My left pedal came loose in a race some days ago (dura ace 9100 crank). I think due to undertightening but do not know for sure (rode about 2000km before it came loose). Result is that the outside part of the thread is gone. Pedal still goes in smoothly but will only stop wobbling around when screwed in almost maximum. At this point it is secure and can be tightened but I'm afraid it will come loose again due to the partly damaged thread. As it is a power meter crank, it is expensive to replace. Do you think a helicoil from the LBS is a good fix?
by 96121402
8 Comments
Looks like you still have 2/3 thread engagement so I’d just put the pedal back but tighten it up properly this time
Run a tap through it to clean it up but, it looks like you got plenty there to hold a pedal.
looks ok to me, i would put the pedal on from the back side first to clear out the threads before reinstalling it
First screw the pedal in from the other side to straighten the threads. Then screw it in at the normal position. You have enough threads left for a tight connection. Be careful though because you mount hardened steel on aluminium. The pedal should go in with very little force. If you get stuck at the beginning, stop and start again screwing.
If it’s more wallowed out and loose than it looks in the photos, sure. The one and only thing you lose helicoiling it is the money, but on an expensive crank like this, whatever.
Check the pedal bearings, pedals should self tighten. If they don’t it might mean the bearings are on their way out, or you pedal backwards a lot (particularly if you pedal backwards while standing). Luckily it looks like you’ve got plenty of thread left, I’d happily use that still, but check the pedal periodically and make sure it stays tight. Generally 3 or 4 fully engaged threads acheives pretty similar strength to a fully bolted joint. Worst case you tighten it, it strips and you need to go get a helicoil adding.
If there’s nothing wrong with the pedal and it loosens again, it’s a bit of a bodge but you could add a bit of blue loctite. It’s not what you’re supposed to do, but sometimes when things are a bit damaged we need to go a bit outside what you’re supposed to do. It’ll make removing the pedal more tricky in the future, but should stop it loosening.
I agree with everyone else, but surprised no one mentioned after cleaning before install to use assembly grease (as specified by Shimano). This will also help the pedals from backing out in the future.
I don’t know the pedals you have but all Shimano documentation spec assembly grease. https://si.shimano.com/en/pdfs/dm/MCPD001/DM-MCPD001-02-ENG.pdf
That information is on page 12 or 13 of the various PDFs I checked from Shimano’s database
Show this to the people who say pedals self tighten. I have a pedal get loose during riding fortunately I noticed and didn’t damaged my crank now I always use a torque wrench when tightening my pedals.