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Threads repair

Old 08-24-20, 05:54 AM
  #1  
kennyc23
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Threads repair

Have been calling bike shops and none of them will do threads repair. do you know which ones do in NYC?
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Old 08-24-20, 06:13 AM
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Which threads? Although most of us cannot point you to a shop, knowing what threads are buggered might help. A water bottle boss thread is much different than a pedal or threaded headset.
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Old 08-24-20, 06:30 AM
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pedal attachment. usually i would just replace it but this is Sram Red 22 expensive crank so i try to save to do repair.
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Old 08-24-20, 06:47 AM
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Some shops can do crank arm pedal thread repairs with an insert. Some don't, likely most don't. I think your answer will be to call around and ask each shop. I would suggest the older shops first. Andy
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Old 08-24-20, 07:03 AM
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do machine shops do it too?
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Old 08-24-20, 07:09 AM
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The issue with a machine shop is that they likely don't deal with 9/16" x 20tpi left handed threads often enough to have the inserts on hand. This is a thread spec pretty much bike industry only.

I sense a reluctance to call shops and find out yourself. Am I correct? Andy
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Old 08-24-20, 07:17 AM
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kennyc23
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Thanks Andy. i didn't realize 20 tpi for 9/16 is not industry standard. BTW, it is for right arm.
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Old 08-24-20, 07:31 AM
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Sorry, it was my assumption that it was the LH arm. We see far more LH pedal thread issues then RH ones. Good luck. Andy
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Old 08-24-20, 07:39 AM
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I looked up your crank, holy cow! I thought an old DeoreXT crank was hot stuff. It looks like your crank is graphite with a threaded alloy block for the pedal. Just a thought, maybe SRAM does or has recommended vendors for repairs to that crank. Good luck with that.
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Old 08-24-20, 07:55 AM
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Hows bad is the damage? If it's just the lead thread you may be able to "chase" it by threading the pedal in from the back side of the crank arm.
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Old 08-24-20, 08:01 AM
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Thanks. good idea to contact SRAM to see what they say. and find out the cost for just arm replacement.

Last edited by kennyc23; 08-24-20 at 08:09 AM.
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Old 08-24-20, 08:02 AM
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it is the entire length of the threads.
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Old 08-24-20, 08:21 AM
  #13  
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Wow, 'someone' must have Schwarzeneggered a pedal install to do that. Most people stop after turning the pedal 1-3 threads
when cross threading, to go all the way is to ignore the 3-4x increased torque needed to cross thread a large thread.
Ability to repair with insert will depend on how big the alloy portion is, as the insert requires 2-3mm larger diameter hole which
is then threaded by the insert, so alloy block must be at least 4-5 mm larger than the 9/16 hole for the pedal.
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Old 08-24-20, 12:42 PM
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Mel Kornbluh at Tandems East in New Jersey advertises in his catalogue that he will repair stripped cranks, using Helicoil inserts. You could phone him and see if he can repair yours.
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Old 08-24-20, 03:38 PM
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Is this a carbon crank? If so, the threaded part for the pedals might not like being drilled and re-threaded for an insert to be put in it. May just be an insert itself embedded in the carbon.

If your threads are badly damaged, then trying to run a same size tap through it is going to leave too little material to be a decent fix for long.

If it's only damaged at the starting thread or two, then maybe there is hope for just running a tap through it. Or if your pedals have a long enough threaded part to reach all the way through, run them in from the other side and hope they push the damaged part into a better position. Maybe use an old pair.
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Old 08-25-20, 08:40 AM
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Originally Posted by kennyc23
do machine shops do it too?
Machine shops can do helicoil repairs, but may not have the left-hand thread tap and insert required for a non-drive side crank arm. If it's the drive side crank arm, I wouldn't expect a problem.
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Old 08-25-20, 08:54 AM
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Are the treads shot or is it the threaded insert itself that's spinning? Happened to me on my TT bike - had to epoxy the insert back in to the crank arm.
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Old 08-25-20, 09:38 AM
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Originally Posted by conspiratemus1
Mel Kornbluh at Tandems East in New Jersey advertises in his catalogue that he will repair stripped cranks, using Helicoil inserts. You could phone him and see if he can repair yours.
Typical of these forums lots of broadcasting not much receiving. Thank you for your excellent response.
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Old 08-25-20, 09:52 AM
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Originally Posted by kennyc23
Thanks Andy. i didn't realize 20 tpi for 9/16 is not industry standard. BTW, it is for right arm.
...if it helps you, when you call around, this is the threading on a lot of older spark plugs. So places that machine and repair ICE cylinder heads often run into this issue, and might have some 9/16" 20 tpi helicoils on hand, and be willing to install one for you. They do make bicycle specific kits for this, but they run in the$100-120 range, so a lot of places don't bother to buy them. Bicycle co-ops sometimes have them...ours does.
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Old 08-25-20, 10:02 AM
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The bicycle repair business suppliers make pedal thread repair kits ...

2 kinds a sleeve threaded on both sides the stripped hole is reamed , then tapped, then the insert goes in

And Helicoil .. a coiled diamond shape steel wire,, similar process..

Your local shop unwilling to do that, don't own or wont buy the tools to do that.

take the crank off ,

mail it to a shop that is willing to do that, owns the tools , etc..



VAR , France, makes this one..

helicoil type




...

Last edited by fietsbob; 08-25-20 at 10:09 AM.
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Old 08-25-20, 10:03 AM
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...these guys offer it as an online repair service for $25 9which is pretty cheap), but the mailing costs might kill it for you.

- Pedal thread helicoiling service, to repair damaged pedal threads on your crank arm.
- Available for all models of aluminium crank (and most carbon ones such as SRAM) arm providing it doesn't use a steel insert as standard (such as some Truvativ cranks).
- Only available for 9/16" x 20tpi pedal threads (not steel cranks or 1/2" threads).
- Please note that due to the nature of this service, it may not be possible to repair and replace the thread perfectly square with the crank arm. We do drill out the existing thread as a guide though, so it is usually within one degree and almost imperceptible.
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Old 08-25-20, 10:13 AM
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Originally Posted by velopig
. . .. Thank you for your excellent response.
Thanks for totally making my day!
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Old 08-25-20, 10:23 AM
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Park has some info as to the repair method

https://www.parktool.com/blog/repair...-kit-procedure
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Old 08-25-20, 11:12 AM
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Originally Posted by sch
Wow, 'someone' must have Schwarzeneggered a pedal install to do that. Most people stop after turning the pedal 1-3 threads
when cross threading, to go all the way is to ignore the 3-4x increased torque needed to cross thread a large thread.
Ability to repair with insert will depend on how big the alloy portion is, as the insert requires 2-3mm larger diameter hole which
is then threaded by the insert, so alloy block must be at least 4-5 mm larger than the 9/16 hole for the pedal.
Yup. If there is enough meat on the existing bushing to take a helicoil insert, this repair is easy. If not, you'll have to replace the entire crank arm.
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Old 08-25-20, 01:36 PM
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How messed up is it? I would certainly try to tap out the threads first. Other than that, doing a helicoil repair really isn't particularly hard though many shops don't have the kits, but I don't know if the metal insert in those cranks is substantial enough to install a helicoil. There is a zero percent chance SRAM will officially recommend repair, but that doesn't have much relationship to whether it'll work or not.
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