SRAM have announced a major revision to their mountain bike cranks and bottom brackets, a change that's intended to increase bottom bracket longevity, as well as simplify the lineup. The revamp also allowed them to shed a significant amount of weight from the XX1 crankset, and it's now claimed to be one of the lightest options on the market.
Called DUB (Durable Unified Bottom bracket), the most significant update is the change to a 28.99mm spindle for all mountain bike cranks. Previously, SRAM had two different spindle diameters (30mm and 24mm), along with a range of bottom bracket bearing sizes. With DUB, they now offer one spindle diameter and four bottom brackets that will fit all of the existing frame standards.
Where did that 28.99mm number come from? Why not just switch everything over to 30mm spindles and call it good? According to SRAM, their product development in San Luis Obispo, California, tried multiple configurations, beginning with the existing 30mm spindle size, before settling on what they felt offered up the ideal balance of bearing size, durability, and weight. The new bottom brackets have more seals than the previous models in order to keep contaminants like water and dirt from working their way into the bearings. Along with the improved weather sealing, SRAM has gone to metal cups on their press-fit bottom brackets, rather than the plastic cups used previously.
The following video from SRAM provides a little more insight into the concept, as well as a chance to witness some interesting Movember facial hair: XX1 Gets Lighter
All of the cranksets in the lineup have been updated with the new spindle size, but it's the XC-oriented XX1 crankset that received the most significant makeover, one that allowed SRAM to shave 80 grams off the total weight compared to the previous version. Claimed weight for the cranks with a 32-tooth direct mount ring is 422 gram. The weight savings comes from the use of a lighter spindle, as well as a lighter chainring design, where any unnecessary material has been machined off. Not that the performance of professional athletes should be used to justify a purchase, but for what it's worth, Nino Schurter won the World Cup XC overall and World Champs aboard a DUB-equipped bike. Can I Still Get GXP Bottom Brackets?
The DUB cranks and bottom brackets do replace SRAM's previous models, but there's no need to rush out to start hoarding all the bottom brackets you can get your hands on – replacement parts will be available for at least the next three years, if not longer. Keep in mind that it's been eight years since SRAM last updated their bottom brackets – it's not a component that constantly changes. That being said, the update does mean that shops will need to stock bottom brackets that work for SRAM cranks with 24, 30, and
28.99mm spindles, at least for the near future. Good thing bottom brackets don't take up as much space as wheels...
Specifications and Pricing
SRAM's DUB technology will be found on everything from the highest end XX1 carbon cranks to the more affordable aluminum Truvativ Stylo cranks. DH options haven't been announced yet, but they're in the works.
• XX1 Eagle: $515 - $525 | €570 - €585 | £510 - £520
• X01 Eagle: $485 - $495 | €540 - €550 | £480 - £490
• GX Eagle: $135 - $185 | €150 - €205 | £135 - £185
• Descendant Carbon DUB: $260 | €290 | £255
• Descendant 6K DUB: $105 | €115 | £105
• Stylo Carbon: $260 - $310 | €290 - €345 | £255 - £305
• Truvativ Stylo 6k: $105 | €115 | £105
• Bottom brackets: $38 - $50 | €38 - €52 | £32 - £44