger tire. It's interesting how fast the volume goes up. Even 25mm vs 23 mm is about 18%.

(My 39mm Compass tires at 38F /45R would calculate width ratios as 39*38=1482 and 39*45=1755, much less than the 2110 calculated for the OP's 33.5 mm tires...)

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Rolling resistance tests aren't exactly the real world, often run on fairly small rollers with some kind of rough surface. Do they all apply to real world conditions?

But, here's one from a few years ago by Continental. For example, It shows 23mm at about 123 psi having the same rolling resistance as the 25mm at about 92 psi.

These are fairly small effects -- note the truncated scale on the Y axis. And it's kind of odd that the rolling resistance difference between 23 and 25 is larger than the difference between 25 and 28, even though the volume change is larger on the 25 vs 28.

What does anything have to do with tire volume? That is a misconception. You inflate tires of different widths to a pressure that gives the necessary support for that wheel’s share of the total weight load on the bike. In other words for the same load you need the same product of air pressure times contact patch area. That is because force (weight) equals pressure times contact area. If the pressure is too low the tire will just sink low enough that the contact patch is big enough to support the weight. The trick is to have all tires running at about the same % drop, i.e. depression under load. 15% is often recommended. It would make sense to measure Crr at constant tire drop to get a real comparison of different width tires. Forget about volume.
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Old 02-11-18, 01:10 AM
  #27  
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Originally Posted by RChung View Post
I think y'all who are complaining about johngwheeler's test should either chill out or else do your own.

I've done a fair bit of field testing. Maybe this ain't the greatest but it's not junk.
Thanks for the vote of support :-)

Iím well aware that my test lacks rigourous controls - thatís just not possible with the resources available to me.

What Iím looking for are trends in the data, and as far as I can see, I have found some. I will continue to gather data points, and the results may change over time. I donít have an agenda to prove - Iím just curious.

I do think that that is an area that needs more serious research, but there doesnít seem to be a lot of it about. Pro cycling teams must be interested in this stuff, but maybe theyíre still limited by available equipment from their sponsors. I still read a lot of comments on bike forums that ďwide tires canít possibly be faster than narrower onesĒ, but with little substantiation. Iím simply trying to test the hypothesis.
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Old 02-11-18, 01:13 AM
  #28  
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Originally Posted by Spoonrobot View Post
The fact that you're trying to draw conclusions using two different measuring devices that both rely on GPS and also show different speeds in just one of the many things wrong here. The "laboratory of the road" exists but it's done differently than what you're trying to do.

Look, it sounds like you had fun riding your bike and perhaps that's all that matters.
Yes, the GPS results are not very accurate in urban surroundings. But I am using the same GPS units on the same route, so hopefully there is at least some consistency over multiple runs.

This is an unshamedly informal test, but it has shown some interesting trends that I wasnít expecting.
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Old 02-11-18, 01:16 AM
  #29  
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Originally Posted by ColonelSanders View Post
Firstly thanks for sharing the info you have achieved from this exercise.

How did you settle on the tyre pressure for the 32mm Vittoria's?

I would be keen to see you run some similar tests where you go by 5 psi over your current 55-60psi, then another 5 psi etc, perhaps stopping when you are 10 psi below the tyre pressure you had with the Continental GP4000II's.
This is a good suggestion! I used some charts (I think from a Jan Heine article) to get a ballpark for the 32mm tires at my weight (about 80kg bike+rider). Mostly itís just based on feel and a WAG!

Iíll certainly try increases and decreases in pressure to see the effect.
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Old 02-11-18, 02:27 AM
  #30  
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Originally Posted by johngwheeler View Post
the advantages of the wider tires are clear. A lot more comfort, and a little bit more speed. Win-Win!

