Originally Posted by
crn3371
I dropped my rear wheel and measured width between the chainstays where it line up with the tire and got 34mm, so around 3mm clearance between tire a chainstay. Regardless of my measurements my current tire has to be shoehorned in and it sounds like it would only get worse with a wider wheel. It’s looking like if I want new wheels I’ll have to also get new tires, and it looks like 700x25’s are going to be as wide as I should go.
The chainstay clearance is what is critical. 3mm on each side is about the bare minimum you should have there. Any closer and the tire will rub the chainstays on climbs as the wheel and frame flex.
A wider internal measurement on a rim will indeed change your tire's effective width when mounted and inflated. Take a piece of paper and curl it into a tube still open at the bottom. Now open the space on the bottom a little more. That effectively increases the size of the paper tube, correct? I found when I went from 15mm rims to 17mm rims, my tire width effectively increased by 1mm. The height will increase slightly too, so if you are already close to the bottom of the fork, that could be problematic.