My college unicyling club has several Impact unicycles with DD cranks. We noticed that these cranks have a pedal thread insert with a locking ring on the far side. Some of these locking rings are missing and one of the pedal inserts is backing out along with the pedal. The locking ring is round with a 15/16 inch diameter. It is smooth on the outside circumference and threaded on the inside to fit on the adapter that the pedal screws in to. There are two pin holes on one side of the locking ring so that a spanner can be used to thread it on to the adapter.
Could someone please tell me where I can buy these locking rings?
I took a picture and uploaded it here. On the upper pedal you can see that each standard 9/16" pedal has a threaded bushing on it that threads into an oversize hole in the crank. On the bottom pedal you can see that the bushing has a different thread pattern that fits the internally threaded ring.
Does anyone know what these rings are or where I can buy more? I can take more measurements or pictures if it would help. Does anyone have these on their cranks?
As far as I know the threaded insert is never supposed to come out of the crank and should be Lock-tite’d in. The pedals threads should be greased before assembly to prevent them from oxidizing and getting stuck in the crank arms or the inserts.
I’m unsure about the thin lock ring. I would suggest contacting Impact customer support or something of the sort through their manufactorers web site, or possibly even unicycle.com - however I’d be surprized if they suggested anything other than replacing both the crank arms and the pedals. That is ultimately the proper repair proceedure.
I don’t believe the threaded insert design is really necissary. It is an attempt at making a more durable crank arm thread, instead of having the pedals thread directly into threaded holes in the aluminum cranks. However it obviously introduces some problems of its own.
I’m unsure about the thin lock ring. I would suggest contacting Impact customer support through their manufactorers web site, or possibly even unicycle.com - however I’d be surprized if they suggested anything other than replacing both the crank arms and the pedals. That is ultimately the proper repair proceedure.
I think these are Impact Eiffel cranks, no? I have a pair of 150s on my trials. The locking rings have two little divots built into them, which leads me to believe there’s some sort of tool for loosening the rings. I tried a couple times, using a lot of force from a long pedal wrench, to loosen the cranks. I was unsuccessful. My pedals are due for a change, now, and I’m not sure what to do. If anyone on the forum can solve the locking ring mystery, it’d be much appreciated!
Thank you for all the good advice and the video instructions. I used the approach in the video but decided to first try it with red Loctite in case I ever need to remove the insert. If that fails, I will escalate to the permanent J-B Weld epoxy. I also plan to call Unicycle.com to see if they have the lock rings. I already tried calling Impact Unicycles but I was unable to find a phone number.
I dont see any case where you’d need to take that insert out of the crank. This is why I always go JB-Weld. It’s in there, forever, no need to worry about the backring anymore. And if it fails, do it again!
I had to re-do one I think after a few years of abuse. But I have lots of cranks with this on.
My concern is still how to remove pedals when there is an insert. Is there a particular tool for holding the ring steady while loosening the pedal? I tried to remove my pedals the other day, and they just turned without un-threading. I was unable to get a “bite” on the ring with pliers. In your video, you attached two screws/bolts to a board. Is that the tool for holding the ring in place? Part of my problem is that I don’t understand the mechanics of my Eiffel cranks (compared to my Nimbus cranks without inserts). Is the secret to pedal removal to keep the ring from spinning?
Sorry if I am not understanding something that has already been explained. Thanks for the help!
Following up on my original post, Impact Unicycles never responded to my message. However, Unicycle Dot Com sent me the lock ring to secure the insert. I used red Loctite on the insert and the lock ring so hopefully that will hold. However, I plan to use J-B Weld on the inserts if they come loose again.