I’m a custom bicycle frame builder and teacher in Michigan that has been interested in not only your quest to find a good Mixte type of frame for yourself but also the educational process you go through as your knowledge increases.

Back in the classic and vintage era most bicycle frames were made out of steel. In order to meet various price points the quality of the steel in frames varied a lot. Most posters on C&V already know this but I’ll tell you anyway. Usually bike store frames had stickers on the seat tube to let buyers know what the frames were made out of. The cheapest bicycle frames were made out of low quality steel (with low carbon content) that had to have increased wall thickness to stand up to everyday use and abuse. These were the types of bicycles sold in department or discount stores. Somewhere I read that the average expected distance ridden on one of these bicycles during its whole life was around 75 miles. Just above them are frames made out of “Hi-ten” (what was said on the sticker) which means high tensile steel (with more carbon added). This is usually the lowest quality of steel used in bicycles sold in bike stores. Because it is a stronger steel, the tubing did not need to be as thick. It isn’t just a weight issue but is also reflected in the ride quality. The next step up is “chrome/moly”. This is short for steel that contains chromium and molybdenum alloys. Some tubing manufacturers used other alloys but that isn’t important to understanding basic tube qualities. Its greater strength makes it stronger and therefore less of it is needed. And finally, at the top end are “double butted” tubes. This means that during its manufacturer, the middle part of the tube is made thinner than the ends although the outside diameter remains the same. Reynolds 531 and Columbus SL are examples of double butted tubing. This is done for several reasons but the reason you might care the most is that frames made out of double butted tubing have a better ride quality. Your goal is to find a mixte made out of double butted tubing if possible. Most likely because they are at the top of the food chain they were also made with greater care and finer details.

There are variations on the steel used in bicycle frames to save weight.For example, some frames were made out of Reynolds 531 straight gauge tubing.The decals usually but not always indicated if the tubing was straight or double butted.Sometimes better tubing was used in the main front triangle and cheaper steel in the fork and back end.In order for a company to be price competitive they mixed higher and lower quality tubes to keep the price as low as possible because that is what the buyer was basing their decision on more than what the frame was made out of that they didn’t understand anyway.