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  1. #1
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    Solder Pedal to Crank Arm? Good Idea or Bad?

    Yeah... I'm stupid... I know... I wasn't paying attention when changing pedals and I stripped out the first 3 threads on my left Dura-Ace 7800 Crank Arm. I managed to get the pedal in by reverse threading from the other side. However... I'm concerned that it won't hold. Do you think soldering the back of the pedal bolt to the backside of the crank would hold it in longer? Or am I just thinking stupid again?

  2. #2
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    Solder won't do any good, if you could even get it to adhere to the aluminum of the crank and the steel of the pedal. Either a helicoil insert, if one could be found in the proper size, or adding aluminum via TIG welding and retapping would work. Myself, I would just keep an eye on it for a while and see if it loosens in use.

  3. #3
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    I'd helicoil it. It'll work fine then. Worst case would be to get a new crank arm

  4. #4
    Paste Taster Retem's Avatar
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    ebay a new left side dude they are usually alot cheaper than the drive and you can use what ever track road as long as it is da
    I am dyslexic so bear with my posts.... [SIGPIC][/SIGPIC]

  5. #5
    Sir Fallalot wroomwroomoops's Avatar
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    Quote Originally Posted by noahjwhite
    Yeah... I'm stupid... I know... I wasn't paying attention when changing pedals and I stripped out the first 3 threads on my left Dura-Ace 7800 Crank Arm. I managed to get the pedal in by reverse threading from the other side. However... I'm concerned that it won't hold. Do you think soldering the back of the pedal bolt to the backside of the crank would hold it in longer? Or am I just thinking stupid again?
    Did you strip those 3 threads totally, or do they hold at least a bit? I would, in any case, suggest that you clean the threads with alcohol (both pedal and crankarm), let it dry and apply loctite. Screw in the pedal real strong ("like a gorilla" as LóFarkas would say) and leave it set for 2 hours. Should be safe.

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    Tap out the threads in the crank first and screw in the pedal as you normally would with a bit of grease. Then if it doesn't hold drill and tap it out for a heli-coil.

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    The 3 threads are not totally stripped but darn close. I don't really want to take the pedal out because it took forever to get it in. Lock tight was a good Idea I should have tried that. I think I'll just watch it (and ebay) for a new left crank. Thanks a lot for your help.

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    Quote Originally Posted by noahjwhite
    The 3 threads are not totally stripped but darn close. I don't really want to take the pedal out because it took forever to get it in. Lock tight was a good Idea I should have tried that. I think I'll just watch it (and ebay) for a new left crank. Thanks a lot for your help.
    It sounds like you got it back in straight then and it should be fine as long as there is some grease on the threads. The next time you remove the pedal go ahead and chase the threads with a tap and you should be good to go.

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    Locktite makes a version of its product that you apply after assembling the parts. It wicks its way into the threads. It is green in color and IIRC the number either 290 or 242. Roger

  10. #10
    In beaurocratic limbo urbanknight's Avatar
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    I'd be concerned. If the pedal can't hold all the torque, you're going down... hard. I know it's not economical, but if I think I screwed up a crank, I replace the whole crank. Not worth the risk.

  11. #11
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    Had a friend of mine do that with a MTB crank and the pedal came off on him when we were about 15 miles out in the woods. Completely wallowed out the pedal hole. It was a nice hike though. ;-)

  12. #12
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    Solder is for electronics.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  13. #13
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    Quote Originally Posted by operator
    Solder is for electronics.
    or plumbing..

  14. #14
    cyclist/gearhead/cycli... moxfyre's Avatar
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    Quote Originally Posted by mcoine
    Quote Originally Posted by operator
    Sodler is for electronics
    or plumbing..
    Yep! Either way, lead/tin-based solder isn't designed to provide structural strength. Even though pipes may be held together with solder, those pipes do not bear any external loads. No one would ever frame a building with metal rods soldered together, for example

    This contrasts with silver/brass-based brazing compounds which ARE designed to provide structural strength... such as in lugged steel bike frames!

    In any case, soldering your pedal to your crank is a bad idea. Solder is not designed to join arbitrary metals. I doubt it could bond a steel pedal spindle to an aluminum crank). Ordinary electronics-grade solder is a laughably weak material... you can break a 1/4 rod in a few seconds with your bare hands.
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  15. #15
    so much for physics humble_biker's Avatar
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    you're over thinking the problem. Clean it, prep it, and ride it. If it isn't going to hold you'll find out the 20 miles I bet.

  16. #16
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    ... Helicoil the thing. DA Crankarms are supposedly made of a slightly different aluminum, and thusly I'd wonder if it's more towards weight than overall strength...

  17. #17
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    If it was really hard to thread in then I would suggest dealing with this before you go riding next. Just back it out again, clean the threads, helicoil if needed, and reinstall the pedal. Stripping out a crank arm is not a big deal, just repair it, unless of course you ignore it, and plant your face into the pavement on the next ride.

  18. #18
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    You could try this stuff instead of helicoiling - I have used in static-fastener automotive applications and had good results. As long as you have 50% or more of the original threads remaining undamaged, you'd probably be OK - this would just help to prevent any wallowing of the hole in the area of the damaged threads.

    http://www.permatex.com/products/aut...ead_Repair.htm
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  19. #19
    Senior Member AGuinness's Avatar
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    Ultegra 170

    Ultegra 175

    Pretty cheap... and they look alike, right?

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