Press fit bottom brackets are no longer scary!

"VincentMalamute-Kim" (VincentMalamute-Kim)
08/13/2020 at 22:41 • Filed to: None

I’m gradually catching up to all the new fangled bike tech. I was scared to touch the press fit bottom bracket but the creaking finally drove me to the internet, ordering of tools, parts and I just finished replacing it.

I used Park’s press-fit retention compound after applying their adhesive primer. It’s basically Loc-tite but the instructions counterintuitively says you need the primer to avoid permanently bonding the BB to the bike.

This off-brand multi-fit BB press/remover turned out to be of excellent quality and 1/3 the cost of a single fit Park. But the instructions had phrases like “detonation of bearing” and words like “pilon”. I ended up just randomly assembling the pieces and after a few tries at the correct order, bearing removal and installation went so slick. It’s easier than the old ball bearing BBs and even the cartridge bearing threaded BBs.

A few mistakes. Not enough research - I didn’t know that the non-drive side spindle cover actually sets the crankarm preload. I didn’t know the plastic shim was a last resort crankarm retainer. I started pressing in the drive side bearing having forgotten to apply the retention compound and had to push it back out. I started off on a test ride before remembering the 24 hr cure time. I have a headache - I should’ve worn a chemical respirator near that primer and adhesive.

So it remains to be seen if this worked for the creaking. But this was a good reminder to myself that I can do things I’m scared of. Internet makes things so easy.

Question: what is this rubber tubing coming down from the down tube? It’s not internal cable routing for the derailleurs; they’re good. Cable routing for a dropper post? I was scared to pull it all the way out. I just shoved it back in and ignored it.

DISCUSSION (14)

Nom De Plume > VincentMalamute-Kim
08/13/2020 at 23:42

Lots of complex subjects being asked about.

For starters what flavor of Press Fit BB does your mtb have?

Park is very hit and miss. Grease is decent, tools are worthless nowadays. I expect the dual compounds will work fine. So long as they don’t break down from the constant washing required to keep the bearings in good shape.

There are so many poorly manufactured “holes” depicting the full gamut of ways two surfaces can be out of alignment in a three dimensional world. Someone like myself or Datsuns are forever would have to be physically present to diagnose the root cause.

One easyish way to eyeball it up is pushing the crank spindle through without a NDS bearing installed. You can also measure the diameter of both sides at numerous places to see if one or both sides are out of round/flat spots/wavy. Highly typical is a compound alignment error that places multi-directional pressures resulting in lots of noisy complaints.

I’ll leave someone else to tackle further questions posed.

Highlander-Datsuns are Forever > VincentMalamute-Kim
08/13/2020 at 23:43

The tube is probably for an internally routed dropper as you guessed. Funny thing is that manufacturers are going back to threaded bottom brackets after years of customer complaints about press fit units. I’ve never had any issues with either but I’ve know many people who have had nothing but problems with press fit bottom brackets.

Nom De Plume > Highlander-Datsuns are Forever
08/13/2020 at 23:57

Which is a better answer than stacking inserts or kludging together ways to make the hole smaller and threaded that without fail wore holes in carbon or incessantly squeaked.

As touched on above , this is a frame manufacturing tolerance and QC issue that has to be fudged in any BB product. Not squeaking is not the same as working without friction or wear.

SilentButNotReallyDeadly...killed by G/O Media > VincentMalamute-Kim
08/14/2020 at 00:27

Two bikes here with pressfit frames. One is a BB30 and the other, BB92.

The MTB’s stock bearing with its all oy chassis only survived a couple of dusty seasons and the replacement Shimano unit managed just one due to the dust destroying the plastic chassis. Switched to a Rotor branded version but it creaked as the bearing chassis was too narrow for the frame shell .

Finally ponied up for a Wheels Manufacturing threadless conversion...which works really really really well. It’s basically a massive two part alloy shell that threads together inside the frame shell whilst also doing duty as bearing cups...that allow the bearings to be replaced rather than binning the entire BB.

It was so successful that the DirtRoadie scored one for its GXP style cranks.

No creaking ever ...and very good Enduro bearings to boot.

Highlander-Datsuns are Forever > Nom De Plume
08/14/2020 at 01:01

I have never built a bike that didn’t need the bottom bracket shell chased and faced. I think people assume they give a Shit when originally built.

VincentMalamute-Kim > Highlander-Datsuns are Forever
08/14/2020 at 10:26

oh that’s unfortunate to hear. I should know better but I assumed they gave a shit when they built it. Facing is something you can do at home?

VincentMalamute-Kim > SilentButNotReallyDeadly...killed by G/O Media
08/14/2020 at 10:30

Similar here - I have a BB72 and this one is BB92. I’d read of the Wheels Manufacturing conversion but for $25 I figured I’d give a replacement Shimano BB and the Park glue a try before shelling out $90.

Good to hear that the conversion works though. If I end up on that route.

VincentMalamute-Kim > Nom De Plume
08/14/2020 at 10:37

It’s a BB92 with a Shimano MT500 which I think is Deore or SLX level. I put in an XT MT800 because they’re all so cheap.

My respect for Park is from 40 years ago when they were the reference. I’m saddened to hear about your opinion of them.

You bring up a good point about the root cause. There is always more to know about a complex topic. Applies to press-fit BB’s, pandemics, climate. They are more complex than a single line sound bit.

If the new BB with the glue still squeaks, I’ll try further diagnosis with your suggestions and try to at least fix one alignment issue and face the BB if needed before going to a threaded conversion.

Highlander-Datsuns are Forever > VincentMalamute-Kim
08/14/2020 at 11:08

You need specialty tools that are typically too costly for the home mechanic to do a “Chase and Face” I think that a lot of the problems from press-fit bottom brackets is that the faces of the shell are not perfectly aligned and just that little bit of out of alignment causes the shells to loosen and bearings to go bad.

$385

https://www.jensonusa.com/Park-Tool-BFS-1-Bottom-Bracket-Facer-Set-BFS-1

VincentMalamute-Kim > Highlander-Datsuns are Forever
08/14/2020 at 11:23

Thanks. yeah, probably a bit much for me to invest in for my two PF bikes.

Nom De Plume > VincentMalamute-Kim
08/14/2020 at 14:35

Not all PF standards are equal. The end result when they really don’t work is a mechanic or rancher or machinist or engi-nerd makes something deviate from perfection in such a way that it counters the issue creating friction.

Less severe option is a BB imprecise to start with that uses deformable plastic in a way that absorbs the force enough to allow rigid metal spindles and bearings to take less of the strain. This is the route Shimano takes.

VincentMalamute-Kim > Nom De Plume
08/14/2020 at 15:47

“ This is the route Shimano takes.”

Figures.

Nom De Plume > VincentMalamute-Kim
08/15/2020 at 06:39

Not their high point in performance, but recognized as the best of all the manufacturer’s PF BB’s. The issue doesn’t lie with anything in their product line.

VincentMalamute-Kim > Nom De Plume
08/15/2020 at 11:15

I mis-interpreted your paragraph about Shimano. Thanks for your insights.