dmanthree

Yes, I know, this topic has been beaten to death. But I recently, and inadvertently, switched to 25s after riding 28s. Same brand and model. The rolling resistance site did a comparison test that showed the wider tires had less resistance, but my real-life "test" shows the opposite. I was running Conti 4000s II 700 x 28 but flatted out the front tire on glass. The rear was kind of worn, so I decided to replace the set. A trip to the LBS revealed that they had only the 25s in stock, so I bought them. Well, they handle better, and roll easier. I'm faster on the narrower tires. Go figure. Why? Hell, I don't know. Less weight? Less wind resistance? Honestly, I don't care. But I'm sticking with this width from now on. Maybe they're a better match for the wheels I'm using?

HTupolev

What wheels are you using?

Aubergine 

My reading of the evidence that wider tires are faster should better be stated as "tires with a specific construction can be faster if they are wider." In other words, when tires are not made with that construction (specifically, with sidewalls that are very supple and have a high thread count in the carcass), they won't necessarily be faster when wider. I would suggest that the tires you are using don't have the construction necessary for width to improve the ride.

On my own bikes, which use both sewups and good clincher tires (Compass and Pasela) the wider ones do tend to be a smidge faster, as well as more comfortable. I should test them with Gatorskins sometime to see how different widths react. (I like Gatorskins for durability and puncture proofityness, but they definitely are rougher-riding tires than Compass and Pasela.)

Dean V

Don't think anyone is saying 28's are faster than 25's unless it is a very poor road surface or you are not a very fast rider.

Aubergine 

Here are a couple pretty experienced people.

https://cyclingtips.com/2016/08/cycl...and-pressures/

rpenmanparker 

He is talking about GP4000IIs. Do you really think that is not a high thread count, supple sidewall tire? No, it isn't cotton or silk, but I don't think that was the basis for the rolling resistance conclusion.

Aubergine 

I'll be honest and confess I have no experience with the Contis, Robert. Thanks for the info.

dmanthree

The stock DT Swiss 470DB that came on the Roubaix.

dmanthree

I've seen multiple "tests" where the wider version had a lower rolling resistance than the narrower tire. However, that's under lab conditions, not real world. Also, the make and model of wheel may affect results. My conclusion is based on road riding with a single set of wheels on one bike. In other words, YMMV.

WhyFi

You don't mention PSI for either tire - what were you riding the 28s and 25s at, respectively? And how did you come across the "faster/rolls easier" conclusion? I recently swapped from a very good set of 30s to a very good set of 25s - the ol' butt dyno says that the 25s are a little faster, but the ol' butt dyno is easily confused.

jamesdak 

Hmmm, I've not set any PRs on the larger tires but they are right there with my top times. I haven't seen the GP4000s II 700 x 28 tires slow me down any when I swapped them for the 700 x25. And the big old Challenge Bianca Strada 700 x 30 tires on the Orbea have seen plenty of rides in the 19 mph avg range which is fast for me. In fact, I ran the Orbea for 25 miles one day along with doing 25 mile laps on two other road bikes sporting the GP4000s in 700 x 25. The Orbea was the fastest of the day on the identical routes.

So there you have it, solid proof of.....nothing..... LOL!



My fastest century ever was done on this one with a Gp4000sII 700 x 28 on the front. Not enough room on the rear to run one. The 28 actually measures over 30mm though.

asgelle

No. You say you're faster. There's no evidence to believe that's true, much less that tires are the reason.

dmanthree

OK, my average speeds on the same rides under the same conditions are higher.

Your call.

Believe me, don't believe me, it doesn't matter.

dmanthree

I ran both sets at 100/105, which seems to work well for me.

jamesdak 

For optimum performance tire pressure should change when tire sizes change. Especially if the same brand/model.

In case of the GP4000s II at my weight of around 190 I run the following:

23c = 90/100 F/R
25c = 80/90 F/R
28c = 70/80 F/R

This will vary a bit according to what rims the tires are on.

TimothyH

OP's experience is the opposite of my experience.


-Tim-

asgelle

Have you given any consideration to the fact that conditions are never exactly the same from one moment to the next?

dmanthree

Yes, but when I'm faster day in and day out on the same routes, what other conclusion can i draw? The only variable changed was the tires, nothing else. Temps are close, wind is about the same, etc.

Doge

Somehow I thought so.
Anyway I agree with the OP for general paved roads and an enthusiast cyclist they will go faster on 25, than 28s.

dim

from what I have learned:

for fast .... you need to match the tyre width to the rims

for comfort..... go wider with less pressure

watch this video:

Doge

OP - I think your test is valid - for you. You bring more credibility to it because of your prior experience and you were kinda single blind on this.

Labs tend to isolate things and we use terms like "faster tire" which I think means tested to lower Crr.
What we all care about - I think - is what makes the faster rider on the bike on that road. Road, comfort, all come into play.

As I posted elsewhere I almost always test real world with an eye on lab reports, and understanding the physics.
I got to do this on me for some 5 years commuting on a nice road bike.
I got to do this on my son until he go too old and annoyed.
I found what is best for me is not best for him. His fastest bike setup uses 22/23mm tires. Mine 25mm plus.

WhyFi

That's pretty high and it doesn't make any sense to me to run both at the same pressure. At the same pressure, I can't say that I'm surprised that you see no benefit to the larger tires.

Doge

They are faster. Why is there a need to support it?
You happen to be using what many pros are using (width) while others are still using thinner.

Likely reasons are less mass and slightly more aero. Labs do not test side to side motions and course corrections from hitting little bumps.

The case may be thinner/more supple - even the same brand.

scozim 

I "feel" faster on 23's, sometimes 25's. 28's are on my gravel and errand bikes and I like that comfort ride a lot.

I'm not a racer and don't really care about the science. 30+ years of riding and I've found tire preference is about as much rider specific as saddles so I don't really worry about all the research. I buy what I like, what I have good experience with or what's best for my road conditions. Now, if I could just find a 700X19 that we all rode in the 80's that would be "sweet"

DrIsotope

Agreed. Unless the OP is north of 230lbs, those 28s are waaayyy overinflated. He's running higher pressure in 28s than I run in 25s @ 200lbs.