Let's talk Schwinn steel tubular welded rims

[WillWork4Parts]

Just wanted to reiterate, I rode one of my lightweights the other day with early S6 rims, and I do not miss rim brakes with hardened rubber pads catching on weld seams! Lol

Wanted to share this strange tidbit here too. Diagonal knurling on the inside of this S7 rim from a 61 bike. Regular knurling outside.

 

[SirMike1983]

The lightweight S6 rims even have different knurling. The knurling on a 1950s S6 will be different from a 1970s S6 which are both different from the 1940s stainless S6. I guess different rolling machines were used at different times and on different S6 rims.

I will say the S6 is a more robust rim than the single-layer Lobdell type rims from before WWII. I just built a pre-war set of Lobdells up into wheels this weekend after working with S6s for previous several wheelbuilds. Those Lobdells are pretty slinky compared to the post-war S6. The Lobdells can be pulled true with the spokes more easily, but I suppose that also means the bumps will also throw them out of true more easily.

 

[Schwinn Sales West]

The lightweight S6 rims even have different knurling. The knurling on a 1950s S6 will be different from a 1970s S6 which are both different from the 1940s stainless S6. I guess different rolling machines were used at different times and on different S6 rims.

I will say the S6 is a more robust rim than the single-layer Lobdell type rims from before WWII. I just built a pre-war set of Lobdells up into wheels this weekend after working with S6s for previous several wheelbuilds. Those Lobdells are pretty slinky compared to the post-war S6. The Lobdells can be pulled true with the spokes more easily, but I suppose that also means the bumps will also throw them out of true more easily.

The knurling is not left from the tube rolling machines.

It's the electric welding machine step that leaves the knurling. Easy way to view it, is one knurling wheel side was positive charged, and the other knurling wheel side was negative charged. It "arc welded" the inside edges of the rim to the center/outside of the rim. It was double wall in the high stress spoke hole area.

It was a great concept, but the quality of the butt seam finish "left something to be desired" in many cases.

John

 

[cyclingday]

 

[GTs58]

Just wanted to reiterate, I rode one of my lightweights the other day with early S6 rims, and I do not miss rim brakes with hardened rubber pads catching on weld seams! Lol

Wanted to share this strange tidbit here too. Diagonal knurling on the inside of this S7 rim from a 61 bike. Regular knurling outside.

View attachment 1782982

View attachment 1782981

View attachment 1782979

May 61 stamped axle and the Approved Schwinn (German?) hub. Would you happen to have the serial number off the frame this came off of? I have a few 1961 Corvette 5 speeds and none of them have the Approved front hub. I'd really like to know when Schwinn stopped making this hub.

 

[WillWork4Parts]

I don't have the bike, it was a friend's wheel set that was removed when he got them. He bought them from a guy that parts a lot of stuff out. Doubtful that he would remember what frame it came from.

 

[Bryan Akens]

I actually have seen one Araya 20 inch rim that was an S7......very rare I would say....Thanks for an intersting article.....Love those S2s!!!

 

[coasterbrakejunkie1969]

I actually have seen one Araya 20 inch rim that was an S7......very rare I would say....Thanks for an intersting article.....Love those S2s!!!

Yes I have a set

 

[Schwinn Sales West]

If you look closely at the two photos @cyclingday posted above, you will see a notation on the top photo showing the location that they placed a special rim measuring tape during production. In the second photo it shows this location marked "1B", it's just on the shoulder of the inside of the rim. This is how they determined the actual tire diameter, but they measured it in rim circumference.

The flat metal was rolled (or formed) into a tubular rim, but it was one long straight rim. At the end of the tube rolling machine, the rim material went into another machine that rolled the straight section into a round rim. During the machine set up, and ongoing quality control during the day, they "hand measured" the rim circumference and set the machine to cut off the rim at precisely at the correct size.

It was this measuring tape that determined that they manufactured the correct rim size and if a tire would fit properly, or fall off a rim. The rim diameter, or Schwinn used the circumference method was the most important issue, the "hook side" or "straight side" is not a critical issue for the tire/rim fit. Anybody that has ever tried to put a 1.75 tire, on a 1 3/4 rim will confirm it's the difference in circumference. The two numbers might be mathematically interchangeable, but the tires will not interchange.

More Schwinn Trivia

John