25mm vs 32mm tires, unscientific testing

[rides4beer]

I've been experimenting with tire widths, from 25mm to 32mm. I've found that comfort and grip with 32mm is great, and doesn't give up as much speed as you might think. Obviously you need to have room to fit 32's, something to keep in mind, at least with the GP5000s I'm running is that they are not only wider, but also significantly taller than 28's.

I recently did two rides on our local 7 mile TT loop. Six laps, going hard, averaged 22.5mph on 32mm, and 22.8mph on 25mm, both GP5000s.

Same wheels/kit/position. On my wheels the 32's measure almost 34mm, and the 25's measure right at 27mm. Wheels are 50mm deep, 19 internal, 27.5 external. So not perfect 105% with the 25's, but close. 23mm might be a hair faster, not sure I want to buy another set of tires to test tho (if someone would like to donate a set, I'd be happy to try them out lol). Over a 43 mile, almost 2 hour ride, I saved about 1 minute with the 25's. Temp/wind/effort felt similar.

Not exactly scientific, but I don't think it's as big of a deal as people make it out to be, at least for average riders. Obviously, if you're chasing seconds and podiums, then optimize everything. I'll keep the 25's on the 50mm wheels for races and TTs, and keep the 32s on the stock wheels for training rides. If your roads are bad, like some are around here, I've found that you'll actually be able to go faster with the larger tires because they're more comfortable, and you're less fatigued from not getting beat up as much. The TT loop I used is pretty smooth, so that didnt' come into play.

Not trying to convince anyone, ride what you want and works for you, just adding some info for anyone who has been hesitant to try larger tires.

[RUNTHAT]

Thanks for the info, and your real world review. I recently went from 28s to 32s (both tubeless) and the added comfort with lower tire pressures is noticeable.

[mrlobber]

Nice

However, weather conditions are extremely important so that would be nice if you could post the exact time and approximate location of your rides so that we could look up the "speediness of the weather". "Wind felt the same" and atmospheric pressure can play really big difference, especially if part of your rides are shielded by trees and/or impacted by passing cars.

Myself, I've done similar loops with difference of 2kph per ride (which at 31-35 kph is more than 5% of speed difference), just "owing" to trees blocking crosswinds and traffic intensity.

[rides4beer]

Nice

However, weather conditions are extremely important so that would be nice if you could post the exact time and approximate location of your rides so that we could look up the "speediness of the weather". "Wind felt the same" and atmospheric pressure can play really big difference, especially if part of your rides are shielded by trees and/or impacted by passing cars.

Myself, I've done similar loops with difference of 2kph per ride (which at 31-35 kph is more than 5% of speed difference), just "owing" to trees blocking crosswinds and traffic intensity.

True, def a lot of factors. It can get windy on this loop, so I used the wind predictor to try to pick a similar forecast with low winds for both rides.

32mm ride: https://www.strava.com/activities/3447191308
25mm ride: https://www.strava.com/activities/3550177253

[GamecockS2K]

Pretty cool info. It's always fun to do tests like this.

Were you using a power meter, or just RPE?

What is your weight?

What air pressures were you running?

[kode54]

I felt 32mm tires too wide...and 28mm not enough. Ending up in the middle with 30mm tires is a nice compromise.

Nice test, although my legs plays a larger part than the temperature or atmospheric pressure. LOL

[AnkitS]

Were you using a power meter, or just RPE?

Strava shows estimated power so there was no power meter used.

[rides4beer]

Pretty cool info. It's always fun to do tests like this.

Were you using a power meter, or just RPE?

What is your weight?

What air pressures were you running?

RPE, no powermeter yet, but I do plan to get one eventually, I'll prob do it again when I have real power measurements.

185lbs

80/85 in the 32's and 90/95 in the 25's. Surface on this loop is pretty smooth. For normal road riding I run lower pressures for comfort.

[RyanH]

I hate to burst your bubble but when I was doing aero testing in the field, even holding identical wattage changes in temperature from day to day was resulting in up to 30 seconds or more differences per 3.1 mile lap. Unless you're doing a full Chung analysis then these types of anecdotes are only misleading.

[FactoryMatt]

Low torque ebike would be a good testing platform. Put it in eco mode and spin. But yea so many variables. Smooth or old chipseal. Avg speed. Psi. Paired wheel etc

[Butcher]

I get weight weenies, less weight is less weight. When it comes to tires I'm lost. If you want to run some fat tires, they will be slower. How much? I do not know or really care that much. If it makes you work harder because you are more comfortable, have at it. I'm just sold on fatter tires are slower.

It may be that the roads I'm not are not as bad as your's or I've just hardened up with the 23's I have.

[rides4beer]

I get weight weenies, less weight is less weight. When it comes to tires I'm lost. If you want to run some fat tires, they will be slower. How much? I do not know or really care that much. If it makes you work harder because you are more comfortable, have at it. I'm just sold on fatter tires are slower.

It may be that the roads I'm not are not as bad as your's or I've just hardened up with the 23's I have.

There's no doubt that they're slower, I've just always been curious about how much slower. I absolutely agree that when every second is on the line, then skinny is better (or at least properly matched to the width of the rim). But for average riding around, especially if the roads are a little rough, I don't think we give up that much speed with wider tires.

[bm0p700f]

The test shows they were as fast as each other within the margin of error which is unknown.

In any case my conti gp5000tl 25mm tyres are 25.5mm wide on a 19mm internal width rim.

[Lewn777]

I think this depends on the roads, not so much the tires.
I've used 23mm a fair deal, 32mm once or twice 28mm on many occasions, and 25mm more often, not a huge difference incrementally but from 23mm to 32mmm is a huge difference. Pure descending, on questionable surfaces 32mm absolutely, safer and more fun, in fact if you were to attempt a downhill Strava segment then 32mm Conti GP5000 would be near the top of my list. Smooth road/climbing, then 23mm, lighter and faster rolling. I think you have to have a look at your local road surfaces and make a compromise just as people do with crank length. What might be ideal in Dubai, might not work so well in the UK. Also rider weight must be an important factor, surely 23mm tires are going to work better for someone that's 55kg than someone 85kg. For the average person 25mm to 28mm is probably ideal, no coincidence the pro peloton uses 25mm.

[tomycs]

Out of all things aero for clothing, frame, wheels depth, handlebar I felt an impact, more for some, less for others. The 105 rule is the one I would say I never felt anything. It's ok from a theoretical pov, on some of my setups it happens, but I'm not obsessing abt it, I rate hub quality and braking performance higher when evaluating a wheelset.