Safe tire clearance recomendations.

[Cicli]

So,
I will be building up my new Crown Jewel this afternoon. I am currently on 25mm Vittorias and would like to be able to run a 28 but dont want to plunk down for tires that wont fit. Would the math be simple? Subtract 1.5 mm to the clearance at the brake bridge and fork crown?
Whats a safe clearance? I dont want rub anywhere. None inside the chainstays or under the fork crown.
Thanks.

[fa63]

I like having at least 3 mm clearance on all sides.

[oldpotatoe]

So,
I will be building up my new Crown Jewel this afternoon. I am currently on 25mm Vittorias and would like to be able to run a 28 but dont want to plunk down for tires that wont fit. Would the math be simple? Subtract 1.5 mm to the clearance at the brake bridge and fork crown?
Whats a safe clearance? I dont want rub anywhere. None inside the chainstays or under the fork crown.
Thanks.

It would be that simple if tires, when inflated, matched the size 'number'. Often they don't plus rim width and type also has an effect on actual width. Go to LBS that will install and measure. It's nice to have 3-4mm, so if ya pick up a rock or piece of crud it doesn't score the frame or fork.

[parallelfish]

You may find that the brakes are the limiting factor and not the frame and fork. That is the case with one of my bikes.

Predicting the final size of the mounted tire is difficult, given the range of rim widths available, and the fact that marked tire sizes often do not reflect reality.

[pdmtong]

It would be that simple if tires, when inflated, matched the size 'number'. Often they don't plus rim width and type also has an effect on actual width. Go to LBS that will install and measure. It's nice to have 3-4mm, so if ya pick up a rock or piece of crud it doesn't score the frame or fork.

You may find that the brakes are the limiting factor and not the frame and fork. That is the case with one of my bikes.
Predicting the final size of the mounted tire is difficult, given the range of rim widths available, and the fact that marked tire sizes often do not reflect reality.

^ this and ^ this

it is maddening. was using belgium C2 with open pave 24. no problem. tried 2015 bora with conti 42K 25 and tire hits the bottom of the brake - wheel cannot be installed.

I asked the forum, most concur conti is the fatest 25 out there.