Win-win + win. Improved puncture resistance at lower pressures.
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Old 02-11-18, 08:44 AM
  #31  
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Very scientific

Very scientific...Very scientific.....🔎🔍🔍📝📝🚴🚵🚀⬇▶🔢🔠▶➡🚻🚺😊😊

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Old 02-11-18, 08:53 AM
  #32  
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Can a wider tire just roll faster because the cracks or surface in road do not slow down the roll as much as say a very narrow tire as it goes over that same crack..??.
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Old 02-11-18, 09:01 AM
  #33  
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Originally Posted by rossiny View Post
Can a wider tire just roll faster because the cracks or surface in road do not slow down the roll as much as say a very narrow tire as it goes over that same crack..??.
Listen to the podcast previously posted. It's long, but an interesting listen.

Originally Posted by JSCjr View Post
A good summary of the results and why these are counterintuitive can be found here.
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Old 02-11-18, 10:40 AM
  #34  
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Originally Posted by johngwheeler View Post
Thanks for the vote of support :-)

Iím well aware that my test lacks rigourous controls - thatís just not possible with the resources available to me.

What Iím looking for are trends in the data, and as far as I can see, I have found some. I will continue to gather data points, and the results may change over time. I donít have an agenda to prove - Iím just curious.

I do think that that is an area that needs more serious research, but there doesnít seem to be a lot of it about. Pro cycling teams must be interested in this stuff, but maybe theyíre still limited by available equipment from their sponsors. I still read a lot of comments on bike forums that ďwide tires canít possibly be faster than narrower onesĒ, but with little substantiation. Iím simply trying to test the hypothesis.
Thanks for the test. Like others have pointed out, there are a lot of aspects on your tests that diminish the scientific value of the results. But this test points out fine that on commuting speeds good quality wider tires (30-35mm) are usually just as fast as a 28mm but more comfortable.
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Old 02-11-18, 10:46 AM
  #35  
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Originally Posted by johngwheeler View Post
I do think that that is an area that needs more serious research, but there doesnít seem to be a lot of it about. Pro cycling teams must be interested in this stuff, but maybe theyíre still limited by available equipment from their sponsors.
I know for a fact that some pro teams have done this research but because they view the findings as providing a competitive edge they don't usually share them.
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Old 02-12-18, 01:56 PM
  #36  
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My thought is that because the OP felt that the Vittoria's "felt slower", he was sub-consciously (or consciously) pushing just a little harder to make up for it.
And there's your faster speed.
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Old 02-12-18, 02:12 PM
  #37  
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Originally Posted by rossiny View Post
Can a wider tire just roll faster because the cracks or surface in road do not slow down the roll as much as say a very narrow tire as it goes over that same crack..??.
Yes. Though, it isn't the width per se, but the generally corresponding lower tire pressure. The lower pressure allows the tire to deform around the bump, rather than the bump lifting the entire bike and rider into the air. The force that goes into raising the elevation of the bike/rider is essentially force that is deducted from the forward kinetic energy of the bike/rider.

I think the important takeaway from all of this is that the tires are close enough to each other that it is possible for the speed difference to be obscured by the margin of error in an experiment. Granted, the margin of error of the OP is large, but other tests (bikerollingresistance) have shown the tires to be quite close as well. The Hypers very well might be objectively faster on crappy roads. (I've had 40mm hypers and 28mm GP4000s for what it's worth).

Having had both tires...I generally agree with the assessment of the OP. I feel like the GPs have a slight edge on good roads, but it really is so close as to say any difference could easily be attributed to my imagination.

On bad roads, I'd say the Hypers are definitely faster. They roll faster, and you do feel more confident going over broken pavement, pedaling over stuff you would unweight yourself on with the GPs.
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Old 02-12-18, 03:03 PM
  #38  
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Originally Posted by popeye View Post
Unless you can control for wind you have nothing.
Agreed. Wind changes everything.
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Old 02-12-18, 03:14 PM
  #39  
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Maybe only marginally related, but GCN tested three bikes on some stretches of cobble. A road bike, a cyclo cross and a mtb. The roadbike was the slowest, then the CX and the winner was the mtb. It seems there is some merit to the idea that fatter tyres roll better om rough road and that may as well be the case here.


