Need help/advice regarding BB30/Crank arms loose?

[jonbrackenridge]

Basically when I first got the bike 6 weeks ago I went on a ride and the bolt through the BB that connects the too cranks worked loose and the left crank came off completely, luckily I was close enough to a shop and they put it back on and tightened it right up, now 5-6 weeks on the the whole thing feels loose again, I've checked the bolt and that is stil tight to where it should be on the torque wrench, I can hold both crank arms and push and the BB / bolt that connects the too moves through the bike each way around 1/2 inch,

Hope that makes some sense somewhere along the line don't know what would case it still to move with the bold been tightened up solid.

 

[Rob3rt]

Sounds like it is missing a spacer or the wavy washer.

 

[jonbrackenridge]

Is that easy to spot or? It's a boardman carbon, really don't want to take the bike to ANY halfrauds if I can help it but if its expensive or can damage anything else I will let them deal with it.

 

[Rob3rt]

Get the brand and model of your crankset, find the manual for it online (manufacturers usually have these as PDF's on their webpage) and see how it is meant to be fitted. Taking note of the parts needed. Then check they are on your bike!

If it is tightened up to the specified torque and there is excess room on the spindle for it to have side to side play in the bottom bracket shell, then there is something missing or not fitted correctly.

 

[Playpen]

I had this frequently on a Cube with BB30. Adding a few drops of thread lock to the crank arm axle and the crank bolts has pretty much eliminated this for me (a few quid from a motor supplies shop).
Never got to the point where the crank arm fell off tho! Could always feel that it was working loose with pedaling action and gear changes not being precise.

 

[lpretro1]

It's under warranty so you need to persist with Halford's until it is right - which it clearly is not. If you don't it will end up costing yuo money to get it fixed

 

[Edge705]

picture tells a thousand words? can you upload one?

 

[jonbrackenridge]

I can upload pictures but not sure if they'd show anything, is there a way to upload videos?

 

[Edge705]

Looks like an FSA chainset to me most likely alloy gossamer or the type anyway the bottom bracket is contained within the bike that is to say there is an alloy housing inside the bike which holds the bearings (sealed bearing cartridges) these will likely be recessed a little and then there will be a metal spacer to bring it flush to the frame and then a plastic maybe metal paper thin washer. The chainset end should be pushed directly against this thin washer (or there may be a spacer as well to account for triple or compact chainsets). On the other end you should have exactly the same i.e. bearing, followed by spacer, followed by paper thin washer, but then there should be a wave washer (wavy washer) this washer is to take up slack under load. the left crank arm is pressed against this wavy washer. The left crank arm has a bolt (you mentioned earlier) but is should also have a retaining hollow housing bolt. what I mean is that there should be no gap whatsoever between the main bolt and the crank arm (without the hollow housing bolt there will be a few milli space). The hollow housing bolt acts as a crank puller meaning you should never have to remove it. Once you have all these parts and once the crank set is tightened between 38-40nm then there should be no play whatsoever. If there is then you have something missing Judging from what you have said it might well be the wave washer but if you don't have the hollow housing bolt then the main bolt will likely work lose anyway. Does it say gossamer on the chainset end? As suggested above if its new get it back to be looked at but my only concern would be if something's missing and its been tightened up without the said parts then you may have an issue, if so, best to be honest and say you made a short term repair (i.e tightened it up) just to get you home. Check out the FSA website as mentioned above and look at the diagrams for your crankset (they call a chainset crankset)