Tightening Crank Bolts

[IanT]

Hi,

First real post - so please be gentle.

I have a Carerra Vulcan, fitted with Truativ cranks. This week, I noticed a creaking from the bottom bracket area, so gave the whole crank region a thorough inspection.

All looked in order, however, I did notice that the left hand crank bolt (non-drive side) was relatively loose - in fact, I could undo it with just a short allen key.

Upon trying to tighten it, I noticed that - although it did seem to be tightening, there was a loud click every turn of the allen wrench.

Now, the logical part of my head says that it's probably nothing more than the crank arm nipping itself up on the square taper of the crank. However, being a relative novice to cycle mechanics, I just thought it wise to check with those in the know before I tighten too far and do some damage.

Foolishly, I did ask the Halfords Bike Hut, where I got the bike, for their advice. The guy told me that the bolt needs tightening to 50 NM - although, he could not find his torque wrench, so could not check it.

I do have quite a good toolkit, so can easily torque the bolt up myself. But, as I say, although I'm very familiar with car mechanics, cycle mechanics are a new ball game for me.

Equally, I'm a little paranoid as my wife and I are doing a charity ride tomorrow. Only 23 miles - but mostly around a largely unoccupied island. So I do not fancy a long walk through the country!!

Any advice will be greatly appreciated.

Thanks,

Ian.

 

[Andy_R]

50NM sounds a little excessive to me, I would have thought around 30 - 35NM. Bear in mind its the interference fit of a square taper that really holds the crank in place and the bolt is there to stop the crank sliding down the taper and losing the joint. What sort of bolt is it - steel or alloy? If its alloy you could run the risk stripping it if you go too hard on it.

 

[Alien8]

There's some ballpark torque settings here for various components.

Most the crank bolts they list fall in to the 300/400 in-lbs, 34/45 Nm, so I guess 50Nm isn't completely mad but could be on the high side.

WRT the clicking, can't say I've ever had that on a crank bolt. Maybe the thread is dry - did you put any grease or copper-ease etc on the threads?

 

[RecordAceFromNew]

I would follow this. I would also suggest greasing the bolts, ensuring they go in without having cross threaded, before tightening.

 

[IanT]

Thanks to everyone for the replies.

That Park Tools site is very hand - and going by their recommendation, I have torqued up to 45 NM - which is consistent with their recommendations.

I made sure that the bolt was cleaned and applied a light covering of Copaslip to it before re-installing.

Thanks for the help.

Best regards,

Ian.