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25mm vs 32mm tires, unscientific testing

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25mm vs 32mm tires, unscientific testing

Old 06-03-20, 04:53 PM
  #26  
Seattle Forrest
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Originally Posted by rubiksoval View Post
You don't have the slightest semblance of any idea of what else was the same.

You don't know about wind, tire pressure and rolling resistance, temperature and humidity, position, clothing, etc.
In the OP he said it was the same clothing and same position. He didn't mention wind unless I missed it, this seems like an honest attempt so I think it's safe to assume if there had been a notable difference he would have noted it.
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Old 06-03-20, 04:57 PM
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Originally Posted by Seattle Forrest View Post
In the OP he said it was the same clothing and same position. He didn't mention wind unless I missed it, this seems like an honest attempt so I think it's safe to assume if there had been a notable difference he would have noted it.
Sure, but it's yet another example of an unmeasured variable that may or may not impact how hard he was pedaling at various sections of the ride.

Again, the biggest factor is power. Feeling like output/effort is the same is just a feeling. It may or may not have anything to do with actuality. That's the crux of my post.

For some reason someone felt compelled to go off on a tangent about it.
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Old 06-03-20, 05:01 PM
  #28  
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Originally Posted by rubiksoval View Post
So is that a snide remark to detract from the apparent issue of you never using a power meter and failing to understand its significance in a matter like this?
I don't own a power meter. I do understand the significance. What I don't buy is your implicit argument that the power outputs differ enough from each other and the estimates to exactly compensate for the differences in the tires so that, by magical coincidence, everything that is measured is nearly the same.

By far the simplest explanation for why all the reported numbers are the same is that the width of the tires doesn't make a significant difference.
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Old 06-03-20, 05:09 PM
  #29  
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Originally Posted by wgscott View Post
I don't own a power meter. I do understand the significance. What I don't buy is your implicit argument that the power outputs differ enough from each other and the estimates to exactly compensate for the differences in the tires so that, by magical coincidence, everything that is measured is nearly the same.

By far the simplest explanation for why all the reported numbers are the same is that the width of the tires doesn't make a significant difference.
It's an explicit argument.

Clearly you don't. Thanks for the confirmation.
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Old 06-03-20, 05:20 PM
  #30  
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Originally Posted by rubiksoval View Post
No they're not.

Those tires could be 30 watts slower and he simply put out 30 watts more to make up for the difference. You have no idea. Neither does he.

"Unmeasured differences that are unknown." Yeah. That's the point.

Again, if you don't understand what a power meter does, this is a pointless tangent.
This is correct. The Strava estimated power is meaningless, being based solely on speed, as you said earlier. He could have had a brake dragging on one test, Strava would say power was the same. That said, a quick trip over to BRR says that at the same comfort level, i.e. 4.5mm drop for both tires, RR is .1 w less for the 32 per tire. At recommended pressures, 15% drop, it's .7w higher for the 32, per tire. There's also the aero component. If someone wants to do the calculation we could see the theoretical time difference. The OP doesn't mention tire pressures, a significant omission. And all that said, these are pretty neat tires. I haven't gotten cut #1 yet on our tandem.
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Old 06-03-20, 05:21 PM
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As a definitive non-roadie, some of you commenting on this thread are re-inforcing the "roadies are tools" reputation.
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Old 06-03-20, 05:22 PM
  #32  
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Better test than in the other thread comparing new & old bikes,

& seeming to come up with near same speeds in spite of getting off & pushing the old bike up some hills on the test loop.
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Old 06-03-20, 05:27 PM
  #33  
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The average cadence is also the same, so we do have an idea whether the OP was pushing harder, independent of speed and estimated power.

