Repair guides › Drivetrain

Replace Mid BB bearings

Sealed cartridge bearings pressed into a large BMX BB shell. Mid and Spanish shells take sealed bearings pressed straight into the frame (Mid: 41 mm bearings; Spanish: a smaller 37 mm bore). American shells press in cups or larger bearings; Euro shells thread in like a road bike. Spindle size must match the bearings (19, 22 or 24 mm).

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Tools

• Ball-end hex key set (1.5–10 mm): Park Tool HXS-1.2 Professional L-Shaped Hex Set ($$)
• Bike grease: Park Tool PPL-1 PolyLube 1000 ($)
• Soft mallet + star-nut setter: Rubber mallet + star nut setting tool ($$)
• Press-fit BB press + cup remover: Park Tool BBT-90.3 + Park Tool HHP-3 ($$$)

Compare Good, Better and Best for each tool

Steps

1. Remove the cranks and spindle.
2. Drift the old bearings out from the inside with a long punch or a long socket extension, working around the bearing.
3. Grease the shell, press new bearings in square (a headset press or a large socket on the outer race).
4. Refit spindle, spacers and cranks.

Signs it needs doing

• Rough or gritty cranks
• Play after removing slack with spacers

Problems this fixes

• Clicking or ticking when pedaling
• Creaking when climbing or pedaling hard
• Pedal or crank feels loose or wobbly