Advertise on Bikeforums.net



User Tag List

Results 1 to 15 of 15
  1. #1
    Newbie
    Join Date
    Sep 2011
    Posts
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Classic Error : Stripped Left Hand Threads

    I have had the Giant Boulder for eight years. The hard plastic, covering the pedals was splitting. I picked up a new set of pedals and began to take off the old. The fact that the left pedal used left hand threads completely went out of my 70 year old mind. Commonly called a "senior moment". Using a force arm on the wrench, I turned the bolt on the pedal the wrong way, thus stripping the treads in the alumium crank arm. I am going to get the pedal unscrewed and try to epoxy the new pedal in place, as the damage is already done. Or : Suggestions?
    Best,
    Steven in DeLand

  2. #2
    Senior Member
    Join Date
    Sep 2010
    Posts
    2,867
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    Steven: The crank arm can be drilled out and tapped for a threaded insert called a Helicoil, which will restore your threads. Check with your local bike shops or less likely, a machine shop. You will need to end up with a 9/16x20 left-hand thread. You could also buy a replacement left crank arm. I wouldn't recommend epoxying the new pedal into the stripped crank.

    Whatever approach you take, be sure to grease the threads of the new pedals before you mount them to prevent seizing of the dissimilar metals. I recommend Tef-Gel. Stainless steel pedal washers may also help get them loose when the time comes.

    Use a proper pedal wrench when you mount the new pedals and torque them well, loose pedals are the leading cause of stripped crank threads. It sounds as if you were able to exert plenty of force with the tool you used, though.
    Last edited by dsbrantjr; 09-25-11 at 08:37 AM. Reason: add pedal torque comment

  3. #3
    Senior Member MudPie's Avatar
    Join Date
    May 2004
    Location
    Southern California
    Posts
    1,874
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by dsbrantjr View Post
    Steven: The crank arm can be drilled out and tapped for a threaded insert called a Helicoil, which will restore your threads. Check with your local bike shops or less likely, a machine shop. You will need to end up with a 9/16x20 left-hand thread. You could also buy a replacement left crank arm. I wouldn't recommend epoxying the new pedal into the stripped crank.

    Whatever approach you take, be sure to grease the threads of the new pedals before you mount them to prevent seizing of the dissimilar metals. I recommend Tef-Gel. Stainless steel pedal washers may also help get them loose when the time comes.

    Use a proper pedal wrench when you mount the new pedals and torque them well, loose pedals are the leading cause of stripped crank threads. It sounds as if you were able to exert plenty of force with the tool you used, though.
    +1. I'd highly advise against epoxying the pedal into the arm. You might want to check and see if your LBS has an extra crank arm to sell from the spare parts bin. Bonus if you don't mind if it looks different. The only salient specifications are crank length arm, and bottom bracket style.

  4. #4
    Senior Member Homebrew01's Avatar
    Join Date
    Jul 2004
    Location
    Ffld Cnty Connecticut
    My Bikes
    Old Steelies I made, Old Cannondales
    Posts
    16,030
    Mentioned
    7 Post(s)
    Tagged
    1 Thread(s)
    Buy a new (or used) crank arm and be done with it.
    Epoxy is not something I would use where my life is at stake.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  5. #5
    Don from Austin Texas
    Join Date
    Jul 2009
    Location
    Austin, Texas
    My Bikes
    Schwinn S25 "department store crap" FS MTB, home-made CF 26" hybrid, CF road bike with straight bar, various wierd frankenbikes
    Posts
    1,170
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by roysclockgun View Post
    I have had the Giant Boulder for eight years. The hard plastic, covering the pedals was splitting. I picked up a new set of pedals and began to take off the old. The fact that the left pedal used left hand threads completely went out of my 70 year old mind. Commonly called a "senior moment". Using a force arm on the wrench, I turned the bolt on the pedal the wrong way, thus stripping the treads in the alumium crank arm. I am going to get the pedal unscrewed and try to epoxy the new pedal in place, as the damage is already done. Or : Suggestions?
    Best,
    Steven in DeLand

    Did you get the pedal all the way on cross-threaded, or only a few threads? If the latter, simply get hold of a left-handed pedal tap or pay your LBS to run the tap through starting from the good threads on the inside.

    Don in Austin

  6. #6
    Senior Member Homebrew01's Avatar
    Join Date
    Jul 2004
    Location
    Ffld Cnty Connecticut
    My Bikes
    Old Steelies I made, Old Cannondales
    Posts
    16,030
    Mentioned
    7 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by Don in Austin View Post
    Did you get the pedal all the way on cross-threaded, or only a few threads? If the latter, simply get hold of a left-handed pedal tap or pay your LBS to run the tap through starting from the good threads on the inside.

    Don in Austin
    I think the pedal was already on, and he kept tightening it (instead of loosening) with such force that the threads stripped out. Thus, I would assume there's not much left in there.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  7. #7
    Pwnerer Wordbiker's Avatar
    Join Date
    Jun 2005
    Location
    Pagosa Springs, CO, USA
    My Bikes
    Road, MTB, Cruiser, Chopper, BMX
    Posts
    2,900
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It can be retapped, no problem.

    Here is the process. If you don't feel up to taking it on, call around for a shop that offers this service. The repair taps are quite expensive.
    Quote Originally Posted by ahsposo View Post
    Ski, bike and wish I was gay.

