PF30 Bottom Bracket Loosening Unevenly?

Looking for a bit of guidance. I got an Orbea Terra in March and everything has been great until this week when a creaking coming from the bottom bracket started. It wasn’t constant but got worse this morning on my long ride. On closer inspection the chainring side seems to unevenly loosening itself - see pictures below. On the wider side it’s a shade over 2mm and on the narrow side it’s less than 1.5mm. Bottom bracket is an FSA MegaExo PF30. No issues on the non-drive train side, photo for reference.

Unfortunately I don’t have a particularly good relationship with the bike shop who supplied it any longer, so if I have to go back I’m keen to be as clued up as possible on the issue and how it may have arisen. I haven’t crashed and there have been no heavy impacts to the drive chain crank arm. I’m having a proper look at it with a friend tomorrow who has a good toolkit but would be keen to hear any thoughts from the forum - thanks in advance!

It looks like the bottom bracket is ‘walking’ out of the frame because of a poor fit - that could either be a poorly made BB, a frame that is out of spec, or some combination of the two.
As far as fixes, without a way to measure the frame very accurately to measure the bore and offset of each side of the bottom bracket, you’ll just be throwing parts at it. Hambini is the only one I know of that will measure and custom fit bottom brackets, although I expect that to be a lengthy and expensive option.
The next option would likely be going to a metal shell BB, and install using loctite (641? Do not quote me, I’m not in the workshop at present) and activator. The downside with this option, is the problem will manifest again if the root cause is an out of spec frame.

Is your BB metal or delrin? There may be the option of using a delrin BB as well to take out some of the slop as they can be oversized from factory and deform into the frame shell, but this is not my preference.

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If you got in first hand in March I’d be heading back to the shop, I know you don’t have a good relationship now but you should have some purchasing rights since it’s well under a year.

Unless it’s some mega rare unobatanium frame Hambini wouldn’t be my first call unless the shop/manufacturer was paying, a lot of his work online looks to be custom to specific problems which has to be pricy.

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occam razor - maybe just take the crank off and press it back in?

I had a similar experience with a BBright BB - pressed it back in - worked fine for another year or so until I replaced it with a Wheels Manufacturing threaded one per a refresh of the bike

Edit - Yeah my point similar to firemunki is Hambini would be overkill

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Thanks to all @Stephano and @firemunki I’ll try to get the threads back in place tomorrow but if it ‘walks’ back out again I’ll take it back the bike shop to sort it with the manufacturer.

Just as an update, my friend and I managed to reseat the BB properly using a G clamp and a couple of bits of plywood to protect the BB. it went back in very easily and now looks like the non drive train side again. If the creaking restarts and it ‘walks’ out then it’ll be back to the bike shop for Orbea and the shop to sort out between them. Thanks for the help, will report back if there’s further information.

Maybe this is a daft question, but how on earth can the cup move outboard by 2mm of there is a pre-load in the bearings? Surely the non drive side crank arm must have moved along the splines by 2mm for this to happen, or there was already 2mm of play in the system at the start.

Mike

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Great question. The Shimano crank is held by the two bolts on the NDS, if they are tight it can’t move.

If the crank hasn’t moved it would logically be that the cranks never had the free float removed (aka pre-load, although personally I don’t say pre-load as it doesn’t need pre-loading, just free play taken out). If the free float / gap was removed then perhaps the BB wasn’t fully home.

Either way I would be taking the BB properly apart to measure and inspect, but it might be ok to have just pressed it home and tighten the crankset back up.

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excellent point @themagicspanner seems that either the bearing wasn’t pressed in fully to begin with or that the NDS crank wasn’t preloaded using the end cap before the pinch bolts were tightened.

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Yeah I’m pretty bereft at the origin of the problem as the cranks still felt rock solid after I identified the problem on Saturday. I’m hopeful that it was just someone not paying attention when the bike was set up in factory and/or checked in the shop, but this ties back into the now poor relationship with the bike shop, There’s just been too many small problems over the last couple of years, e.g. the headset was loose after a few break-in rides and that IMO is 100% on the bike shop if the bike arrives flat pack. Hopefully tightening up with the G-clamp is the end of the problem, but if not Orbea and the bike shop will be dealing with it and sorting it out.

I’d be concerned that the BB pressed back in “very easily” using a G clamp.

I’d also think that the crank had a little bit of ‘float’ from not doing up the crank arm fixing bolt properly. It is also possible the spacing is a bit narrow and a required spacer was not installed.

ETA: … IIRC, FSA bottom brackets utilize a wave washer?

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Sorry maybe I misspoke there a bit - it went back in straightforwardly, I more meant the process was very easy. There’s no way I could have pushed it back together using my hands for example.

If it goes awry again I’ll raise the issue of the spacer with the bike shop as it shouldn’t be happening.

Yes, FSA have a wave washer to keep some degree of pre-load in the BB bearings but that is required with their cranks as they have no way of adjusting the distance between the arms, unlike on Shimano cranks where the non drive side arm slides along a set of non-tapered splines.

Mike

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The preload amount is minimal.

The purpose of preloading bearings is strictly to keep the balls rolling rather than skidding (not that it really even matters in a crankset that rarely spins faster than 120rpm, but so be it).

It has nothing to do with retaining the housing. The wave washers used in BB/crank assemblies are typically very light, like 50 lbs fully compressed. In fact, all wave washers are very light, nothing like a Belleville washer stack in an industrial application that might deliver a few thousand pounds of force for the same sized spindle diameter.

Unfortunately this is probably typical Hambini Reaming material.

“Inadequately” engineered and manufactured frames, i.e. most of them, assume that that the BB shell is an infinitely rigid body, which it is not. Flex as you pedal can work the BB cups loose if the BB fit is loose or sloppy to begin with.

Solution for you: probably find a metal to carbon adhesive to glue the loose cup back in. I’d probably get a new BB while you’re at it since it’s going to be semi permanent, so might as well start as fresh as possible. They’re cheap anyway.

If the adhesive fails, you can either reglue or go the Hambini route with a single sided press fit BB.

In the assembly shown above there is no wave washer and the non drive side arm should have been pre-loaded onto the bearings (with a suitably small force - hence the plastic hand tightening tool and screw). This should eliminate all lateral movement within the bearings and make it impossible for the cups to walk out by 2mm without something else moving, if the thing was put together correctly in the first place.

Mike

That makes sense. I recently did some work on a BBRight system with FSA BB and Shimano crank, and I recall seeing a wave washer (although I can’t verify that would have been correct either). I am just tossing ideas at this point, although I lean toward my initial thought of poor tolerances, and possibly poor initial installation.

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Update: the bottom bracket has started to walk out of the shell again so have contacted the bike shop. Will update you along this journey :joy:

loctite 609 is the correct application for this

But but but but but but HOW is it moving if the BB is fitted correctly? I don’t get it.

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