Any WIRE BEAD (32-630) 27 x 1 1/4 TIRE WILL BE PERFECT (630mm is the International (metric) bead seat diameter)
You've gotta use the "stiff" WIRE BEAD bike tires on the old tyme straight side rims.
YOU CANNOT INFLATE THE TIRES TO THEIR MAXIMUM INFLATION PRESSURE!!!
Well, you could if you wanna be an idiot and test for yourself, what can likely happen when you do that. (tire can come off the wheel, and you'll be in a world of hurt as you bounce off the pavement/asphalt.
This NEVER REALLY was a problem UNTIL the more modern road-bike crowd started riding clincher wheel & tire combinations that routinely recommended very high tire pressure.
The well-meaning, know-nothing idiots, among the "serious cycling crowd" would brag that they run at 105 psi or 110 psi, so you know that well the person riding the ancient Schwinn for the first time, assumes that he must inflate his tires to 90 psi. Well ol' dumb dumb Joe, sets out riding the old Schwinn at 90 psi or above, and while traveling about 17mph to 19mph making a soft right turn along a winding slight downhill, road with no automobile traffic, the dang tire comes off the rim, and Joe crashes and breaks his left clavicle, two ribs, and injures both knees, among other more minor injuries.
BACK IN THE early1970's, folks did not usually have AIR COMPRESSORS at home to INFLATE CAR TIRES or BICYCLE TIRES. YOU HAD TO GO TO THE SHELL STATION or THE AMOCO, or TEXACO STATION (service, filling stations that had pump jockeys that would pump your gas, wipe your windshield). They all had several FREE Air Hoses that either the attendant-pump jockeys would do it for you, or air hoses on the side of the building nearest the rest rooms where adults or children could inflate bicycle, mini-bike, motorcycle, car tires, etc. If you ever worked summers pumping gas during 1973 and earlier before SELF-SERVE gas stations became common, you remember the sound that typically happened on average about once every two days, and that loud BOOM would be some kid or adult not paying attention while trying to top off their bicycle tire(trying to slightly inflate it) . Having the literally blow-up (explode) is at least better when you are inflating it and not riding it. Yes, you can inflate it to a considerably high PSI and you likely won't ever have it explode, so you can imagine it takes an inattentive dummy to do that. What typically happens is either the pressure is too much and BOOM, or you then get on and ride the bike a short distance on a hot summer day, and the heat, contributes to even greater pounds per square inch Tire Air Pressure, and it goes BOOM, sounds like a shotgun blast. But for STRAIGHT SIDED Wheels, the tires themselves will begin to come off of the wheel rim, it could blow-out the tube with a BOOM as the inner tube tries to escape from the slight opening with the tire beginning to come off, but often the Tire is so far into the process of coming off, that the inner tube doesn't get pinch squeezed to where it blows before the tire comes off the rim. *ANYWAY, this is Never A Desireable Situation!!
Despite whatever the heck that the bicycle tire sidewall says that the MAXIMUM possible PSI air pressure could be, DO KEEP YOUR TIRE PRESSURE IN A REASONABLE, REALISTIC 65PSI to 75PSI ABSOLUTE MAXIMUM!!
If you do so, you will NEVER EVER EXPERIENCE ANY PROBLEMS EVER from the old tyme Straight Sided RIMS, as long as you adhere to ONLY USING replacement tires that have a WIRE BEAD, as the original equipment and the replacement tires of the 1970's era and earlier did have!
USE you Thumb to Squeeze & Press the tire, to check if it is adequately INFLATED.
If you are using a typical HAND floor type bicycle pump which has the typical Dynamite Plunger T handle, you are gonna stop trying to INFLATE the tire once it gets adequately INFLATED, and BEFORE the PSI is excessive. Even if you put a little bit too much, it is only going to be maybe 2 to 3 PSI extra which is NOT GONNA MATTER ONE BIT!
Too many people, however use the electric air compressors which run off your cars cigarette lighter plug, or 110v house current.
They often dial in the "NUMBER" that they WRONGLY think it should be, and with no effort, the air compressor machine will overly inflate your bicycle tire because you told it to do so by dialing in 90PSI or 95 PSI. You could encounter a serious situation by doing that and then riding the old straight sided wheeled bike with the WRONG, extremely high pressure setting that your buddy, Beauregard Bentley says is correct because his 2012 Bianchi runs 100psi. *PAY ATTENTION TO THE REQUIRED LOWER TIRE PRESSURE RANGE THAT IS REQUIRED FOR the old tyme Straight Sided WHEELS!!! *
---------Just because some Doofus tells you that his 2015 SPECIALIZED or 2012 BIANCHI runs 100psi and that your old bike needs about 90 psi, does not mean that that Doofus knows anything at all about ancient bicycles and the requirements of straight-sided wheels. Even if that Doofus works as a technician in one of your local bike shops. Unless, the bike shop person is at least 60 years old, he/she won't remember the era when straight sided rims were commonly used.
