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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 12-22-04, 11:35 AM   #1
ZenNMotion
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fixed gear/ road hub- no lockring?

I'm building a fixed gear using an old threadon road hub with a Dura Ace track cog. I've build others but always used Surly cogs which apparently are thinner at the threads by 1.5mm or so than the Shimano. I've always used a bottom bracket lock ring and loctite with the Surlys for extra security to prevent the cog from unscrewing when I torque back the cog to slow down (using a front brake, no rear brake).

My problem is this- the thicker Dura-Ace cog does not leave enoungh threads on the rear hub to allow the use of a lockring. I've never had a problem with a cog unscrewing with my usual setup with the lockring. I would like to build my rig with no rear brake, just using the Dura Ace cog, loctite, but no lock ring. My question is a little bit of engineering science. Is a thicker (more threads) cog less secure (more likely to unscrew) than a thinner cog used in combination with a lockring? Assuming that the total number of engaged threads is approximately the same, is the resistance to the backpedaling torque going to be the same? Remember, this is not a track cog with reversed threading for the lockring-
Thanks!
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Old 12-22-04, 11:42 AM   #2
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I'm no physicist, but I think the resistance would be greater w/ the thinner cog and the lockring. You see, with the thick cog, all of the torque is being applied directly and efficiently to all of the occupied threads (since the teeth of the cog are presumably centered, the force applied is distributed evenly). But with the thinner cog and the lockring, the torque is applied to the lockring via friction from the turning cog, which is, I think, a less efficient way to do it (sort of like the difference between unscrewing the lid to a jar by grabbing the sides of it (efficient) and unscrewing it by pressing your fingertips against the top of it really hard and twisting (not so efficient)). But, like I say, I'm a lawyer, so I'm better qualified to tell you whom to sue when the cog fails than whether the cog will fail in the first place.
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Old 12-22-04, 12:19 PM   #3
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Use loctite and run a front brake. It's the smart way to go.
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Old 12-22-04, 12:21 PM   #4
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get a real hub. stop making garbage.
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Old 12-22-04, 12:36 PM   #5
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both solutions are bad. Lockring + hub will more likely strip your. Lockring only will be more likely to spin off. Since you are running a front brake the cog only makes more sense to me.
However, Locktite should not be needed on a properly set up bike and track hub is the only decent solution.
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Old 12-22-04, 01:14 PM   #6
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Quote:
Originally Posted by Ya Tu Sabes
I'm You see, with the thick cog, all of the torque is being applied directly and efficiently to all of the occupied threads (since the teeth of the cog are presumably centered, the force applied is distributed evenly). But with the thinner cog and the lockring, the torque is applied to the lockring via friction from the turning cog, which is, I think, a less efficient way to do it
I'm no physicist either, but I think you've got it kinda backwards. For the cog to stay in place, the force you apply to it by pedaling or braking must be less than the resistance on the threads. A wider cog means more threads means more resistance means you can apply more force. Threads alone will never supply enough resistance to be really safe though, so that's why you need a good hub and a lockring to keep everything in place. The lockring is counterthreaded, so it's providing mechanical resistance to braking torque rather than frictional resistance, same for the lip on the inside of a good track hub for forward torque. If you don't have a good hub you're gonna mangle the threads when you pedal hard, and if you don't have the lockring you're gonna spin it off eventually.

[edit]
Just realised I misunderstood the point ya tu sabes was making. With the lockring threaded the same direction, it depends how tight you get everything. A narrow cog with a tight lockring will have more resistance, because the pressure of the lock ring against the cog is increasing the friction against the threads - it's as if you were "spreading" the threads a little. As soon as the lockring loosens a little you loose that extra resistance, and sabes is right.

Last edited by superstator; 12-22-04 at 01:45 PM.
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Old 12-22-04, 01:30 PM   #7
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Originally Posted by isotopesope
get a real hub. stop making garbage.
The whole bike came from the garbage (curb) or my parts box. This is now a nice 17lb bike for winter training, position set up exactly like my Ti road racer, that I've spent less than 50 bucks on, including cog, paint, and bar tape. I could throw it all away, and just buy a Bianchi Pista for 500 bucks too. But that's not the point is it? I think Frankenfixies are very cool- I have a couple now, and have built a couple others for friends. There's always parts-mix challenges, but they always work out. Recycled as much as possible is a matter of pride. From each , I've learn something and have a unique, nice "new" bike that costs almost nothing. I'm sure I'm not the only one in here doing this!

Last edited by ZenNMotion; 12-22-04 at 01:45 PM.
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Old 12-22-04, 01:35 PM   #8
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Quote:
Originally Posted by superstator
The lockring is counterthreaded, so it's providing mechanical resistance to braking torque rather than frictional resistance, same for the lip on the inside of a good track hub for forward torque. If you don't have a good hub you're gonna mangle the threads when you pedal hard, and if you don't have the lockring you're gonna spin it off eventually.
It's a ROAD hub. Not counterthreaded.
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Old 12-22-04, 01:42 PM   #9
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Quote:
Originally Posted by Ya Tu Sabes
But with the thinner cog and the lockring, the torque is applied to the lockring via friction from the turning cog, which is, I think, a less efficient way to do it (sort of like the difference between unscrewing the lid to a jar by grabbing the sides of it (efficient) and unscrewing it by pressing your fingertips against the top of it really hard and twisting (not so efficient)). But, like I say, I'm a lawyer, so I'm better qualified to tell you whom to sue when the cog fails than whether the cog will fail in the first place.

