# How Do You Loosen a Stuck Cog?



## lonesomesteve (Mar 26, 2008)

I'm sure there's another thread here addressing this, but I couldn't turn it up with the search engine. Anyone have any tricks for getting off a track cog that's stuck? I've already bent my chain whip, and then tried backing my bike up against a wall and stomping on the peddle. It's still stuck. Yes, I took the lock ring off first.


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## CleavesF (Dec 31, 2007)

Oil the threads and tap...tap...tap... Do that for like a week. Multiple times a day. The oil will work into the threads slowly by diffusion and soon enough... bang! it'll come off. 

Patience is key. Or you can try brute force which usually breaks something, either you or the bike.


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## asterisk (Oct 21, 2003)

Try reversing the rotafix method.


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## lonesomesteve (Mar 26, 2008)

asterisk said:


> Try reversing the rotafix method.


Thanks, that's a nice trick. Unfortunately I still wasn't able to get it off. So I guess I'll go with a combination of the reverse rotafix approach with some oil and patience. 

After some more googling I found a suggestion for an approach that sounds like a great way to get a Darwin award. The suggestion was to take off the lock ring and do skid stops until it breaks loose. Say what? I value my life too much to try that approach.


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## Mambeu (May 19, 2007)

lonesomesteve said:


> After some more googling I found a suggestion for an approach that sounds like a great way to get a Darwin award. The suggestion was to take off the lock ring and do skid stops until it breaks loose. Say what? I value my life too much to try that approach.


Couldn't you just loosen the lockring just a touch, maybe a quarter turn, and then try this? It seems like that would still let the cog break free but it wouldn't be able to really come unthreaded.


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## Touch0Gray (May 29, 2003)

if you have a training stand and brakes, that works, Clamp it in, hang on to the back brake and pedal backwards.


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## ukiahb (Jan 26, 2003)

*you need a longer whip...*

you can make your own chain whip with a longer arm, I made this one and it has never failed to whip even the most recalcitrant cog into submission (i.e. loosening)


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## Gene Kahn (Jan 17, 2008)

WHAT ABOUT HEAT? Well this is my ultimate solution for many stuck threads, after
years of boat work. I use a hand torch (propane) to heat up frozen stuck threaded parts. Simple physics - something expands. Probably will burn up a lot of stinky oil, tho. I keep the blue flame close to the work area, about 1-1/2 inch, and keep it moving to spread the
heat around a lot. Suggest you do out outside, wear big gloves, have fire ext handy. 


Gener.


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## wim (Feb 28, 2005)

*Active imagination.*



lonesomesteve said:


> After some more googling I found a suggestion for an approach that sounds like a great way to get a Darwin award. The suggestion was to take off the lock ring and do skid stops until it breaks loose. Say what? I value my life too much to try that approach.


Spinning a cog off isn't life-threatening, especially under controlled conditions. If it were, I should be dead long ago.


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## JCavilia (Sep 12, 2005)

*Thermal expansion coefficients*



Gene Kahn said:


> WHAT ABOUT HEAT? Well this is my ultimate solution for many stuck threads, after
> years of boat work. I use a hand torch (propane) to heat up frozen stuck threaded parts. Simple physics - something expands. Probably will burn up a lot of stinky oil, tho. I keep the blue flame close to the work area, about 1-1/2 inch, and keep it moving to spread the
> heat around a lot. Suggest you do out outside, wear big gloves, have fire ext handy.
> 
> ...


Heat works in a lot of situations, but the problem with this particular application is the differing materials. Even if you try to confine the heat application to the cog, some heat will be transmitted to the hub shell. Aluminum expands much more than steel as it warms, so the connection will tend to get tighter unless you you can really control the heat movement.

Probably the answer is as Cleaves suggested: a combination of penetrating oil, repeated impact/vibration, and time.


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## ukiahb (Jan 26, 2003)

JCavilia said:


> Heat works in a lot of situations, but the problem with this particular application is the differing materials. Even if you try to confine the heat application to the cog, some heat will be transmitted to the hub shell. Aluminum expands much more than steel as it warms, so the connection will tend to get tighter unless you you can really control the heat movement.
> 
> Probably the answer is as Cleaves suggested: a combination of penetrating oil, repeated impact/vibration, and time.


also, cogs and bearings are hardened, so high heat from a torch would probably be a bad idea...hmmm, maybe I should make a few more uberwhips and see if I can sell them ;-)...also, FWIW applying antiseize to the threads (auto parts stores carry it) when installing the cog makes it much easier to remove later


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## Touch0Gray (May 29, 2003)

take the wheel off, wrap the cog in a piece of chain, clamp it in a big bench vice. Turn the wheel, bet it comes right off. You are trying to turn the wrong piece


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## CurbDestroyer (Mar 6, 2008)

A long time ago I was told 3 Gorillas and Stu Thompson, but that was some time ago.


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## tobu (Dec 19, 2004)

Touch0Gray said:


> take the wheel off, wrap the cog in a piece of chain, clamp it in a big bench vice. Turn the wheel, bet it comes right off. You are trying to turn the wrong piece


+1

You might also consider freezing the non-cog area with a spray.


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## tron (Jul 18, 2004)

Touch0Gray said:


> take the wheel off, wrap the cog in a piece of chain, clamp it in a big bench vice. Turn the wheel, bet it comes right off. You are trying to turn the wrong piece



I did some searches recently and youtube videos seemed to show that something like this was the most effective way.


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## tbyrne (Dec 29, 2004)

For penetrating oil, try PB Blaster - best I've ever used.


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## Touch0Gray (May 29, 2003)

tbyrne said:


> For penetrating oil, try PB Blaster - best I've ever used.


I'll second that.....


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## tihsepa (Nov 27, 2008)

Is this thing off yet? If not hit it with a air hammer. The cog will be junk but off.


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## Touch0Gray (May 29, 2003)

A from Il said:


> Is this thing off yet? If not hit it with a air hammer. The cog will be junk but off.


unless there so much galvanic corrosion that the hub is toast too......shoot, you could just crank the vice down on the cog and turn the wheel, Even an expensive cog is cheaper that a new hub and the trouble of lacing in up


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