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Discussion Starter · #1 ·
Hi guys, I have a Vitus Sentier 27 and after a few rides the crank fell off, okay so I tightened it back on and now whenever I go back out it eventually slowly walks itself back off even though the two Allen bolts are tight. I've only had the bike for a month. I've also tried Loctite but still walked off.
 

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You should have preload cap, which threads into the internal threads of the spindle shaft on the non-drive side. That should prevent the crank arm from walking off. Do you have one?
 

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Discussion Starter · #3 ·
You should have preload cap, which threads into the internal threads of the spindle shaft on the non-drive side. That should prevent the crank arm from walking off. Do you have one?
Yes I have the preload cap but even with that tightened the cranks walk off.
 

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I had that happen recently on one of my bikes. Seemed to be ok after I torqued the inner bolt first, then the outer.
 

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Install arm loosely. Add cap and tighten down lightly with your hand (1-2 Nm torque). This brings the arm against the bearings. Tighten pinch bolts, alternating sides. Don't just tighten one and the other. Torque should be 12-14 Nm - which is pretty high - more than I would do if I was guessing.


In your first pic, is the top cap still attached to the crank? It should thread into the crank spindle. The cap is ultimately the most important piece to prevent walkout. It almost looks sheared off.. Do you have a pic of it?

Also, does your crank arm have the plastic retaining piece on it? That should also prevent the crank from fully falling off.
 

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Discussion Starter · #6 ·
Install arm loosely. Add cap and tighten down lightly with your hand (1-2 Nm torque). This brings the arm against the bearings. Tighten pinch bolts, alternating sides. Don't just tighten one and the other. Torque should be 12-14 Nm - which is pretty high - more than I would do if I was guessing.


In your first pic, is the top cap still attached to the crank? It should thread into the crank spindle. The cap is ultimately the most important piece to prevent walkout. It almost looks sheared off.. Do you have a pic of it?

Also, does your crank arm have the plastic retaining piece on it? That should also prevent the crank from fully falling off.
Thanks for the response, I tightened the pinch bolts to the right torque and I tightened the preload cap the best I could. I’ve had the guy at the bike shop tighten it before already but it always manages to walk itself off again. I’m going to go for a ride in an hour and I’ll do some hard riding and see if it walks off again.
 

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Do you have the “safety plate” that’s supposed to keep the arm from falling off?

1940147
 

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Do you have the “safety plate” that’s supposed to keep the arm from falling off?
The preload doesnt keep the arm on, its basically the safety plate that does. arm will always fall off without the safety plate flicked down, no matter how hard you tighten the pre-load or the 2 bolts.
 

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The preload doesnt keep the arm on, its basically the safety plate that does. arm will always fall off without the safety plate flicked down, no matter how hard you tighten the pre-load or the 2 bolts.
I am not sure that’s true. My previous xt cranks didn’t have that thing in place, and never fell out for years. If the cranks are coming off when properly torqued, something else is going wrong.
 

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The preload doesnt keep the arm on, its basically the safety plate that does. arm will always fall off without the safety plate flicked down, no matter how hard you tighten the pre-load or the 2 bolts.
It's amazing that my XTR crank arms don't fall off considering that the first thing I did when I got them 1000s of miles ago was to rip out those stupid safety plates.

I think SnowyMX's cranks are defective and should be replaced. My LBS says they warranty Shimano cranks for this problem from time to time. It doesn't appear to be as prevalent as the glued together crank arms falling apart.
 

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I am not sure that’s true. My previous xt cranks didn’t have that thing in place, and never fell out for years. If the cranks are coming off when properly torqued, something else is going wrong.

Agree, I've personally run a Shimano crankset for several years without that safety tab thingy. Never a problem.
 

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It's amazing that my XTR crank arms don't fall off considering that the first thing I did when I got them 1000s of miles ago was to rip out those stupid safety plates.

I think SnowyMX's cranks are defective and should be replaced. My LBS says they warranty Shimano cranks for this problem from time to time. It doesn't appear to be as prevalent as the glued together crank arms falling apart.
May I enquire why you removed the tabs?

They may be defective or worn/rounded
 

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The preload doesnt keep the arm on, its basically the safety plate that does. arm will always fall off without the safety plate flicked down, no matter how hard you tighten the pre-load or the 2 bolts.
don't know your mileage but I toss those lawyer tabs immediately and have never lost or had a loose shimano 2 bolt spline crank no matter how I ride, smash it into rocks...long hill climbs torqueing it ...I am having a heck of a time understanding how this can come loose....those two bolts are all that is needed

preload to snug up to the bearing
then crank them bolts evenly, 1/4 turn, then the other, repeat, until about 14nm each.
 

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I've had those installed on some but not all hollowtech cranks and never had a problem. It should be easy enough to take it out and inspect though. I never had a crankarm walk off once the cap was preloaded and the arm was properly torqued. Hope he can solve it.
 

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all I can think of, is there is some schmoo or a pebble or piece of metal
in the slot, preventing full tightening of the clamp

I mean, what is this crud anyway ? clean that outta there

1940187
 
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I have also been having this problem with a set of XTs. I have lost the lawyer tab and the preload cap. The last thing I tried was removing as much grease as possible, put thread lock on the pinch bolts and tightened them as much as i felt safe doing. The crank has stayed on now for 3-4 rides so I hope i am in the clear.
 

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all I can think of, is there is some schmoo or a pebble or piece of metal
in the slot, preventing full tightening of the clamp

I mean, what is this crud anyway ? clean that outta there

View attachment 1940187
This is where I'd start. That, and alternating the bolts a little at a time since if you fully torque one before going to the other it can make the other feel tight even though it's not.

Never lost a Shimano crankarm since they went to this 2 bolt system.
 

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I have this problem on my XT.

You all want to know what happened to me at a full strength uphill interval training and the crank arm falls off? I rolled off the levee trail and barely hung on to the bushes. Major scrapes on knee cap. Looking at the scar now as I type.

I torqued per Shimano, had safety pin, and used locktite.

OP, after your original incident, the internal microsplines got stripped a bit. It can no longer tighten properly which is why it keeps falling off. Check the inner splines to see if any of the grooves appears partially gone.

To Shimano’s credit, I caused my own original damage. I failed to tighten to torque on the crankarm when I first got them, then went to jump off a large flight of stairs. The crankarm didn’t fall off during this incident, but rotated fully out of place. After that the inner grooves were slightly stripped. Nothing I do can keep it tight for more than a few rides. The feeling of not knowing when something will fall off is very dangerous.

After my levee accident, I just sucked it up and bought a nee crankset.
 
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