Guide to 650B Conversions on Soma Frames

Jason's Double Cross Disc 650b Conversion

[Parts of this article as been updated to reflect model changes] We get a lot of questions whether our 700c (or 26") wheel frames can be converted to 650b/27.5" tire size and what would the maximum tire width they can use, if it is possible. So we thought it would be nice to make a post covering this over our current line.


Model: Double Cross Disc    Convertible?: Yes
The Double Cross Disc (pre-2020) makes a great 650b conversion project. It's bottom bracket height is about the sames as our Grand Randonneur 650b frame, which means you can swap in 650b tires as narrow as 33mm and not worry about pedal strike while road riding. For light off-roading we'd recommend using tires 38mm to 47mm. You won't be gaining much in tire clearance as the Double Cross already fits 700 x 42c; maybe 3 - 5mm more. What you will gain is the ability to run fenders with 650b x 42 tires and more stable handling because of the lower bottom bracket. But a lower bottom bracket also means you need to be more careful about pedal strike on dirt trails.
Maximum tire fit with fenders: 650b x 45mm  
The 2020 Double Cross has a 4mm lower BB drop, so we recommend 650b tire at least 42mm wide. (updated 1/22)

Model: ES, Stanyan, 
Convertible?: Yes
The ES has been a popular bike for 650b road conversions. You would need to switch the brakes from 57mm reach brake to 73mm reach model such as the Tektro R-559. (Some rims may require 76mm reach brakes)
Bottom bracket height will be lower than with the average 700 x 23c tire no matter 650b road tire you choose, so avoid cornering like your doing a crit. We recommend 38mm to 42mm wide tires. Max tire fit with fenders: 650b x 38mm

Model: Wolverine 
Convertible?: Somewhat
Nearly any 700c disc brake bike can be used for a 650b conversion project. The Wolverine is no exception; however in our opinion there is very few compelling reasons to do.
It already fits up to 29 x 1.95" tires. Going 650b will not allow wider tires. Its bottom bracket height is more like a road bike than a cyclo-cross bike, so it's on-road handing is pretty good. Using a 650b x 38/42 will lower the bottom bracket height further where you may gain advantage in stability some desire for on-road loaded touring, but of course you'll also be reducing cornering clearance and off-road capability. Using 650b x 2.0" you get the about the same BB height as 700x32c CX knobbies ( just enough for some off-road fun). We recommend nothing smaller than 650b x 38mm. Best reason to convert is to be able to fit 2.0" tires with fenders. (updated 2/18)

Buena Vista Disc with 650b x 50 Cazadero tires

Model: Fog Cutter, Buena Vista (Disc)
Convertible?: Yes
Nearly any 700c disc brake bike can be used for a 650b conversion project. Using a 650b x 38/42 will lower the bottom bracket height slightly where you may gain advantage in stability that some desire for on-road loaded touring, but of course you'll also be reducing cornering clearance. We recommend nothing smaller than 650b x 38mm (updated 1/22)


Model: Buena Vista (Rim Brake)
Convertible?: Yes
42cm size (designed for 26" wheels): It is doable, but there isn't a compelling reason to do besides trying a larger, narrower, higher pressure tire. You would need to swap to 57mm reach road brakes, if the 73mm reach brakes you already have don't work. Bottom bracket will be raised, but it is a non issue in this case. There may be additional toe overlap with the front wheel. Max. tire size: 650b x  33  (fenders will not fit. This is a limitation of the brakes used; not the frame.)

The larger Buena Vista sizes are designed for 700c wheels: You would need to swap in 73mm reach brake like the Tektro R-559 or Dia-Compe 750's. The frame has a low bottom bracket height to begin width, so stick with 42mm wide tires to avoid pedal strike or just learn to check your pedal position when cornering.

Model: Saga Disc  
Convertible?: Somewhat
We don't recommend converting the 700c models, because it will lower the bottom bracket height too much to ride safely.
For the 26" wheel model, it is quite doable without much consequence. A 26" x 1.95 tire has almost the same diameter as a 650b x 42b. However running a 650b x 1.95" knobby will definitely take away the possibility of using fenders.

Model: Juice    
Convertible?: Somewhat
You can swap in 650b wheels on any disc brake 29er, but there isn't a compelling reason, except maybe you want a lower bottom bracket for road/commuter use. But your center of gravity will still not be as road-optimal as on our our Grand Randonneur frame or CX frames. Pre-2018 Juice does not have clearance for a 27.5+ (i.e. 27.5 x 3.0" tires) conversion. 2018 and later Juices will fit 27.5 x 2.8" tires. (updated 1/22)  

Model: Rush  
Convertible?: No
There isn't enough clearance for 38mm wide tires. You might fit 33mm tires, but in our opinion there isn't compelling reason to convert it. Bottom bracket won't be high enough to run this as a fixed gear after conversion.

Model: Pescadero    
Convertible?: No
The Pescadero already uses long reach road brakes. A 650b tire would require even longer reach rim brakes which don't exist. (updated 2/18)

Model: Soma Saga (Canti)    
Convertible?: No
Most cantilever brakes don't offer enough adjustibility to fit 650b rims. Some have had luck using brakes with long slots. We do not have an official brake recommendation. (updated: 6/16)

Model: Smoothie   
Convertible?: Somewhat
According to one Smoothie owner, there is just enough clearance for 38mm wide tires with 23mm wide rims. We cannot confirm this is so on all sizes of Smoothies though. (updated: 6/16)

Model: Double Cross (Canti)    
Convertible?: No
Most cantilever brakes don't offer enough adjustibility to fit 650b rims. Some have had luck using brakes with long slots. We do not have a brake recommendation. (updated: 6/16)