  8. #8
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,556
    Mentioned
    69 Post(s)
    Tagged
    1 Thread(s)
    It takes a staggering amount of torque to strip a 9/16" thread by overtightening. I'm curious to know how long a cheater bar the OP used, and if it was less than 2 feet, I'd like to see a photo of his biceps.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  9. #9
    Newbie
    Join Date
    Sep 2011
    Posts
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks for all the tips.
    In order to screw this job up, I had removed the crank arm from the bike and wrapped it with leather, than snugged it into my bench vise. A 19/32" open end wrench fit the flats on the pedal very well. Since I could not strip the aluminum thread with just the force that I could exert using the 8 1/4" long wrench, I got the steel tube used to lock down the leveler bars on my travel trailer. The tube is 18" long, with a 7/8", inside diameter. That gave me a 26" long force arm, when I slipped the tube over the jaw of the wrench and hung on it. The first turn was difficult, than as I now know, when the aluminum threads failed, the job got easier. By time I realized my error the threads were toast and were not coming out of the crank arm at all.
    I phoned the local bike shop and they are working on finding me a crank arm, or getting the a bushing to fit into the reamed out hole.
    Thanks again guys,
    Steven

  10. #10
    Senior Member
    Join Date
    Jun 2010
    Location
    Arlington, MA, USA
    My Bikes
    1981 Panasonic DX-2000, 1986 Cannondale SR500, 1991 Specialized Crossroads
    Posts
    123
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    All I can say is that I hope when I am 70, I'll still be riding and maintaining my bike(s), and strong enough to strip a crankarm by over-tightening a pedal. My hat's off to you, sir! Color me impressed.

  11. #11
    Senior Member
    Join Date
    Dec 2005
    Posts
    7,819
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Roy, that method works but probably is faster just go and buy a new crank or crankset as somebody mentioned before. Depends of the way u want to go, besides cranks aren't that expensive if u get a used one, maybe even free.

  12. #12
    Newbie
    Join Date
    Sep 2011
    Posts
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, I hear ya. Going to phone the shops as soon as they open up. I went to two shops in DeLand, FL., yesterday. Both were closed up. Gone! Sad commentary on the world economy today!
    Tastewar : Thanks for the kind words! My only answer is to say first, all credit goes to God for giving me a body that, if I try, can keep going. Secondly, as a steward of this body, I must keep up exercise. I bicycle 10 to 20 miles a day. Granted, I am in FL. with no hills to speak of. I lived most of my life in Maryland, where I bought the Giant, Boulder bike. The trails around the reservoir were brutal and today, I could not do it. I tell anyone who ask, that the secret to keeping fit is to "give" to yourself at least one hour per day and keep up that one hour or more exercise. And I mean sweat creating exercise. My dentist said that she does not have time to do that. She is in her late 40s. So, I ask her how much time she spends generating cash in her practice and she said 40 hrs./week. I then ask her if she could get up one hour earlier, or go to bed one hour later, because after spending 40 hrs./week generating cash, she really needs to give her body at least 7 hr./week, doing exercises, in order to keep the body going! That is the way one must look at it.
    In my 70th year, I am no where near ready to sit in front of the TV and wait for the grim reaper! God willing, I will keep on biking for another 20 years.
    Best,
    Steven

  13. #13
    Senior Member Homebrew01's Avatar
    Join Date
    Jul 2004
    Location
    Ffld Cnty Connecticut
    My Bikes
    Old Steelies I made, Old Cannondales
    Posts
    16,030
    Mentioned
    7 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by roysclockgun View Post
    Yeah, I hear ya. Going to phone the shops as soon as they open up. I went to two shops in DeLand, FL., yesterday. Both were closed up. Gone! Sad commentary on the world economy today!
    Tastewar : Thanks for the kind words! My only answer is to say first, all credit goes to God for giving me a body that, if I try, can keep going. Secondly, as a steward of this body, I must keep up exercise. I bicycle 10 to 20 miles a day. Granted, I am in FL. with no hills to speak of. I lived most of my life in Maryland, where I bought the Giant, Boulder bike. The trails around the reservoir were brutal and today, I could not do it. I tell anyone who ask, that the secret to keeping fit is to "give" to yourself at least one hour per day and keep up that one hour or more exercise. And I mean sweat creating exercise. My dentist said that she does not have time to do that. She is in her late 40s. So, I ask her how much time she spends generating cash in her practice and she said 40 hrs./week. I then ask her if she could get up one hour earlier, or go to bed one hour later, because after spending 40 hrs./week generating cash, she really needs to give her body at least 7 hr./week, doing exercises, in order to keep the body going! That is the way one must look at it.
    In my 70th year, I am no where near ready to sit in front of the TV and wait for the grim reaper! God willing, I will keep on biking for another 20 years.
    Best,
    Steven


    You can find left crank arms on Ebay for little money. If you want an exact match, it may be more difficult. Make sure you match the length (170mm, 172.5mm etc...) and type (square taper, octalink etc...)
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  14. #14
    Newbie
    Join Date
    Sep 2011
    Posts
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I found a local shop that had the left crank arm, new, for $18.09 out the door.
    Thanks,
    Steven

  15. #15
    Senior Member
    Join Date
    Dec 2005
    Posts
    7,819
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Great

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •