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Old 02-20-09, 07:11 PM   #1
buckfifty
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new pedals won't screw in

i recently removed my old pedals. the right one was a breeze was take off but the left was a pain. now i can't seem to install the new left pedal. could it be stripped? i did get a couple small metal shavings after i removed the left pedal but i didn't think it would be enough to render it unscrewable. any suggestions or tips?

thanks
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Old 02-20-09, 08:14 PM   #2
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Which way did the left pedal unscrew? It is reverse theaded, so turning it the "normal" way would strip the threads and make a few shavings. You may need to look for a new left side crank arm.
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Old 02-20-09, 08:18 PM   #3
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Left pedals are usually threaded left-hand, so make sure you're turning it the proper way.

You may just have the threads goobered up a bit where you can't get it started. I would think a good bike shop could fix that if the crank arm is worth the trouble.
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Old 02-20-09, 08:22 PM   #4
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Since the R pedal went in ok that suggests you have the correct pedal threading for the crankset.
Clean the L crank pedal threads with a bit of solvent to get rid of any grease and gunk, ditto the
pedal threads and eyeball closely for damage. If the crank threads look a bit or more buggered up
you can try screwing in the pedal from the inside of the crank, this may straighten out some
buggered up threads. Screw in all the way but you don't need to torque it. Remove and try
screwing the pedal in from the correct side. Might work. Buggered threads though are easily
stripped further. Left cranks are cheap to replace. Generally easier to replace than rethread.
Tapping won't help buggered threads, as the problem is metal loss. In theory inserts can be used
but for a L crank, non DuraAce or equivalent, cheaper to replace. If the pedal can be screwed in
ultimately but is a little 'loose', riding stress will rapidly remove the rest of the intact threading in
the soft aluminum of the crank and the pedal will fail. I once buggered one by inadvertently putting
a Fr threaded pedal in a 9/16x 16 TPI crank. Thread pitch is same but diameter of Fr is smaller by
about 1mm. Took 3mi to totally bugger the crank.
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Old 02-20-09, 08:26 PM   #5
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Once you are sure that you are unscrewing/screwing in the correct direction(remember, backwards rotation- like if the wheels were turning backwards- is to remove both pedals, forward to install) make sure you have the correct pedal(should be marked with a L/R). If the starting threads are buggered, try screwing in from the other side of the crankarm to clean the threads.
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Old 02-20-09, 08:47 PM   #6
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If you managed to remove the left pedal by unthreading it the normal (counterclockwise) direction, it's safe to say the threads in the crank arm have been destroyed.
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Old 02-20-09, 08:53 PM   #7
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If you managed to remove the left pedal by unthreading it the normal (counterclockwise) direction, it's safe to say the threads in the crank arm have been destroyed.
And that took some cranking Sure it's not the first time it's been done tho.
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Old 02-20-09, 09:15 PM   #8
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thanks a lot for all the suggestions. i was able to thread it through the inside and try to fix the threads. no problem at all. however, when i attempt to screw in from the correct size, when i am able to grab a thread to begin screwing in, about halfway through it begins to get more resistant. i stopped so i don't cause any more damage to the threading.
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Old 02-20-09, 09:25 PM   #9
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Sounds like you need to purchase a tap to clean up the threads.
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Old 02-20-09, 09:52 PM   #10
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any links or info to point me into the right direction? thanks
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Old 02-21-09, 12:25 AM   #11
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any links or info to point me into the right direction? thanks
Here is a link for McMaster Carr. This is considered the engineers bible. These people have just about everything anybody could ever need to make, build, or fix anything. The link should take you to the page for left handed taps. You will need a 9/16" tapered tap. I think it will need to have either 16 or 18 threads per inch. Very important to check this detail. Looks like this tap will set you back about $24 plus shipping.

http://www.mcmaster.com/#2584a592/=ozj0m

On the other hand, your LBS will probably have the correct tap and will be able to determine if your crank arm is too damaged to be fixed or not. I doubt if they would charge any more to fix this than the tool would cost. You will have to decide which way to go.

Good luck.
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Old 02-21-09, 02:16 AM   #12
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An easy way to remember pedal threads is this: They tighten in the direction of the front of the bicycle - even upside-down. And they loosen in the direction of the rear of the bicycle - even upside-down.
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Old 02-21-09, 06:01 AM   #13
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You could try these guys. They ship same day up till 8pm.

