Many thanks to Sam Bennett of the RAF Cycling Club for this article!!

How to…..

replace external bottom bracket cartridge bearings

How many of us have been a little too eager with the pressure washer? Especially over the winter months, after a cold wet ride and wall you want to do is get indoors to a hot coffee.  I was a bit disappointed to find that on pulling my bike out of the garage for  SSMM, that due to water ingress the bottom bracket bearings had seized.  This was causing them to slip on the crank axle, which if not noticed would have damaged that too.

 

Replacement bearing cups were going to cost me around £36, as they come complete.  By replacing the bearing cartridge itself, you can upgrade your bearing to a higher standard whilst saving £20.

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Firstly remove your cranks in the normal manner taking note of spacer and washer positioning.

Remove the primary seal by gently prising it out with a screwdriver or suitable implement.  Then unscrew the cups from the frame using the appropriate BB tool.

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Identify the bearing by getting the code off the seal.

 

This Race Face, X-Type was a: 6805-2RS, which means it is 25.0 x 37.0 x 7.0 mm with ‘non-contact seals’.  More about the seals later.

Contact a bearing supplier (in Yellow Pages) and order the part.  I use SMB Bearings in Carterton, (01993) 842555.

 

Quote the bearing code, and stipulate that you want ‘contact seals’.  These will give you better dirt and water protection than the ‘non-contact seals’ normally supplied.


 

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To remove the old bearings, place the cup on a suitably sized socket to support the cup, bit with sufficient clearance to allow the cartridge bearing to fall out.

 

Use a parallel drift to tap around the inner race until the cartridge comes free.  Tapping the inner race will probably result in damage to the old bearing but as you are replacing them this doesn’t matter!

 

Once removed, clean the cup.

To fit the new bearing, place it in the cup and ensure that it is correctly aligned.

 

Then place the cup and bearing in a vice with protected jaws and ensuring that the bearing is still aligned, close the vice until just a small amount of the bearing is still visible.

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To drive the bearing fully home, select a socket that will contact the outer races, but not damage the cup or the bonded rubber on the cup that forms part of the primary seal.

 

Place the socket and bearing assembly in the vice and close again until a solid resistance is felt.  This is the bearing fitted.

Now just place a little grease around the secondary seal and the bonded rubber on the cup before gently pressing the plastic primary seal back in using the vice to keep it parallel.

 

Screw the cups back into the bottom bracket, torque up and reassemble the crank and axle assembly.

You have just saved yourself £20 and up graded your bearings.

 

You can ask for stainless steel bearing which will offer even greater longevity, but these will cost around £22 each.

 

Any questions on this, feel free to email me:  sam@rafcycling.org.uk