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105 Crank won't stay tight, Help!(5 posts)

105 Crank won't stay tight, Help!Offroadnut
Aug 28, 2002 6:47 AM
My 105 chain ring side crank loosens up about every three or four rides. I took it to my LBS and they put teflon tape on it and tightened it. Still loosened up. I have used blue loctite. Still comes loose. Should I be torquing it down or does this just happen? I ride this bike four days a week.
Thanks
Square taper or splined BB?TJeanloz
Aug 28, 2002 7:04 AM
Is it 9speed or 8speed? It should not come loose, ever, if you torque it to spec (50 Nm for splined, 38 Nm for square taper).
Square taper or splined BB?Offroadnut
Aug 28, 2002 8:57 AM
It is a splined 9speed. Excuse my ignorance but what is Nm? I have a torge wrench that does foot pounds.
Nm = Newton-Meters, the metric standardTJeanloz
Aug 28, 2002 9:10 AM
The next thing to check is that your splines are all intact, and that the grooves they fit into on the crank are intact.
Torque ConversionSlip Stream
Aug 28, 2002 10:09 AM
Check out http://www.onlineconversion.com/torque.htm for an online torque converter. And there is a chart at http://www.parktool.com/repair_help/FAQindex.shtml along with instructions and advice.

Splined Shimano cranks are torqued to about 30 ft-lbs. Bottom braket to about 50 ft-lbs.

But, it is odd they are coming loose. You should really be able to hand tighten them with a standard allen key to a reasonably tight fight. You should not need teflon tape for your crank. Using it could create a gap.

Are you experience a strange noise or does it feel loose when you crank? If so it is most likely your bottom braket. Take the crank off of both sides. Remove the bottom braket (standard left-to-loose threading). Clean male and female threads. Do not be afraid to use a brush to really clean them. Wrap both sides with a singe layer, once around of teflon tape and torque. If this does not solve your problem, do it again with a wider width (more threads covered) of teflon tape.