What's up with S-2 and S-7 wheel sizes anyway?

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Rollin' on 20's
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Jul 22, 2007
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Originally posted in a Swap Meet thread by Iven. I moved it here as a better place for the discussion. Please feel free to join in with all Schwinn tire sizing questions regarding S-2 balloon tires, S-7 middleweight tires, S-5/S-6 lightweight tires, as well as dimensional tire information.


Re: Vintage Schwinn Rim Set

New post by iven on Thu Jan 31, 2013 1:37 am
i dont mean to * in your thread or anything but i need to rant about something related..

so i rode my 5spd schwinn stingray over to an LBS and asked about tires 'the front is almost gone, the back already blew out' anyway..
i grabbed a 20x1.75 tire and asked if it would fit the schwinn S7 rim and if 'since the tire is a Repo maybe it has a Larger bead like the S2 tires do.
then the owner of the shop asked me in a snide voice 'whats the difference in 20x1.75 and 20x1 3/4' and thinking mathamatically yes 1.75' = 1.3/4'
as far as i know, but he said 'well Not when it comes to Tires'
so ok i know they are a difference in size when it comes to inch/mm in tires but still. then he started to rant on about how i need the S2 tire..
ok i get that, then hes like Nagging on me then about 'i have been in this buissness for a long time and i know what im talking about' blah blah.

like ok, i wasnt questioning if he was correct about what tires i need or what, i was trying to ask if i need an S2 tire what does it mean that my rims are Stamped S7 ????

But NO He got even more Snotty with me and was tellin me off about how "There Is No Such Thing As An S7"

uhm.. well why are my rims Stamped S7 then?
thats all i wanted to know, but no he had to go and try to tell me off or something cause he couldnt understand i was asking what my Rims are..

god, sometimes being young sucks, people don't take you serously when it comes to building things. its a realll Kickkk in the side.

i dont go to bike shops cause i need to buy their marked up parts, i go cause they have something i can get now and 'some' of the people are nice to talk to, man needless to say i wont be heading back to that store..
that guy is straight up disrespectful.

so i ask here, whats up with S2 - S7 wheel/tires :roll:
Frank Schwinn had an idea after the war to make a little more money with his new middleweight bikes. Equip them with odd size tires you could only buy at the Schwinn dealer. Ka-ching! 8) No mystery here. Follow the money. Gary
Well, I learnt something new today... I didn't even know there was different sizes aside from the standard 12.5, 16, 20, 24, 26 etc...
I guess that is what comes with living in Australia, where we didn't get the "cool" bikes... :roll:

I love messing up sizes anyway, my latest two bikes run 240/50/16, 140/60/16, mt90/16 and one "standard" 20x1.95 freestyle bmx tire... :mrgreen:
I pity anyone who buy's one of my bikes secondhand and tries to find tires at thier local bike shop!

Schwinn used proprietary bicycle wheel sizing through many years of production in their US factories.

Bikes across the range used different and often confusing tire sizing. It's confusing to modern suppliers and new owners of vintage Schwinn bicycles.

Other companies in general did not follow Schwinn's lead on tire sizes, though some of these sizes became the standards which survive today. To add to the challenge, similar but incompatible tire sizes have some overlap in nominal sizes.

1) Balloon tire and Middleweight models. The 26" standard balloon tire is frequently found on older Schwinns, modern cruiser and mountain bikes, and most non-Schwinn brands of middleweight and heavyweight bikes. These are commonly 26x2.125 tires, and this is also the size for Schwinn's S-2 rim. Other brands often used 26x1.75" tires for their middleweights. Generally, any 26" non-lightweight tire fits these rims, e.g. 26x1.75, 1.90, 2.1, 2.125, 2.35, etc. For vintage bikes, a Schwinn Phantom, Panther, B-6, Spitfire, or mountain bike will use these tire sizes. Newer model Schwinn Cruisers, Deluxe 7's, and some ladies models will use them as well.

2) Schwinn's S-7: The original middleweight tires, introduced for 1955, used a narrower tread than the traditional tires (1-3/4") but filled the same outside diameter. This is important to understanding the concept behind these different sizes: the rolling diameter was the same. Therefore with a thinner tire, the rims were made larger. Schwinn applied this idea to tires for 26", 24", and 20" sizes. NONE of these tires fit a rim of the S-2 spec. Frequently, a new owner needing tires for a middleweight model, visits a bicycle shop or store, as mentioned above, and finds out they do not carry 26x 1-3/4" S-7 tires. I have found that choices are few, and tires must be ordered in many places: no local dealer keeps even a pair in stock. (I've gotten my LBS to carry 1 pair of these and S-6 tires!) You and I also know that 1-3/4" and 1.75" are supposed to mean the same thing, but in the world of bicycle tires, they define two different specifications that are not interchangeable due to rim diameter.

