I have a Shimano UN26 cartridge bottom bracket (68 x 123) now making a noise but cannot detect any wobble on the non-drive side at the same position around 11 o’clock position. I’ve checked everything; seat post, checking crank bolts etc. but it made no difference. I’m guessing it could be time to replace it, had the bike since 2014 and done around 15000+ miles and also ride in all weather

Thanks Andy

  • 1
    I think you've answered your own question here - cartridges are not intended to be serviced, so when they go dry or crunchy it's time for a new one. The UN26 is not particularly expensive, its just a lot of faff to install. Other than needing two specific tools you should be able to do it yourself.
    – Criggie
    Aug 14, 2022 at 19:24

1 Answer 1


You've gotten excellent miles on that bottom bracket and they are relatively inexpensive. Here are the specific tools needed to replace a Shimano cartridge bottom bracket: Crank puller. crank puller

Here is Park Tools' description of the crank puller. The photo above shows on the left side of the tool the end that is used for removing splined spindle cranks. You'll actually be swapping that with the end that's on the right side of the tool. It's for square taper bottom brackets.

Next is the bottom bracket tool: Bottom Bracket tool

Removal of the cartridge bottom bracket cups begins on the left, non-drive side. Here the threads are right handed (normal) and the left cup will loosen when rotated to the left. The right, drive, side is left hand threaded. This side contains the cartridge body (basically everything but the left cup) and will loosen by turning to the right.

A couple tips to go with the instructional I link to below. First, get yourself a long handled adjustable wrench. The wrench flats on the BB tool (BBT22 & 32) are 32mm and will accept that size socket if you choose or the BBT-22 will accept a ⅜ inch drive ratchet. BB cups are typically tough to break loose as time and the use of thread lockers really fix the cups in place. Thus, a long handled wrench is advantageous in removing the old BB. Beware that less expensive bottom brackets feature plastic cups, especially on the left side. While the plastic is quite durable when new, time and sunlight combine to make it brittle in it's old age. It's quite common to bust the ring of splines off without moving the threaded aspect Getting the BB tool fully inserted into the cups splines and keeping it sunk deep as you turn the wrench will help prevent such a failure. Finally, a key factor in successful insertion of the new BB is completing meticulous thread prep of the BB shell. Clean the shell's threads very well. My preference is to use grease on both the shell threads as well as the threads on the new BB cups. My opinion is grease allows you to reach the appropriate torque which is key to preventing a future of BB creaking. Removal is less of a knuckle busting chore when grease is used as thread prep.

Here is a link to Park Tools' instructional article on 1threaded bottom brackets, one type of which is the cartridge bottom bracket, aka, "integrated spindle" BB.

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