Mountain Bike Reviews Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hi,

I am installing a MT-8100 Crankset on a Santa Cruz hightower with 73mm threaded BB. This should mean that the 2.5mm spacer should go on the driveside, right? Installing like this gives me an messuared chainline on approx 54,5mm, without ut approx 52mm. Also the spacer makes the chain grind the chain guide (which it did not do before).

I moved the spacer to the none driveside (where it should be, right?) and have no chain rub on the guide and the chainline looks good. Can this cause any issues?
 

·
damned rocks...
Joined
·
2,553 Posts
Are you sure you have the FC-M8100 and not the FC-M8120, the M8120 has a chainline of 55mm.
With a 73mm BB shell one BB spacer should go on the DS, moving it to the NDS simply will offset all the crank assembly to the left by 2.5mm, I doubt this will impact you negatively, but the human body can surprise you sometimes. You can try to install the BB without any spacer, but depending on the cranks you have, you may not have enough spline depth on the spindle to assemble it that way and have enough room to correctly preload the cranks and the BB.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Awesome! Cheers.
You are right. It acutally is a M8120. The problem with the chain guide still occurs though. This make me believe the Spacer already was on the NDS already (cant remember)..
 

·
Registered
Joined
·
1,054 Posts
Boost or non boost frame? There are two 8100 cranksets. The FC-8120-1 and the FC-8120-B2. The 8120-1 has a 55mm chainline the 8120-B2 has a 51.8 chainline. So if your frame is boost you would need the 8120-B2. Chainline for a boost frame should be 51-53mm.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #5
Boost. Alright.. So as I run now with a approx 52mm chainline without spacer should be ok?


How do you like your Rascal btw? Seem like an awesome bike!
 

·
Registered
Joined
·
1,054 Posts
At 52mm you should be good.
I love it thanks for asking. I had a V1 Following before the Rascal. The Rascal is a better bike for where I ride. Central Texas rocky limestone with tons of ledges.
The Rascal doesn't hang up on the ledges like the Following did.
The Rascal is 2# heavier than my Following was but pedals like it's lighter. Fantastic bike so far.
 

·
Registered
Joined
·
75 Posts
I have a V1 Hightower with the M8000 cranks. When I ran the spacer on the drive-side it didn't work very well. Moved to the non-drive side (which Shimano states is the correct position) and it was much better. I am also running the OneUp chainring on it. IMO, Shimano's chain lines are a bit aggressive.

It shifts well in this setup, but still drops the chain on back pedal. I can imagine it would be much worse with the spacer on the drive side, pushing the chainline further outboard.
 

·
Registered
Joined
·
1,054 Posts
When I first built my bike I was using the M8000 that came out of the previous bike. New bike was boost previous bike not. So I needed to space the BB making the Q factor asymmetrical. Bought an M8000-B and works like a charm.
 
1 - 8 of 8 Posts
Top