Fix my creaking Sram Cranks

GX Eagle cranks creaking like billyO. Replaced the BB, creak still there.

A month or so ago the non drive side crank fell off. They haven’t been the same since.

Cleaned them off, regreased, replaced nice and tight, still the creak persists.

When I look at the bolt the threads appear a little shiny, like squashed if that makes sense? But it goes in fine and there is no lateral play.

I am going to try and get a new bolt before replacing the crank. Any ideas what the bolt is called for searching purposes, like the part number or something to identify it?

Regardless, I need a quick fix as I’m going on a big ride tomorrow and be can’t be listening to that infernal noise every rotation.

Some online forums suggest putting plumbers tape on the bolt thread? Would this be so it goes in when you screw it, wouldn’t it all bunch up at the bolt head?

A creak would only come from contact points, these would be where spindle meets BB, bolt meets spindle, spindle meets crank arm, and where the bolt sits in crank

Any other ideas please? Do you reckon the cranks are knackered?

Assuming these are GXP are you doing them up to the correct torque? I’ve literally never had a crank fall off – seems odd.

I’m running Truvativ Stylo gxp on one bike and NX Eagle dub on the other and no creaks so far on either.

What BB is installed? Checked all the bolts are done up tight? Any bolts on chainring to be checked?

Pedals been greased recently?

Are you sure it is the cranks and not suspension pivots/bearings?

It’s a standard gxp BB. The chainring can’t come loose coz of the design but I have checked them yes.
Pretty sure the crank arm came off coz I hadnt done it tight enough.

Is there an easy to test the bearings on the suspension?

I had this recently on gx eagle and think the source was grit and dirt between chainring bolts and the chainring.

I spent a fair bit of time trying to isolate the problem and in the end I did take bb, cranks and chainrings all off for a thorough degrease and clean to be totally sure though. I liberally greased the bb threads and used threadlocker on the chainring bolts and a fair bit of grease on the crank spline. Non drive crank arm bolt itself didn’t need any grease, just 54nm torque.

If the cranks have fallen off while riding then the splines on the crank and/or the axle will very likely experienced fretting due to pedalling loads while they were loose, which will be the cause of the resultant creaking. The cranks and axle splines are no longer the same shape as they should be and so don’t have the interface they should have with each other. Due to this it doesn’t matter if the splines are clean and greased and the bolt is fully tight, the cranks will creak. You say its a GPXP crankset so the axle may be steel, the spline damage will be focussed on the alloy splines in the crank arm. If you can get a new crank arm and bolt you may be OK.

I suspect you may be right looseone (apt name) because I did cycle it for a couple of miles when it was loose. I had done this before on shimano cranks and done no damage. I’ll know better next time. Thanks