Discounting it with special pleading and appeals to unmeasured differences isn't compelling.
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Old 06-03-20, 05:34 PM
  #34  
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Originally Posted by wgscott View Post
What I don't buy is your implicit argument that the power outputs differ enough from each other and the estimates to exactly compensate for the differences in the tires so that, by magical coincidence, everything that is measured is nearly the same.
It doesn't have to be a magical coincidence, particularly as a .3mph difference is not "nearly the same" considering the sorts of things that the thread is discussing. If I do "the same ride" on two different road bikes (or on the same road bike) on similar days at a similar fitness level, it's not terribly uncommon for me to see numbers within .3mph; it's also not terribly uncommon to see differences larger than that. I don't think it says much of anything.
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Old 06-03-20, 05:39 PM
  #35  
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Originally Posted by rubiksoval View Post
Sure, but it's yet another example of an unmeasured variable that may or may not impact how hard he was pedaling at various sections of the ride.

Again, the biggest factor is power. Feeling like output/effort is the same is just a feeling. It may or may not have anything to do with actuality. That's the crux of my post.

For some reason someone felt compelled to go off on a tangent about it.
I know that it's amazing how much different factors can influence the power you're putting out. That's why I bought a PM. Even though I knew this fact before I had one, it's still amazing when you see the numbers. My cat decided I wasn't getting much sleep last night, I'm getting ready for a hilly 25 miles after work, I think my avg and normalized power will be lower than normal and I'll feel like I'm working as hard as I ever have. Measured power is obviously the last word on the matter.

My personal take is that this definitely suggests tire size has a very minimal impact on speed. It's obviously not proof. (For the record, another variable is that different size tires were used on the same wheels; it's well known that the interface between tire and rim affects aerodynamics. We don't know how far each tire size was from ideal for those rims.)

@wgscott has been sharing a lot of detail about how RNA works, efforts personally undertaken to keep it stable in the lab, etc. I would defer to @RChung in matters of power, use or measurement, because the guy clearly knows a lot more about it than I do. And I'd defer to @wgscott about matters of science, including what counts as science.
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Old 06-03-20, 05:42 PM
  #36  
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Originally Posted by Carbonfiberboy View Post
This is correct. The Strava estimated power is meaningless, being based solely on speed, as you said earlier. He could have had a brake dragging on one test, Strava would say power was the same. That said, a quick trip over to BRR says that at the same comfort level, i.e. 4.5mm drop for both tires, RR is .1 w less for the 32 per tire. At recommended pressures, 15% drop, it's .7w higher for the 32, per tire. There's also the aero component. If someone wants to do the calculation we could see the theoretical time difference. The OP doesn't mention tire pressures, a significant omission. And all that said, these are pretty neat tires. I haven't gotten cut #1 yet on our tandem.
Can't rule it out, but I think we should start from an assumption that @Rides4Beer isn't an idiot.
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Old 06-03-20, 05:46 PM
  #37  
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Originally Posted by Seattle Forrest View Post
And I'd defer to @wgscott about matters of science, including what counts as science.
As a physicist, I'd say he's out of his depth in this discussion.
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Old 06-03-20, 05:59 PM
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Originally Posted by wgscott View Post
The average cadence is also the same, so we do have an idea whether the OP was pushing harder, independent of speed and estimated power.
Nope. That the average speed and average cadence are similar does not mean that the power/resistance is similar. With the same gearing, cadence, and speed, I could be soft pedaling with a tailwind or busting my ass into a headwind.
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Old 06-03-20, 06:05 PM
  #39  
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Originally Posted by noimagination View Post
When I was a young lad, the main streets in town were paved, but the side streets were gravel. The U.S. and state highways were paved, but most of the county routes, National Forest roads and the roads on the Bad River Reservation were gravel. Every summer, in town they would spray the gravel streets with waste oil (petroleum, not cooking oil) to keep the dust down. I bet they don't do that anymore.
What's funny is that you probably had a bike that could ride on gravel, but you didn't know it because "gravel bikes" hadn't been invented yet, amiright?

I was born in AZ but actually grew up in Massachusetts in one of these smaller bedroom communities. My street was narrow enough that it didn't have lines marking lanes. They painted lines on it once but it just wasn't wide enough so the next time they "re-paved" it the lines were gone and never replaced. Repaving consisted of spraying down some oil on the street and then covering it with sand and very fine gravel. Whatever stuck was the new road surface.