Good point. We should therefore sue the peanut butter makers to force them to pack it in tubes.

Someone on the fixed gear gallery forum sent me this link- though the method described probably permanently fixes to cog to the hub as I cant imagine getting it off later- though it's an easily replaced juck hub, so I'm gonna go for it. The italians are much less litigious than we are apparently.

http://204.73.203.34/fisso/eng/schpignone.htm
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Old 12-22-04, 02:47 PM   #10
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Quote:
Originally Posted by ZenNMotion
The whole bike came from the garbage (curb) or my parts box. This is now a nice 17lb bike for winter training, position set up exactly like my Ti road racer, that I've spent less than 50 bucks on, including cog, paint, and bar tape. I could throw it all away, and just buy a Bianchi Pista for 500 bucks too. But that's not the point is it? I think Frankenfixies are very cool- I have a couple now, and have built a couple others for friends. There's always parts-mix challenges, but they always work out. Recycled as much as possible is a matter of pride. From each , I've learn something and have a unique, nice "new" bike that costs almost nothing. I'm sure I'm not the only one in here doing this!
Keep recycling Zen. Garbage bikes rock.

Use a front brake. I'd use the wider cog and loc-tite. Don't backpedal at all until you've got a lot of miles on it. And don't rely on backpedalling to stop.
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Old 12-22-04, 03:08 PM   #11
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Quote:
Originally Posted by superstator
Just realised I misunderstood the point ya tu sabes was making. With the lockring threaded the same direction, it depends how tight you get everything. A narrow cog with a tight lockring will have more resistance, because the pressure of the lock ring against the cog is increasing the friction against the threads - it's as if you were "spreading" the threads a little. As soon as the lockring loosens a little you loose that extra resistance, and sabes is right.
How about two bottom bracket lockrings if you could fit them? Anyone ever try that?
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Old 12-22-04, 03:36 PM   #12
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Originally Posted by BlastRadius
How about two bottom bracket lockrings if you could fit them? Anyone ever try that?
Pressure on both sides would make the lockring in the middle 'float'. You'd get a tiny bit more resistance, but not enough to be worth it.
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Old 12-22-04, 04:26 PM   #13
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[QUOTE=superstator]If you don't have a good hub you're gonna mangle the threads when you pedal hard[QUOTE]

Huh? How is pedalling hard going to mangle the threads? How is it different than pedally hard with the freewheel attached? Perhaps because of how thin the Surly cog is?

The new Surly cogs have a wider thread than the D-A cogs, so says my LBS.

You may want to try another old freewheel wheel. The the width of the freewheel threading varies from hub to hub. This probably has more to do with no room for a lockring than the cog width does. Sheldon has a page that list cog widths. They vary only about 1 mm, that is not a lot.
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Old 12-22-04, 05:24 PM   #14
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Quote:
Originally Posted by isotopesope
get a real hub. stop making garbage.

Get your nose out of the air- I've never had a problem with a thread-on road hub and a lock ring. There is nothing garbage about it. I'd take my old Campy Record hubs any day over the me-too wannabe track crap that is flooding the market... half these Suze hubs feel like their bearing came from the beach.
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Old 12-22-04, 05:26 PM   #15
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[QUOTE=Adker][QUOTE=superstator]If you don't have a good hub you're gonna mangle the threads when you pedal hard
Quote:

Huh? How is pedalling hard going to mangle the threads? How is it different than pedally hard with the freewheel attached? Perhaps because of how thin the Surly cog is?

The new Surly cogs have a wider thread than the D-A cogs, so says my LBS.

You may want to try another old freewheel wheel. The the width of the freewheel threading varies from hub to hub. This probably has more to do with no room for a lockring than the cog width does. Sheldon has a page that list cog widths. They vary only about 1 mm, that is not a lot.

Thanks for the info- actually they vary by 1-2mm (Sheldons table) which is enough to make it possible/impossible to thread on a lock ring as the thickness of the lockring is only about 2-3mm. In the future I think I'll try to use Surly cogs for conversion bikes for that reason.
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Old 12-23-04, 09:13 AM   #16
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Originally Posted by filtersweep
Get your nose out of the air- I've never had a problem with a thread-on road hub and a lock ring. There is nothing garbage about it. I'd take my old Campy Record hubs any day over the me-too wannabe track crap that is flooding the market... half these Suze hubs feel like their bearing came from the beach.
i'm actually trying to keep peoples faces off of the pavement thanks to poor planning and bad advice. but whatev's. road hubs, track cogs and locktite unite! we have "me-too wannabe" track bikes to make!!
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Old 12-23-04, 09:32 AM   #17
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Originally Posted by isotopesope
road hubs, track cogs and locktite unite! we have "me-too wannabe" track bikes to make!!
Yeah, built by wanna-be's like Sheldon Brown. That guy is always giving bad advice, he doesn't know a thing about fixed gears or bicycles in general
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Old 12-23-04, 10:33 AM   #18
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Originally Posted by riderx
Yeah, built by wanna-be's like Sheldon Brown. That guy is always giving bad advice, he doesn't know a thing about fixed gears or bicycles in general
How this for advice(quoted from the page you linked to)?

