merckx89

So I have had my fixed gear for almost two years now and have about 2500 miles on it, mostly commuting but some training as well. Today I was trying to take the rear cog off because I wanted to swap over to 1/8 inch chain, cog, and crank, but could not for the life of me get the cog off. The shop where I work broke a chain tool trying to get it off, and then I took it outside to try skidding it off. Did about 10 minutes of trying to do that but to no avail. Is there any way to get it off? If not, what is a decent wheel to start looking at. Preferably prebuilts. The ones that are on it now are just the stock open sport laced to no name hubs 3x, and have held up fine. Not trying to get something super light, durability is much more important (these one have not been trued since I've had them, and are still perfect).

stevo9er

Could you maybe cut it off? I have no idea.

merckx89

How would you cut a cog off without damaging the wheel? We had everyone in the shop stumped, though someone did say there was a tool we could try that fits in a vice and you use the wheel as leverage, we just have to find a shop who carries it.

corter

i'd just go for a formula type prebuilt, although I'm a big believer in 3/32 chains. formulas are sealed and durable, you can get a wheelset for arond $100, I ride one that's been fine for 6 months.

stevo9er

Beats me

CliftonGK1

If you can heat the cog w/o damaging the hub, you might be able to unstick it from the hub.
When I rebuilt my old Vespa engine I had to use that trick to unstick some gear cogs.

Ill Mitch

Try this: https://204.73.203.34/fisso/eng/schpignone.htm

Those instructions are for installing a cog, but just reverse it and it works for unthreading a cog too.

TheFroodAbides

^^yes, try the reverse rotafix, pull hard, your wheel has lasted this long, right? or, put your cog in a vice (use bits of wood to protect your cog if you want to keep it) and, again, turn your wheel, hard.

tx_what_it_do

take off the lockring

merckx89

That's essentially what I did by skidding on it with no lockring attached. Also putting as much pressure trying to packpedal it on the ground, still nothing. The wheel in vice thing is the tool I am waiting on (should be mid next week), that's my last hope.

tx_what_it_do

um.. citrus lube, then reverse rotafix?

sit that hoe on a bike stand, dont just dangle the seat on the arm thing clamp the post/seat tube on there, reverse rotafix that ***** and it should come off. if not, i dont think anything will work.

skidding will only do as much as the traction of the tires can withstand. rotafixing is claimed to be able to do away with the lockring, but can be reversed by reverse-rotafix. iunno i've messed with the rotafix method and it seems to work pretty well.

skippingstones

i've done the reverse rotafix. it took a bit longer than i thought. if your cog is like mine was, it might not look like it's going to unfreeze at first, but just keep at it and hopefully it will just release. it'll be satisfying when it goes.

oh, and really grease up that new cog.

dudezor

See if you can get a long pole to fit over the handle of a chainwhip for heaps of extra leverage and have someone hold the wheel secure while you yank down on the sucker. Soak the the cog in WD40 or similar overnight beforehand too. I had a bast4rd of a cog a while back that I bent my chainwhip on and thought would never let go too, but this technique ended up working.

And yeah, don't forget to grease the thread on your cog next time either ;-)

merckx89

So the reverse rotafix method didn't work. It was me and a friend of mine who can bench like 200 and weighs like 250 both pulling the wheel and it still wouldn't come lose. Time to give up on it? Anyone want to buy a set of fixie wheels with a free 16 tooth cog on it for cheap?

The LT

Stick the whole thing inside of a freezer before you try to take the cog off. Since the hub is aluminum and the thermal coefficient of expansion of aluminum is larger than steel(the cog), cooling it down will shrink the hub more than the cog allowing you to reverse rotafix the cog off.

Heating can also work if you can keep the majority of the heat on the cog and not transfer it to the hub

craigmoyer

Try tightening it even more. When I worked on semi trucks, we'd get stubborn bolts all the time, one way we got rid of them was using tons of PB blaster, then tightening them down, then trying to loosen them up again.

Hope that helps.

pyroguy_3

Kroil. Way better than wd-40. If I were in your situation, I would soak some (whatever viscous lubricant you have handy) into the threads of the cog/hub interface, then take a rubber mallet/hammer/beating stick and give it a few good taps to try and break the seized parts loose. You'd be surprised what a few good whacks can do for stuck parts. Also, if you're planning on scrapping the cog, take a cold-chisel and a good solid hammer, place the cold chisel on one of the teeth, hitting it so that it is loosening the cog, and try to break it free that way. A few quick blows works better on seized parts I've found. Good luck. Oh, and how cheap are we talking here (for the set of wheels, if you don't get it off)?

sp00ki

you did do it reverse of those directions, right?

merckx89

1. I don't have a freezer big enough and I don't think ice would be cold enough, though maybe some dry ice
2. Tried tightening it down to begin with, but I'll try it again
3. Never heard of kroil, but will look it up, did try the chisel to begin with
4. Reversed the directions. Put the chain under the cog and tried to roll the wheel forward.
Like 75 bucks for the wheels if I cant get the cog loose. with the cog they would be 250 with tax at retail.

pyroguy_3

You would have to be careful with the dry ice, or liquid nitrogen for that matter, as the intense cold could be detrimental to the integrity of the metal. I've only dealt with heat-treating, not cryo-treating steel, so I can't be 100% on that one.

Also, you can get ice pretty cold. To get a pretty cold ice bath, i forget the exact temperature, mix some ice and ethanol, should get a fairly cold temperature. I guess you could maybe switch out ethanol for denatured alcohol, which if I remember correctly is just methylated ethanol (so you can't drink it...), or maybe even isopropyl alcohol (rubbing alcohol). Or you could always go the saltwater and ice route.

Philatio

Not to be a dick or anything, but your buddy that's 250 and can only bench 200 isn't very strong. I only bring this up because you used it as an example of how much force you used to work off the cog. When I was lifting I maxed out at 200 and weighed 145.

merckx89

He may not be that strong, but between the two of us it should have been easy. If I need a bodybuilder to get this cog off then screw it, it's going up on craiglist.

geeknerd99

How about installing a tiny chainring and backpedal(jump)ing?

I'd go PB Blaster, let it soak in, and then use the chain whip we rigged up with a BMX grind chain. With a like, 6 foot cheater bar. Anything more than that and it's time to think of more macho solutions. Like craigslist.

pyroguy_3

dynamite and a crowbar. That combination has got to work.

geeknerd99

You must be called pyroguy for a reason.

Now, using explosives to drive a crowbar? That's my kind of cog removal.