In this post, complete with video, I show you how to remove and fit a BB90 Bottom Bracket on a Trek road bike (in this case my carbon Trek Domane 4.3, which I bought in 2013).
You will learn:
🔨 what tools you need to remove a set of seized BB90 bottom bracket bearings
🔩 how to use a bottom bracket press tool to fit new Trek BB90 bearings
🔧 how to avoid the plastic dust cover being pushed out when you reinstall the crankset
I filmed the video as part of a series where I stripped down and then renovated my 7-year-old Trek Domane 4.3 endurance road bike.
You can watch all of the videos in the series, in order by checking out this playlist.
How To Remove & Fit A BB90 Press Fit Bottom Bracket
This was actually the first and so far only time I’ve removed and fitted a bottom bracket (of any sort), so whilst the video will likely include things you shouldn’t do, at least you can see that it’s doable by someone with only a very modest amount of bike mechanic acumen.
Things You Will Need
Let’s start with the bike. Clearly this post/video is most relevant for bikes with press fit bottom brackets. In my case that’s a 2013 Trek Domane 4.3.
The BB90 bottom bracket standard, which is a proprietary Trek design, involves two sealed bearings being pressed directly into the bottom bracket shell within the (carbon) frame.
The bearings have actually done quite well, lasting 6.5 years of all year riding on the muddy roads of Derbyshire and a cleaning regime that I would describe as, er, sporadic.
However, during a deep clean that was meant to be ahead of replacing just the headset bearings, I realised that one of the bottom bracket bearings was also a bit ‘grindy’. A full bike refurb was on the cards. By the time I’d acquired all the bits to do this, the bearing had totally seized up.
New BB90 Bottom Bracket Bearings
A light Googlewacking suggests that no one’s a particular fan of the BB90 standard. As mentioned, the bearings are pressed directly into the carbon shell and if they don’t fit exactly then it can cause creaking.
Apparently, over time, the carbon shell into which the bearings fit can get worn, increasing the diameter of the cups (so many random words…). It seems the power I am throwing down is insufficient to cause such wear, so this wasn’t an issue in my case.
Despite this, whilst you can buy equivalently sized sealed cartridge bearings, I decided to play it safe and buy the official Trek BB90 kit (which is also suitable for BB95 bottom brackets).
The kit which comes with two sealed bearings and a plasticky inner ‘sheath’.
Step 1: Remove the Pedal Cranks
Erm, I don’t appear to have shown this in the video (or indeed in any of the other videos in the bike renovation series).
You can Google this to work it out for the groupset you use.
I’ve got Shimano 105, so it was a case of using a hex (or Allen) key to remove the pinch bolts on the non drive side crank. I used the specific Hollowtech plastic circular tool to remove the plastic ‘preload adjuster’ and the non-drive side crank could be slid off the spindle. Then, said spindle, which is attached to the chainrings, could be pulled out of the bottom bracket from the drive side.
Finally, the fox (amateur mechanic) could see its prey (the bearings…).
Step 2: Get The Old Bearings Out
For this I invested in the correct tool, a Park Tool BBT 90.3 press fit bottom bracket bearing, er, tool.
(Extra tip in brackets: for this whole job, use the right tools. Trying to hack either the removal or insertion of press fit bearings is a recipe for disaster, with a risk of doing irreparable – or at least expensive-to-fix – damage to your bike frame.)
You basically insert the pointy end of the BBT 90.3 through the middle of the bearing you are seeking to remove and then pull it as it pokes out from the other side of the bottom.
As you pull it through, the splayed splines of the tool compress together until there is a click as it passes fully through the bearing. The splines of tool are then sat against the inside rim of the bearing. Stop pulling.
Now you need to hammer (yes, hammer) the pointy end of the BBT 90.3 tool such that it pops out the bearing.
You can either do this carefully, and try to catch the escaping bearing and tool. Or you can whack it with gay abandon and delight in the clanging sound as the BBT 90.3 bounces along your garage floor.
Repeat for the bearing on the other side.
Step 3: Clean Out The Bottom Bracket Shell/Housing
The real step 3 is probably to remove the plastic inner ‘sheath’ (in my top ten favourite words), because a replacement comes in the Trek BB90 kit.
However, mine (my sheath) seemed in pretty good nick, so I just left it in there and gave it a good clean. Ahem.
The remainder of step 3 is to give the whole bottom bracket region, particularly where the new bearings will be seated a good clean. I used kitchen roll and lashings of GT80. Sue me.
Step 4: Apply Grease
A key step in any velomech scenario: a liberal application of grease.
As per the video, I applied grease around the inside of the bottom bracket cups, where the bearings were about to be seated.
My trusty Zinns
Step 5: Press In The New Bearings
It’s time for another specialist tool.
The key thing (as I understand it) when inserting press fit bearings is to make sure they go in straight. This is all the more important for carbon frames when you ab-so-lutely, pos-i-tively do not want to crack your bottom bracket (or any bit of your frame).
So you’ll want a press tool.
This is a threaded metal rod with handles that spin on the thread. You put the metal rod through the middle of the bottom bracket and then slide the new bearings onto the rod (in the orientation in which you want them pushing into the BB housing).
You then slide specifically-sized metal discs (known as drifts) onto the threaded rod and then tighten the handles such that the drifts push inwards on the bearings, applying a consistent force such that the bearings are pushed straight into the bottom bracket.
And here we see me turning the handles and pushing the new bearings into place (without cracking the carbon frame…):
I bought a Wheels Manufacturing Universal Bottom Bracket Press tool. It wasn’t super cheap but it is good quality and comes with specially designed reversible drifts that can push in bearings with a range of different diameters.
As it happens, the BBT 90.3 bearing removal tool came with a pair of BB90-sized drifts, so I could have got away with buying a cheaper press. However, I plan to press many more things in my quest for bike mechanic mastery, so I was happy to invest in a more whizzbang tool.
And thus the new bearings were installed:
Step 6: Reinstall The Crankset
Again, exactly how you do this will depend on the groupset you are using.
I do have one twop twip to think about when you are reinstalling the spindle through the new bearings.
The Trek BB90 kit that I bought differed slightly from the original bearings that I removed in that the new ones have a plastic insert that both reduced the inner diameter of the bearing and (I assume) acts as a bit of a cover to protect it from the elements.
If you use the official Trek kit (or similar), when you push the spindle through the bottom bracket, make sure to press against the cover-cum-reducer on the opposite side to avoid it being pushed out. Once the cover has been popped out from the bearing, it is a devil to get back into place without cracking or creasing it.
Step 7: Bask In The Warm Glow Of Your Own Smugness
That’s pretty much it. Whilst it took a bit of time, and a reasonably significant investment in new tools, I successfully managed to install two new bearings in my BB90 bottom bracket.
Both the removal of the old bearings and the insertion of the new ones was pretty straightforward. I actually found that I enjoyed it. And, yes, there is a certain amount of smug satisfaction derived from tackling, and completing, a non-run-of-the-mill bike maintenance task.
Tools and Parts
Here are the tools and parts I used in completing this job:
- Trek BB90/95 Bottom Bracket kit
- Park Tool BBT 90.3 Bottom Bracket Bearing Tool
- Wheels Manufacturing Bottom Bracket Press