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Discussion Starter · #1 ·
Okay, so I will admit that there have probably been a couple dozen posts about this, but I am confused and tired so please bear with me.

I have an old bike that I am trying to convert to a fixed gear. It is currently set up as a singlespeed using the original wheels. Really I would prefer not to buy a new wheel or completely mangle the original wheels. I have read Sheldon Brown's article saying that you can use an old bottom bracket lockring to help hold the cog to the wheel but was told by a LBS that these lockrings weren't actually threaded the same as the track cogs. They didn't recommend doing it, and said I should get a new wheel or buy a cog and spot weld it to the hub. What do people think?

PS I will post pics when I am done with this little project

James
 

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The BB lockring is rather worthless on a suicide hub. I have used red loctite WITH A FRONT BRAKE without any problems.

Jimi_Lee said:
Okay, so I will admit that there have probably been a couple dozen posts about this, but I am confused and tired so please bear with me.

I have an old bike that I am trying to convert to a fixed gear. It is currently set up as a singlespeed using the original wheels. Really I would prefer not to buy a new wheel or completely mangle the original wheels. I have read Sheldon Brown's article saying that you can use an old bottom bracket lockring to help hold the cog to the wheel but was told by a LBS that these lockrings weren't actually threaded the same as the track cogs. They didn't recommend doing it, and said I should get a new wheel or buy a cog and spot weld it to the hub. What do people think?

PS I will post pics when I am done with this little project

James
 

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You'll find this is a point of contention for fixed riders. Some people use a freewheel hub with a track cog screwed on without a lockring or with a bottom bracket lockring threaded next to it, others believe it's a death wish.

The problem is that only pressure is keeping the cog and lockring screwed on. With a true track hub the lockring threads on in the opposite direction than the cog on a seperate set of threads. This makes the lockring actually tighten against the track cog when pressure is applied to the cog rather than loosening both the cog and locking on a freewheel hub setup.

For example look at a this photo of an ENO hub with one side threaded for a track cog and the other threaded for a SS freewheel. Notice the step in the threads on the right side, that's for the lockring to thread on aside the track cog.

Do some more searching and you'll find more info and arguements on either side but my preference is just to get the right tool for the job. You can find inexpensive rear wheels on eBay all day. A true fixed hub combined with a lockring is a little insurance and piece of mind that your cog won't unthread, lock up the rear wheel, and send you on a trip over the bars into the concrete.

edit: Welding the cog onto the hub would also work but why go to all that trouble?
 

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Welding wouldn't be much trouble at all if you were set up for it, should only take a minute or so. The problem is, as with all weldments, that the "conversion" is quite permanent, and if you're not careful you could accidentally go all the way through and weld a bearing to the bearing surface, thereby ruining your hub.

You also face the fact that most hubs are aluminum and many track cogs are steel, those two don't weld together nice, especially in a load bearing situation, it's possible (with a TIG welder and a crap-load of skill/metallurgical knowledge) but not reccomended.
 

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What's your riding style?

Do you expect to be the hard-core fixie guy who uses back-pressure for a lot of your braking, including skid-stops in panic situations? Then you probably should get a proper track hub, as asterisk advises.

On the other hand, if you put a (front) brake on the bike, and use it for most hard stopping, I think a freewheel hub can work fine. My fixies have freewheel hubs. I clean the hub and cog threads well, use plenty of blue loctite, usually skip the bb lockring (there's often not room for it anyway) and thread the cog on tightly, and in perhaps 7,000-8,000 miles on two bikes (4 different rear wheels) in the last few years I've never had a cog loosen even a little bit. I do use pedal pressure for gentle braking, but I use the brake a lot.
 

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Discussion Starter · #7 ·
I had already read several articles about converting to a fixed gear and talked to several people. The confusion came from all of the resources telling me different things. I have access to welding, but am not very good at it and it isn't a TIG welder. The rear wheel is the original, and almost perfect, Sunshine (Sansin) wheel which was made from steel (I think). Also, I have access to a lot nastier products from loctite then just their red (401) and blue products at work.

As for my style of riding, I am not sure yet. I was planning on keeping the front brake on for the time being since this is my first fixie. But I have ridden them before and none of the bikes had brakes.

I was told by the LBS that the old BB lockrings have a different pitch thread then the track cogs and will mangle the threads. Is this true?

James
 

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For steel on steel welding just about any welder should do great, you're still looking at a permanent modification though.
 

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Discussion Starter · #9 ·
One of my goals was to not make the wheel unusable in the future. Which is why I am hesitant to weld anything to it. Also, I do not want to damage the threads on the hub if the BB lockring is pitched differently. Then again going over the handlebars has never been fun and I am pretty ambivalent about investing in a new wheel if i don't have too.
 

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Jimi_Lee said:
I was told by the LBS that the old BB lockrings have a different pitch thread then the track cogs and will mangle the threads. Is this true?
James
Track cogs, freewheels, and english BB lockrings are all threaded at 1.37 x 24tpi, right-hand thread. So, a BB lockring will thread on there fine, and help to hold just like two nuts on a bolt - not great, but better than nothing.

The confusion comes in because track hubs have an additional threading for a lockring in addition to the cog, and that is threaded differently, at 1.29 x 24tpi left-handed. As was mentioned, that really locks things on, because if the cog tries to unscrew, it also tries to screw the lockring on tighter. But, that's a hub you don't have.

I do not suggest the following:

I ride (with both brakes) on a converted (respaced and redished) wheel without either a lockring or locktite. I tightened it on very well with a chain whip and am running a fairly tall gear, so I don't have the strength in my legs to unscrew it, and usually brake rather than resist, which I reserve for minor speed-control. Following some of the discussions here, I loosened it manually and tried a spin-off under controlled conditions. I found:

1) It's fairly obvious when a cog breaks free and begins to unscrew.
2) It takes (for my rig) five full wheel revolutions for the cog to unscrew. That's a surprising amount of distance and time to get your legs going the right direction, or to stop properly (obviously, this is only for a brake-equipped bike.)
3) On a track hub, there's a concern that the cog will unscrew and jam against the dropout, causing an immediate lock-up of the rear wheel. On a converted hub, there's much more space available, so it's less likely to be a problem, especially if it's a seven-speed conversion. In the event of a full unscrewing, there would be loose parts rumbling around that could cause trouble, but the threat isn't as great as with a track hub. With my setup and manipulating things in every imaginable way on the workstand, I couldn't find a truly dangerous scenario, though could see where other setups could have problems, and there was some risk of minor damage.
4) The real source of danger is when using a fixed/free track hub with a track cog instead of a freewheel threaded on thee free side. There, the space to the dropout is very small, and there's no facility for a lockring of either type. That is the real 'suicide' setup, and the wisely safe have applied those lessons to converted hubs as well.


When I went to my LBS looking for a BB lockring for the same reason, I was told the same thing you were. I went out to the car, got the wheel, and threaded it onto the hub. I handed it back, and use another shop now.

The welding thing doesn't sound great to me. I have aluminum hubs and steel cogs, so it's impossible anyway. And if I didn't like the gearing I guessed at the first time, or simply wanted to experiment...

Like I said, I don't recommend doing what I do. There's every possibility that I'm as lucky as I am stupid.
 
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