I’m looking to change my Deore cranks and chainring but not sure what SLX cranks will fit.
The BB is BB-MT501 with M6120, 30T ring, 55 mm chainline cranks.
So think I need the following Shimano FC-M7120 SLX Crankset 55mm Chainline 170mm. Will these fit the BB?
https://www.biketart.com/products/shimano-slx-fc-m7120-12-speed-mtb-crankset?variant=40809099690163
Can’t find them with a chain ring so does this need to be a particular fit/offset?
Or is it just as simple as buying one of these?
https://www.biketart.com/products/shimano-slx-sm-crm75-single-chainring-m7100-m7130-12-speed
Thank you.
Shimano build the chainline into the crank axle not the chainring (as SRAM do) so the chainring will be straightforward.
Personally I find a 52mm chainline (M7100) works much better than a 55mm chainline (M7120) on a 148mm boost frame, especially in the lowest gears.
The only reason I can see for going 55mm chainline is if you have clearance issues with frame or tyre.
These chainrings are really nice: https://uniteco.bike/shop/drivetrain/chainrings/shimano-chainring-direct-mount/
If you want M7120 cranks in 165mm length without a chainring I have a set to sell that have seen around 50 miles use, no scuffs. DM if interested.
Deore 6120 to SLX 7120 will be a straightforward swap, both have 24mm axles so your BB will remain the same.
As above SLX M7100 will give a better chainline than M7120, if it clears your frame go with that. Both will fit your BB
Merlin have SLX M7100 with 32T chainring for £67.50 at the moment
https://www.merlincycles.com/shimano-slx-m7100-single-12-speed-chainset-with-chainring-180723.html
Thanks all. Does the ‘FC’ on the FC-M7120 from biketart mean anything fitment wise?
As for the chain line fitment. What’s the best way to check for clearance? It’s all alien to me! I can take photos if that helps to give an idea of clearance.
FC means "front Chainset" or similar from Shimano, they will all be FC M7100 to indicate it's a crankset and the series / model.
This is current clearance with 55mm. On the largest cog.
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Hard to tell from the pictures but with a M7100 crankset you will 3mm closer to the frame on either side, so measure the chainring to frame distance. With M7100 you will need to remove a 3mm spacer on each side. I can't tell form the pictures but you probably have to remove the BB cups to remove the spacers.
When I went from 7100 to 7120 the 3mm spacers are on the crank axle, not on the bottom bracket, one 3mm spacer each side of the crank. No need to remove BB cups. BB spacers remain the same for your frame BB shell width.
Yes - there’s no need to change BB spacers. The 52mm chainline option looks like it’ll clear as long as you’re not planning to increase chainring size significantly.
