Left pedal/crank arm.... Quacking!

[PocketFrog]

No, seriously, stop laughing! - it's making a duck-like noise and I have no idea what's causing it!

I set off on a ride on Sunday and all was going great until I got a few miles in and the bike started calling for it's webbed-feet chums every time I put any pressure on the left pedal. I did an about turn and headed back but did the following tests on the way:

• Only pedalling with the right foot clipped in - Duck free.
• Pedalling with the left shoe unclipped but with pressure on the sole of the foot - The Return of Daffy.

When I got home I noticed that i'm missing the crank bolt from that side... second time i've lost that bleddy thing, Evans must think i'm collecting them! - Could it be that?

Any ideas what I can do to fix this without investing in a duck call and a shotgun?

 

[Globalti]

Crank bolt? Do you mean the big recessed head bolt in the middle that holds the crank onto the axle?

If you've lost two you've got a problem, stop riding and get the bike checked. The noise you're hearing is probably the crank working loose on the axle and you could do some very expensive damage. The fact that they are working loose tells me the damage is already done and it's impossible to tighten the bolt enough. Is the bike in warranty?

 

[accountantpete]

+1

I'd get a drop of Loctite 242 or similar and coat the thread of the new crank bolt to stop it undoing.

 

[PocketFrog]

Crank bolt? Do you mean the big recessed head bolt in the middle that holds the crank onto the axle?

If you've lost two you've got a problem, stop riding and get the bike checked. The noise you're hearing is probably the crank working loose on the axle and you could do some very expensive damage. The fact that they are working loose tells me the damage is already done and it's impossible to tighten the bolt enough. Is the bike in warranty?

Yeah, I only got it in January so i'll get it checked out. Cheers!

 

[Smurfy]

On a square taper crank/BB these bolts should be quite tight. Mine are marked 38-42 Nm.

I use grease on the threads, and a dry fit between the tapers. If you grease the tapers be careful not to tighten the bolts so much that the cranks develop a crack.

 

[PocketFrog]

OK, I fixed the quack thanks to your assisance!

Forgive my crude explanation but i'm still a bit green on the 'parts' side of my bike!

The part I am missing (and have lost twice) is this:

But I fixed the 'quack' by tightening these:

I have no way of measuring how tight but i'm pretty sure going on how easy they were to tighten that they were nowhere near 10.8Nm, I guess Halfords (who recently 'serviced' the bike didn't bother to look at anything like that) - Anyhoo, just waiting for the centre 'bolt' from Evans and i'm back up and running!

 

[accountantpete]

You have a Hollowtech II chainset not square taper.

If you look at that photo you will see something blue - that is the threadlock which the bolts should have to stop them unscrewing.

The big bolt you are missing is to adjust the preload - you tighten up so that there is no movement in the cranks but don't overtighten or you will ruin the bearings.