Today Shimano announces new crankset and derailleur options to suit a wider range of rider preferences and mountain bike setups.
There are two new cranks, including an XTR option, which feature 55mm chain lines. The additional chainline spacing options aims to offer more clearance, should you need it. Currently, Shimano offers 51mm and 56.5mm options, both for use in conjunction with Boost rear axle spacing. The issue that Shimano is trying to remedy is not so much in terms of drivetrain performance but more so in regards to the current trend for thicker chainstays, and how sometimes chainring clearance can be an issue.
The FC-512-1 will be available in Deore or non-series models but they're essentially the same crank.
Shimano offers two new cranks, the FC-M9125-1 and the FC-512-1, which will probably be better recognised by their respective series names as XTR and Deore.
Shimano also announces a new, shorter Deore XT rear derailleur. This new model will offer greater ground clearance and is designed specifically with a 10-45T cassette in mind, which Shimano already manufacture. When designing a rear derailleur, the length of the cage is hugely important. The bigger the difference between the smallest and largest cog, which can be as large as 41T in Shimano's range, means the cage has to be longer to provide adequate tension to the chain.
There is also the benefit of being able to run less b-tension. This is because of the comparatively smaller lowest gear. Brands go some way to tailor the path of the derailleur to ensure that the top jockey wheel is an appropriate distance from the teeth of the cassette, irrespective of the gear that's selected. A 10-45T cassette, thanks to a smaller differential between the smallest and largest cogs, should allow for the b-tension to be lower and achieve a crisper shift in the middle and outer ranges of the cassette. A shorter cage can also mean less twisting forces are being put through the derailleur, which in turn can also aid shifting performance.