3) Stingrays: The classic Schwinn Stingray used 20" S-2 rims and tires in the rear, and an S-7 rim in front. This was done to imitate the look of drag cars of the era. The rear wheel is compatible in size with common BMX and other 20" tires. The front wheel size is not, and few suppliers make the needed 20x 1-3/4" tire. This S-7 size was used front and rear for other kids' bikes: Fairlady, Stingray Junior, Stingray II, Lil Chik, Bantam, and 20" Typhoon.

4) 26" Lightweight tires. Here is probably the greatest chance for confusion with old bikes for Schwinn and non-Schwinn lightweight owners. At one time, the "English bicycle" became very popular. Every company built 1 spd, 3 spd, 5spd, and 10spd bikes for the market using 26x 1-3/8" tires. Schwinn called theirs the S-5, later the S-6 (no dimensional changes between the two.) Other companies used the so-called EA-3 spec for their tires and rims. Typically these wheels are used on Raleigh, Columbia, Huffy, Murray, and many other brands of lightweight bikes. The EA-3 spec calls for 590mm rim bead diameters. Schwinn's lightweight models were also very popular in this period, and they made millions of Collegiates, Breezes, Speedsters, Racers, Travelers, and other models using the S-5/S-6 rim specifications. The Schwinn size was also labeled 26x1-3/8", but the rim bead diameter is 597mm. Either size of tires will not fit the other type of rim. When ordering new tires for S-5/S-6 rims, the suppliers commonly call these 26x1-3/8"x1-1/4" now. I don't think that helps clear it up a lot.

5) Other lightweights: 27" bikes were considered higher-end or racing bikes in the 60's and 70's. Schwinn produced a lot of these too, Varsities, Suburbans, Continentals, Paramounts, Sports Tourers, etc. Schwinn called their 27" tires S-6 models as well, but in this case the world agreed: There is just one size for 27" tires for all brands. The modern metric sizes 700c and 650c were not introduced until after Schwinn stopped producing bikes using the older specifications, so typically there will not be confusion when ordering these tires.

I'm sure there are some important details I've left out but I think that covers the basics, and I hope that now you're less confused about the tire sizes and what their uses are.

I agree with all except the point that the metric sizing (700c, 650B, etc) wasn't introduced until after Schwinn stopped the nonsense. Actually, while it wasn't common in the USA, those sizes have been around for a very long time. They originated as French standards - the number designated tire OD and letter the width. "A"s are narrower than "B"s, etc. But several of the proprietary sizes that Schwinn developed are the same as what previously existed. The middleweight 26x 1-3/4 has an ISO rim size of 571 mm - the same as 650C. The common 26x 1-3/8 is technically a 650A size, whereas the Schwinn variation of 597mm is actually the same as the earlier British standard of 26x 1-1/4. That's why modern tires that fit that rim are marked 26x1-3/8x1-1/4. Not simply to distiguish it from "normal" 26x 1-3/8, but to designate that fits the overlapping Schwinn & British standards. There's a lot of that throughout the sizing ranges.
I thought 650's used a 584 ISO?

700's use a 622
S7's use a 571
Normal 26's use a 559
S6/S5 use 597
GTV said:
I thought 650's used a 584 ISO?

700's use a 622
S7's use a 571
Normal 26's use a 559
S6/S5 use 597

You've got to pay attention to the letter designation as well as the number. It was similar to the different 26" designations, as the format dictates the overall diameter of the inflated tire. Instead of a number to designate width, the French used a letter. "A" was narrow, "D" wide. But like with 26" tire formats, as the tire got narrower, the rim has to get larger in diameter to maintain the rolling radius. 700C is 622, but a 700A, B or D would be different. That's moot, since those sizes have fallen out of usage, but the issue is complicated by the fact that most common tires today for a 700C wheel are skinny, even though the size started out as a wider format. The 584mm size you mention is equal to a 650B. 650C, however is 571mm as I said, and 650A is 590. See Sheldon's write up as a reference: http://www.sheldonbrown.com/tire-sizing.html
Thank you for the education :)
The hard part is finding them. I ride a 40 yr old Schwinn unicycle (24 x 1.175 S7). I need a new tire. I find brick pattern treads on most (all are very expensive) and in contacting the seller, nobody wants to guarantee it will fit my unicycle rim. Because of the way a unicycle moves on the ground, non-smooth treads wear away very quickly. The original tire had a couple of grooves for water shed that encircled the tire The apex or ground contact part of the tire was smooth, which enabled me to ride for years on the same tire. I will continue my search and pray for a perfect match
The hard part is finding them. I ride a 40 yr old Schwinn unicycle (24 x 1.175 S7). I need a new tire. I find brick pattern treads on most (all are very expensive) and in contacting the seller, nobody wants to guarantee it will fit my unicycle rim. Because of the way a unicycle moves on the ground, non-smooth treads wear away very quickly. The original tire had a couple of grooves for water shed that encircled the tire The apex or ground contact part of the tire was smooth, which enabled me to ride for years on the same tire. I will continue my search and pray for a perfect match
The true unicycle tires are 60 psi a newer S-7 tire will be 45 psi. They do come up for sale but not often.
Sizes on tires are names not exact measurements. And they are completely different from cars and different from motorcycles and scooters. Fortunately few new tire sizes have had been added since 1940. A few that come to mind are the kids bike 14 & 18 & 22. And 32" monster wheels brought to the bike industry from horse sukly racing. Up until the 1920s, almost every maker had their own size. Only in the bike industry are 28" wheels bigger than 29ers.

