Bottom Bracket Installation

Step 1:  Components & Compatability

This guide is for installing a Monocrome Bottom Bracket (MCEBB001) into a Shimano HT2 mountainbike crankset.  These instructions also apply to Shimano HT2 and Raceface X-type bottom brackets used in mountainbikes.

Spacer Diagram for MTB External Bottom Brackets

Step 2:  Bottom Bracket Spacers

Bottom brackets (BB) come with three spacers, each 2.5 mm wide.  Depending on your BB width and use of a BB mounted derailleur or chain-guide you may need 3, 2, 1 or no spacers.  Consult the diagram at right.

Step 3:  Preparation

Frame threads need to be clean and free of burrs.  Likewise the end faces of the BB shell need to be clean and square.  If in doubt have the BB threads chased and the ends of the shell faced.  For steel frames a light coat of grease will prevent corrosion of the threads.  For aluminium frames the anodizing and thread-locker on the Monocrome BB cups provides adequate lubrication if the threads are clean.  If in doubt a light grease is better than none.  For titanium frames ti-prep or other anti-seize is required to prevent the aluminium cups cold welding themselves to the titanium.

Step 4:  Bottom Bracket Installaion

Start on the drive side, choose the appropriate number of spacers and thread the drive-side bottom bracket cup in anticlockwise by hand.  Snug it with a good fitting tool to 40-50 Nm of torque.  Install the centre sleeve and the non-drive cup, again with the appropriate number of spacers.  The non-drive cup threads in clockwise and again is torqued to 40-50 Nm.  If the bottom bracket comes with Big Steel bearings it will have separate bearing gaskets.  Install the gaskets with the writing side outwards.  They will need the crank to hold them in place.

Step 5:  Crank Installation

Separate the cranks by loosening off the pinch bolts in the non-drive arm, flicking up the locking tab and unscrewing the adjuster screw in the end of the axle.  You may need to wiggle them apart.  Insert the drive side crank through the bottom bracket and slide it all the way home.  Insert the non-drive crank and push it home.  Now insert the adjuster cap and with your fingers on the tool, tighten it gently until the sideways play just disappears.  Insert the plastic stopper plate to catch the adjuster cap and tighten the crank pinch bolts to 12-15 Nm each.  It is very important that the adjuster cap is not over-tightened.  Just a little too much torque can cause great side-load on the bearings which greatly reduce their lifespan and make pedaling unnecessarily harder.

Step 6:  Troubleshooting

Cranks feel tight and won't spin freely:

•  Check adjuster cap isn’t too tight & side-loading the bearings.
•  Remove cranks and check bearing rotation with your fingers.

Cranks feel loose and wiggle:

•  Check adjuster cap isn’t too loose.
•  Check pinch bolts aren’t loose or damaged/stripped.
•  Remove cranks and check bearing rotation with your fingers.
•  With cranks out, check condition and fit of the plastic caps.

Bearings feel “crunchy” or do not turn by hand:

•  Your bearings have either worn out or corroded and need replaced.
•  Shockcraft has replacement bearings for Monocrome, Shimano HT2, Raceface X-type, FSA MegaExo, Hope, Enduro, Truvativ GXP bottom brackets and many more.

Water and/or rust are found inside the bearing cups and/or centre sleeve:

•  Moisture has entered your BB, usually along the crank axle and can't get out.
•  Shockcraft can CNC machine Storm Drains into your BB cups to allow moisture to escape and prevent this recurring.

Written by:
Dougal
Shockcraft

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