The problem with the road surfaces where I'm at now is just that I live at the edge of civilization here in the valley. I can ride just 3-5 miles in one direction and be in the middle of town with decent roads and whatnot, or 3-5 miles in the other direction and be in the middle of the desert. Some of the little side roads like the one leading from the back of my housing community out to a more main road haven't been repaved in many years and are just absolutely horrible for a bike. If all the roads were like that I'd just stick to mountain biking, because it's annoying as hell when my routes take me on roads like this. I could get where I'm going and avoid some of these roads but the alternative is some 4- or 5-lane north/south or east/west artery road with craploads of cars doing 60mph in a 45mph zone and all I have is a little 18-20" margin to the right of the white line. So my main routes are mostly crafted with getting the mileage I want without getting annihilated on some of the main drags, though to get longer mileage eventually I've got to do some time on some of the larger roads too. For me, riding with the fatter tires (fat only compared to traditional road cycling) is a no-brainer. The 32mm tires I've been riding have been way nicer on these crappy stretches of road than 25mm or even 28mm were. I've been thinking for a while that I wanted to try out the 35mm version of the Rene Herse tires in the rear on my bike, and it arrives on Friday. First thing I do once I mount it will be to ride out the back of my housing area onto this awful stretch of road and test it out. I'll probably start with a pressure of 5psi less than I've been using in the 32mm version and see how it goes.
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Old 06-03-20, 06:12 PM
  #40  
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Originally Posted by tomato coupe View Post
As a physicist, I'd say he's out of his depth in this discussion.
Perhaps, but it might be more compelling if you leave me out of it and focus on why the the presumed numerical values of data not reported are somehow more convincing than the numbers that have been reported.
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Old 06-03-20, 06:16 PM
  #41  
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Originally Posted by WhyFi View Post
Nope. That the average speed and average cadence are similar does not mean that the power/resistance is similar. With the same gearing, cadence, and speed, I could be soft pedaling with a tailwind or busting my ass into a headwind.
Yes, we would have to know that the gearing used was similar as well. What we are seeing is that for every value that is reported, the numbers are quite similar.

Remember, I am arguing against the assertion that the report it useless.

Neither the OP or I have argued that it is definitive. (I personally think there is a bit more to it that the OP allows.)
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Old 06-03-20, 06:39 PM
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Originally Posted by wgscott View Post
Yes, we would have to know that the gearing used was similar as well.
No. Again, speed and cadence being the same doesn't mean that effort is the same. If you're in your 50/17 combo, spinning at 90 rpm, you're going to be going the same speed regardless of whether you're on billiard table flat road or if you're going up a 3% grade. The efforts will be wildly different, but the speed will still be the same for the same gearing and the same cadence. So the fact that the speed and cadence is similar strongly suggests that the gearing is similar, but it still doesn't give us anything that we really want to know. What we want to know is whether one is faster. Faster = less resistance, be it rolling resistance, drag or suspension losses. There could easily be a 20w difference between these efforts and a power meter would show that.
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Old 06-03-20, 06:40 PM
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Originally Posted by wgscott View Post
Perhaps, but it might be more compelling if you leave me out of it and focus on why the the presumed numerical values of data not reported are somehow more convincing than the numbers that have been reported.
What is the single biggest factor that determines the speed of a bicycle (on flat ground)?
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Old 06-03-20, 07:08 PM
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Originally Posted by wgscott View Post
Yes, we would have to know that the gearing used was similar as well. What we are seeing is that for every value that is reported, the numbers are quite similar.

Remember, I am arguing against the assertion that the report it useless.

