Sprocket too wide, no room for lockring

I’m building up a fixie using a rear wheel that has a freewheel type hub.

I screwed on my new Dura-Ace 7600 track sprocket last night (16T x 3/32"), and the flange on the sprocket is so wide that it took up the whole threaded section of the hub, leaving no room for the lockring (an old BB lockring as suggested by Sheldon):

The red arrows show the width of the sprocket flange. The sprocket itself is not very thick at all, maybe 2-3mm. But the flange takes up the whole hub as you can see.

The lockring I was hoping to use is hanging off the skewer in the photo, marked with the blue arrows.

As I see it, there are four possible solutions:
[ul]
[li]Return the sprocket for one without such a wide flange,[/li][li]Grind about 2-3mm off the flange myself with the angle grinder,[/li][li]Take the sprocket to a machine shop to get the flange machined down (expensive?), or[/li][li]Not use a lockring, which according to everything I’ve read would be a bad idea.[/li][/ul]

Would it be easy to find a sprocket that doesn’t have such a wide flange, or do I have to resort to the grinding option? The steel looks pretty hard and it wouldn’t be easy to do a clean job.

New sprocket buddy. Those older style ones where wider to space the the chain off the spokes. Either be really careful sand it down etc. Or buy a new one. its up to you.

I would get a spocket with a narrower flange. I think you are right about the grinding, would be very hard to fo a clean job.

So your using a non-stepped thread with an old BB lockring?

Can you post a link to this on Sheldon’s site? I couldn’t find it.

Is anyone else running this setup… non-stepped thread with BB lockring?

It works just fine if you do it up real tight (rota-fix) and loctite the shit out of it. There’s been a few threads on it before search for “suicide”

This. A BB lockring wont do… much, as it’s not a real lockring.

[quote="SanEsteban "]
So your using a non-stepped thread with an old BB lockring?

Can you post a link to this on Sheldon’s site? I couldn’t find it.[/quote]
Here’s where Sheldon describes the BB lockring approach:

I’d be nervous using this system too.

I real lockring works because of the reverse threading, right?

Rotafix it and ride … best to run a back brake but avoid skipping and skidding too hard and all is good!

Yeah. If the cog unscrews, it hits the lockring and tightens it up, as long as its reverse threaded.

Rotafix is win, and the BB lockring wont really do jack (probably because scrawny arms do up the faux-lockring and your big beefy legs try and undo the cog?)

What if I have scrawny arms AND scrawny legs?

Well if you rotafix it, you are using the whole bike as a chainwhip, so you will be fine.

I must admit,
When i first heard the term ‘rotafix’ a while ago, I thought it was a thread locking agent like ‘loctite’ purely cause it has such a cheezy ‘captain obvious’ sounding brand name haha…
then someone dropped some knowledge on me and it all made sense.

I’m very sceptical of suggesting this rotafix method for any skidding…

Lots of track riders don’t use a lockring; regularly changing sprockets and apparently the extra weight make lockrings annoying and they can coast to a halt by applying a bit of resistance if they get injured.

‘Rotafix’ is an easy and effective way for a track rider to get the sprocket on and off without a chainwip, I would not trust it to last for a second in a skid… a skid applies exactly the same force, albeit in the opposite direction, and off comes your sprocket.

You’d be surprised.

You’d be surprised.
[/quote]

That’s what I’m worried about. A suprise is the last thing you want when you have no brakes! :stuck_out_tongue:

i threaded my old hub when i did a skid and ripped the lockring off. ran it without a lockring for about a month and never had an issue… loctite + rotafix + riding up some big hills worked fine…
didnt skid on it tho. but i didnt wind it off once.

also, a sprocket and a lockring on the same thread in the same direction should work without a problem. as long as the lockring is done up to a different torque to the sprocket.

I’ve used double nuts on heaps of stuff for cars (mainly on turbo exhaust manifolds where the vibrations are high) where one nut would rattle off by itself, but with 2 nuts worked fine.

obviously a reverse thread is ideal.

Although in that situation, there’s no torque trying to unscrew either nut.

Asssuming I go with Rotafix + Loctite, where exactly do you put the Loctite? On the part of the hub that the sprocket’s thread engages with? Or on the part of the hub that the sprocket buts up against? And once it’s dried, how hard is it to remove the sprocket again, e.g. to try a different gear ratio (something I might be doing a lot once I get my fixie finished)?

You’ll want to use a loctite called “super stud lock 262” It’s the strongest one last time I checked. You can get it off but you’ll have to rota-fix it off with someone holding the bike really well. You have to clean the threads of the hub, lockring and cog with brake clean first (or other appropriate solvent) then apply the loctite to the threads of the cog and lock ring just before you put them on. Rota-fix the cog up as tight as you can then stick the lockring on as tight as you can. Make sure the lockring you are using has nice crisp rebates in it so you don’t go slipping off.

As good as this solution is in the short term, still go out and get your self a proper track wheel when you can afford too. And run a brake, if in the unlikely event it does come undone you’ll want to be able to stop. :stuck_out_tongue: