# Shimano external crankset question



## samh (May 5, 2004)

I'm thinking of getting an external crank but review said: 

"I have less than 100 mi on my new rig and ran into what appears to be a design flaw. The end cap on the non-drive side crank arm is made of plastic or nylon...can't say for sure cause mine is gone! It broke and fell out and I didn't notice until my crank arm worked it's way off during a steep ascent...no good!"

Is this a problem?


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## robdamanii (Feb 13, 2006)

I've had 3 or 4 outboard bearing cranksets from Shimano. No problems with the cap if you use it as intended: bearing preload. If you strip off the threads on that cap, sure it'll disappear. The review describes something that suspiciously sounds like he/she forgot to tighten the pinch bolts holding the arm on sufficiently.

I wouldn't let something simple like that nylon cap stop you from buying an otherwise great crank.


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## maxxevv (Jan 18, 2009)

The review fella obviously didn't have his crank pinch bolts tightened correctly/properly. 

I have used this design since the inception of the 7800 groupset back in '03. Absolutely zero problems if installed correctly. BTW.. I install and fix all my bikes myself.


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## Cut.Aussie (Mar 19, 2011)

Ok, I think this guy is talking about the small plastic "dress" cap the screws into the end of the non drive side crank to cover up the hollowtech tube, that all it is, think a hub cap on a car wheel, its not structural at all, its just something to make it look pretty.

So as others have said, its seems he did not correctly tighten the two socket pinch bolts that hold the non drive side crank arm, that's not a design defect but rather poor workmanship on behalf of whoever fitted the crankset.


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## robdamanii (Feb 13, 2006)

Actually, it's not a "dress cap" but it's designed to preload the bearings.


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## Cut.Aussie (Mar 19, 2011)

robdamanii said:


> Actually, it's not a "dress cap" but it's designed to preload the bearings.


Agreed, that's it's use before the the left crank is tightened but after the crank is in place and tightened to the correct torque (106 - 122 in. lbs.) it serves no real purpose anymore and can be removed without effect.

The original poster seems to be inferring that this plastic cap failing allowed his crank arm to come off, clearly that is untrue, while Shimano has it's occasional problems, this cheap plastic cap is not one of them.

By the way, the bearing a preload torque of 6-13 in. lbs. or 0.7 - 1.4 Nm


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