Powertap Pro wheel keeps coming loose

16simon

Hi all, I recently bought a second hand (but only 5 months old and well looked after) Powertap Pro wheel. I've raced on it four times now, and it's come loose in two races. The first time was a time trial on a hilly course when I got out of the saddle to get over a short sharp climb, but the other time was a crit on a flat circuit when I'd been sat down the whole time.

I've tried two different skewers, but had this problem with both. There is no play in the bearings, the skewer is not coming undone, but at a certain point the wheel feels wobbly and when I get off and check it is loose in the frame.

I try not to overtighten the skewer (AFAIK this can compress the bearing and shorten it's life) but I'm pretty sure that I am doing it it tight enough. I've never had a problem with wheels coming loose before anyway.

Any ideas what might be causing this? Have any other Powertap wheel users had this problem?

fearby

What about the cones????

http://www.cyclepowermeters.com/17mm-co ... -441-p.asp

schweiz

I've never had it happen with my power tap hub. I can't see why the hub would be the cause to be honest as the axle is a continuous tube.

What skewers have you tried? How much tension do you use (judge by at what point between lever fully opened and fully closed it starts to 'bite'?) What is the drop out material and what is the QR material on the serrated clamping face?

There's lots on here about skewers and their relative merits. The general consensus is that shimano, with their enclosed cam are better. Sheldon Brown has plenty to say on the topic. http://www.sheldonbrown.com/skewers.html

I've just gone back to using the Shimano Ultegra ones that came with my commuting wheels (ultegra hub with CXP 33 rims) after a the KCNC ones I've been using pretty much trouble free seemed to be loose on the rear the other day. The only problem I'd had previously was when a bike shop didn't do them up tight enough.

I have to admit that going back to the Shimano ones reminded me how much less closing force is required to get a a high clamping force. Like you, I'm concerned about loading the bearings too much by over-tightening the quick release but I have always been careful but the KCNC, Van Nicholas, Sun Ringle and Mavic skewers that I use on my wheels are all open cam and all have to be fastened fairly tight. I was always told that the QR should start to bite as it goes through 90 degrees (fully open being 0 and fully closed being 180 (or 190 on some). I would have the KCNC biting at 80 to get a good clamping force.

doyler78

Make sure that the powertap hub caps (don't what to call them) are fully tightened. I know my cassette has seperated from the freehub body on the powertap as it wasn't fully tightened when I received it (at least I didn't touch it as I didn't even know you could take them apart). This is to allow you to change the freehub to suit your groupset. If it's not fully tightened that perhaps is stopping you seating the wheel properly.

16simon

Thanks Schweiz, very interesting article by Sheldon, I've never really thought about skewers that much

Both the skewers were indeed open cam, so I'll have a go at tightening them up more. It's still strange that this problem has only occurred with the PT wheels. Perhaps because I'm conscious that the hub has delicate expensive bits inside, I was more delicate than usual when clamping the QR closed?

schweiz

It's the only thing I can think off to be honest.

As fearby said, my first though was the cones need adjusting, but you say that there's no play in the bearings. Are you completely sure?

more from sheldon here

http://www.sheldonbrown.com/cone-adjustment.html

16simon

Well, the LH end nut can be undone by hand, but this shouldn't be a problem when the wheel is clamped into a frame... I think. Will try and gently nip it up with a cone spanner.

schweiz

IMO the nut shouldn't be able to be opened by hand. It is a locknut so with one cone spanner you should hold the cone in the position that loads the bearings as desired and then the lock nut should then be tightened up against the cone...it should be tight.