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=58871631
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Old 02-21-09, 07:28 AM   #14
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You will need a 9/16" tapered tap. I think it will need to have either 16 or 18 threads per inch. Very important to check this detail. Looks like this tap will set you back about $24 plus shipping.
Pedal threads are 9/16"-20tpi and that's a non-standard tap so an LBS is the best place to try.
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Old 02-21-09, 08:02 AM   #15
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Pedal threads are 9/16"-20tpi and that's a non-standard tap so an LBS is the best place to try.
And guess who makes a matched set of left and right:

http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Last edited by Shimagnolo; 02-21-09 at 08:39 AM.
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Old 02-21-09, 08:32 AM   #16
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And guess who makes a matched set of left and right:

http://www.google.com/search?hl=en&q=park+"tap-6"&btnG=Google+Search&aq=f&oq=
Link doesn't work. Sure, Park, Var, Campy and other bike tool makers provide the specific 9/16"-20tpi left and right pedal tap sets but they are an extravagance for most home mechanics.

In the OP's case, I expect the threads in his crank arm are so badly mangled that a tap won't help. He probably needs a new crank arm or a helicoil in the old one.
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Old 02-21-09, 08:41 AM   #17
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Link fixed. BF's auto-url feature choked on it.
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Old 02-21-09, 08:50 AM   #18
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This won't fix the crank arm but it's happened to me once.

I bought some $10 pedals from the LBS. Went to install them and wtf, the left side is a no go. They were both right side pedals but were marked left and right.
Took em back and and of course the dude at LBS said, that can't be right, here let me show you how to install them.
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Old 02-21-09, 08:54 AM   #19
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This won't fix the crank arm but it's happened to me once.

I bought some $10 pedals from the LBS. Went to install them and wtf, the left side is a no go. They were both right side pedals but were marked left and right.
Took em back and and of course the dude at LBS said, that can't be right, here let me show you how to install them.
The dude couldn't just hold them side-by-side and see that the threads were the same???
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Old 02-21-09, 08:59 AM   #20
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Pedal threads are 9/16"-20tpi and that's a non-standard tap so an LBS is the best place to try.
No to mention that the left side tap is left-hand thread, which is even more non-standard.
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Old 02-21-09, 09:04 AM   #21
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No to mention that the left side tap is left-hand thread, which is even more non-standard.
Exactly, which is why you have to buy them in sets and that costs even more.
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Old 02-21-09, 01:29 PM   #22
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This won't fix the crank arm but it's happened to me once.

I bought some $10 pedals from the LBS. Went to install them and wtf, the left side is a no go. They were both right side pedals but were marked left and right.
Took em back and and of course the dude at LBS said, that can't be right, here let me show you how to install them.
I've seen this as well. Pedal marked with L/R that are clearly either R/R or L/L. Hilarity ensues upon pedal installation attempt.
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Old 02-21-09, 07:58 PM   #23
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I've seen this as well. Pedal marked with L/R that are clearly either R/R or L/L. Hilarity ensues upon pedal installation attempt.
On top of those markings, most pedals have notches cut into the spindle for the left pedal.
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Old 02-21-09, 09:59 PM   #24
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I was shortening a set of Ultegra crank arms for my tandem stoker. After drilling the new holes, I needed to thread them, so I bought a set of 9/16" X 20 taps (Park Tap-6) from an e-bay vendor. I paid around $32.00 for them. They're not cheap. The package said they were not recommended for cutting new threads in a new hole but that is exactly what I did. Slow and easy with plenty of oil worked just fine.

edit: I would think any bike shop worthy of being called a bike shop would have a set on hand for chasing/cleaning threads on customer's bikes.

Last edited by Skipper; 02-21-09 at 10:05 PM.
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Old 02-22-09, 08:19 AM   #25
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edit: I would think any bike shop worthy of being called a bike shop would have a set on hand for chasing/cleaning threads on customer's bikes.
True, but if the OP really managed to remove a left pedal by turning it the wrong way, there are no threads remaining to clean up, just a ragged, oversized hole. I marvel at the torque that must have taken.
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