Bicycle Mechanics - how many threads is enough on a fixed hub?
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10-23-06, 11:21 AM
I have re-built fixed flip-flop hub laced with brand new spokes to a new rim. I've never ridden on this, but one time overtightened a crappy cog onto it, causing stripping on what I thought was the cog at the time. However, in taking off the cheapo cog, I have realized that about 1/2-2/3 of the threading on the fixed side of the hub has been stripped. It still threads on, but only to what's remaining. Do the missing threads mean I'm going to eventually strip the entire thing, or will putting on a high-quality cog, coupled with the lockring, be sufficient? I'm a light rider, use a brake and don't do much skidding or hard backpedalling.
What sayest thou? Should I worry?
10-23-06, 11:27 AM
if you only screwed the cog on halfway, up to where it hit the stripped threads, you'd force it onto that part the first time you rode it. the lockring stops it from unscrewing when you skid, but you would pedal forwards and force it onto the stripped part...and then it wouldn't be tight. i wouldn't risk stripping a cog for something that won't work.
10-23-06, 12:02 PM
Hub is probably toast.
Your only trick may be throwing on a BB spacer ring or two to cover the stripped threads, and put on the cog after them, onto the intact threads, if there are enough. Problem is, you'll probably not be able to put on a lockring. Chainline will also change.
But if it's a flipflop, just use the other side.
10-23-06, 12:13 PM
But if it's a flipflop, just use the other side.
If it's not a flip-flop hub, you could use it by picking the cog you want and JB-welding it onto the threads, then installing the track lockring. This would basically be permanent, but would allow you to use the hub, likely without problems.
One other thing: unless the hub is really high-flange, JB-welding the cog onto the threads will mean that you can't replace a broken drive-side spoke. So, definitely don't do this if the hub is a flip-flop and you can use the other side.
10-23-06, 12:15 PM
Oh, to clarify: you really want both the cog and the lockring to grab good threads all along their width. There isn't any leeway, really. If you can't put on a lockring, you can still ride it suicide, of course.
10-23-06, 01:42 PM
I realize from the responses I was unclear about the stripped area. Here is a diagram of where it's stripped:
KEY: II = wheel
!! = lockring thread
:: = good cog thread
?? = stripped thread
Sorry I wasn't clear the first time, but the good threading is at the base, on the hub-inward side, closer to the plane of the rim.
Am I still toast? It's fixed/free, so lockring threading on only one side. Since it's all new but for the hub, should I go about re-lacing a new hub on?
10-23-06, 01:56 PM
That's how I understood it first, too. If the stripped part is good enough at least to support a spacer, you can try to bring th cog out to the good threads. You know how wide each part is. Search the SS/fixed subforum for "suicide" =running a fixed cog on freewheel threads. There's a recent thread about it. It works ok most of the time. Your call to use it or relace to new hub. If you have a brake on, suicide is not too bad at all.
10-23-06, 02:00 PM
Yeah, your diagram is the way I was thinking of it, too.
You could run it as-is, "suicide" style, and run the risk of stripping the remaining threads and having the rear hub be totally useless. Or you could JB-Weld the cog onto the hub threads, which would make it much less likely to strip but also mean that you can't remove it if you want to put a different cog on or replace a drive-side spoke.
10-23-06, 02:06 PM
Huh, okay. I'm guessing no one's heard of being able to chase new threading on. I wouldn't imagine it's possible, but contemplated. Isn't a fixed hub supposed to have harder metal than a thread-on cog to prevent just such a disaster?
Sea Green Sky
10-23-06, 06:43 PM
I'm guessing no one's heard of being able to chase new threading on. I wouldn't imagine it's possible, but contemplated.
You can't chase new threads on, only clean up what's there. When it was stripped that metal was damaged or broken so chasing with a very large die or a sprocket might move some metal around and make it look better but it will not be solid. Ever. There's only so much metal there and it's already been cut once, you can't add metal and cut it again. (Well, ok you can. It's done to cams and cranks all the time, but it would be more than a new hub anyway).
Chasing threads really only works, if at all, for inside threads like a nut or BB.
10-23-06, 07:42 PM
Yeah, huh, that's pretty much what I assumed. Thanks for solidifying my hunch. I think I might go and get myself a new hub, maybe use this with the freewheel side for a singlespeed beater or something.
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