Soma Riff Frame

Soma Riff Frame


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Installments available between $20 - $1,500 with Genoapay logo What's this?

The Riff is our hardtail frame for 27.5″/650b wheels. (It replaces the B-Side model) While the B-Side showed our tendency of not following the latest trends, the Riff is pretty modern in geometry and features. Tough IRD Broski Sliding Dropouts allow you to go single-speed or geared or even run hub gears. Also new is internal seat tube dropper post routing. A modified chainstay allows fitting even some double cranks with “plus size” 2.8″ wide tires without needing to invest in Boost parts.

Additionally the Riff is available in a belt-drive ready version.

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  • Tange Prestige heat-treated butted CrMo steel; butted CrMo rear end
  • Geometry is optimized for 100mm travel 27.5″ forks and will handle 120mm forks great too
  • Disc brakes only (ISO tabs)
  • Standard or Belt-Drive compatible versions available (split for installing belt is on the seatstay.)
  • IRD Broski Sliding Dropouts allows geared and single-speed builds with easy wheel removal
  • In 2021 these come ready for 142 x 12mm Thru-Axle hubs. (Can be converted to 135mm spacing for traditional QR hubs with IRD aftermarket inserts)
  • S-bend seatstays and chainstays
  • Rear rack and fender eyelets
  • CNC-machined 44mm headtube: Will take 1-1/8″ fork steerers with a ZeroStack 44 headset or tapered fork steerers with a ZS44 upper assembly and external cup (EC44) lower assembly
  • 31.6mm post size/34.9mm frt. der. size/34.9mm seat collar, 73mm bottom bracket (English threads); 400mm+ post recommended
  • Recommended tire size: 27.5 x 1.95″ – 2.8”
  • Color: Pelham Blue
  • Wt: 5.35 lbs. (Belt-Drive compatible versions weigh slightly more)
  • Sizes: XS(38cm), SM(41cm), MD(44cm), LG(47cm)


Build your custom Riff with ABC. We love to get into the details to build the bike of your dreams. Whether you’ve just got a trip in mind, a complete build idea, or a picture of something you like. Give us a call or email [email protected] with your custom bike build inquiries.

Gates Carbon Belt Drive Suggestions

Rohloff Hub:
46t front x20t rear x 113 belt – 437.7mm chainstay setting

Single Speed:
46t front x28t rear x118 belt – 444.5mm chainstay setting

Component Fit Information:

Bottom bracket shell: 73mm wide with English threading
Headset type: Will take forks with 1-1/8″ steerers with a ZeroStack 44 headset or tapered steerers with a ZS44 upper assembly and external cup (EC44) lower assembly
Seatpost size: 31.6mm OD x 400+mm length Includes internal routing port at seat tube for dropper seatposts
Seat collar size: 34.9mm
Front derailleur clamp diameter: 34.9mm
Front derailleur type: Low clamp, top-pull
Hub fit: Standard dropouts fit 135mm QR hubs. (IRD Broski aftermarket inserts to convert to 142x12mm thru-axle)
Chainstay adjustment range: 427 – 445mm (ideal to keep dropout in the center or front of the slot)

Who would you recommend trying 650b/27.5″ mountain bikes? [The 650b wheel size (27.5″) is an established tire size, but is relatively new to the MTB market. It is sits almost in the middle between the traditional 26″ and the newer 29″ tires.]

This is a tough thing to give an explanation to especially to someone who has only ridden 26″ wheeled mountain bikes. To these folks there isn’t anything deficient with 26″ wheels at all. That’s how the collective mountain bike community felt before the 29er came along and we had something different to compare it to.

And for the last few years, we’ve had folks that swear that the 29″ wheel is the best MTB invention since the suspension. And others who’ve tried it and hate it. And we have some that own both types of bikes. It is from this paradigm, we make the statement that one tire size does not ideally suit every rider.

We feel the 650b to be the “happy medium” between 26″ and 29″.
Who do we think should try 650b?
1) Those who feel 29ers were a little to unwieldy and slow to accelerate.
2) Those who liked the 29ers rolling advantage, but didn’t want to give up the steering quickness of a 26″ bike.
3) Those who want big wheel benefits, but find most 29er frames are a little too big for them.
4) Those who find 29er wheels a little heavy. 650b will be noticeably lighter.
5) At one time we would’ve recommended that if you are 6′ 2″ and over you are better off with a 29er, but we know of a couple of folks who are over 6′ 2″ and prefer 650b over 29ers (at least with full suspension bikes). And we also know women under 5′ 5″ who love their 29ers. Really it boils down to ride style and personal preference.

Practical, durable, comfortable, affordable, customised bicycles for the everyday cyclist… these are the primary forces shaping Soma’s ideology.

Additional information



Action Bicycle Club