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Old 02-12-18, 03:20 PM
  #40  
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Yeah for the short section of the pave, but overall for the race, road bike still the ideal choice.

And the MTB was only 10 seconds faster than the road bike for the pave section whereas I would bet difference for overall whole race, road bike faster by minutes.
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Old 02-12-18, 03:29 PM
  #41  
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Sidewall deflection is what causes most rolling resistance. Wider tires roll faster because they exhibit less sidewall deflection.

At a certain point weight, and to a lesser extent aerodynamics will become a penalty and returns will diminish. In general however, a slightly wider tire will roll faster because of less sidewall deflection.





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Old 02-12-18, 03:34 PM
  #42  
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"only" 10 seconds faster i 3.5 minutes ... that is 500(!) in tree hours. My only point is that it seems fatter tyres are in fact faster on rough surface and that it is not out of the question that the hypers are the faster tyre on OPs particular roads. Of course if you race on mixed surfaces, you must decide the best compromise.
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Old 02-12-18, 06:30 PM
  #43  
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Originally Posted by Racing Dan View Post
Maybe only marginally related, but GCN tested three bikes on some stretches of cobble. A road bike, a cyclo cross and a mtb. The roadbike was the slowest, then the CX and the winner was the mtb. It seems there is some merit to the idea that fatter tyres roll better om rough road and that may as well be the case here.

https://youtu.be/QvO74sZxVs4
Originally Posted by zymphad View Post
Yeah for the short section of the pave, but overall for the race, road bike still the ideal choice.

And the MTB was only 10 seconds faster than the road bike for the pave section whereas I would bet difference for overall whole race, road bike faster by minutes.
Originally Posted by Racing Dan View Post
"only" 10 seconds faster i 3.5 minutes ... that is 500(!) in tree hours. My only point is that it seems fatter tyres are in fact faster on rough surface and that it is not out of the question that the hypers are the faster tyre on OPs particular roads. Of course if you race on mixed surfaces, you must decide the best compromise.

The mountain bike was fitted with a 38T chain ring on the crank, surely they would have been spinning out at times, which might be why Simon said he used less power on the mountain bike run?


Interesting video for sure, but I do wonder about other things like, is 2.2" the optimal tyre width for that course, or would something like 1.95" be better?


Also whilst one of those guys was 10 seconds faster on the mountain bike, the other guy was only 5 seconds faster.


I wonder how well a bike with drop bars, a 46/36 crankset and the ability to take at least 2" tyres, would have done on that course?
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Old 02-12-18, 07:10 PM
  #44  
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I just replaced a set of Schwalbe One V-Guards in 700x23 with a set of Continental Ultra Sport II in 700x25.

The Contis definitely are not faster, especially on smooth pavement. I'd say the Rolling Resistance site's review for both tires are accurate.

In terms of handling, the wider Contis feel squirrely on fast turns. No idea whether that's a characteristic of the Ultra Sport II, but I suspect it's more due to squeezing wider tires into narrow rims. My bike's Araya CTL-370 rims have an inner width of 14mm or 14.5mm and the bike was originally fitted with 700x18 tires. The Schwalbe Ones in 700x23 handled great, tracking curves like they were on rails. But 700x25 may be pushing the optimal handling limits. Not a big deal since I don't race and don't anticipate needing to take turns fast.

The wider Contis feel much plusher where it counts, on chip seal and bad pavement. If I can put more energy into forward motion rather into absorbing road chatter, that's a good thing overall. The main hindrance I found last year was riding farther than 30 miles. After that point neck pain from an old C2 injury overwhelmed everything else. So it'll be interesting to see how the softer riding Contis feel over distance.

Too soon to say whether the wider Contis might be more efficient overall, and not simply more comfortable. I still haven't regained my strength from a month-long bout with flu.

