Your Schwinn Tire Sizes Frighten Me

8ball · Jul 15, 2018

I generally rustore heavy and middleweight Schwinns and fitting new tires on S2 and S7 rims still confuse me. This time I’m fixing up a lightweight... a 1961 Schwinn Racer (K136521). I need tires and hope you can help.

Its tires were shredded and I tossed them thinking all I needed was the 26" x 1 3/8” measurement to buy replacements.

Schwinn tire sizes remain a mystery to me. And I don't want to screw up buying the wrong tires.

What is the correct metric... (12-345) number... for these Schwinn wheels, please?

A source to buy these tires even better. I’m going to try and find gum-walls with an aggressive tread. Thanks in advance for your help.

Wildcat · Jul 15, 2018

They look like original wheels, they may have an S5 or S6 stamped on them somewhere. Wheels may have been changed out over the years, but a 61 racer would have come new with S5 or S6. Schwinn made theirs a little larger so you had to buy their tires, regular sizes won't fit over the rim. Here's a quote from greenephantom.com:

"26" Skinny wheel Schwinns, Racer, Breeze, Collegiate, etc

Schwinn Lightweights like the Breeze, Racer, and Collegiate used S-5 or S-6 rims, and are most often found in the 26" wheel size. (S-5 and S-6 26" rims are the same size, just the cosmetics are different.) These came with Schwinn-specific 26" x 1 3/8" tires with a Bead Seat Diameter (BSD) of 597mm. Non-Schwinn skinny wheel 26" bikes use a similar-looking but physically smaller wheel that takes a 590mm BSD tire. That 7mm makes all the difference between a tire that fits and a tire that doesn't. (It should be noted that lugged frame imported Schwinn "Collegiates" from the 80s used a standard non-Schwinn sized tire.)"

Wildcat · Jul 15, 2018

I took a closer look at the Racer. Hopefully it's just a distorted photo, but the forks and frame look bent. The forks can be straightened but usually a frame bent near the head tube is a problem. The top tube and down tube a couple inches back from the head tube seem to have a slight bend, like the bike ran into something, and bent the forks also.

8ball · Jul 15, 2018

Hi Wildcat, thanks for your advice and comments. Yes, the fork was bent. I straightened it with some heat.

I would think there must be a '(12-345)' style tire size/number for a modern tire that will correspond to a Schwinn 26x1&3/8 S5 or S6 (as you indicated - thanks for info) rim...

... but if I understand you correctly, I need to be looking for 'Schwinn s5 s6 tires' and forget my '(12-345)' search?