Drive side crank self-loosening

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Drive side crank self-loosening
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flag bobish
Posted: May 11, 2009 at 19:27 Quote
My drive side crank loosens up on its own. Anything I can do to fix it? I've already tried to tighten it so tight so it won't loosen up but then cranks don't spin.
flag neex
Posted: May 11, 2009 at 19:50 Quote
bobish wrote:
My drive side crank loosens up on its own. Anything I can do to fix it? I've already tried to tighten it so tight so it won't loosen up but then cranks don't spin.

What kind of cranks?? You could be tightening a self extracting bolt??? Is that possible? Are the threads stripped? Would a little blue Locktite help?? Just trying to help not to flame. Maybe some more info would help.

Thanks,
A.
flag bobish
Posted: May 11, 2009 at 20:05 Quote
they are truvativ hussafelt cranks. sorry, meant to put that in the original.
flag bobish
Posted: May 11, 2009 at 20:06 Quote
Pretty sure the threads aren't stripped otherwise the bolt wouldn't thread in the first place right?
flag StevoFS
Posted: May 11, 2009 at 20:06 Quote
Hussefelts are known for that.....Just gotta have someone stand on the allen key and get the damn thing extremely tight.
flag bobish
Posted: May 11, 2009 at 20:09 Quote
I've tried to make them really tight but if I tighten it too much then the cranks won't spin.
flag StevoFS
Posted: May 11, 2009 at 20:10 Quote
bobish wrote:
I've tried to make them really tight but if I tighten it too much then the cranks won't spin.
Never had that happen to me though....Thats odd.
flag Gravis7
O+
Posted: May 11, 2009 at 20:13 Quote
I have the same problem with hussefelt cranks, nothing much you can do except carry an allen key wherever you go to make sure they dont come loose mid ride and ruin your whole day.
flag neex
Posted: May 11, 2009 at 20:17 Quote
bobish wrote:
Pretty sure the threads aren't stripped otherwise the bolt wouldn't thread in the first place right?

Yes and no. It might thread in and then break loose under load. A perfect example would be a stripped crank arm thread that almost allows you to extract the arm but not quite when a load is applied to remove it. I had this happen a few weeks ago with an old Octalink crank arm (never happened before to me with a crank arm ever).

Take a good look at the bolt and the threads of the axle itself. Most of those will take an insane amount of torque though. Those cranks... do they have that x-type bb?? If so, would removing a spacer help?? Is it possible that the DS crank arm bolt isn't bottoming out entirely? In other words, if there's an extra spacer on the spindle/axle pressing against the crank arm, you won't be able to seat the arm properly and the bolt won't be fully bottomed out. I don't know if this makes sense to you or not or if I am just rambling. It's a little hard for me to explain properly. How many spacers did you use when installing this crank do you know? I would try removing one (especially when you said that tightening it too much causes resistance in the crank). If the spacer are set properly this should be theoretically impossible because if the bolt is bottomed out, overtorquing it should only damage the bolt itself or the threads in the spindle but it shouldn't actually make the interface between the crank and the bb shell any tighter.

Sorry if this confuses the situation or if these cranks don't take the x type bb.

A.
flag neex
Posted: May 11, 2009 at 20:31 Quote
Gravis7 wrote:
I have the same problem with hussefelt cranks, nothing much you can do except carry an allen key wherever you go to make sure they dont come loose mid ride and ruin your whole day.

Double check that you are actually bottoming out the bolt and that you have the correct amount of spacers (if required). I find it hard to believe that these cranks give this problem to everyone who sets them up. If so, I would be barking at the R&D team...

A.
flag aslfgb
Posted: May 12, 2009 at 9:31 Quote
My friend has the same exact problem, I talked to sram and they said to "torque it to specs" but thats obviously not the problem. He still hasn't figured it out.
flag srobinson
Posted: May 12, 2009 at 20:43 Quote
As much as it sucks, your cranks are toast. Once you've let them come loose once, they will never stay tight again.

I'll try and explain it the best I can. I assume you've taken the arm off and looked at it, and if you haven't, do it as it will make more sense. The BB spindle has a 6(?) point sline on it, that is tapered towards the frame (the further you push the crank onto the spindle, the tighter it gets). What happens is when the bolt backs off the first time the crank arm can work back and forth and side to side and when this happens it puts a slight wear on the softer aluminum spline in the crankarm. Note: this isn't always the cause, but is often the culprit. Sometimes it happens due to normal use. Anyways the end result is the same. When you tighten down the crank bolt the spline is no longer tight, even though it may appear to be. This means it can rock back and forth just a tiny amound on the spindle depending on the load applied to it. Every time it moves, it pushes the bolt with it until it eventually comes loose again.

The only way to fix it is by replacing that damaged aluminum spline, and to do so you have to replace the crankarm.


@neex: for future reference they are not an X-type and require no spacers.
flag bobish
Posted: May 12, 2009 at 21:44 Quote
Thanks srobinson, that's kinda what I thought the reason was but I thought I would see if there was anything I could do to fix it. looks like I'm shoppin for new cranks when I get some money.
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