On my SS roadbike (carerra subway zero) I've got truvative isoflow cranks on a square taper BB and every time I take it out the non drive crank arm starts to work loose. I've tightened the he'll out of it but the same always happens.

Any ideas?

you've damaged internal taper of the crank arms by overtightening. try loctite applied generously to the taper on the bb and then tighten – little bit loctite on threads.

the only solution is to buy shimano, seriously 🙂

Probably not fitted correctly to start with, once they've been ridden loose the taper they rely on gets distorted and won't hold.A new crank (correctly fitted ) is your best bet, usually cost in the region of £11 for similar quality.

Had this issue with most truvativ cranks i've owned – every time i've replaced with shimano as a reliable fix!
Try some loctite, should last longer before coming loose and if you plan on sticking with them, always take a multi tool out with you.

Whilst you're mentioning Shimano I had quite some issues with my old LX crank. Repeatedly came loose….
I also have XT 760, 770, XTR 960, 970 amongst others all that have been faultless!
In the end the only way to keep the LX on the axle was to remove the little clip that sits in the slot on the crank end to allow more deflection & loctite the bolts in.

Had the same on a pair of Truvativs I owned. Would never touch them again.

This:

bobgarrod – Member
you've damaged internal taper of the crank arms by overtightening. try loctite applied generously to the taper on the bb and then tighten – little bit loctite on threads.

One bodge worth trying is inserting a home-made shim to take up the 'slack' caused by the damage to the taper. A sliver of coke can works well. You *may* get a bit more life out of them this way.

New crank needed, £11 or so? (confess I have not tried a loctite repair).