you're running 28mm tires on your Ultimate?? I am impressed. The Litespeed Arenberg I just bought came with 23mm tires and I want to go with 28mm but I am concerned about clearance where the chainstays meet the bottom bracket. I haven't measured it yet and I need to but by eyeballing it the clearance on the current 23mm tires looks to be approx 4mm per side. The brakes front and rear definitely have enough clearance and the fork certainly just has clearance but that chainstay/bottom bracket junction has me concerned. Any thoughts?[/QUOTE]
It would be safer with 25mm tires if your tolerance is too tight.
I tried mounting a rear wheel with 28mm tires on a newer LS, they do have enough clearance but depending on the frame it is a little too close for my comfort.
this is a shimano c24 wheel with a Conti 4k 28mm tire at 90 psi on my 2007 Ghisallo.
left me about 2mm on each side. The tire does not touch but in real road condition it just might with a hard bump.
Same wheel mounted on a 2006 Firenze about 3mm clearance on each side.