Originally Posted by jonathanf2

I've been dabbling on and off with 28c GP5K tires lately, and I had to take them off because I thought they felt horrendous. On the flats my maximum speed is a bit higher with 28s, but for some reason I feel like I'm struggling on the climbs and forced to exert more effort.

Originally Posted by jonathanf2

I don't think 25c to 28c on paper is that big of difference, but my legs are telling me otherwise the moment I hit some elevation. I think the difference in rolling resistance is quite noticeable. I tried pumping up the 28c tires higher pressures and it still didn't have the responsiveness I like with 25c tires.

On flats I do think I can reach faster potential speeds on 28c tires. If I was riding on long stretches of smooth flat tarmac, I don't think I'd have a problem with them. It's when it comes to stop-&-go riding and climbing where the difference appear. Yet, when it comes to gravel none of the issues I've mentioned really bother me.