Schwinn Lightweight 650b Tires


Look Ma, No Hands!
So, first things first- the bike in the photo is a 1972 Schwinn Speedster that my bicycle cleaner monkeys were wiping down in the garage for me. It’s not the bike I have a question about but it’s an electroforged Schwinn lightweight from the 70s, so close enough.

Yesterday I grabbed a black 1970 Schwinn Racer that I spotted in an old lady’s yard leaning against a shed. She said $10 and I didn’t even give it a second thought. It’s rough but I have a thing for those bikes. The s5 rims are absolutely toast- like, you can poke your fingers through the rust holes, toast. The frame looks okay.

I’m going to use it as an excuse to try some different rims out. I have several of these bikes that need wheels and would like to find a modern alternative to hunting down used, often rusty, often overpriced original wheels to put on bikes that, although I love them, I am well aware wouldn’t bring $100 at a garage sale. I ordered some SunRingle CR-18 alloy rims in the 590 EA3 size to try out. I’m going to rebuild the Sturmey Archer 3-speed and lace it to those rims. This would give me about a dozen options for tires.

I also keep looking at 650b size rims and wondering if they’d fit a lightweight. Anyone ever tried them?

I like the idea of having options in case Kenda gets any ideas about discontinuing the K23s. I also don’t love that they’re the only tire choice at this point. It would be nice to have a replacement wheel with abundant tire options, better braking, strong, lightweight construction, and a polished finish to mimic the original wheels. I’m going to try out some mad scientist experiments on this bike and feel no guilt for modifying it since it’s spent 20 years sitting under a tree.



Wore out three sets of tires already!
I went through the same thing with an old 64' racer wearing S5 Rims.
The 650b (ISO 584) is a bit smaller than the Schwinn S5/S6/EA1 (ISO 597) and looks it. When you put road tires on them, they are 25" diameter. I think I read that the size originally used wider and taller sidewall tires for tandems. The taller side wall initially putting them in the 26" category.
There is also the English EA3 (590 ISO) rim size. I am kind of surprised they still sell that size. Its not a 650b. They also look a bit small on the racers if keeping the fenders on. That size is considered an English three speed size.
I ended a size up to 700c (ISO 622) which is a hair larger and also looks it. They still fit under the fenders, yet barely, which is a different look also. Hundreds of tire options from slicks to knobbys.

The aluminum Weinmann 2120 model has a similar look to the Schwinn S5 but are like hens teeth. I had a pair on a Racer last year in 700c size.

I found that the Racer I had was stodgy and thumped down the road in its original condition, Very sturdy and stabile but nothing to do with the word Racer. The wheels and tires made a big difference in the way it felt while riding it. I went a step further and put a different fork on it and it rode like a Cadillac after that.
Of course by that time its more of a custom bike than a Schwinn Racer.


Look Ma, No Hands!
If the new bike has brakes like the bike in the picture, it looks like the shoes are all the way down. Going bigger on the rim size might be a better idea than going smaller.
Good point. I’d be willing to swap calipers, if necessary. I’ve seen longer Weinnman calipers. I haven’t seen a lot of rim swaps on Schwinn lightweights that were very well documented. I’m going to try the 590s and take lots of pictures and document what is required and then do the same with 650b and then 700c. I’ll post everything when I’m done so others have a reference. I think a half-destroyed $10 Schwinn is the perfect test mule for this kind of thing.

Alan Brase

Look Ma, No Hands!
Watching with interest as I apparently have some kind of addiction to buying lost soul brazed Schwinn frames. And it seems EVERY ONE is missing its original S-6 rims. Further complicating my quest is that since these all have 120mm rear spacing, at some point I might fit one with a Sturmey 4 speed which seem quite plentiful in UK, BUT they are all 40 hole models. I guess if I'm gonna build a hot rod the first place to start would be alloy rims.
Any further news on this would be appreciated.