Actually Schwinn sold 20" slicks to fit either size of rim. Depends on the age of the bike and where it was made. I just went through this for a batch of Schwinn Lil Chiks, not to be confused with the Lil Slik, and some off brand imitations. The closing of the Chicago factory in 1983 should have been the end of all the S-rims. After that the bikes were usually imports and didn't have the S-rims.

Those "proprietary" Schwinn sizes were rooted in the French metric sizes. Schwinn was from Germany and routinely bought many parts from Europe. Spokes, pedals, chains, hubs. From Germany, France, Switzerland. Schwinn was big believer that the American public was metric phobic so stuff got labeled in inch measurements.

There are only a couple sizes that are no longer being made. Kenda and some other companies keep making some of the "Schwinn" sizes.

The 26x1 3/8 wheels. Yes, there is the Schwinn version and the British version. Some of the older tires were labeled just 26 x 1 3/8. Some added the "to fit EA3" or "to fit S6" on the tire side walls. I used to see hand made signs at non-bike stores trying to state that these tires would or would not fit Schwinns as they got to deal with all the returns. Before ERTO and ISO none had the bsd on them. More fun is Raleigh sold wheels to other bike companies. Some of the USA companies bought 3 speed wheelsets from Raleigh during the bike boom for their 3 speed bikes. If a non-Schwinn USA brand bike has a Sturmey Archer hub, it usually (but not always) has the EA3 rim. Schwinn would buy SA & Shimano 3 speed hubs and build the wheels with their rims. If it has a Shimano hub, it it can have either but more often a EA3 rim. Some companies just bought complete bikes with their name put on it. I once owned a pair of Huffy Sportsmans. One had a 3 piece crank frame (made in the USA) with S6 wheels, and the other had an import frame with EA3 wheels. Just knowing the brand of USA bike wasn't enough to guarrentee getting the right size.

Another reason for Schwinn sizes were the import duties imposed on certain sizes that were meant to protect the USA bike industry. Schwinn could spec 650B from Europe, a size not mentioned in the tax code but they advertised them as 26 x 1 1/2 for the metricphobic.

the S2, S5, S6 and S7 were made in several different diameters and spoke drillings.

You see on this 1973 chart the S2 was sold in 16, 20 24 and 26".


Schwinn Rim Reference 1973
The chart was updated often.
Very good reminder the USA is the new kid on the block and stuck with so many hand-me downs. "Where all men are Free", to be contradictory.

The writers left out Kelvin and Whitworth.

Reminds me of a day when we were kids. My mom was redoing the wall in the basement stairway. Ripped out the old horse hair plaster to install fiberglass batting and new masonite panels. She would call out me measurements and we would cut the panels and sent them in. But nothing fit. This went on for all day. Later in the after noon we discovered her yard stick was broken off on one end.

Nasa lost a spaceship due to a mix up in measurements. Oops, a $125M goof.
It is a funny episode, but most of them were still stock British measures until I were young. I remember being taught that an inch was originally the length of three grains of wheat, but I never checked despite having spent my summers lying in the grain trailers as they cut the corn (wheat) in the back field...
Yeah, those Brits. The measurements were based on arbitrary items. At least the Metric system is based on controlled scientific observations so anyone can figure them out without having to travel to England view to the gold standard in some display case. And the Olympic marathon official distance is from Windsor Castle to the former White City Stadium in London.

Mile vs Imperial mile vs nautical mile anyone? How far is a "click" anyhow.
Fluid ounce vs weight ounce.
Gallon vs imperial gallon? Are there any Candian gas stations with Imperial gallon pumps left? If you want to pretend your car gets better mileage get your gas across the border.
How many ways of measuring tire pressure. PSI, Atmospheres, KPA, millibars, inches of mercury, ...
Whitworth wrenches are fun, a 1/4 wrench fits a bolt with a 1/4" shaft, not a 1/4" nut. Withworth assumed all 1/4" bolts would have the same size head. I bought a set for my vintage British bicycles.

I think that SNL skit could have had the other guys named Whitworh, Kelvin, Celsius, Farenheit, etc.