• KulAdventures

Rocky Mountain Flatline Pro Bottom Bracket and Crankset Change

Due to some play in the pedals of my Rocky Mountain Flatline Pro I decided to replace my crankset and bottom bracket (BB) in preparation for a trip out to Whistler for some DH riding.


Bike beforehand with the MRP Camber Crankset

My old set was a MRP Camber crankset which I am told is no longer made so based on some recommendations I was going to go with a Race Face Chester Crankset which is geared towards DH riding and has a 83mm BB.


After getting the new crankset and BB I got to removing the old crankset. Here are the tools I used:


-BB Wrench

-6mm/8mm/10mm Allen Sockets and 3/8" socket wrench

-Pedal Tool

-Grease


First remove the pedals with the pedal tool.. Once removed use the 10mm to remove the crankset cover bolt:

Then remove the 8mm crankset bolt:

Once the bolts are removed then you need to remove the non-drive side crank arm (on the MRP Camper the drive side has the shaft, however on the race face chester the non-drive side has the shaft).

Once the none-drive side crank is removed you can use a rubber mallet to break free the center shaft and the drive side and shaft should pull out pretty easily.

Once removed I transferred my chain ring and chain guard over to the Race Face Chester crank.


Once the chain ring and chain guard are attached I went back to switch over the BB. Using the special removal tool remove the non-drive side first, keeping in mind that is normal threading (clockwise to tighten).

Next remove the drive side BB in the same manor, keeping in mind that this side is reverse threaded (counter-clockwise to tighten). Once removed set that BB aside and clean up the threads and mounting area.

If you have a chain guard as I do you will have to play with the bushings on mounting the BB (took me a few times), but these instructions are covered with the crankset. Mine came with three 2.5mm spacers, which ended up 2 on the non-drive side and one on the drive side. Also, if you have a caliper, measure the BB distance to make sure it is within specs (specs will be in manual of crankset).


Make sure to use a lot of the grease when installing. You can always wipe away excess, but it will help with any repairs later if its not seized up.

New BB with one 2.5mm spacer on the drive side

Tighten down the drive side and then install and tighten the non-drive side keeping in mine the threading (normal on non-drive side, reversed on drive side).

Install the crankset and make sure chain lines up with the chain guard, if not readjust the spacers as needed. Once its right, tighten down the crankset with the 8mm allen socket (torque value varies, refer to manual).

Non-drive side with two 2.5mm spacers

Once its all tightened up make sure everything spins smoothly. There will be a little bit of friction for a while, but it should spin pretty freely. Once everything seems tight and no play install the pedals.



TIP ON CRANKSET REMOVAL:


So since I had to pull my crankset out a few times to adjust the spacers and I do not have a special tool to do so, nor did I want to hit it with a hammer I decided to try something, which actually worked really well. All this is done with the 8mm crankset bolt removed.


I used the BB tool and since mine had an open end it could fit onto the non-drive side BB with the crank arm installed. From there you could loosen the BB (with the creank arm still there) which will separate the non-drive side from the drive side and separate the crankset (similar to the special tools they make). The only concern people may have is that this is putting pressure on the bearing/seals to separate both, however there is already pressure on those when you crank the 8mm socket bolt down to tighten the crankset, so I cant image it would be an issue, but use at your own risk. The best bet is to get a tool, if you can.


I used this method about 2-3 times when installing my BB and Crankset while adjusting the spacers with no issues. Worked really well.




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