Arnold Ziffel

Finally riding a big boys bike
The 650a size is the common "everybody else but Schwinn" 590mm 26 x 1 3/8.
I am told by friends that this size is still popular in Japan.
You do have some very good tires that are manufactured for this common 590mm tire.
I do have friends that have ordered some so called best/better 590mm 26 x 1 3/8 tires via the web from web bicycle stores/parts suppliers in the U.K. and France. This was between 2019 and mid 2021 when several friends purchased their 590mm tires direct from suppliers in France & England at what I was told at the time was a reasonable cost including shipping to the USA.
I seriously doubt that the tires they acquired are really any better than most any other 590mm with a name on the sidewall that isn't as well respected of a name brand of tires.

I am fairly certain that the stock Schwinn L.S. 2.8 Weinmann sidepulls on your Speedster/Breeze/Collegiate/Racer/Traveler/CO-ED etc, whatever name variant that has the 597mm S5/S6 Schwinn 26 x 1 3/8 37-597 wheels,
will function with the common-everybody else 590mm (650a) 26 x 1 3/8 590mm 37-590 common bike wheels.
The adjustment slot of the L.S. 2.8 Weinmann sidepulls should accomodate this 7mm difference, with the brake pads secured in nearer the extreme bottom of the slot. As long as your 590mm rims are relatively round & circular, my belief is that you should have no problems whatsoever running the common-everybody else 590mm wheels in a electroforged Chicago Schwinn 597mm twenty six lightweight. I put together an otherwise nice looking blue March '68 Collegiate frame, with a 590mm Rigida Super Chromilux steel wheel set taken from a 1984 Sears Free Spirit Sunbird burgandy-burnt cherry colored Korean made lugged frame and 3 piece cottered crank(see 1984 sears spring catalog, it was the base model 10 speed there...) That Korean made lugged frame is light and nicely built compared to the older PUCHs and gaspipe Murrays & AMF trash that Sears might have used in the seventies. The reason that I pirated the Rigida wheelset and its Shimano RS rear derailleur for the older heavy Collegiate frame was because that particular 1984 base model Free Spirit Sunbird only came in one frame size in diamond (mens) and one frame size in step through (womens), and the Free Spirit Sunbird 10 speed frame was too small for the person that I was building it for. He also preferred the simplicity of just five speeds and the size of the old Collegiate frame was perfect size for him, and I told him that he'd never break the Ashtabula one piece Schwinn crank and the simplicity of servicing the bottom bracket with fresh grease.
I did install a chromed metal dork disk on the rear Rigida 590mm wheel taken from the 1984 ten speed.
Originally it had a yellowed clear plastic dork disk on that '84 ten speed.
It made a nice five speed with that wheelset on the march '68 Collegiate frame. The 1984 Sears F.S. Sunbird 10 speed's freewheel had the same 28 teeth low gear as a sixties era Collegiate. The Shimano RS rear derailleur is a heck of lot better than the Schwinn Approved Huret Allvit that sixties era Collegiates had.
That March 1968 Collegiate frame has Weinmann 810 sidepulls (EXACTLY THE SAME AS L.S. 2.8 which is what they were stamped for 1969 models and later) You see Schwinn designated that this SCHWINN specific identification code be stamped into the brake calipers from 1969 model year on in lieu of the Weinmann 810 stamping as seen in 1968.
You see this "code" was helpful to factory employees and Schwinn dealer service folks. I can tell you how to decipher it, as the numbers aren't what you might initially think they are. The tenths digit (the number to the right of the decimal) gets multiplied by 3/32. This calculated result gets added to the 2 (the number to the left of the decimal).
What this then tells you is that it is 2 24/32 inches in distance from the center of the caliper's mounting bolt to the center(middle point) of the slot that the brake pad gets bolted to.
I told you that it was different than you expected.
2 24/32 reduces down and is equal to 2 3/4" ........thats for the 597mm twenty six bikes having the L.S. 2.8 / Wein 810
Now for example, you know that the 27 inch (630mm) SUBURBAN & VARSITY have the shorter reach L.S. 2.4
Knowing this its calculated length from the center of the caliper's mounting bolt to the center (middle point) of the slot that the brake pad gets bolted to...................................So the SUBURBAN/VARSITY L.S. 2.4 would calculate to 2 12/32 or 2 3/8"
................Sorry to bore you and boggle you with this minutia but just forget that , and focus on the fact that you can swap out the SUBURBAN/VARSITY's L.S. 2.4 sidepulls with the current L.S. 2.8 sidepulls on your Collegiate-Speedster etc 597mm twenty six lightweight model.
................What this would do for you is that it should allow for you to use a (622mm) 700C wheelset. Look the 27 inch wheel is 630mm and the 700C wheel is 622mm. The brake slot area should allow you to accomodate a round 700C (622mm) wheel without any problems at all.
..............You can purchase newer, better designed sidepull designs that provide better overall braking operation than those sidepulls of 40 years ago and earlier, but unless you're intending to cruise at an 18mph average pace or greater, there is really no reason for such an upgrade. As you know, the Continental and the Suburban are pretty much the same, as they are both an upgrade over the Varsity model since both the Suburban & the Continental share the same tubular front fork while the Varsity has the ashtabula blade fork. The Suburban does have the same exact L.S. 2.4 sidepull Weinmanns as the Varsity.
The Continental has the same tubular front fork as the Suburban does, but the Continental has CENTER PULL brakes instead of the sidepulls that the Varsity/Suburban has.
............With good fresh brake pads, the old Weinmann sidepulls are just fine, if you're not riding down a steep hill while it is raining. There isn't much difference in the electroforged Schwinn lightweight frames of the same era between whether they were a 597mm Collegiate type variant or a Varsity/Suburban 630mm twenty seven wheel bike. The Collegiate type variant simply has longer reach Weinmann sidepulls. Sure some very large frame sizes were offered in seventies era Varsities/Continentals that weren't available in any other earlier electroforged lightweights. Seventies era Collegiates and Suburbans were offered in a greater range of frame sizes & larger possible frame sizes for both men and women than was typically available on sixties and fifties era lightweight Schwinn models. Generally, Schwinn lightweight frames from 1966 & later are slightly superior to 1965 & earlier frames. Schwinn made really great durable frames so it mostly only matters whatever you personally prefer.

