As for NEW replacement tires, check out some very recent threads over there on CABE. (GOOGLE c.a.b.e. forums )
There are discussions on the NEWEST schwinn brick tread pattern tire that one Chinese tire manufacturer has recently begun to produce.
The folks that have bought and installed them seem to be extremely happy with these tires.
The consensus from the folks is that these are the best tires that have ever been offered in terms of quality and fit.
I don't have a classic middleweight SCHWINN but my beach house neighbors ride them. This NEW Chinese tire that is made in the old SCHWINN size looks really good and it has a more bulbous, sort of balloon like appearance since the contact patch portion of the tire seems less rounded and more car-like with a perhaps more square shaped, wider appearance, though it may not actually be any wider than the sixty year old originals that they mostly copy.
The tires are relatively inexpensive but it seems that only certain merchants with a clientele of folks who ride ancient Schwinn middleweights have them in stock in the USA. The cabers over on the c.a.b.e forums will direct you to who has them in the USA or other web sources direct from China or Hong Kong.
Weight would be no issue for these super-strong ancient Schwinns.
The idiotic reply from someone that somehow that replacement Aluminum wheels would be stronger than the original chromed steel wheels is just laughable!
Yeah, the aluminum wheels would be lighter, and LIGHTER IS TYPICALLY PREFERRABLE TO THE LIGHTWEIGHT-Road Bike ENTHUSIASTS.
This ain't no dang lightweight road bike!! It is a very heavy, slow speed cruiser where ride comfort and stable manners of the traditional tourist handlebars give effortless upright riding in comfort albeit at VERY SLOW (by roadbiker standards) SPEEDS.
You've got plenty of steel spokes lacing those steel rims to the hubs................ Those are rock solid, heavy, and strong UNLESS severely rusted which as we can see, that bike looks almost brand new, though it is almost 60 years old.
The idiotic comment about the Wheel Bearings is laughable too! The person who mentioned that is absolutely clueless!
It is not a lightweight road bike! Everything on that "Middleweight" SCHWINN is heavy and overbuilt to withstand much more abuse than you could ever hope to do to it, even if you did try your best to abuse and destroy it!
SCHWINN took pride in using the best quality bearings that were the most durable and longest lasting.
UNLESS DAMAGED FROM RUST -or- UNLESS DAMAGED FROM BEING REPEATEDLY RIDDEN WITH ZERO GREASE, the bearings will likely be perfect and would only at best, need to be cleaned and re-greased.
The one thing that you gotta watch out for when Large and Tall adults decide to hit the road on ancient Schwinns and other ancient cruisers IS THE SEATPOST HEIGHT.
You gotta watch out that you do keep MORE THAN THE MINIMUM PORTION inserted in the seat post tube of the bicycle frame.
IF YOU NEED MORE, MY RECOMMENDATION WOULD BE TO PURCHASE A PHYSICALLY LONGER Chrome Plated 13/16" diameter Schwinn SEATPOST.
They are easy to find because Sting-Ray banana seat bikes had very long ones. By doing so, you'll simply have a much much longer portion down in the frame tube for the seatpost. Yeah, it will make the bike slightly heavier because of the additional weight of the more lengthy seat post..............who cares as it is a cruiser and not a road bike. My recommendation for the CHROME PLATED version is that my belief is the Chrome Plated Version is more rigid and my belief is that would be better for someone nearing the 300 pound weight range. WALD currently makes reproduction 13/16" diameter Schwinn type seat posts in various lengths. I don't think it matters in terms of what is stronger, the current production 13/16" diameter posts that WALD makes today, or the original Schwinn 13/16" diameter posts of the fifties through the seventies. Obviously you don't want to try to use the smallest frame sized bicycle with a super-jacked up, long seatpost if you're the size of an NFL lineman or an NBA center, but something like your middleweight Schwinn is more than big enough.
Yours is a great looking bicycle. Ride it proudly and have fun in the sun on it!