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The bottom bracket on my MTB is loose. I am able to slide it from side to side as can be seen in this video:

https://photos.app.goo.gl/CWmA8afBaA6GtDvq6

It seems to be a pressfit BB I have. I have tried tightening when reinstalling the crank arms, but the BB is still able to slide from side to side. I have added some photos.

Which parts should I replace to resolve the problem?

I am not experienced in maintaining bottom brackets. I have tried googling and watching a lot of videos, but it is still somewhat confusing to me (standards, tools, removal/installation process etc.).

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1 Answer 1

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It looks like your BB cartridge is no longer pressed into the frame shell. When you removed the cranks did it just sort of fall apart? That is a signal that for whatever reason the BB is worn so that the interference fit is no longer sufficient. You should be able to remove the cranks without the BB falling out.

You generally replace the entire bottom bracket unit with a press fit and you have a reinforced composite plastic SRAM GXP bottom bracket which is definitely a single use consumable unit.

For you a GXP compatible (the crank spindle standard) bracket is required. Most cartridges will fit either 68mm or 73mm wide bottom brackets which are the two widths you’ll find in a modern bike.

You need a bearing press to install a new unit which can be as simple as a threaded rod with nuts and large washers of a bigger radius than the BB.

press fit bottom bracket press and removal tool

They are readily available online for a small price or you can construct your own if your hardware shopping options are sufficient. The pictured version came with the T shaped removal tool which is inserted inside the shell against the bearing and bonked with a hammer using a drift until the bracket half comes out.

Why the BB became worn/misshaped enough to fall out is another question. If your riding style involves a lot of out of saddle high power low rev cranking you might want to consider a less budget BB made from metal for the replacement. Or maybe the BB was just old and needs replacement.

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  • Thanks for the insights. The cartridge didn't fall out when I removed the cranks, but it was very loose, and I could easily remove it with my fingers. I will measure the bottom bracket shell dimensions and the crank arm spindle and buy a replacement BB and install it. Mar 10, 2023 at 14:48
  • I’ve got a PF30 version of that BB. They last me about 2-3 years. It might just have been your BB’s time to go. Otherwise they are perfectly good units. Mar 10, 2023 at 21:28
  • I can see from a date stamp on the removed BB unit that it is dated back from 2014. So probably just worn out. Will buy replacement and install. Thanks for input regarding installation tool Apr 15, 2023 at 4:36
  • I now installed a new bottom bracket, and it solved the problem. No looseness or play anymore. I bought a (rather cheap) bottom bracket press that made the job quite easy. May 14, 2023 at 9:47

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