Mechanical Standards

tyler_derden said:

Is there a web resource or some other source I haven't been able to locate that lists standard dimensions of bicycle parts- things like front and rear wheel fork spacing (or wheel hub width), seat tube diameter, etc.?

Thanks,

TD

There are no standards. Bikes have been built for years, with some countries even having their own standards. Some standardization came about with ISO,but it's not universal. In many cases the current standard like rear dropout spacing depends on the application.

There are some parts that have a standard dimension, and there are some that don't. It would make bicycle mechanics' lives a little easier if there were standards for a number of parts on a bicycle.

For instance, you mention seat tubes, they come in a variety of sizes (I'm going to assume you mean diameters). Not a huge issue compared to some, but something to work through.

Almost all front wheels have an "over locknut" dimension of 100mm. And most single (non tandem) road bikes built after about 1990 have a rear "over locknut" dimension of 130mm. Before that they vary from 120mm to 130mm for multispeed hubs. Mountain bikes after about 1993 have an "over locknut" dimension of 135mm. What is the "over locknut dimension you ask? That's the distance between the locknuts on the axle that rides against the frame dropout to hold the wheel into the frame. It's an important dimension for wheelbuilders.

Thread pitches and angles have settled into a few (mostly two) common dimensions, but you still have to be careful, especially when working on a classic frame, like something from France, Belgium and more commonly Italy. You also have to be careful of what direction the threads are cut; clockwise - "righty tighty" or counter clockwise - "lefty tighty".

My suggestion for you is to invest in a few measuring tools. First, a tape measure with both SAE (inches & feet) and metric (MM & CM). Next get a good metric vernier caliper with a depth gauge and learn how to use it. And (I won't say last) a set of metric thread gauges, again, learn how to use them. Take good care of them because little is truly static in the modern world of bicycles (thank you (not really) Shimano).

Bob