Bicycle Mechanics - Stripped Crank Thread

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View Full Version : Stripped Crank Thread


Synchronize
12-02-10, 04:16 PM
Hey guys. I just stripped the left crank thread on my Mercier Kilo TT. It's a Truvativ Touro crankset and I'm looking to buy just a left crank arm rather than replacing the whole crankset.
What should I know about compatibility with the bottom bracket etc?
Is there a reason (other than long term durability) not to go with a cheap arm from the interenet (i.e. http://directbicycleparts.com/product/rpm-left-165mm-arm-black-sku-cr2125-qc53.htm)
Thanks!


Chris_in_Miami
12-02-10, 04:38 PM
Pedal threads or dustcap/puller threads? If it's the former, you can have a heli-coil insert installed and you won't need to worry about compatibility.

Synchronize
12-02-10, 04:55 PM
They were the pedal threads.


Dave A
12-02-10, 05:59 PM
Pedal threads or dustcap/puller threads? If it's the former, you can have a heli-coil insert installed and you won't need to worry about compatibility.

+1 : http://www.jensonusa.com/store/product/TL308B00-Union+Pedal+Tap+And+Bushing+Set.aspx?SSAID=418273 The whole kit is spendy, but most bike shops will install one for you for a reasonable amount

Dave

Bianchigirll
12-02-10, 06:11 PM
is the length correct? the crank in the link is only 165mm. what size is the crank on your bike?

if you shop does it go for the helicoil, then cut down on the one pedal mounts and dismounts

Synchronize
12-02-10, 06:42 PM
The stripped thread is on the crank arm, where the pedal screws in. I really don't think buying a kit makes more sense than just replacing the crank arm.
The one currently on my bike is a 165 mm. That's why I linked to it.
Essentially my question is am I going to have any compatibility issues if I go ahead and buy that crank arm?

Dave A
12-02-10, 07:54 PM
Essentially my question is am I going to have any compatibility issues if I go ahead and buy that crank arm?

No, it should work, assuming the original mounts on a JIS square taper BB, which I think it does. The only potential issue would be a possible change in width...ie, the new arm may locate the pedal farther away from, or closer to the center of the bottom bracket, etc. Although, if so, I would guess that its not significant.

FBinNY
12-02-10, 09:02 PM
....if you shop does it go for the helicoil, then cut down on the one pedal mounts and dismounts

Will somebody please get a shotgun and put this old canard to rest?

The stress of one foot mounts/dismounts is no higher than that of standing when climbing a steep hill. This is well with the range of acceptable load, and less than when 250# riders stand and pedal, and has no effect on pedal thread issues.

john hawrylak
12-27-10, 06:58 PM
Synchronize, thanks for posting this. I had same question and was glad to find the heli-coil repair option

fietsbob
12-27-10, 07:16 PM
Many Bike shops have the tools , a double threaded sleeve, of steel

will be stronger than the original aluminum

which was not strong enough for someone who rode too long on a loose pedal.

DieselDan
12-27-10, 07:26 PM
I got a pile of left crank arms, all square taper. Much easier and cheaper then going the helicoil route. Next time, remember the pedal threads are backwards on the left side.