T Stew

Guess I need to do some better testing myself. So far my 23's are still faster but to get better results I need to try multiple sizes of the same model tire, and get a bigger pool of tests to get standard deviations and such worked out. Perhaps next year, as I am in full marathon training now for my fall marathon, and cycling is tapering off for me.

So many threads on this subject about wider is better, but I don't see fat bikes on TdF. This is a multiple variable equation not a 1 variable equation.

Some of my variables for my typical ride... 145 lb rider weight, 22 lb bike, 23mm Veloflex Masters (110-125 psi seems fine), and a nice smooth paved rail trail. Smooth as butter with the high pressure 23's, so no advantage in comfort needed with a wider tire, at least for my normal trails. I've also run 25mm GP4ks, and 1 1/8 - 1 1/4 Pasela TGs. If the road is rough I prefer the 1 1/4" Paselas. Will do some more testing at some point, and maybe by then I can get my speeds up a little more so the aero effect comes into play more. Aero loss is a lot smaller part of the equation if you're well under 20mph, but becomes more significant the faster you go, obviously.

69chevy

According to the research of Josh Poertner, pressure above 110psi slows you down on any road surface.


Tire Pressure - Stop Guessing And Read The Science | TRS Triathlon

RJM

CyclingTips Podcast, Episode 9: Rethinking road bike tire sizes and pressures | CyclingTips


Here is a podcast I just listened to today about this very thing. Right on point.

Banzai

I'm going to listen to that soon. Read the summary, and I'm interested. I have to agree; I absolutely FEEL faster on my 25s, but my times suggest otherwise.

Banzai

Now the debate begins as to what is the optimum amount of "fatness" in the tire. I think we'll all agree that a 4 inch fatbike tire is NOT the fastest.

seypat

That is a very good listen! Thanks for putting up the link.

Bah Humbug

The sweet spot for me is 23mm tires on 23mm rims.

T Stew

This was not a scientific test that applied to every possible scenario and your generalizing the results, much like saying wider is better. It's not that simple, it is going to vary based on several variables. Even in that same article it was pointed out that the world record was set on 300psi skinny tires (on an indoor track), so it depends on more than just pressure (or width). Similarly he says "we find optimal pressures quickly move toward 110-120psi on excellent concrete surfaces" so my 110-125 ballpark (varies, I try pressures all over the place) is, well, in that ballpark. But without knowing what type of tire he used, and what size, it's impossible to compare directly. Also we already know he weight was significantly different than mine. All that being said, these tests are chasing relatively minor differences... good for elite races trying to shave off seconds, but for me cruising at 18-20 mph or whatever the difference in a few psi isn't going to add up to a hill of beans.

But wider is better they say!

RJM

Not wider is better, but lower pressure is better provided you aren't running on a smooth track....supple, high quality tires are also better.

And of course it is up to yourself to experiment to find your optimal pressure.

Chi_Z

a 28mm tire would kill the aero advantage on most rims, all that money down the drain

Banzai

I'm not altogether certain that you really listened that closely...

69chevy

From the article..

“Keep in mind that 110 is the highest pressure you want under the most perfect imaginable conditions, with asphalt that hasn’t even been driven on yet. It starts dropping quickly from that. I tell people and they think I’m crazy. But then they’ll actually try it at 90 or even 85 psi, and they come back and say that they are having much better results.”

Did you read it all?

HTupolev

Tell that to my hardtail!

T Stew

Nor I am that you comprehend my post.
Yep, did you read mine?

What I find most amusing is when they said, and you quoted "But then they’ll actually try it at 90 or even 85 psi, and they come back and say that they are having much better results." Have people really never even bothered to try other pressures before? Are they completely clueless to try things for themselves?

When it comes to these small differences that mainly apply to racing, which I am no pro, so deffer to what the elite racers do. You'd think they'd have that nailed down perfectly with the stakes that are on the line today. Of course that is not scientific but it doesn't need to be, it needs to be real world for their individual situation. Tire pressures seem to be a bit of a secret but some simple google searching will reveal some more info, like this article about TdF racers in '16 " Around 115 psi in the front and 125 psi in the back for the road stages and 130-135 psi for time-trial stages. And we drop that by 10 or 15 for rainy days.” Maybe if they would have aired down 50 psi lower they could have shattered the record by minutes!

