Bolt Circle Diameter

My take? The best BCD is 50.4/80BCD like the vintage TA Cyclotourist, and Stronglight 49D. Those are jim dandy, but opt for one with a standard JIS extractor like the offerings from Velo Orange, SunXCD or vintage Sugino (PX and Super Maxy) and others. I welcome more narrow-wide chainring offerings (at the time of writing, the only know such ring is a TA 38T, available from Cyclodonia in France or I’s in Japan).

Why 50.4/80BCD? This pair allows a wide range of tooth counts, including some very small and large rings, but at prices less dear than the (very, very nice) Rene Herse 3-bolt and the White Industries VBC cranks. And I think they’re beautiful.

The State of 650B Rim Brake Compatible Rims

What are the rim brake compatible (non-disc) 650B rims these days? Below is a table of options. Most are made by Velocity (including the below offerings from Pacenti and Soma). I hope this is useful for all of the dozens (literally dozens) of readers!

Measurements above are given in millimeters and grams. Pricing may vary, prices given above are base prices from the Interwebs. Some of the polished Velocity rims are $30 more. Specs subject to change. I try to get this right, but am held harmless in the event of error. Should an error occur, please notify me.

If I’ve missed anything or if you can fill in the gaps above, please leave a comment and I’ll incorporate it into the table.

650B Conversion Tire Clearance Repository

What bike(s) have you converted to 650B? What tires fit?

Have you converted a bike? Comment below with the following and I will update the table:

  1. Make
  2. Model
  3. Year (or era)/serial number/distinguishing feature(s)/color
  4. Frame size
  5. Largest 650B tire that fit
  6. Any 650B tire(s) that you tried that didn’t fit
  7. Brakes used in conversion
  8. Other comments

Tire Size and Air Volume

Air volume was calculated in MS Excel with the following formula (this example is for 650B/584ISO with 38mm tires):


This will give results in cubic millimeters. Volumes above have been convert to liters (dividing by 1 million), rounded to the nearest tenth.

Some variances may be introduced from rounding, unit conversions, and other factors.

This is all white coat, clean room, armchair nerdery stuff only. Real life measurements of tires can vary based on many factors including miles, rims, tubes, production batch, etc.

Tire weights are manufacturer published weights, except for Schwalbe which were 100% fabricated for my own amusement.