MrCjolsen

Is the rolling resistance significant or negligible, given the same tire pressure?

I guess you can tell I'm tire shopping.

rufvelo

I've settled on 25 front and 28 rear for comfort due to the terrain, kevlar belted for reliability.

Can't detect any increased rolling resistance from the 23s I always used, and at > 100psi, the lack of pace is due to my lack of fitness - can't really blame the tires any more

lsd87

Hope this helps: https://www.sheldonbrown.com/tires.html

MAK

The guy who runs an LBS told me that an MIT study has proven that 25c tires actually have less rolling resistance than 23c tires at the same pressure. He said that it had to do with 23c tires ovaling when the riders weight is added while 25c tire retain their roundness where the rubber meets the road. (Note - We are talking about a frontal view of the tire meeting the road and not the sideways view of the tires diameter.) It sounded logical and he knew that I wasn't shopping at the time but just browsing. I tried to Google the article but couldn't find it. Does this make any sense to one of you "in the know"?

Wildwood

I run 25 front, 28 rear on one of my bikes and I like it except for the fact that the 28 has almost zero clearance under the brake; never ride it if the streets have any moisture to hold grit on the tire. Not a single flat in over a year on this bike. I run 23 front/25 rear on my "fast" bike. Maybe I'm deceiving myself but I think more rubber at the rear means fewer punctures.

johnny99

Good article. He says the "at the same pressure" argument is bogus.

pakole

I cannot say that I am in the know, but this make sense when you consider the forces involve. If both tires are using the same rubber compound with the same thickness for the side walls, then it would only make sense that the 23c would a larger frontal footprint than the 25c. As one maintains the pressure, decreasing the width of the tire decreases the force that the air pressure can provide to keep up a load. Thus, the 23 needs to generates a bigger footprint to obtain the force necessary to withhold the load. While the footprint of the 23c and the 25c should be the about the same. The energy needed to deform the tire to have the footprint is greater in the 23c than the 25c. Althrough, there is another to consider with a smaller width assuming the thickness of the tire is the same, (I do not know the validity of this statement for 700c tires) the mass of the tire and the air is dereased thus, the rotational interia is decrease which also decrease rolling resistance, but since I do not have any numbers before I cannot tell which is which. Anyway, I have thought to much about this. I should get out and do 20 laps.

EXCALIBUR

I switched from 28c to 25c on both front and rear tires a long time ago. The rolling resistance is far less on the 25 c tires. I am also able to ride in a larger gear and travel a few mph's faster on the 25c's.

AnthonyG

You need to take construction quality into account in the equation. I've gone from cheap 28c tires (Maxxis) to top quality 25c tires (Vredestien) and the Vred's win hands down for ride quality as well as everything else even though there smaller. So if you were comparing 25c and 28c versions of the same tire there may not be a great difference but if your comparing different models then other differences will be greater than 3c.

Try the Vredestein Fortezza's in 25c. As an alround top performer with a great ride and excellent durability there excellent.

Regards, Anthony

merlinextraligh

We currently run 25c's on our tandem. The bike feels a lot more responsive than it did with 28c's. (wich is consistent with the rotating wieght being lower) Haven't done any empirical tests, however.

I wouldn't ride 28 c's unless 1) you value comfort way more than speed, 2) you're going to ride some extremely rough roads, such as gravel, or 3) you absolutely cannot tolerate ever getting a flat.
We've found that Specialized Armidillos in a 25c are robust enough for a tandem with a team weight of 350 lbs, and riding a regular loop that includes a short section of gravel.

Don Cook

The rolling resistance of the 28c will be less that the rolling resistance of the 25c given the same pressure, material and manufacturing specs. This is due to:
1. Most rolling resistance in a tyre is caused by sidewall flexing as it rolls (under weight)
2. The larger tyre at the same pressure as the smaller tyre holds more air and thus is capabale of supporting greater weight. If it's weighted the samne as the smaller tyre it will have less weight induced sidewall flexing.

Don Cook

Oh, and this has been measured and confirmed using real bicycle tyres in lab environments. Now, does it really make any difference in how much "rolling resistance we feel? You gotta be kidding. This is purely academic and I doubt a factor in any kind of riding that you and I engage in.