Sprocket too wide, no room for lockring

[Hakucho]

Sprocket too wide, no room for lockring « on: April 10, 2009, 01:06:00 PM »

I'm building up a fixed gear bicycle 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:

• Return the sprocket for one without such a wide flange,
• Grind about 2-3mm off the flange myself with the angle grinder,
• Take the sprocket to a machine shop to get the flange machined down (expensive?), or
• Not use a lockring, which according to everything I've read would be a bad idea.

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.

[Gypsy]

Re: Sprocket too wide, no room for lockring « Reply #1 on: April 10, 2009, 01:25:49 PM »

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.

[SanEsteban]

Re: Sprocket too wide, no room for lockring « Reply #2 on: April 10, 2009, 01:34:37 PM »

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?

(an old BB lockring as suggested by Sheldon):

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? 

[Bender!]

Re: Sprocket too wide, no room for lockring « Reply #3 on: April 10, 2009, 01:38:45 PM »

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"

[spud]

Re: Sprocket too wide, no room for lockring « Reply #4 on: April 10, 2009, 06:10:15 PM »

It works just fine if you do it up real tight (rota-fix) and loctite the shit out of it.

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

[Hakucho]

Re: Sprocket too wide, no room for lockring « Reply #5 on: April 10, 2009, 07:08:49 PM »

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

(an old BB lockring as suggested by Sheldon):

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

Here's where Sheldon describes the BB lockring approach:

http://sheldonbrown.com/fixed-conversion.html#freewheelhub

[horatio]

Re: Sprocket too wide, no room for lockring « Reply #6 on: April 10, 2009, 07:26:34 PM »

It works just fine if you do it up real tight (rota-fix) and loctite the shit out of it.

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

I'd be nervous using this system too.

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

[rogaine]

Re: Sprocket too wide, no room for lockring « Reply #7 on: April 10, 2009, 07:44:12 PM »

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

[spud]

Re: Sprocket too wide, no room for lockring « Reply #8 on: April 10, 2009, 07:53:27 PM »

real lockring works because of the reverse threading, right?

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?)

[Hakucho]

Re: Sprocket too wide, no room for lockring « Reply #9 on: April 10, 2009, 08:56:28 PM »

... 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?

[spud]

Re: Sprocket too wide, no room for lockring « Reply #10 on: April 10, 2009, 09:28:25 PM »

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

[Sime]

Re: Sprocket too wide, no room for lockring « Reply #11 on: April 10, 2009, 09:48:42 PM »

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.

[SanEsteban]

Re: Sprocket too wide, no room for lockring « Reply #12 on: April 10, 2009, 11:03:41 PM »

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. 

[spud]

Re: Sprocket too wide, no room for lockring « Reply #13 on: April 11, 2009, 05:07:32 AM »

I would not trust it to last for a second in a skid

You'd be surprised.

[SanEsteban]

Re: Sprocket too wide, no room for lockring « Reply #14 on: April 11, 2009, 09:31:11 AM »

I would not trust it to last for a second in a skid

You'd be surprised.

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