23mm for Aero or 25mm for Rolling Resistance

Equipment
1

Hey there,

i’m using 25mm GP 5000 on alloy rimes (veltec speed AL) with 42mm depth. Old V-Profile, nothing spectacular, but i’m quite happy with it because i can use latex tubes with rim brakes without blowing it on decends. The 25mm tyre builds a bit wider than the rim. Not quite good for aerodynamic.

I need a new pair of tyres. So what do you think, whats better? Go for 23mm for better aero or go again with 25mm for better rolling resistance?

Thank you

2

The difference is likely something like 1 watt either way. I’d probably go wider, for better grip, comfort and RR.

3 Likes
3

Could not agree more. Chasing an aero gain from a 23mm tire on a set of alloy rims may be an exercise of scientific curiosity, at best.

Hands down, 25mm, don’t even think about it.

4 Likes
4

If you were time trialling with deep section carbon rims and an optimised position there are marginal opportunities around 23 vs 25mm tyres depending on your rim depth and width. (as I do)

Given modest section alloy rims, and what what I read into your post, road riding, then I have found 25s to be a definite uptick in comfort and handling over 23mm tyres. I have run both latex and tubeless GP5000. They seem to roll very nicely and are more comfortable than 23s, which adds to the speed.

Having the right pressure is as much a factor in RR.

5

28mm, seriously there isn’t a lot of difference in aerodynamics but there is in comfort (and real world speed)

2 Likes
6

Don’t know what bike he is riding, however there are limited capabilities of rim brakes accommodating a 28mm tire. Not out of the question, but my experience has been that 28s are more easily fitting on older steel frames than modern carbon ones. I can fit a set of 28mm gravel kings on my 1983 Raleigh and there’s no chance i could do that on my Emonda SLR with the identical calipers.

7

Oh well my point still stands, wider tires are probably faster in the real world. A while ago I saw a youtube video where they did a wind tunnel test with different tire widths, the difference in the wind tunnel between the different sizes was less than a minute over 40km but in the real world that means that wider tires are probably fast due to less bouncing around which costs a lot of energy

(can’t find the video now though)

8

Oh totally, this is not in question. Just keeping it to the OP’s request for tire choice, there’s no point in the awareness of a potentially faster option if he can’t use it.

Edit: he can apparently :slight_smile: - based on this, i would also likely move to a 28mm recommendation.

9

Thank you for your clear answers … looking pretty dumb right now :slight_smile:

But when you read too much, you can easily geht caught and start to overthink things.

I had 28mm and changed to 25mm. What feels pretty good since the 28mm seem to annoy me with their “ice cone” look on my 24mm wide rim.

10

I am easily confused, but after reading many reviews and my experienced, here is my summary, and it depends :unamused: .
For tires:

  • If you’re going for that KOM or beating your comrades on hill climbs, keep as light as possible, which implies 23mm. Providing the road is relatively smooth. If it is rough, then you need to go wider.
    Many times long climbs have breaks (less gradient), and I find getting a lighter tire and wheelset is easier to spin back up to speed. If my tires and wheels are wider, I have some issues to get them back up to speed.
  • For rolling terrain, keeping an aero wheel set is more advantageous, so a deeper wheelset and wider tire works for me.

For the wheelset measure the width of the outer rim. That will give you an approximate dimension on the best aero wheel-tire combination.

  • For my old wheelset, they are very light (<1400g), but the outer rim width is 22mm, so the tires for these wheels seem to go better with 23mm. The combination seems to best for climbing and a better match with this wheelset. I’ve run 25mm and 28mm on these 22mm outer rim width wheels, and that is a bad combination for aero, with the tire balloon out well past the rim.
  • For my newer carbon wheelset (also light (~1400g), their outer rim width is 25mm, so they go very well with 25mm tires.

I don’t have any measurements, but my climbing wheels seem very easy to spin up climbs, where my deeper wheelset seem to be harder to spin up again if I loose inertia. On the flats, rolling terrain, and for very long rides, the wider, at lower pressure, are BEST.

Hope that helps

11

Do you have any reference table or formula?. I want to see the difference between 32mm, 35mm, 38mm. Thanks