Help movement on cranks / bb

sketchley

Just cleaned the bike and started to adjust gears as i've have been having some problem with front mech so decided to reindex them. All fine except it wasn't quite index right on the front mech. After much frustration I noticed some play in the cranks :shock: . This isn't wobble where one pedal goes inwards and the other outwards on the diagonal, there's not movement that way at all, this is the both cranks moving side to side together on the horizontal. If I place my fingers on the chainring side and push it move inwards and the done drive side crank move out with it, same the other way. No wobble though if a hold both cranks and shake.

I'm guessing one of the cranks has come loose or worse something in the bb has gone wrong. What should do I do next?

EKE_38BPM

Get a new bike. Its the only way to be certain to eliminate the problem.

Loose BB cups? Try tightening them.

sketchley

EKE_38BPM wrote:

Get a new bike. Its the only way to be certain to eliminate the problem.

Loose BB cups? Try tightening them.

Loose bb cups... Don't have tool for that. I do need n+1 though....

fossyant

What cranks. If BB30 or outboard bearings then the preload needs adjusting. Simple job but varies depending upon manufacturer.

sketchley

fossyant wrote:

What cranks. If BB30 or outboard bearings then the preload needs adjusting. Simple job but varies depending upon manufacturer.

ShimanoI 105 cranks, bb no idea. It's a genesis equilibrium 20. http://www.genesisbikes.co.uk/bikes/roa ... m-20/specs

jzed

If its anything like my Planet x. The left hand crank clamps onto a chain set axle. So loosen the left crank, slot tighter together with the crank bolt, retighten.

davis

Aye. Wot JZed said.

Take off the LH crank (loosen the pinch bolts *FIRST*!), and put it on tighter.

cjcp

Yep, take the LH crank arm off, gently tap the chainset in, add the left crank, screw the cap in, then tighten pinch bolts.

sketchley

Ok, sound easy. Do I need special tools to do that?

veronese68

No, usually just allen keys. Loosen pinch bolts on the left hand crank, tap the drive side in, tighten screw in the middle of the left hand crank (not too tight, torque figure is low) then clamp up the pinch bolts.
All good = Pour yourself a beer.

cjcp

You'll need the tool which tightens the cap on the left crank. The Park BB tool has this. Can bring mine in tomorrow if you want to meet on Millbank.

sketchley

@cjcp offer of the tool is great, I'll take you up on that. However, should I ride the bike? The play is a couple of mm.

cjcp

I've had a crank arm fall off before. Try undoing the pinch bolts and then undoing the cap. If you can, undo it and follow the steps above, tightening the cap manually. I've ridden without a crank cap before, but the crank worked it's way loose after a few journeys.

sketchley

Brilliant thanks everyone job done. I loosened the pinch bolts, pushed the cranks together, then tightened the cap with my fingers and then did up pinch bolts. Indexing the fd was much easier then! Although I'm not 100% happy with front gears I think the fd is still sticking slightly having kept jamming recently with winter crud. It's working ok but doesn't seem to want to move the extra bit at the top via the shifter which mean a bit of rubbing in 50/12 but does move if a push it.... Might take it off and clean and lube it properly any tips?

veronese68

Tip; take it off, clean it and lube it.
You hit the nail on the head already. Clean with a bit of degreaser, rinse off, then lube each pivot point with a drop of wet lube. Work it through it's entire range of movement to make sure the lube has worked it's way in. Refit and set up and you're good to go.
If it all works pour yourself a beer.
I did mine the other day and it made a huge difference. Should go and have that well earned beer really.

sketchley

Job for next weekend that, plus I've drunk all the beer. I have red wine though....

veronese68

Red wine works, go for it. I'm always willing to lend a hand if you want to stop on your way home. I can help with fettling as well as drinking.

cjcp

Veronese68 wrote:

Red wine works, go for it. I'm always willing to lend a hand if you want to stop on your way home. I can help with fettling as well as drinking.

veronese68

cjcp wrote:

Veronese68 wrote:

Red wine works, go for it. I'm always willing to lend a hand if you want to stop on your way home. I can help with fettling as well as drinking.

I really should get a beer fridge in the garage, all welcome. I will be doing lots of fettling with the longer evenings. I need to finish the motorbike and put it up for sale.

gtvlusso

Sketchley wrote:

Brilliant thanks everyone job done. I loosened the pinch bolts, pushed the cranks together, then tightened the cap with my fingers and then did up pinch bolts. Indexing the fd was much easier then! Although I'm not 100% happy with front gears I think the fd is still sticking slightly having kept jamming recently with winter crud. It's working ok but doesn't seem to want to move the extra bit at the top via the shifter which mean a bit of rubbing in 50/12 but does move if a push it.... Might take it off and clean and lube it properly any tips?

Torque up the pinch bolts too - usually 5 to 8 Nm.....Should avoid this happening any time soon.

sketchley

Hmmm need torque wrench......

veronese68

5-8Nm is not very tight. Nip it up, then do the other, then back to the first and go round once more for good measure. As you tighten one screw it decreases the load on the other so that will take a smidge more. You don't need a torque wrench for that, it's not that critical. Just don't put your back into it.
If you're still not comfortable I'll see if my torque wrench goes that low. It's more for car use so may be a bit strong. You are more than welcome to stop by. Have you got my mobile number?
I'm sure we won't have to blame Wiggle this time.

Paul E

Never used a torque wrench on mine, I just do the plastic bearing preload widget tightish with my fingers and nip the bolts up with an allen key, never had any problems

gtvlusso

Veronese68 wrote:

5-8Nm is not very tight. Nip it up, then do the other, then back to the first and go round once more for good measure. As you tighten one screw it decreases the load on the other so that will take a smidge more. You don't need a torque wrench for that, it's not that critical. Just don't put your back into it.
If you're still not comfortable I'll see if my torque wrench goes that low. It's more for car use so may be a bit strong. You are more than welcome to stop by. Have you got my mobile number?
I'm sure we won't have to blame Wiggle this time.

5 to 8Nm is a guess - I think my FSA crank was 15Nm.....but I would not want the op to strip threads.

Nipping a bolt up is a fair point - we all do this on metal to metal stuff. However, crank bolts, I feel are a bit like car wheel bolts, they come off - you lose big time. They are more than likely tested to a certain torque value - therefore I would torque them up as I have a torque wrench. Anything involving carbon frames should be tightened with a torque wrench......

cyclingprop

I've a bike torque wrench that does go that low... but it's at home. Any friendly bike shops on your way home?