BB90 Replacement

NewStew
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BB90 Replacement

Postby NewStew » Wed Oct 25, 2017 6:09 pm

Bit the bullet and decided to buy the tools and replace the bearings in my Trek Domane 6.9 BB90 bottom bracket. It looks pretty easy if a gentle hand is used and one is patient and pays attention to the details. The only question I have is grease, carbon assembly paste or just press them in dry? Or is it a job for some form of loctite.

I hate creaking, but also hate risking damage to the frame, so want to get this right.

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Duck!
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Re: BB90 Replacement

Postby Duck! » Wed Oct 25, 2017 9:04 pm

If Trek haven't lifted their game the bearings are likely to just fall out....

If tolerance is good and the fit is firm, use grease when fitting the new bearings. If the tolerance is loose, you're going to have problems whatever you do.
I had a thought, but it got run over as it crossed my mind.

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ValleyForge
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Re: BB90 Replacement

Postby ValleyForge » Wed Oct 25, 2017 11:34 pm

Duck! wrote:If Trek haven't lifted their game the bearings are likely to just fall out....

I'm thinkin' Sikaflex.
Ha ha ha! Cookies on dowels.

NewStew
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Re: BB90 Replacement

Postby NewStew » Thu Oct 26, 2017 11:18 am

Duck! wrote:If Trek haven't lifted their game the bearings are likely to just fall out....

If tolerance is good and the fit is firm, use grease when fitting the new bearings. If the tolerance is loose, you're going to have problems whatever you do.


Bearings are still tight in the cups and I have never had a creak from the bottom bracket on this bike in over 2 years - mind you I want to keep it that way so fingers crossed. So with a carbon frame should I use grease (I have a tube of red devil grease) or carbon assembly paste?

Patt0
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Re: BB90 Replacement

Postby Patt0 » Thu Oct 26, 2017 11:30 am

Grease.

My first bb90 bearings lasted 8000km before they took on some water and one got a little rough. Replaced them with cheap ebay bearings. Since then I replace the grease between the outer seal and the bearing seal every 1500km. They are now at 13000km and perfect.
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NewStew
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Re: BB90 Replacement

Postby NewStew » Thu Oct 26, 2017 12:10 pm

Patt0 wrote:Grease.

My first bb90 bearings lasted 8000km before they took on some water and one got a little rough. Replaced them with cheap ebay bearings. Since then I replace the grease between the outer seal and the bearing seal every 1500km. They are now at 13000km and perfect.


Sounds like a similar story to mine - I got about 9,000 km out of the OEM ones before the non-drive side seized and they were replaced by Trek Store in March and now the non-drive side one is rough as guts again after winter and another 2000-3000 km. Will take your advice on the regular greasing between the dust seal and the bearing, especially during winter.

Patt0
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Re: BB90 Replacement

Postby Patt0 » Thu Oct 26, 2017 2:42 pm

Change it asap. if the bearing seizes and spins in the carbon it will chew out the carbon very quick.

The bearings off ebay are branded the same as the OEM bearings.
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NewStew
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Re: BB90 Replacement

Postby NewStew » Thu Oct 26, 2017 3:08 pm

Patt0 wrote:Change it asap. if the bearing seizes and spins in the carbon it will chew out the carbon very quick.

The bearings off ebay are branded the same as the OEM bearings.


Yeah I have the bearings and the tools on the way. The last one seized but the crank spindle still had enough grease on it that the bearing was still firm in the shell - thankfully!

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