Has your frame gotten a Boost? Boost is essentially a widening of the front and rear axle configuration to further increase overall frame, fork and axle junction stiffness. Most Boost forks have expanded from 100 to 110mm, and the rear drop-outs to 148mm. Let that sink in for a minute. Wasn't it just yesterday the most common rear width was still 135mm? Well, a number of frame companies are willing to bet that wider is better, and components need to be in step, because big players are involved. With the release of new DynaSys11 systems from Shimano, the M8000-B1 XT Crank Arms are Boost ready with a 3mm wider chainline and overall stance. Just like the standard version in every other way, the Boost version can be set-up to run a 30, 32, or 34T single chainring with the DynaSys11 groupsets. Efficient, simplified shifting is the calling card for 1x11 systems, and Shimano delivers the optimal mix of durability and light weight matched with consistent shifting performance and enhanced chain management with XT. The excellence of XTR is carried down through the M8000 line-up, with fewer exotic materials and concessions to the weight-focused crowd.

The proprietary 96mm bolt circle diameter is ready for your chainring choice and provides the right balance of stiffness and strength. The new, compatible 3D composite chainrings feature stainless-steel teeth that have been engineered tooth-to-tooth for the chainload of each ring option, maximizing chain retention regardless of cassette cog position This Dynamic Chain Engagement system increases chain retention force by 150%, drastically decreasing the risk of chain drop. The lightweight Hollowtech II crank arms are exceptionally stiff and strong, and resilient to trail abuse. The M8000 crank arms can be used with either 68 or 73mm bottom brackets. Due to the variety of frame BB standards today, the crank arms do not come with one. Shimano has updated the BB with the MT800 threaded version, with smaller, more efficient bearings, better protecting seals and reduced weight with the new smaller, threaded cup size. The Press-Fit version has also seen the bearing/seal upgrades.

The 1x11 system pairs the chainring of your choice with either an 11-40, or 11-42 cassette, giving you terrific range. The XT M8000-B1 Crank Arms are sold as a modular option and the chainring mounts from behind the spider. You buy the crank arms, chainring and BB separately to match your frame requirements and gearing preference. We expect this new XT group to once again be our best selling Shimano mountain equipment. If you ride/want a Boost frame, we have you covered. Return to Top