is it a known problem that aldhu crankset becoming loose.?
i have just had this recently installed with a power2max PM.
I kept the ultegra chainrings.
i am wondering if is just that the LBS did not torque the crankset to spec or they are just coming loose?
sadly there are no alternatives to keep using the power2max but with rotor cransket. unless i go and change everything and move to quarq or something.
what are your experiences with rotor cranks? should i worry and have to carry a torque wrench around. I want just to ride without worrying the crankset is going to come off or get loose.
on a side note. I am astonished how little knowledge LBS have of power2max. they look at it like a novelty item. they are just used to deal with quarq, 4iii stages and assioma…
I am sure that the LBS where i brought he P2M to be installed don’t know how to do it. ;(
I’ve had an aldhu crankset for two years now and had no issues with loosening. The torque spec is 35-40. No power meter attached, but I do have that bling aero crown.
You need to tighten that bolt with a 1.5ft+ torque wrench. If you don’t, it’ll come loose. If it wobbles enough, you deteriorate the crank arm / spindle interface.
You need to set that Tq, back the bolt off a touch, then re-torque it.
Mine hasn’t worked loose, but I’ve done less than 1000kms on it. I remember having trouble applying the required torque when installing, I did get there in the end using a long torque wrench I had from playing with cars.
My rotor Aldhu cranks have come loose a few times now.
possible causes I think are too many spacers (though I’m running the specced amount from the manual). I have a use a big torque wrench to tighten to 40nm, so I’d say theres room for improvement on the design - we’re not all screwing up doing up a bolt.
One friend who’s also got rotors has said he started using threadlocker on the bolt threads.
It is certainly a thing but I’ve found it to be very specific to some items. I’ve 3 bikes with Rotor crank sets and only 1 crank arm would always come loose - though I can’t yet say what the final resolve was (whether it was the bike, it had no spacers). I’ve replaced the axle and crank arms (for shorter) on that bike but not put in enough miles to see if it happens again.
I would start with the spacers, then thread locker then consider a new axle and crank bolts.
I would guess that once they’ve come loose a few times while riding, the thread tolerances may never be the same again?
p.s. I don’t know how to offer the correct number but found the manual to be contradictory, have a printed version that came with a product that is different to the web version.
Running a set of alu and a set of carbon rotor cranks with seperate P2M. Been installed on Cervelo R5, Dogma F and SL8 since 2021 and ridden 40k km in all weathers with no issues…had occasional ticking noise requiring maintenance and eventually new Bb but never had one come lose…
Yup, have 3 crank sets, one arm/axle or bolt interface was likely duff / the tolerances were not sufficient. The only fix was swapping them out but it’s a good reminder.. had a mate who had no idea what the collar did.
The preload collar is not useable at all on any of my rotor cranksets when installed with the specced number of spacers , I.e. it’s fully backed out, and the system is already preloaded by the spacers.
It’s possible to remove spacers and then use the preload collar instead. But there’s no difference to the bb spin down, or any play in the crank.
If you are not using the collar then you are not securing the crank onto the axle - you would just be tightening it against the spacers which isn’t ideal.
The 40nm should be crank onto axle, not crank against spacer.
If you are sure you are using the correct number of spacers then it might be worth checking your bottom bracket. Depending on the design it could be unscrewed slightly increasing the effective width.
2 different bikes with 2 different Bb standards. Both are fine, recently installed and have no issues.
Shimano BSA & BB86 wheelsmfg.
The loosening I describe has happened 3 times total over about a year.
In one case recently, it was a week after having my bike ‘serviced’ - it had multiple mechanical issues since so my suspicion is aimed fully at the mechanic, who will never get any business from me again.
It has also happened on the other bike though, which that mechanic hasn’t touched
No clue on the cause there. The BB is fine, the spacers were as specced, the preload collar was fully wound back and the bolt torqued to spec. I’ve taken it apart, cleaned everything, and reinstalled, though with 0.5mm fewer spacers to see if there’s any change - can’t see any difference at this point, there’s no play in the cranks, the BB spins freely
I strongly suspect though that this is a design flaw with rotor cranksets, and any crankset with a single central bolt - they should specify loctite on install at least.