I sometimes ride with lower pressure than that, and actually air down to 60 or so on the rollers to make the workout noticeably harder when I'm training with limited time. BTW when I said I've run 110-125 you do realize that includes exactly what he said... 110 on perfect asphalt that's never been driven on, hint hint. When I've pushed it up higher to 125 (just a few times, if you must know, I'm probably most often around 100/110 when I'm using 23's) the results where within my standard deviation. It's possible I was 5 seconds slower or something *gasp* but that was within my standard deviation.

Anyhow I do like to see some real testing, both in ideal conditions and real world, not that any of this makes much difference outside of a race though. I'm not disagreeing with his results per se, just that it means a certain number applies to all situations. BTW my ride last night was at 75/85 psi.

Banzai

Well, one of the big takeaways of the podcast is that referencing what the pros have been doing, and treating that as valid, or as something that has already been well figured out, is absolutely wrong.

Part of the reason for that is that those pros are subject to the very same decision making errors that we are, in this case flawed perception based on assumptions associated with road vibration, and the peculiarly tenacious power of "conventional wisdom" that inspires people to so vehemently defend it.

wphamilton

It looks like you had a lot more of the stops and slow-downs on the first graph which could account for the slower speed at the same power. At least there are a lot of down spikes in the cadence and power, if not actual stops and slows, so there was possibly something different going on.

This part is no doubt true.

Scarbo

Banzai, do you really think so? I know that it is commonly said that the pros are stuck in some sort of conventional mud; but I have trouble believing this--especially these days, when there is much more money in the sport and there has never been so much pressure to produce victories. No, I think that in their training camps, they have arrived at some pretty realistic ideas as to what works and what does not--in the real world.

In any case, I choose to obsess over increasing my own fitness levels rather than a few millimeters of tire width and their associated pressures . . .

Scarbo

I do have some follow up questions at this point:

1) How do the wider tires stand up to punctures, generally? In my current set-up (Michelin PRO4 Endurance 700x23; 120psi) I rarely get flats and I appreciate this very much since I ride, often, in areas in which I don't get a cell phone signal.

2) What are "good" fat tires?

3) My rims are all standard (19mm); so if I were to get wider tires, just how wide could I go without having to spend a fortune on a new wheelset (assuming, of course, that there were not any other compatibility problems)?

Thank you.

Banzai

Yes. That was another takeaway from the podcast: that it to a lot of confrontation with the data to convince those pros to overcome their assumptions. Now, however, 23mm tires are all but extinct.

And yet another takeaway was that Mr. Poertner's testing IS real world, as opposed to the steel drum tests that provided the numbers that drove pro racing equip choices.

These points are why I asked if you had listened.

Scarbo

Oh. I guess I was busy having too much fun on my bike (you know--the one equipped with those SLOW 700x23s pumped up to 120psi). I'm going out again now!

Cheers!

Banzai

The podcast also talks about punctures, and about "good" tires.

Banzai

Ah. So because you were out riding your bike, you get to comment extensively on a podcast that you didn't even listen to. Awesome.

I rode too. I wouldn't have commented on the podcast had I not sat down to listen to it while reading this thread.

rm -rf

A rolling resistance test, comparing the same tire in different sizes

It's not clear what kind of roller surface was used. Larger tires are way better on rough roads.
These GP4000S tires are very supple and fast.

From my post in a previous tire size discussion:

DrIsotope

Anyone who conflates professional bicycle racing with the real world has missed all of the points entirely. They share virtually no specifics in common. The Pros move at speeds where aerodynamic drag is enemy #1, and they don't really give a crap about comfort. All is sacrificed in the name of speed. That's how racing works.

If anyone chooses to be that weekend warrior, on a super-stiff CF frame and 700x23s, making every effort to be the fastest guy to the coffee shop every Saturday... hey, go for it. I guess someone has to win the race no one else is racing.

rm -rf

Jan Heine and wide tires

As usual, Jan takes things to extremes, running 42c tires on his road bike.

From his blog post on tire widths

His 41c tires: "They weigh only a little more (the difference for two tires is less than half a water bottle)." That's around 300 grams or about .3 pound. I just don't see the need for this.

He also says:
"For me, tires narrower than 30 mm are hardly worth considering. And even 30 mm tires feel compromised on many roads."
Heh.

Air volumes

His point about air volumes is interesting, though.
Compared to 23c:
25c: 18% more volume
31c: 54% more volume

I'm running 25c GP4000S tires on wide 25mm rims, so they measure close to 29mm wide, so they are effectively 28-29c tires. They seem just as fast as my older wheels, and are very comfortable on rough roads.

At 170 pounds, I use 78-80 psi front, and 90-95 psi rear with this setup. I could probably use even lower pressures. But this works for me.