Play in old splined cranks

Hi all,

I’ve got a ~17 years old Qu-ax trials uni in my collection that is equipped with the Qu-ax 10 spline hub. I lately used its 145mm cranks to test them on a friend’s 24" muni from the same decade (which originally has 170mm cranks). After putting the cranks back onto my trials the right crank has some play which I can feel when riding with changing load (e.g. when idling). Could be that this was already there before swapping cranks but I didn’t notice it as much as I now. There was no such play when the cranks sat at the muni btw. I’ve already asked Qu-ax if this issue is known from that generation of hubs and they couldn’t help me any further than proposing more torque on the screw that clamps the crank onto the hub (pretty quick reaction though for such an old-timer question). Now I think I reached a pretty high torque (15Nm or something around that on an M6 screw…?) and still the crank can move a little bit.
Does anybody have experiences with this? Can anyone advise anything more than what Qu-ax did?
If I don’t do anything about it I guess over time it will wear out and finally a new hub and new cranks will be due.


Have you tried rotating the cranks on the splines to see if they are tighter in other positions?

Yes, I have tried that, too. Not in all 10 possible positions though, so that might still be something to try…


Another thing you could try would be swapping the cranks left to right on the hub.

I hadn’t heard of any issues like this when these cranks were more in use, so I don’t think it’s very common.

If I were to guess I’d say that the play was always there and now that they have been removed and replaced its more noticeable due to any dirt or rust that was in the groves has been dislodged.
You could tighten the splines by using a center punch to dent the top of every other slpine, test fitting occasionally.
I’ve also used a little crazy glue in situations like this to remove play. You can dissolve the crazy glue later with acetone if you want to get rid of it.

I’m not familiar with that hub but I would have to agree with 29erKay in that you should try rotating the cranks to other positions since there are ten. Maybe you just installed them in a different spot than previously and perhaps the old spot was just right.

Hi @martin,

The torque you mention feels a bit on the low side somehow. I did a quick search and for an ISIS hub with its M12 bolt, it is more around 40Nm (Schlumpf hubs: general discussion. - #1026 by DavidHood).

In your shoes, I would remove the cranks, thoroughly clean the interface on the hub and crank, grease the spline, and mont the cranks again by gently torquing up until there is a big resistance (or if you have a torque wrench you can start by targeting 25 to 30Nm except if you get a very big resistance before that).

While not being perfect, those 10-spline were sturdy so moving them from a qu-ax hub to another should not be such a concern.

Fortunately we don’t have to rely on feelings here. I’m talking about the M6 bolt that pulls together the gap at the end of the crank. The M12 bolt you are talking about is the one that goes into the end of the ISIS axle. And while 40 Nm is indeed still on the low side for an M12 bolt, 15 Nm on an M6 bolt is pretty much already (the table in the link lists bolts of a pretty high strength category)

That’s basically what I’ve done so far. I’ve even replaced the grease with anti-seize assembly paste as it is used to increase the friction on such connections.

Just to double-check: You’re saying that by using a center punch I could try to deform some of the splines slightly so that eventually the play might disappear? Interesting approach, I’ll leave this as last resort.

Action items for me:

  1. Try all 10 possibilities.
  2. if 1. doesn’t resolve the issue sufficiently, swap cranks left to right and vice versa and repeat 1. in that setup.
  3. If none of that helps, try to make the splines a little bit wider with a center punch.

Thanks so far, I’ll report back even though it might take some time!

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…which is a M8 bolt actually, sorry for that mistake. That gives us somewhat more possible torque but doesn’t change the story completely. Anyway, the fact that I know this now means that much sooner than expected I found the time to check your ideas. And even though I was almost certain that I had checked another position on the splined axle already I only had to go one position further to get the crank fixed. When the crank was not fastened I could move it quite a lot in all positions. In contrast to that the left crank could not be put onto the axle easily. So there is a difference but anyway, I think I got it solved much easier than expected.
So thanks again for all the good advices, now going on that uni feels much better again because I don’t have the constant feeling of destroying something.