UKC

Hello, after a bit of advice regarding a new bike. Took me a little while to work out the strange pedal cycle on my new bike looks to be a loose bottom bracket and I have covered nearly 60 miles. Is this likely to have damaged anything and when I take it back to the shop should they be replacing anything (ie bottom bracket due to wear)
cheers

In reply to trennie23:

Probably not a problem - is it the BB or the crank taht's loose? If you have an old style square taper BB they can sometimes work loose and then creak, but that's normally cured by tightening the bolt that holds it on. 60 miles won't have cause significant wear I'd have thought.

In reply to trennie23:

If it arrived loose then they should replace the bb. Just make sure it was not loose in the frame as this could have damaged the frame meaning that would need replacing.

In reply to beardy mike:

unfortunately I know nothing about bikes so that's why it took me a while to figure it out. If you grab one pedal everything feels tight and solid but if you grab both then there is movement up and down.
Brand new bike so wasn't expecting any problems straight away.

In reply to trennie23:

OK - look at the cranks - is there a silver bolt surrounded by a black piece of plastic? The axle between should be about 15mm in diameter. If so, then you most likely have a square taper bb. If you have movement on one side only, then it would suggest that it's not the BB moving in the frame shell, but the crank moving on the BB axle. That would not happen if you had anyting other than an old style BB (square taper, ISIS, Octalink). Newer systems with wide axles would be moving side to side when you tug on them.

In reply to trennie23:

Do you have a link to a webpage with the bike spec?

In reply to beardy mike:

Bikes at home at the moment so i'll have a look when I get back. Its a trek Marlin 7 and the spec just says it has a sealed bottom bracket which didn't help much. Holding both pedals firmly it is there is movement up and down so it seems the BB is lose or wobbling in the frame.

In reply to trennie23:

I don't think it does any damage.

In reply to trennie23:

OK - just lookind up the cranks that are on it, so you have a square taper BB. What I would suggest is that if you have a large enough Allen key, you try tightening up the side which is loose. If it's as I think it is, then it should wind in until it's tight. So if that allen bolt is tight, then as you think there is a different problem. Is it left hand crank or right hand?

In reply to beardy mike:

nearly done at work so i'll have a look when I get home. ~Thanks for the advise and i'll post the results later on.

In reply to trennie23:

Just had a look and the cranks feel tight but you can hold the pedals and the bottom bracket wobbles up and down in the hole in the frame. I guess something could be tightened up but I'm not sure what, if any, damage that movement will have done to the bottom bracket or the frame itself?

In reply to trennie23:
Right OK, so look at the bottom bracket - looking at it as if you were riding it, is there a gap between the bottom bracket shell (should either be silver or black) and the BB shell in the frame? i.e. does it look like i hasn't been wound tight against the shell?

In reply to beardy mike:
As I say i'm rubbish at bike mechanics but looking down there is a 8mm gap from the edge of the crank to the edge of the bottom bracket if that is what you mean. Crank is solid but the black bracket definately moves in the frame and I don't know how to tighten that up

In reply to trennie23:

That sounds reasonably serious. If the cranks are tight on a sealed square taper b/b then there really shouldn't be any significant movement. Perhaps a hint of movement but no visible movement. If the bearings are fecked then I'd expect them to replace the b/b without any grumble. I'd be more worried if the bracket is moving about in the frame. That could have done some serious damage to the frame.

In reply to trennie23:
TBH, if it's a brand new bike with less than 60 miles on it, I'd be straight back to the shop with it, rather than mess about.

However, this should tell you everything you need to know if you want to have a look yourself: http://www.parktool.com/blog/repair-help/bottom-bracket-service-cartridge-t...

NOTE the different thread directions, so you turn each side the right way to tighten/loosen.

You'll also need a crank tool to get the cranks off first - see other pages on site above.

You don't need the Park tools, although they are very good quality - other good ones are available for less.

Also see Sheldon Brown's website for serious geekery on the subject.

In reply to trennie23:

Not quite, I mean on that side there will be the bottom bracket body which should be screwed down tight against the shell. If the BB is not screwed home fully it is possible there could be movement. So ther should be the crank, then a gap with the axle, then the edge of the BB (silver or black) then the painted frame shell body. If it's loose there would be the silberblack bit, then a gap (exposing threads of the BB) and then the frame. If that's what it is, then yeah, I'd take it back and get it inspected. I still doubt it would have caused damage, but better to let a mechanic sort it out as they will have the right tools.

In reply to beardy mike:

Thanks for your input, going to have to take it back to the shop and see what they say.
Unfortunately it is 90mins away which serves me right for not buying from the local shop I guess

In reply to trennie23:

Def take it back to the shop - it is possible that if the BB is loose in the frame you will have damaged the threads on the latter - I've done this due to ignorance and it was quite a costly repair

There should be no play at the BB at all (well tiny bearing clearance which you shouldn't notice).

Phone the shop and ask for advice. Be prepared to identify where the play comes from. On a sealed bearing system with square hole cranks this could be:

- Between the cartridge and the frame - probably a source of creaks rather than loose feeling play. Usually relative harmless but should be fixed by tightening the cart up before it becomes worse and damages the frame, probably requires a special tool.

- Between the spindle (the turning bit) and the cartridge - cartridge probably needs replacing since these are hardly every user serviceable. Needs a special tool to do and the cart might cost a few quid, definitely shouldn't have failed this early, back to the shop.

- Between the spindle and the crank - simply put the crack hasn't been tightened up properly. This is usaully simple to do (remove the dust cover on the crank, tighten with an allen key). Note of caution - it is possible to strip the thread here so don't over do it, ideally use a torque wrench and check with the shop first since it is so new).

If the cranks seem firmly connected to each other then it is one of the first two. From your previous posts it seems unlikely you have the specialist tool to fix this so speak to the shop.

Unfortunately sealed BB units are prone to being shite from day 1 and it isn't uncommon for this to happen.