Stop crank bolts loosening

So does that mean the bike should not be ridden immediately after cranks are installed? Would make sense.

Oops tynan beat me to it

yep, that is not the problem

its that the bb is titanium and it has been interacting with the aluminium of the cranks

hence the dry compacted powder residue on the tapers

What you dont have titanium cranks!? cheap skate

ok, when i was doing it to recommended value it felt like it was about to go "pop!"

Yep, you need to apply the kind of torque that normal experience tells you will break something - ie: it feels unnatural - we simply so not stick 40Nm into anything in our daily lives - but that is what you need to apply.

Aluminium bolts are usually given a much lower torque rating for the same crank/BB set up than for steel or Ti bolts.

Something to bear in mind

Alloy crank bolts are only retaining bolts, you need to torque down the crank onto the spindle with a steel bolt, then remove it and replace with your alloy bolt.

So does that mean the bike should not be ridden immediately after cranks are installed? Would make sense.

Yes !! Ideally, although if you find yourself in the middle of the London the Brighton with loose crank - you are going to have to ignore this rule - but generally it's not a good idea.

so what crank bolts are suggested - both for tightening and actual use?

so what crank bolts are suggested - both for tightening and actual use?

Whatever you want - Steel, Ti or alloy.

But with both Ti and alloy - use a steel bolt to mount.

Good thread, lots of useful info about torque and related products. +many

As far as I remember Royce does Steel, Al and Ti crank bolts. I guess the most devoted weight weenies would go for Al?

finally as the torque wrench arrived yesterday I got round to doing the cranks

frustratingly my local homebase had no fine emery paper so used a dremmel polishing head to clean some of the aluminium oxide out of the crank splines. wiped bb tapers and cranks with meths and then copperslipped the splines. crank applied to 16Nm as per manufacturers instruction

left for an hour (actually being a sad bastard i decided to do every bolt on the bike to correct torque)

took bike out for spin, seems to be much much quieter, had to push really hard on cranks to get a lot of creaking (am assuming that the ti frame will always sing to me a little bit)

just to check put the torque wrench on the bolts and they had not moved at all

am still concerned that 16Nm is v low but will see how it goes

The bolts that hold my cars (steel) brake discs onto the (alloy) hub bells are meant to be done up to 16Nm, which I thought extremely low also.

In my case it is to allow for thermal expansion of the disc as they get to 800 degree's if used on the track.

16Nm will hold them onto the hub assembly despite trying to get 1,500 kilograms of Volvo to shed 120mph of speed ASAP.