HAVE NO WORRIES, NEARLY ALL THE MAJOR BICYCLE TIRE MANUFACTURERS DO STILL MAKE A GOOD SELECTION OF 27" (630mm) TIRES!!!**
...Now, of course, your local bike shops will not stock any 27" (630mm) tires BECAUSE IN THE MINDS OF THE LOCAL BIKE SHOP FOLKS, ANY BICYCLE THAT IS FIVE YEARS OLD IS REALLY ANCIENT. They want to sell you a New bicycle. They will tell you (BS) that there isn't much available in 27 (630mm) and that they are now hard to obtain. They will also tell you that the industry went away from 27" (630mm) wheels , way back in 1984, being replaced by 700C (622mm).
(this last statement is true)
They will refuse to order 27" (630mm) tires for you, BECAUSE THEY WANT YOU TO UPGRADE TO A NEW BIKE, and their effort to order and stock 27"(630mm) tires does nothing to perpetuate the myth that 27"(630mm) tires are hard to obtain.
****There are a bunch of the huge national & international online web bike shops & parts vendors that have tremendous selection and competitive prices and minimal or free shipping. In addition to the major USA based online web bike shops & parts vendors, you do have major players in England, France, and Australia that are great too. One thing to be cognizant about when ordering over a certain dollar amount (probably ~ $600 or more) that you may cross a threshold that subjects you to customs fees and duties, depending upon the country in question and the total single transaction amount. I don't know the exact applicable threshhold so do not rely on my information because I do not know. I am simply saying that you should be aware and read up and investigate this prior to placing any international order of any significant size.
There are so many quality huge online web bike shops, BikeSmiths, Trailthis, Bell's Bike Shop are just a couple of well known names. (Do your own due diligence and investigate inventory stock and pricing & shipping costs among everybody out there, and not just those three that I named there.) The bay & Amazon too. Many of the major online web bike shops have an ebay store. Be sure to check all the sources because you might find that XYZ company has slightly better pricing or sales promotion on one platform or another or on their website.
.....................REMEMBER that 27"(630mm) TIRES DO HAVE MANY MANUFACTURERS PRODUCING THESE!!!
...........It is ONLY the SCHWINN (597mm) 26 x 1 3/8 (37-597) tire for COLLEGIATES/BREEZE/SPEEDSTER/RACER/CO-ED/sixties era TRAVELER/ and other Schwinn variants with the 597mm wheels from the 1940's thru 1982 Chicago close....these and ONLY THESE (597mm) for SCHWINN 26 x 1 3/8 (37-597) ----Just Have KENDA as the only current supplier---!!!
As you know the COMMON (non-Schwinn) 590mm 26 x 1 3/8 tires for OTHER MAKERS' WHEELS do have plenty of different manufacturers producing them. Again, you won't find them in any local bike shop, and you might find that the selection here in the USA among the big web sellers is fewer than the 27" (630mm) tires, but there are plenty as that 590mm size is still popular in Japan, and it has been essentially the world wide defacto "3 speed city bicycle tire" for nearly 80 years. You can get very nice MICHELINS and other European brands & Japanese brands, although you might have to source them from France , the U.K. or Japan to get certain treads and premium tire offerings, outside of the half dozen to ten different typical NON-SCHWINN OTHER MAKES' 590mm offerings from the various Chinese tire makers.
..........Save gasoline, save time, let your fingers do the walkin' and the delivery truck will deliver the needed new tires to your doorstep typically within 6 days, even within that time frame, sometimes for getting stuff from the UK, France or Japan. I don't know how that happens when my wife mails a small package to our daughter in another city in the USA, less than 500 miles away, and it takes nearly ten days, and she spent more to mail it Priority Mail. I guess the US Postal Service isn't paying their employees enough to recruit and retain them, since so many that are over 50, with decades of service, have retired. My Amazon Prime orders do always arrive on my doorstep within two days.
Full service filling stations existed long after 1973 I was a “pump jockey” in ‘83,
I routinely receive packages via usps from all over the country in good condition in much less than ten days,
I’ve receive international packages in a timely manor - ten days average
Suburbans are good bikes, more practical than the Continentals and Varsities. And I second everything that @Arnold Ziffel said. I also have blown a modern 27" tire off the rim by running the pressure given on the sidewalls (luckily without crashing) but they'll run all day at 70 psi.
The S-6 rim tires on most if not all of the models were not high pressure tires. Smooth wall rims and a cheap Taiwan high pressure tire at 90 psi wouldn't be prudent as a previous US Pres would say. Schwinn's Breeze Sports Touring tires that were used on just about every model had a 65 psi max pressure and the "puff" gumwall had a 75 psi max.