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Discussion Starter · #1 ·
The threads on one of my XX1 crank arms got f'ing destroyed. There's nothing left in there to tap.

Does anyone know of any way to repair this?

Thanks!
 

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Discussion Starter · #4 ·
Heli coil is something that I've used ,don't know if you could find one for a crank arm.
yeah, I just saw helicoil right before posting. How exactly does it work? I looks like it's a double sided threaded coil that bites into the existing metal, and then provides an already tapped surface? Or do they come in a form that is smooth on the inside and can be tapped to the exact spec?
 

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Discussion Starter · #5 ·
Contact SRAM - their warranty stuff is pretty good.
Contacted SRAM through Colorado Cyclist, where I originally purchased them. SRAM claims I crossed the threads (which I absolutely did not) and will not replace them. The right crank arm thread is damaged too, but they "don't know how it happened".

anyways... I told Colorado Cyclist that I was pretty disappointed with SRAM trying to blame me for something they can't even diagnose properly. We'll see what happens.

It's my first SRAM product, I've always purchased Shimano prior to this. Not a great beginning to my new (and possibly concluded) relationship with Big Red.
 

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I would never trust a helicoil repair for the crank/pedal threads, I've seen way too many failures.
 

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Discussion Starter · #7 ·
I would never trust a helicoil repair for the crank/pedal threads, I've seen way too many failures.
yeah, I know helicoil as a solution seems a bit too optimistic... those kinds of forces seem like they'd be far too much at such a critical stress point.

so I'm more or less screwed? (get it? screws have threads! ba dum tsssshhhh!)
 
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I would never trust a helicoil repair for the crank/pedal threads, I've seen way too many failures.
+2 on the Helicoil, it's not really designed for this application. I don't have a ton of great advice but you could try two things. First, you could have a local machine shop build up the inside with a welder and then redrill and retap the crankarm. Alternately, you could have the same shop thread a section of stainless tubing (inside and outside), then drill and tap the hole to accept the threaded stainless tubing and mount the stainless with heavy locktite or (ironically) J.B. Weld. This would provide a stronger repair than a helicoil but both fixes would compromise the strength of the original part to some degree. If it were me, I'd build the threaded stainless adapter.
 

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Discussion Starter · #9 ·
+2 on the Helicoil, it's not really designed for this application. I don't have a ton of great advice but you could try two things. First, you could have a local machine shop build up the inside with a welder and then redrill and retap the crankarm. Alternately, you could have the same shop thread a section of stainless tubing (inside and outside), then drill and tap the hole to accept the threaded stainless tubing and mount the stainless with heavy locktite or (ironically) J.B. Weld. This would provide a stronger repair than a helicoil but both fixes would compromise the strength of the original part to some degree. If it were me, I'd build the threaded stainless adapter.
I like the threaded stainless adapter idea... it's worth a shot at least, since I'd be tossing the damaged crank arm anyways.

The machine shop could presumably thread the outer surface of the adapter in the direction of the pedal stroke, thus possibly adding a bit more security as the threads would bite instead of loosen. Or is that wishful thinking?
 

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Discussion Starter · #10 ·
Contact SRAM - their warranty stuff is pretty good.

edit - assuming it was not destroyed by someone putting a left hand threaded pedal into a right hand threaded crank arm or vice versa. That will be easy to tell by them looking at the failure.
No, I absolutely babied the hell out of these cranks arms. I put Crankskins protective film on them before very gingerly finger tightening the pedals into them. I was more careful with this installation than I probably was holding my daughter after she was born (can't believe I just admitted that). Which is why SRAM's attitude about the warranty claim is really annoying.
 

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No, I absolutely babied the hell out of these cranks arms. I put Crankskins protective film on them before very gingerly finger tightening the pedals into them.
You did torque those down with a wrench after you finger tightened them didn't you?
 

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Discussion Starter · #14 ·
I was riding along, and my left pedal just popped off. Took most of the aluminum in the thread insert with it.

And while removing the other pedal in order to send back to SRAM, I noticed the threads on the other crank arm were f'd up too. Which SRAM apparently can't explain.
 
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I like the threaded stainless adapter idea... it's worth a shot at least, since I'd be tossing the damaged crank arm anyways.

The machine shop could presumably thread the outer surface of the adapter in the direction of the pedal stroke, thus possibly adding a bit more security as the threads would bite instead of loosen. Or is that wishful thinking?
That's probably not a bad idea, but I'm not sure if your shop would have a left handed tap in either size and if I were doing it I would try to avoid buying a tap. the insert would be threaded on a lathe either right or left handed, but the Arm would require a tap. threading both inserts with right-hand threads on the outside and mounting them with stud and bearing mount, loctite or JB should hold fine. You may consider having them form a small shoulder on the insert as well and recessing it (slightly) into the crank arm.
 

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What type of pedals did you have installed? You didn't accidentally use 1/2 threaded pedals instead of 9/16 right? I made that mistake once... and had a similar experience.

Best of luck.
 

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That sucks, but given that a replacement crankset is $240, you will rapidly approach that in machine shop costs unless you have a friend that will do it for beer. The pedals probably weren't tightened properly and worked loose, which wallowed out the holes.

I'd be tempted to just try drilling and tapping the spindles on a cheap set of pedals, and threading a bolt and washer in it from behind. Assuming that the hole in the crank arm is still a fairly tight fit to the spindle, the shoulder on the spindle should allow it to clamp tightly with a bolt on the back side.
 

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That sucks, but given that a replacement crankset is $240, you will rapidly approach that in machine shop costs unless you have a friend that will do it for beer.
This.

I doubt there's a DIY approach that will work in the long term, outside of welding and recutting the threads. This is an area that gets a lot of repetitive stress.

Regardless of your view of SRAM, I find it hard to believe that the threads failed on their own. On both sides. At the same time.

Sorry, I think you effed 'em up somehow. If they'll offer you a replacement deal, I'd take it.
 
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