I like to diy bike maintenance, and as a result I occasionally break stuff, but mistakes are an essential part of learning, so I keep reminding myself… (see last weeks question on threaded candy SL: stripped spindle or nut? :x)
This week I’ve started messing with something that I have no idea about, and can’t afford to brake/replace. Last week I first noticed my crank bolt wasn’t tight, so I did it up. Today I noticed it has worked loose again - this time really loose. I know riding them when loose can stuff the spline, and I really want to avoid that.
My cranks & BB looks exactly like this:
Q1. What should I do? (More than one may be the correct answer)
a) Tighten the bjeesus out of it, check often, repeat.
b) Purchase a quality torque wrench, and then tighten to spec
c) Use some loctite anti-slip on the threads. If so, which one?
d) Buy a new bike
e) Start drinking. Clearly I’m too sober to diy anything.
f) Other, please specify
Q2. I don’t own carbon anything, so is a torque wrench a good investment? Who uses one on their bike/s, what for and how often?
I have a set of Truvativ Rouler cranks on my road bike. I had a similar problem with a loose bolt, however I was dumb enough to over tighten it so the head broke off… yes, crummy Aluminium bolts.
Just be sure to get the head size the same size as your fittings.
Otherwise, if you are stripping threads, you are WAY overtightening. I’d suggest stepping down your gear ratio from 52-15 and stopping the 'roids.
Make sure all parts are thoroughly cleaned and greased, then ‘firm’ pressure is enough on a 10-15cm lever (for all parts other than bottom bracket where you should use a longer lever).
G’day Mark,
MIght not be the case with yours but some Truvativ and FSA external BB cranksets are notorious for slipping. Partly a design problem - on some variants the spline/crank interface doesn’t have quite enough taper for a good interference fit before the spline bottoms out. If you have spacers behind your BB cups the problem is made worse.
(see the ‘wrenching’ section of RBR for lots of discussion on this).
I had a similar issue with an FSA SLK crankset a couple of years ago. After a dialogue with FSA I ended up using Loctite 621 on the splines (this a special loctite that isn’t a threadlock per se, the compound is designed for the sheer forces that occur in joints like splines - it’s available from specialty tool shops, most bike shops or auto parts places won’t have heard of it) AND a couple of wraps of plumber’s teflon tape around the crank bolt.
Note - for the 621 to work the splines must be scrupulously clean. No traces of grease of other crap. It also needs a good 24 hrs to cure before you ride it. It’s then a pig to undo when time comes for a new BB.
Really, if a crankset needs friggin’ loctite to hold together under normal use it’s got something fundamentally wrong with it. IMO, if you want to run an external BB system, future occurrences of the problem are best avoided by dumping this crankset on ebay and buying something that really works, like a Shimano. The pinch bolt system they use is dead simple and simply works (my FSAs were on my crit bike and gave me the shits to the point where I did just that, dumped them on ebay and bought Dura-Ace).
Thanks for all your considered opinions, thats awesome.
As luck would have it, a mate just dropped around in his work car, and had some loctite threadlocker - so old that the label had worn off, but that hadn’t let him down yet. Just enough left in the bottom of the bottle - Bonza.
After pulling the crank arm off for the first time, I was 1) surprised how much grease had made its way from the bearing onto the spline & bolt, and 2) how little the area of the crank arm actually makes contact with the spindle. The design is dodgy.
Ahh well, came stock on a complete pompino, had 18 months of use. If it comes loose again I’ll remove the spacers from behind both crank arms, and try again. If that fails, could be time to upgrade to old school.
Time will tell if my story runs true to yours Capt C, thanks for that. I do love a DuraAce happy ending.
Thanks also SanEstban. I agree that to torque may not be necessary, and I will try to exercise some learned restraint. Also liked the link, is that what Areosmith/Run DMC sung about, Walk this way, Torque this way? It clearly pays to torque back.
Will be sure to update with any further breakdowns.
yeah i have very similar cranks on my mtb, and had heaps of problems with them coming loose, even though i followed the installation instructions including correct torques etc… design flaw i say…
loctite pretty much did the trick, or at least for a couple of years. they came loose again recently, and i just tightened them, but now they are creaking so fckn much, and will no doubt come loose again soon… POS…
Given all the feedback here about how the design of these cranks seems to create problems, I think you should take them into a bike shop, and make a warranty claim.
If necessary, ask that the truvativ rep call you(or email you) so you can make your case. Surely there is other bad feedback about these cranks on other sites which you can refer to. You should gang up and make a group complaint.
At worst, you’ll be in the same situation you are now.
At best, you’ll have a new set of cranks.
Sales reps always have overstock especially for servicing warranty claims… it’s no skin off their nose to help you out. And if they don’t, write a letter to Truvativ.
This is the process I went through with a set of FSA cranks which weren’t true… I got a new (upgraded) set.
