The difference seems to be as much in the rims as in the tires.
I even double checked to make sure someone hadn't laced up a set of Raleigh Westwood rims but they do say Schwinn.
I've got an older Park PTS-1 tire seating tool, and so far its not helped. The old tires and new tires fit the old rims, but not the new rims. The 'new' tires are tighter, but not as tight as on the new set of wheels. I thought the rim was going to bend I had to pry at the bead so hard to get them on. I bent two of my steel tire levers.
Side by side both rims look identical but I've got no way to actually measure the diameter of the bead seat area.
I've soaped the tires up, left them in the sun, even broke out a heat gun but they will not seat. About 8" of the bead is always down in the middle of the rim. The fact that the new tires fit on the old rims and do seat, (although with a bit of a fight), tells me the rims are different somehow.
The LBS had one Kenda 26x1 3/8x 1 1/4" tire in stock, so I gave that a try, it was even tighter than the original tires, so much so I gave up. Then I noticed in comparing the two tires that the new Kenda tire, that was marked Schwinn S6 or EA-1 on the sidewall but also has the 37x590 size on the other side??? Every marking on my older 'new' tires and the original tires compares exactly with the new Kenda tire except for the ISO size and the lack of "S-5" being included. The new tire is clearly marked 'Fits 26x 1/14 Straight Side EA-1 English & Schwinn S-6 rims' but its marked 590 ISO**********
The tire fits on a standard, 590 rim. Its clearly mis-marked.
Regardless of the new, wrongly marked tire, the original and new old tires I have still won't seat on the rims. (Those are marked 37-597).
I've tried soap, tire grease, heat, tire pliers, bent two tire levers, and inflated them to 75 psi trying to get them to 'pop' onto the bead but no go. Since they're from the exact same lot that the old tires were from, they should fit. (remember they fit the old rusty S5 rims just fine, just not the new shiny S5 rims). I also dug out a spare bare S5 rim and the new tires slip on and fit that rim just fine too.
Obviously the new Kenda tire is of no use here but now I have to worry about other tires being mis-marked or mis-labeled in someway.
The original tires that were on the S5 rims I'm fighting with are too far gone to use, I'm not sure when Uniroyal quit making bike tires or even quit making 'chain tread' but they're clearly different in someway.
I've not had the tube try to pop out or blow out, there's little chance of that happening with as tight as these tires are. Even overinflated with 8" of tire in the spoke bad area, there's no space for the tube to slip out and the tire is not trying to de-rim at any point. Getting them back off a real nightmare.
I've been working on bikes for years and never had a pair of tires fight me like this.
I think the wheels I'm trying to switch to may be older, or at least the tires that were on them look older but the rims, are clearly marked Schwinn S-5 and the tires are clearly marked 37-597. I'm wondering now if there were variations in the old Schwinn rims over the years too. The best I can do is measure the circumference of the bead seat with a cloth tape. The original rusty old S5 rims are 2 mm smaller than the new rims. The original rims measure 597mm on the money, the S5 rims I'm trying to use measure 598.5mm. I wouldn't think that 1.5 or 2mm would make much difference but its proving me wrong.
Did Schwinn ever use a different standard? I'm starting to think these S5 rims are some how different than those on the bike now.
Appearance wise however, they look the same, although they do have more defined markings on them. They were laced to a mid 60's era hub but after 55 years, who knows where they've been or what's been done to them.
I don't have any original "Schwinn" tires that aren't made in Taiwan, but something tells me that good older American made tires wouldn't be giving me all this trouble.
