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?
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.
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.
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