I bought a new power meter from Power2Max (Adhu). The first ride was 120 minutes and all good. Day 2 I couldn’t make it ten minutes without the crank arm coming loose. I used red locktite overnight but still today it kept coming loose. I watched a video and didn’t have any of the plastic spacers in so I put 2 on each side to remove any gap but only made it 2 minutes before it was loose. About 5 years ago I bought the Type S that has been great except the battery cover breaking off hence the replacement. This new design has a tiny screw that you can tighten after setting the arm with zero play and I tightened it as tight as I could get. The arm still slides off. Any suggestions? I emailed them but hoping there is some tips I’m missing. I have installed 5 of these on friends bikes over the years with no problems.
What type of crank arm and bottom bracket system is it? Sometimes when a crank arm loosens up it becomes damaged because the metal of the crank arm is much softer than the bottom bracket axle. Pull it off and take a good look at it and see if the spline interface looks like it’s all mangled.
Thanks, it still looks brand new to me. It’s a Trek BB90 with new bearings installed at The Trek dealership before installing the new power meter. It’s Power2Max NGeco ALDHU Rotor crank arm. Single Allen tool to tighten the center until no play then a small screw to tighten on the side (to clamp around the shaft).
… is there a torque printed on the crank screw & is it applied ?? … f.x. RotoR 3D+ crank arms have 35 to 40 Nm … other wise the screw has no self adhesive surface contact force …
I’m feeling pretty stupid now. It clearly says ‘Tighten 35/40 Nm to install’ on the screw. I feel like that will compress the bearings way to tight but I’m going to go buy a torque wrench and try that. The video to assemble this type just shows to tighten to remove play. I just checked my old Power2Max and my wife’s and both screws say the same thing. I’ve never done that before and I have cleaned them pretty regularly. Thank you thank you.
… loosen the preload nut to the widest option before applying the torque to the crank arm screws … then set the preload nut to remove play in the axle and tighten the preload bolt … just for fine adjustment use washers if needed … https://rotorbike.com/catalog/german/downloads/dl/file/id/71/product/1128/manual_aldhu3d_en_es.pdf
Yep. Set the preload nut first. Second, torque the bolt as per the label. It is usually quite high torque required for the crank bolt.
… doing it my way the preload nut thread is save …
The pamphlet helped out. I picked up a torque wrench and Holy Crap that is tight!! The problem was the preload nut wasn’t tight (open) against the crank arm. I couldn’t turn it into the crank any further and assumed it was open all the way. Because it wasn’t fully open it was making the system too tight when torqued to spec. I put the small Allen tool into the screw head and tapped it with a rubber mallet another full turn and half into the crank arm. That gave me enough gap to torque the system to spec then back off the preload to close the gap. It spins very nicely now and there is no way it is coming loose. I can’t say thank you enough.
(I hope that all makes sense. If not, the short answer is Slowtwitch saved my sanity.)
Nice … have fun riding !! … … sometimes the preload nut stucks a bit … sorry I didn’t mention … and yes, the widest gap for play means tight to the crank arm … check for the play after some rides …