Now, I don't believe that the (684mm) 650b wheelset has any chance of fitting the existing Weinmann 810 / L.S. 2.8 sidepulls that are standard equipment on the 597mm S5/S6 twenty-six lightweight chicago schwinns. I think you'd need a longer reach caliper, but I've not tested such a potential adaptation to suggest a caliper application that would fit. My suggestion is that if you're going to go with something requiring such a long reach, you should see if a more modern-efficient, better designed sidepull caliper set up is available than something from prior to the mid-1980's when the reach gets that lengthy. That is just an opinion as I have no data saying its bad or good, its just a head-scratching concern that I'd be concerned about. Look at it this way, what good is having new fangled, spiffy lightweight wheels with great tire rubber IF the brake caliper's arms are so long and flexy that the braking is not nearly as good as say using old 590mm non schwinn steel wheels from 50 years ago and the stock weinmann sidepulls that are factory equipment on your 55 year old Schwinn. Thats my head scratching concern, and I don't know if its valid or not, but heck I'd sure want to know before going down that path for 684mm (650b) wheelset. Someone that has done the 684mm (650b) swap may be able to provide input on how to go about it.
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Alan Brase

Look Ma, No Hands!
Arnold. thanks for that. My head is spinning with all those numbers, but I have some definite conclusions. But FIRST in your last paragraph, you say 684mm (650b) and I'm guessing you mean 584mm, which would indicate a further 3mm (radius) stretch of the existing over wrought brake arms?
The very best of all this is perhaps I'd want to go the OTHER WAY? and put on 700C tires for which I already am always keeping an eye open, since I've fitted such rims to my P13 Paramount. (Yes still have some tubulars, but wasted on this elderly rider.)
I'm beginning to see it now: my patinaed red frame 1943 New World blackout single speed with some modern 700c rims and tires. Very strange experience, I predict. This frame was coaster brake model and I might just enjoy it this way. I'm guessing about a 60 gear single speed will be just fine for extended travel on the local bike trail, a converted interurban rail line that follows the river valley for over 60 miles. Railroad builders a century ago smoothed out all the hills.