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Fixed Cog occasionaly Slips

Old 12-05-09, 03:37 AM
  #1  
cnnrmccloskey
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Fixed Cog occasionaly Slips

I have a formula flip flop hub that I recently purchased and the first day I rode around on the fixed side after a couple of miles my cog would start to slip back, maybe an eighth of a turn, when I got home I discovered my lockring was loose I tightened it back up and every thing was fine for a while until it started to do it again. when I got home I took the cog off and inspected the threads for damage but there was none (on the cog or lockring threads) I put it all back together Really tightened the hell out of the lockring and kept riding. Fast forward two months of daily fixed riding with no problems then today it slips again.
for the time being I'm carrying my lockring wrench around me with just incase but I would really like to figure it out.
Also after it slips I generally Flip it to the free side to avoid any potential damage.
sorry the Cog and lockring are both unmarked the cog is 1/8" thats all I can tell you. Up until it slips it feels perfectly solid and its driving me crazy
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Old 12-05-09, 08:26 AM
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You could ask a shop, or alternately tighten it down hard using some version of loctite (I don't remember what colors correspond to what strength of adhesive).
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Old 12-05-09, 02:11 PM
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I am not sure exactly how to explain this but. are you sure the lockring is getting a good 'grip' on the track cog and not bottoming out at the end of its threads? also this is very hight torque area and I think an occasional inspection of the lockring would be in order anyway yes?
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Old 12-05-09, 03:13 PM
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First, all threads have to be perfectly clean. Then make sure to lubricate the threads and especially, the flat surfaces that make contact between the lockring and the cog are also lubricated. Any oil works fine. Now tighten the cogas hard as you can with a chain whip and then tighten the lockring on it very snugly. What lockring tool do you have? Some produce much more torque than others.
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Old 12-05-09, 03:35 PM
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One question, is your lockring left-handed threaded? It should be and a proper fixed gear hub has two sets of threads on the fixed side, a set of inboard right-hand threads for the cog and an outer set of smaller diameter left-hand threads for the lockring. That way as the cog tries to unthread under back pedaling, it tightens the lockring and prevents just what you are experiencing.

A regular right-hand threaded lockring against a regular cog is going to be difficult to keep adequately tight as the torque that tries to unthread the cog also wants to unthread the lockring.

See Harris Cyclery's web site for a description of the function and configuration of these lockrings.
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Old 12-05-09, 03:44 PM
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I regret to inform you that, based on my personal experience, your cog may have mashed the threads on the your hub.

What is the quality of the cog you are using. If it is a stamped one, there are issues with them, irrespective of how tight you cinch them down.

The damage also may have been done in the earlier stages of your story with the constant loosening and then sudden tightening again.

The fact that you have been able to ride for another two months mirrors the experience I had with a Velocity hub (fixed, not flip-flop) in my early days of riding a Shogun steelie I had converted to fixed. Velocity hubs are, I think, essentially Formula hubs. I had loosening, then even after cinching down the left-threaded lockring, the hub thread finally gave way (on a century). This was with a stamped cog.

Once the threads are gone on the hub, there is nothing to do but replace the whole hub. After my experience I went with a Dura Ace cog and have not had one issue since with the replacement set-up.

I also was grateful to several posters in this forum who informed me of the problems at the time.
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Old 12-05-09, 05:15 PM
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Originally Posted by Rowan View Post
I regret to inform you that, based on my personal experience, your cog may have mashed the threads on the your hub.

What is the quality of the cog you are using. If it is a stamped one, there are issues with them, irrespective of how tight you cinch them down.

The damage also may have been done in the earlier stages of your story with the constant loosening and then sudden tightening again.

The fact that you have been able to ride for another two months mirrors the experience I had with a Velocity hub (fixed, not flip-flop) in my early days of riding a Shogun steelie I had converted to fixed. Velocity hubs are, I think, essentially Formula hubs. I had loosening, then even after cinching down the left-threaded lockring, the hub thread finally gave way (on a century). This was with a stamped cog.

Once the threads are gone on the hub, there is nothing to do but replace the whole hub. After my experience I went with a Dura Ace cog and have not had one issue since with the replacement set-up.

I also was grateful to several posters in this forum who informed me of the problems at the time.

That's jumping to conclusions.

Let's verify that the OP has the correct tools and is using the correct technique to tighten everything up to proper torque first.
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Old 12-05-09, 06:35 PM
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Originally Posted by operator View Post
That's jumping to conclusions.

Let's verify that the OP has the correct tools and is using the correct technique to tighten everything up to proper torque first.
As said in my original post the threads are fine, I just took it apart again and verified this.
Yes it is a left threaded lockring,
Yes the lockring does bottom out on the cog
And yes I have the proper tools and as for the proper torque... Tight? Really tight? cause if so yes.

My lbs friend just told me to take it apart clean it regrease it and slap it back together with as much torque as possible. I'll repost if it recurs.

Thanks for all the help
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Old 12-05-09, 08:39 PM
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Be sure the lockring is installed correctly and not backwards.