"If you don't use a proper track hub with a lockring, you really should have two hand brakes. If not, a front brake failure followed by a sudden extra effort at "resisting" could break the sprocket loose at the worst possible time, and you'd be toast!"
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Old 12-23-04, 10:40 AM   #19
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Originally Posted by isotopesope
i'm actually trying to keep peoples faces off of the pavement thanks to poor planning and bad advice. but whatev's. road hubs, track cogs and locktite unite! we have "me-too wannabe" track bikes to make!!
First off, if you run a front brake, and don't skid stop, you'll be perfectly safe without a lockring on a freewheel hub.

Secondly, not everyone has the money to drop on a proper track hub, myself included. What do you propose we do? Not ride? Well, thats not an option for me considering I don't have a car or any other means of transportation.

I found my bike for $10 at Goodwill, its a pretty sweet find, but I can't justify spending another $100+ on a wheelset when I could have, and did just buy a $30 cog and poof! I'm riding fixed gear. My LBS and all my messenger friends and even all my spandex wearing road friends have all agreed that I'm not endangering myself greatly.

Hell, if you're that concerned for our safety send me a track hub and I'll get my garbage off the street.
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Old 12-23-04, 10:50 AM   #20
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Quote:
Originally Posted by Ira in Chi
How this for advice(quoted from the page you linked to)?

"If you don't use a proper track hub with a lockring, you really should have two hand brakes. If not, a front brake failure followed by a sudden extra effort at "resisting" could break the sprocket loose at the worst possible time, and you'd be toast!"
Your point? Do you think it's bad advice? Or are you comparing it to my advice above of a single front brake? I'll stand by that, front brake failure is rare. Your chain could break too. It's all about minimizing risk.
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Old 12-23-04, 11:02 AM   #21
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Originally Posted by Ira in Chi
How this for advice(quoted from the page you linked to)?

"If you don't use a proper track hub with a lockring, you really should have two hand brakes. If not, a front brake failure followed by a sudden extra effort at "resisting" could break the sprocket loose at the worst possible time, and you'd be toast!"
Yeah- and riding brakeless with a "proper" track hub: what happens if your chain breaks? Or you throw your chain? Are you ANY better off? No- it is the same boat- you'd wish you had a redundant braking system.

What are the odds of the front brake failing AND the rear hub collapsing at the same time? Arguably less than encountering trouble riding a brakeless track set up.
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Old 12-23-04, 11:02 AM   #22
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Boy oh boy! All this wrangling and recriminating over the wisdom of running a fixed cog sans lockring! Remember the original post that started this? It only asked, "Assuming that the total number of engaged threads is approximately the same, is the resistance to the backpedaling torque going to be the same?" Can't we save the dire safety warnings and name-calling for threads devoted more directly to such matters?

Let's assume that ZenNMotion knows his/her plan involves some safety risks and focus on the physics question involved, because I'd really like to see some actual physicist jump in here and say, "Ya Tu Sabes, notwithstanding the fact that you got a C- in high school physics, you have accurately answered the question." It would be helpful if this physicist would also include some cool-looking equations.
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Old 12-23-04, 11:37 AM   #23
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Quote:
Originally Posted by riderx
Your point? Do you think it's bad advice? Or are you comparing it to my advice above of a single front brake? I'll stand by that, front brake failure is rare. Your chain could break too. It's all about minimizing risk.

My point is that when it comes to minimizing risk, two brakes is probably the best way to handle the "road hub hack" situation, because I would not trust that sort of setup in traffic.

As for the chain breaking debate, a good chain being used for it's designed purpose is very strong. A threaded road hub being used for something other than accepting a freewheel carrys far less of a guarantee. I don't know what quality front brake you use or how well it's installed, but yes, redundant braking is typically safer.

Granted, this whole debate is going of on a tangent, so I'll leave it at that.
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Old 12-23-04, 11:46 AM   #24
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DERBY!
We need to pick a spot and beat the living tar out of one another. last rider standing gets to state what we should do as far as wheels/hubs/bikes for the rest of our existences. Period.
That is the only logical approach here. No-holds barred, all-out fightfest on fixed gears.
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Old 12-23-04, 11:54 AM   #25
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DERBY!
We need to pick a spot and beat the living tar out of one another. last rider standing gets to state what we should do as far as wheels/hubs/bikes for the rest of our existences. Period.
That is the only logical approach here. No-holds barred, all-out fightfest on fixed gears.
I'm down with that. Let's rock it! \m/
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