Want to change the gear on my pompino, so took the lockring off and expected the sprocket to just fall off. It appears to be screwed on, though – it this normal?
Don’t get what the lockring is for in this case – be good to know so I can buy the right replacement cog, if it has to be threaded or if the lockring can just press it on.

Yes, this is normal. On a fixed gear, the sprocket and lockring screw on in different directions to avoid it coming undone when you back pedal.

Thanks pdw – makes sense. The sprocket seems welded on – is it a case of heaving on it with a chain whip?

Should be. Pedalling tightens it so it can end up very tight.

If you get stuck 🙄 google rotafix…

Check that you screw it on the correct way round, there is a spacer on one side of many sprockets to move it further from the spokes.

And they can be VERY tight. And of course the lockring is reverse threaded, but you’ve got that off already.

When I had my rear wheel rebuilt, guess who forgot to take the sprocket off before disassembling 😳 . Ever tried removing a sprocket with only a flange to hold? Had to half rebuild and ruined half the spokes in the process!

Try putting the wheel back in the bike and stamping a pedal backwards.

Took me about two hours (with breaks) to get the one off of my Mrs’s Genesis. I used a chain whip, WD40 and a rubber mallet

If the lock ring is off and the sprocket is for the bin, try clamping the sprocket teeth between two pieces of wood in a vice so that the wheel is horizontal and the teeth bite into the wood. Turn the wheel like a steering wheel, but only if the sprocket is for the bin, and don’t tighten the vice more than you need to or you’ll bend something

Take the lock rings off and go for a ride, trying to lock the back wheel up a lot. Lots of WD40 or plus gas can help. You will have “welded” alloy to steel which isn’t helping.
If things get really bad you could reverse the wheel so that you are pulling the chain against the thread. Then ride it a lot.
Something else will need reversing as well which may be tricky depending on your chainset. 😉 It works though

chipster – Member
Try putting the wheel back in the bike and stamping a pedal backwards.

^ +1

Traditional methods work best.

If it doesn’t, just go for a ride without the lockring and do some skids. It will come loose at an inopportune moment, but it will come loose. 🙂

Thermal shock helps too. Pour kettle of boiling water over sprocket a few times. Or a cooks blow torch!

seems a shit method of attachment – why do they still use it instead of a short slotted freehub ?

Why is it shit? Has worked perfectly for me for 30yrs or so! I’ve had more problems with freehub systems…

That said, Miche do a screw on carrier, so you can swap between cogs just by removing the lock ring. The cog just slots on.

I think for the track though, simple=better

scaredypants – Member
seems a shit method of attachment – why do they still use it instead of a short slotted freehub ?

See, I’m a simple soul. I use words like freehub when I should invent “fixedhub”, but I imagine you knew what I meant

You could take it to ‘our’ workshop if the back pedalling method doesn’t work, Peter always gets those things undone.
What size sprocket do you want to try? I have one or two hardly used sprockets in my spares box….
Sven

Thanks for the tips – it came off last night ok with some oil, the whip and a couple of bevvies.
Fancy trying a time trial on it (a ten) so need to up the gear inches a wee bit. Does 49×16 (82) sound like the right neighbourhood for a flattish ten? Never done one before.

49×16 gives you 24mph at 100rpm, I would say that’s a good starting point.

Took me about two hours (with breaks) to get off my Mrs. I used a chain whip, WD40 and a rubber mallet

😯