I don't think a 2.5 would clear the swingarm on my '75 Maxi S. I was going to go with a wider fender on the front to go with 2.25 front and rear , but I heard they are hard to find. Even the 2.25 on the rear was iffy. I prefer a little more clearance. The drive chain would have to be way too tight to clear the swingarm. I guess you could add links to the chain.