Neither the OP or I have argued that it is definitive. (I personally think there is a bit more to it that the OP allows.)
I'm in 100% agreement with you on this. The sharpshooters are nitpicking claims that weren't even ever made. I read the OP as saying, in effect, "some folks may argue that 25mm tires are superior to 32mm tires because they want to go fast. Well, I rode the same bike, same route, same wheels, just 25mm vs. the same model of tire but in 32mm, under conditions I was satisfied were similar enough, and the difference was about a minute over a two-hour ride. That's close enough for me." When that minute might matter he'll ride the 25s, when it won't he'll ride the 32s. He can't really be wrong here because his conclusion is simply an opinion. Let's say his power output really wasn't the same, and if it had been there might have been a 2-minute difference in the end instead of 1-minute. Would he be wrong? Only if one values a two-minute difference over a two-hour ride so much that it's not "close enough" for that person, and that again is just an opinion.

Yeah, I wish the OP had a power meter too. I'd like to see that data if he had it. I went with 32mm tires around 3000 miles ago, so one could argue that my liking this OP is just confirmation bias, but in reality I have my own data from those 3000 miles. My own riding data were generated under non-rigorous conditions with many uncontrolled variables, so there's lots of noise, but the takeaway for me is that if there was a speed penalty to me from going to 32mm, the signal/noise ratio of any potential difference in my own performance is too low to be detectable. And that's "good enough" for me. Given the roads I ride on the comfort benefits are immediately and profoundly noticeable, and if there's no discernable performance penalty, that's a win/win in my book.
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Old 06-03-20, 07:10 PM
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Originally Posted by tomato coupe View Post
What is the single biggest factor that determines the speed of a bicycle (on flat ground)?
If it's red or not!
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Old 06-03-20, 07:14 PM
  #46  
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Originally Posted by WhyFi View Post
There could easily be a 20w difference between these efforts and a power meter would show that.
I don't think anyone, including me or the OP, has suggested otherwise.

What I am saying is that in the data that is actually posted, there is no trace of an indication that this is the case, which would be rather peculiar if it were the case.

Also, I am saying what the OP observed is consistent with previously-reported, well-controlled experiments, so taking the numbers you actually see at face value isn't quite as idiotic as some here have suggested.

Can you or anyone point me to a similar comparison where all of the metrics reported in the OP were nearly identical, but where the power meter readings differed significantly?

Last edited by wgscott; 06-03-20 at 07:21 PM.
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Old 06-03-20, 07:26 PM
  #47  
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Originally Posted by wgscott View Post
I don't think anyone, including me or the OP, has suggested otherwise.

What I am saying is that in the data that is actually posted, there is no trace of an indication that this is the case, which would be rather peculiar if it were the case.
How fast will you be going in 50/17 when pedaling at 90 rpm on flat ground?
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Old 06-03-20, 07:37 PM
  #48  
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Thanks for the post, @Rides4Beer! While perhaps not "scientific" enough for some, I think your test at least shows there isn't a radical deference between the two tires as I'd think your data would've shown that. For every day riders where every second doesn't count, it's good to know that a wider tire isn't the end of the world.

My previous bike was a Trek Domane with 25mm tires and my new Domane as of this Spring has 32mm tires. The roads in Wisconsin can be quite awful due to the freeze/thaw cycle, so even though the 32mm tires make me feel like I'm riding a mountain bike, they help cushion the blow of all the potholes! The 32mm tires are mounted on 25mm internal width rims (i.e., a pretty wide rim). While the whole setup is hardly light, the bike literally feels like it's on rails when doing fast, twisty descents.
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Old 06-03-20, 07:45 PM
  #49  
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I've no idea if it's significant, but this is two rides over the exact same route in virtually identical conditions, with no changes to setup or equipment.
I was testing riding strictly by RPE, and the side on the right felt easier, but I actually worked harder to go slower.
The differences between the two rides are similar to what the OP had shown in his two rides-- which is enough for me to agree that without power, we can
never know if the two efforts came down to tires-- just as I can't say for certain what accounted for my 69 seconds.

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Old 06-03-20, 07:48 PM
  #50  
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I also just wanted to say that I'm also impressed at the OP's data simply because he's doing a fast cruise at 22.5 or 22.8mph, while my threshold cruise for an hour or so under ideal conditions on flat ground is about 20mph, and I probably couldn't maintain that for two hours. I aspire to be able to just duplicate his test one of these days.
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