Re-threading TA Specialites crank?
03-29-18, 06:57 PM
#1
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Re-threading TA Specialites crank?
I bought these in a box of parts recently. I was really excited about them until I started to clean the cranks up and noticed some of the threading is missing on the drivetrain side. I tried to thread a French pedal in; the pedal is very loose.
What are the options for a fix? If it was re-tapped the hole would be too large? Right?
Are there other options?
Thanks.
What are the options for a fix? If it was re-tapped the hole would be too large? Right?
Are there other options?
Thanks.
03-29-18, 08:14 PM
#2
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If you will be using French pedals, has the threaded hole perhaps been threaded out to 9/16"?
That would leave less metal engaging the threads.
I had a Shimano LX crankset with stripped pedal threads, though I could get about one full turn of engagement with good thread deep in the hole using a certain clipless pedal with no washer.
I cleaned the threads well and saturated the threading of pedal and crankarm with LockTite Red, then slowly threaded in the pedal and tightened.
I have been riding the bike now for a couple of years, offroad, no problems. I did nce remove the pedal in order to service the bearings, but I was able to remove it without application of heat and it went back together just like the first time. I suspect you have a lot more threading to work with than I did!
I have long wondered if a crankarm having been tapped out from French to English threading could again be used with
French pedals, if it would still take full tightening torque. I will do an experiment one day with a discarded French crankarm and French pedal to find out.
That would leave less metal engaging the threads.
I had a Shimano LX crankset with stripped pedal threads, though I could get about one full turn of engagement with good thread deep in the hole using a certain clipless pedal with no washer.
I cleaned the threads well and saturated the threading of pedal and crankarm with LockTite Red, then slowly threaded in the pedal and tightened.
I have been riding the bike now for a couple of years, offroad, no problems. I did nce remove the pedal in order to service the bearings, but I was able to remove it without application of heat and it went back together just like the first time. I suspect you have a lot more threading to work with than I did!
I have long wondered if a crankarm having been tapped out from French to English threading could again be used with
French pedals, if it would still take full tightening torque. I will do an experiment one day with a discarded French crankarm and French pedal to find out.
03-29-18, 08:19 PM
#3
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A helicoil repair would probably be the best fix. Shouldn't cost too much, if your LBS has a helicoil kit, and that TA crack is certainly worth saving.
03-29-18, 08:30 PM
#4
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Is there a W on the inside face of the crank next to the length number? If so, it is originally threaded English. If not, it is likely French (but not absolutely certain - I have some cranks without the W that fit English threaded pedals).
Either way, I would tap them with an English thread... unless you have a serious need to use French pedals, in which case I would chase them with a French tap.
Either way, I would tap them with an English thread... unless you have a serious need to use French pedals, in which case I would chase them with a French tap.
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03-29-18, 08:33 PM
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I would tap it to standard 9/16" x 20 threading.
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03-29-18, 10:14 PM
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all the pedal helicoil kits I have seen return the threading to 9/16" x 20. Maybe VAR made a metric thread repair kit, but with LH threading also required on one side, I think not.
03-30-18, 07:14 AM
#7
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Just use 9/16 x 20 pedals.
In the early 1970s at Bikecology I saw a couple of ISO-threaded cranks get damaged by people trying to use them with French-thread pedals.
In the early 1970s at Bikecology I saw a couple of ISO-threaded cranks get damaged by people trying to use them with French-thread pedals.
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03-30-18, 10:48 AM
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I have an old TA crank with a helicoil. It seems to work just fine.
I also have tapped out a couple French-threaded Cyclotouriste cranks to accept 9/16” pedals, since I use Speedplay Frogs on all my bikes.
Both options work well, so you should be able to fix the threads perfectly either way.
I also have tapped out a couple French-threaded Cyclotouriste cranks to accept 9/16” pedals, since I use Speedplay Frogs on all my bikes.
Both options work well, so you should be able to fix the threads perfectly either way.
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03-30-18, 10:55 AM
#9
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there is a threaded sleeve repair for damaged pedal threads too . that tool and several repair inserts are available thru bike shop tools.
Helicoil is a coil of diamond shaped wire.. uses a different tool, many engine repair machine shops do that ..
[the 9/16" left hand thread is pretty uncommon outside of bikes.. but you buggered up the right side crank.. ]
..
Helicoil is a coil of diamond shaped wire.. uses a different tool, many engine repair machine shops do that ..
[the 9/16" left hand thread is pretty uncommon outside of bikes.. but you buggered up the right side crank.. ]
..