May not seem to matter, but I had the same problem--a couple times I tightened the lockring but the cog still slipped. I realized the lockring was on backwards so I re-installed it the right way and it hasn't been a problem since.

Last edited by JiveTurkey; 12-05-09 at 08:45 PM.
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Old 12-07-09, 11:45 AM
  #10  
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Originally Posted by cnnrmccloskey View Post
As said in my original post the threads are fine, I just took it apart again and verified this.
Yes it is a left threaded lockring,
Yes the lockring does bottom out on the cog
And yes I have the proper tools and as for the proper torque... Tight? Really tight? cause if so yes.

My lbs friend just told me to take it apart clean it regrease it and slap it back together with as much torque as possible. I'll repost if it recurs.

Thanks for all the help
Calvin from Park Tools suggests not to tighten the lockring down too much. The cog must be tight as heck, but not the lockring. Sorta makes sense. Putting backwards pressure on the cog will tighten it against the reverse threaded lockring. Over tightening the lockring may cause damage to its threads or lockring wrench notches.
Inspecting for damage in the lockring threads can be a little tricky, since there aren't many, and they are internal.
A client of mine was having the same problem (cog slipping). He brought us the wheel as soon as it happened and we were able to take care of the issue by removing the lock ring and cog, cleaning the whole set up, and installing the cog with grease and the lock ring with locktite.
If you go that route, make sure that the lock ring threads are completely devoid of grease.
Locktite 242 (blue) will allow you to remove the lock ring at a later date, should you wish to do so.
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Old 12-07-09, 11:47 AM
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and yes, he was riding a formula hub. That was more than six months ago. He comes by on his bike for other things, but hasn't said anything about the cog slipping. Keeping our fingers crossed.
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Old 12-07-09, 11:54 AM
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Since the OP has a Formula hub (fixed/fixed or fixed/free) it's safe to assume that the fixed cog is secured with a reverse threaded lock ring.

The problem can be one of two things:
The OP is tightening the lock ring without first tightening the cog itself, in other words, tightening the lock ring against a somewhat loose cog.
The other problem may be, as mentioned by someone earlier in this thread, the cog does not have a thick enough shoulder for the lock ring to snug up against when tightened.

OP: Exactly what kind/brand of cog do you have?
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Old 12-07-09, 02:28 PM
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Originally Posted by roadfix View Post
Since the OP has a Formula hub (fixed/fixed or fixed/free) it's safe to assume that the fixed cog is secured with a reverse threaded lock ring.

The problem can be one of two things:
The OP is tightening the lock ring without first tightening the cog itself, in other words, tightening the lock ring against a somewhat loose cog.
The other problem may be, as mentioned by someone earlier in this thread, the cog does not have a thick enough shoulder for the lock ring to snug up against when tightened.

OP: Exactly what kind/brand of cog do you have?
Still no slipping although in the past I've gone upwards of a month without problems then boom.
As said the cog is an unmarked 1/8" it came with the wheel, which was formula laced to an alexrim, and the cog came with it, although as it was used that doesn't really mean much. the lockring does indeed sit nice and snug on the cog, I'll try taking everything apart and doing what park advises and pick myself up some loctite.
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Old 12-07-09, 02:49 PM
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Originally Posted by cnnrmccloskey View Post
As said the cog is an unmarked 1/8".
That's another problem right there. High quality dura ace cogs are < $25 MSRP. There's no reason to run anything ****tier than that. Save $10 on a cog. Pay 10x that rebuilding your wheel.
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Old 12-07-09, 02:55 PM
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Although operator is blunt as usual, he's right. I wouldn't bet my life on a no-name cog. At least get an EAI, and put it on there TIGHT!
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Old 12-07-09, 03:00 PM
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Originally Posted by cnnrmccloskey View Post
Still no slipping although in the past I've gone upwards of a month without problems then boom.
As said the cog is an unmarked 1/8" it came with the wheel, which was formula laced to an alexrim, and the cog came with it, although as it was used that doesn't really mean much. the lockring does indeed sit nice and snug on the cog, I'll try taking everything apart and doing what park advises and pick myself up some loctite.
There's really no reason to use locktite if all components are properly tightened and secured, unless you're riding brakeless or constantly applying heavy backpedaling. If I were you I'd pick up a DuraAce or EuroAsia cog and tighten that sucker down.
On one wheelset I run an EAI cog and no lockring on a Formula hub. I run a front brake but frequently apply backpedal pressure and I've never had a cog loosen up on me, ever.
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Old 12-07-09, 03:15 PM
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You can always use the ss/fg preferred method for cranking down a cog and go for the rotafix before resorting to Loctite.
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Old 12-07-09, 06:35 PM
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Originally Posted by CliftonGK1 View Post
You can always use the ss/fg preferred method for cranking down a cog and go for the rotafix before resorting to Loctite.
I'll give that I try I wasn't familiar with that technique, and yes your all right I should upgrade to a better cog, I've been meaning to do it but Im currently working on restoring a gitane super coarse and all my moneys going to hunting down some vintage campy for it
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