I just purchased a Trek multitrack 750 1996 in black. I found it in almost perfect condition and want to upgrade the tires. What is the max tire size you can run on the 750 without any clearance issues?
A quick Google search turned up a thread at BikeForums that seems to have a consensus that 40mm is about the max size. Depending on the particular tire and how inflated it is, a 42mm tire might fit.