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Broken Left Crank Arm
Hi All,

Just about to head out on a ride this past weekend when the left crank arm fell off.

I have attached a picture which I hope will help somebody explain which part I need to get to fix this problem.

Thanks for the help in advance.

Hi Gary,
Welcome to the forums! Before I say anything can you snap a picture of the other side crank?

If you can also give us this info..

Make/Model ?
Year ?
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
(04-04-2010, 09:27 PM)Bill Wrote:  Hi Gary,
Welcome to the forums! Before I say anything can you snap a picture of the other side crank?

If you can also give us this info..

Make/Model ?
Year ?

Thanks for the reply.

The bike is a 2009 CELL SORA BLADE purchased at http://www.cellbikes.com.au in December 2009. From what I know about the gearset - they are Shimano SORA.

I have also just found an image from the cellbikes website of this years model SORA Blade. The pic shows the left crank arm and what part I believe I am missing.

Thank you very much for adding the pictures, the black piece you are referencing to is more or less just a cap. I did find the actual documents of your crank, one of two of these
. From what is pictured and the looks of your axle splines you may need to replace the crankset assembly from being chewed up. Now before you do lets see what a couple of the other members on here have to say, because I do not want you to just take my opinion alone as I have been wrong before. So just hang loose. If it does need replaced have a Local Bike Shop do it because I think it your frame is Carbon Fiber and the Bottom Bracket assembly even says Do not Disassemble. May be a little expensive but worth it in the long run unless it is something more simpler.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
Thanks for the posts, either of these certainly looks to have the missing screw in cap part. I have also emailed where I purchased the bike from as it is only 3 months old and should still be under warranty too.

Either way, I hope this doesn't turn out to be an expensive exercise. Appreciate the advice - its been a good learning experience if nothing else.


The Cell Blade with Sora components is an aluminum frame. The Do not disassemble label on the BB is telling you not to try and pull the BB itself apart - not to pull the crank arms off the BB axle. Bill is correct - the black cap is 'just' a cap, but you do use it to snug the crank onto the axle before tightening the two bolts on the crank arm to lock the crank in place.

Do check your crank to make sure the teeth are all clean and haven't been stripped off. If the teeth on the crank arm are still fine, and will 'mate' with the teeth on the axle, then you 'just' need a replacement plastic cap and the plastic tool to hand tighten the crank arm onto the axle. You might get both of them for free from your local bike shop.

If the teeth inside the crank arm are chewed up, you might be looking at a new crank - both sides - and axle (which is permanently attached to the right crank arm)
That looks like a "Hollowtech" chainset.
Here is a video of a similar one being removed and re-fitted.
Just the beginning and end are relevant to you but watch the whole lot for future reference.

The "plastic cap" mentioned above is probably used to tension the arm before finally tightening the 2 allen screws. And don't forget the little metal clip shown in the video. It's the screws and clip that hold the arm on!

Here are Shimano instructions:-
Ride hard or ride home alone!

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