Tire size

What is the largest, fattest tire size that fits on a Schwinn S7?  1-1 3/8?  1-1 3/4?  Or larger?

Usually it's the frame that's the limiting factor, not the rim... My rims aren't particularly wide and I've got 2.125's on them no problem.  As long as it's not roadie-rim narrow it'll take pretty much whatever you throw at it, provided the tire fits between the chainstays...

Just to follow up on this one nearly a year later, the only thing that fits on a Schwinn S7-sized rim is an S7-sized tire!  The actual rim diameter is different from "standard" 26" wheels.  Go figure!!

my schwinn takes tires 26x1 3/8 to fit Schwinn S5 or S6 rim.  So far two cycle shops say they have a tire for it but they don't.  They have a tire for an old CCM or Raleigh 26x 1 3/8 rim.  The difference is CCM type has a bead to bead measurement of 590mm  while a Schwinn 26 x 1 3/8 rim has bead to bead measurement of 597 mm.   Not sure what a S7 rim is but Schwinn made all their parts to their own dimensions.  Schwinn was not sold in Canada back in the day so lots of bike shops just figure its like an old CCM.  very frustrating.  Still trying to get tires for my 1968 Schwinn lightweight.  Will post when I find out who in Van sells them. 

Problem with changing rims is that brake pads won't align with new rim.  Several reputable bike mechanics have told me this. You have to install drum brakes.  Can't install disc brakes as you need proper mounts welded to frame.  Looking at $200 or more to install cool big tire on Schwinn Lightweight

Yep, that is a DEFINITE issue... Drums are pretty much the only way to go (my personal favorite route anyhow - WAY better braking)

That said I have replaced tires on a friend's Schwinn lightweight... Duro make a tire that works.  S7-sized tires are also available.