And the weather hasn't been ideal for comparing familiar segments with my best times from last year on the excellent Schwalbe Ones. I've beaten some of my best times recently riding the wider Contis, but those aren't really comparable -- they were heavily wind assisted, both climbing and downhill as the wind has shifted between strong south and strong north winds. It's possible under similar conditions the Schwalbes would have turned in even faster times. I just didn't have the advantage of that much wind assist last year with the Schwalbe Ones, since our peak wind assist season is late winter/early spring to mid or late spring.
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Old 02-13-18, 05:03 AM
  #45  
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Originally Posted by TimothyH View Post
Sidewall deflection is what causes most rolling resistance. Wider tires roll faster because they exhibit less sidewall deflection.

At a certain point weight, and to a lesser extent aerodynamics will become a penalty and returns will diminish. In general however, a slightly wider tire will roll faster because of less sidewall deflection.





-Tim-

That has to be the most unconvincing graphic I've ever seen - as if the narrow tire should be so flat!
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Old 02-13-18, 05:29 AM
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Originally Posted by raria View Post
All of those saying OP should control for power, cadence are missing the point of his exercise.

This isn't a test to see how fast a robot goes on different tyres but how fast a human goes.

His tests beautifully cover the nuisances that *should not* be controlled for. Such as that 32mm tires mean you don't get beat up as much.
Yes. However, one needn't criticize the lack of data on variables like wind; it might be sufficient to simply further analyze the data already available. For instance, it would be interesting to see whether there was any general trend in the results over time. Presumably he had reached a sort of fitness plateau before he started the test of his tires, but an examination of the trend of the results might reveal that he was getting faster before he made the switch, and has continued to get faster on the new tires. Even with tires that performed identically, the results on the second set would be better. But even if the trend was generally upward, if there is a clear break in the trend at the time the switch was made, that would be interesting.
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Old 02-13-18, 07:42 AM
  #47  
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Fair point as usual from @kbarch But I thought he had done his commute so many times that he had effectively averaged out all those issues (i.e. wind, rain, stops etc.).

Originally Posted by kbarch View Post
Yes. However, one needn't criticize the lack of data on variables like wind; it might be sufficient to simply further analyze the data already available. For instance, it would be interesting to see whether there was any general trend in the results over time. Presumably he had reached a sort of fitness plateau before he started the test of his tires, but an examination of the trend of the results might reveal that he was getting faster before he made the switch, and has continued to get faster on the new tires. Even with tires that performed identically, the results on the second set would be better. But even if the trend was generally upward, if there is a clear break in the trend at the time the switch was made, that would be interesting.
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Old 02-13-18, 08:53 AM
  #48  
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Originally Posted by raria View Post
All of those saying OP should control for power, cadence are missing the point of his exercise.
Originally Posted by kbarch View Post
But even if the trend was generally upward, if there is a clear break in the trend at the time the switch was made, that would be interesting.
It's actually kind of interesting that the results were close enough for there to even be a question.
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Old 02-13-18, 05:28 PM
  #49  
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Originally Posted by Stratocaster View Post
My thought is that because the OP felt that the Vittoria's "felt slower", he was sub-consciously (or consciously) pushing just a little harder to make up for it.
And there's your faster speed.
This is also something that I considered, but itís hard to say whether this is true without a power meter.

I may have some heartrate data, which could give me an least an indication if I was working harder.

Good catch!
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Old 02-13-18, 06:26 PM
  #50  
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Originally Posted by kbarch View Post

That has to be the most unconvincing graphic I've ever seen - as if the narrow tire should be so flat!
And also hilarious if it comes from Conti as the graphic indicates. No one, ever, runs wider tires at the same pressure as narrower tires. Dropping pressure is the whole point of going wider.

Which reminds me, for his tests the OP had his Contis overinflated compared to the Hypers, as I commented earlier. Apparently the OP hasn't retested with comparable pressures.
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