Readers’ Rides: Mark’s Vintage Centurion Lemans 650B Conversion


Readers’ Rides: Mark’s Vintage Centurion Lemans 650B Conversion

650b Conversions are a great way to swap out those skinny race tires on bigger 700c wheels for some extra supple cushioning. They are very popular in the randonneuring crowd and today, we’re featuring Mark‘s exceptional example, so let’s get to it!

This bike is a 650B conversion of a vintage Centurion Lemans bike I originally bought used for $75. All of the stock components were not great. The frame is made with Champion #5 so you know it’s got to be durable (Champion’s thickest tubing). I had built up a 650B conversion before with a vintage Univega with 650Bx38s so I knew it might work with wider tires.

Then I stumbled across a Bridgestone 650B fork. I cut and filed down the cantilever studs on the fork and repainted the frame and fork in burgundy. I also recovered a vintage Avocet Racing 1 saddle in matching burgundy and retaped the handlebars in Newbaums’ cotton tape with shellac.

I’ve ridden a few 200k brevet rides with the San Francisco Randonneurs club previously on a SOMA Grand Randonneur with Grand Bois 650Bx42 tires and I really like these tires. While not super fast, they take rough terrain well and avoid flats.

Some local big tech companies that had fleet 3-speed bikes using 650B wheels were frequently dumped in my neighborhood in East Palo Alto. The front dynamo wheel and lighting were repurposed from a couple of these bikes and I built-up the rear wheel with a vintage 6 speed hub and a Shimano 6-speed freewheel.

The bike rides well as a daily and is very fun and nimble with the Grand Bois Hetre 42mm wide tires. I’ve been tempted to add a front or rear rack, but it’s fun as a roadster.

Parts Spec:

  • Handlebars: SR Randonneur with Newbaum’s cotton tape with shellac
  • Stem: Nitto Technomic
  • Bar-end mirror: Cat eye
  • Brake levers: Dia-compe
  • Brake calipers: Tektro 559 long reach
  • Crankset: Sugino RT 46/34 chainrings
  • BB: Shimano sealed cartridge
  • Rear Derailleur: Shimano STX
  • Front Derailleur: SunTour ARX
  • Freewheel: Shimano 13-28
  • Saddle: Avocet Racing I recovered in Burgundy leather
  • Downtube Shifters: vintage Dura Ace clamp-on
  • Pedals: MKS Track
  • Toe Clips: MKS steel
  • Toe straps: Christophe
  • Bell: Crane, alloy
  • 650B front dyanamo hub Shimano Nexus



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