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Replace cranks and bottom bracket

Introduction

This article is for:
  • most bikes for everyday use. They probably have Shimano or Campagnolo components, or compatible;
  • people who don't mind a possibly long and dirty job.


 

WHAT YOU NEED TO KNOW


PRECONDITIONS: You may need some strength and confidence to remove well bedded in components, and you may want to remove the chain before
you start, to make access easier.

TIME: This fix may take 2 - 3 hours the first time you attempt it.

DIFFICULTY: A long and dirty job, and needs some thought.


STEPS


1. When to check your cranks and bottom bracket

2. Remove crank arms

3. Remove bottom bracket

4. Fit bottom bracket

5. Fit crank arms

6. Test

 

1. When to check your cranks and bottom bracket


axle play
If setup feels loose, a play around the axle may indicate worn bearings.
remove lockring
Water builds-up inside the frame and is prone to corrosion.
remove lockring
Drain water from the frame each year helps dealing with the rust.

Setup feels loose: It should feel absolutely solid. A millimeter's play around the axle may indicate the bearings are worn and need to be replaced.

Every 3-5,000 miles/3-5 years: Approximately. This part of your bike receives some abuse from you and the elements, and water builds-up inside the frame so it may also be prone to corrosion.

Drain the frame: Draining the frame every year helps, but sooner or later you need to take it apart, clean, lubricate and put it back together again.

2. Remove crank arms



remove retaining bolt on crank drive side
Use a crank extractor to undo the retaining bolt
screw out inner sleeve of crank tool
Extend the crank puller fully and screw the tool in the crank until it stops
screw in driver of crank extractor
Hold crank still and turn puller clockwise (in) till cranks come off

Insert crank extractor: Unscrew the dust cap and retaining bolt at the centre of the crank arm. Then fully extend the crank puller by drawing back the inner driver from within the outer sleeve. Gently screw the tool into the crank until it stops.

Pull off the crank: Grip the flats of the outer sleeve of the crank puller with an adjustable spanner, oriented so that you can push it anticlockwise with your left hand. (In the picture, we are just holding the crank arm still.)
Grip the internal driver with another spanner and align it so that you can turn this one clockwise. (The extractor in the picture has a handle that screws into the inner driver). With one hand acting against the other, hold the outer sleeve still while you turn the internal driver clockwise. You should feel the inner driver 'bite' and begin to move the crank arm off. Continue to turn the driver until the crank arm slides off the spindle.

  • Remove the crank on the left-hand side:

    Repeat the process described above for the right-hand side.
    Lie the bike on its side ready to remove the bottom bracket.


3. Remove bottom bracket


Bottom brackets have two sides - a cartridge side, which gives access to the bearings unit, and a lockring side, which keeps the bracket in place. The lockring could be on the left, or right hand side - it depends on the manufacturer. Either way, remove the lockring-side first.


remove lockring
Insert bottom bracket tool into lockring to unscrew it.


  • Unscrew lockring: Insert the bottom bracket tool into the splines of the lockring, grip it with a spanner and then unscrew the lockring.

remove lockring
Unscrew lockring (anti-clockwise on Shimano - the usual direction)

On new Shimano bikes the lockring is on the left, non-drive side, and you unscrew the lockring anti-clockwise (the usual way for unscrewing). This may need some force. If it sticks hard, ask someone to tap the bottom bracket tool with a mallet as you attempt to turn it.

remove lockring
Unscrew cartridge (clockwise on Shimano - reverse)

  • Unscrew cartridge side: Then turn bike over and use the bottom bracket tool again to remove the cartridge side - this unscrews clockwise.

4. Fit bottom bracket


  • Grease and identify left- and right-hand sides: Clean and grease the thread inside the frame, on the new bottom bracket sealed unit and the lockring. Check your new unit is compatible. Identify the cartrdige and lockring sides - the cartridge itself may be labelled L (Left) and R (Right) to assist.

 
Remove cartridge (Shimano clockwise)
Screw in cartridge to the right hand side by turning (Shimano anticlockwise - reverse).


  • Screw in lockring and cartridge: Fit the lockring to the left-hand side turning clockwise, just finger tight for the time being. Then screw in the cartridge to the right hand side by turning anticlockwise.

Remove lockring (Shimano clockwise)
Screw in lockring by turning (Shimano clockwise), to tighten the cartridge.


  • Tighten off: Tighten the cartridge to 60lbs pressure, then tighten off the lockring with the spanner.

 

5. Fit crank arms


Check that cranks and spindles are free from grit and grease, and then slide the first crank onto the spindle. Grease the sides before you slide it on. Finally, screw in and tighten the crank bolt. Then repeat for the crank on the other side, after checking its alignment - opposite cranks point in opposite directions.

slide on crank arm
Slide the crank arm onto the spindle, screw in to tighten the crank bolt on one side. Repeat on the other side.

6. Test


Check new setup is absolutely firm: There should be no play around the axle, and the cranks should not wobble, or feel loose when they rotate.

Test ride: Go for a short test ride on a short road, taking a few tools with you. If you feel anything strange, stop and check nothing is working lose (especially the crank bolts).



Results


responsive image

Feel more connected to the bike. Solid.





Bike Fixer

photo of mc

Bike Fixer is a co-op of bikers and web designers.
"mc" grew up car-free in the countryside, and had to ride a bike from an early age - absolute magic! In later life, he survived London traffic and l'Etape du Tour.


Sources

The books below are tremendously helpful, but there is a lot of material to get through.

  • Ballantine, R. and Grant, R. 1994, Richards Bicycle Repair Manual. Dorling Kindersley
  • Downs, T. 2005, Bicycle Maintenance & Repair
  • Haynes 2007, The Bike Book - Complete Cycle Maintenance
  • Park 2008, BBB-2 Big Blue Book of Bike Repair, Park Tools
  • Van der Plas, R., 2007, Bicycle Repair.  Repair and Maintenance of the Modern Bicycle

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