Originally Posted by
YokeyDokey
Here's where I really show my ignorance - these wider tires fit the existing rims? I think the rims are 15mm inside measure. Whatever came with the bike.
I measured the wheelbases of all my rides last night. The giant old Schwinn is the longest, 43", which is the same as a 58cm LHT, but the Schwinn is a 64cm gaspipe clunker, so it's not a candidate. The other bikes were all within a cm of each other in wheelbase. At this point, unless I fall backwards into either a pile of money or a proper touring bike, I'm back to the old Fuji.
It's not the tires that fit the rims that's the problem but the tires you can fit in the frame that are the limiting factor on how wide a tire you can use. Measure between the forks and chain stays where the tires pass through. Give your self a little clearance on each side and see how wide a tire you can fit in there.
Your rims are about the same dimensions as a high end mountain bike rim. I fit 2.3" tires on mine. You can't pump them up to 100 psi but they will fit. That width, however, is overkill. 28mm to 35mm is a good range for the Katy.