Rohloff + Gates Sprocket - Lock-Ring Hopelessly Stuck?

[carlhirsch]

I've got a Bafang+Gates+Rohloff bike from FLX. It's a fun throttle-y deathtrap, but I find the gearing doesn't allow me to leverage pedaling at high enough speeds.

I'm trying to replace the rear sprocket with one slightly smaller, but my (very ebike friendly and skilled) local bike shop has been unable to get the lock-ring loose to make the swap. I've procured Rohloff's tool #8518 but even using that we're making no progress. LBS states they're applying at least 100nm to no avail. They're speculating overtightening at the factory but I'm really starting to suspect they applied Loctite.

LBS states: "If they had a stamped spanner type version of the tool, we'd be able to get it, because no force would need to be applied toward the center of the axle, only in the direction needed to remove it. If there were a way to secure the current tool to the axle, we'd also be able to get it w/ out issue."

Has anybody run into this before? Is cutting off the lock-ring an option?

 

[amberwolf]

If they used loctite, then it depends on which kind they used for what the nondestructive solution might be. Usually heating will work, but how much depends on which type, and you may not be able to safely heat the parts without damaging other things. (I don't know if that's the case or not, but the LBS probably does).

https://www.loctiteproducts.com/en/know-how/build-things/threadlocker-red-or-blue-which-ones-right-for-you.html

https://www.henkel-adhesives.com/us/en/applications/all-applications/how-to/how-to-remove-loctite-2620.html

 

[Chalo]

Like any threaded sprocket or freewheel, the external sprocket on a Rohloff Speedhub tightens from drive torque. You're going to have to get serious with it.

Heat should help, but I would use a butane torch with a pointy flame, and heat the teeth of the sprocket. If you can get it to thermally expand more than the thread it's mounted on, it should be easier to loosen.

 

[Stealth_Chopper]

Dry Ice, & Induction Heat

 

[Chalo]

I just looked up the tool mentioned. It's some belt drive specific thing that doesn't apply to my experience with Rohloff hubs using normal sprockets.

Given that the carrier is splined, though, it shouldn't self-tighten from drive torque. So chances are the lockring is either overtightened or held with threadlocker, like you said. I would heat it gently to about 250F to weaken any threadlocker, before cooling it with a wet cloth to protect the hub's seals. Then I'd use an impact driver to take it off.