Narrow-profile cog recommendation(?)
 

Hi. As a first, fixed gear project, I'm converting an older 80s bike. I am trying to put a 16T cog on a threaded freewheel hub and I'm running out of threads for the lock ring (re-purposed BB lock ring). I can start the threads for the lock ring (maybe a thread and a half), but there aren't nearly enough to fully-engage the lock ring and tightening the ring will probably just strip the threads. The 3/32"-16T origin8 cog that I am bought is 7.3 mm wide. Can anyone recommend a threaded cog with a narrower profile (that would leave more threads exposed for a lock ring) that I could substitute? I plan to use thread locker on the cog and a front brake, but I am not experienced enough to judge whether I can overlook a lock ring with this setup. Does anyone with more experience have an opinion? Add a rear brake and a mouth guard? Thanks in advance.

A lock ring serves little purpose on a normal freewheel hub. I would just use the cog you have without a lockring and use the following method to get the cog really tight. Install a front brake. You are unlikely to break the cog loose, but as long as you have a means of stopping nothing catastrophic will happen.

I’m confused, are you using a multi-speed freewheel hub? Not a track hub? Because if so, you should have enough threading. Also, if you are, it won’t have any reverse threading for a proper lock ring, which I assume explains the use of a bb lock ring? I’m having a hard time imagining why you would t have enough thread for a fixed sprocket, but the ‘rotafix’ method suggested above ^^ is what you should do. Maybe also add some loktite for extra security? I sure hope you weren’t planning on doing skids with that setup. Use a front brake and you should be fine.

some photos of your hub and sprocket would be very helpful in properly addressing the problem.

I only have two freewheel hubs in my collection, but it was the same situation with them, only about 1 thread left after a cog went on. If my hubs were threaded all the way to the end, there might be enough for a BB lockring, but they're stepped down to an unthreaded section for the outer 1mm or so. Not sure if that's common or not.

If you're concerned, buy or build a wheel with a proper track hub. It's among the easiest wheels to build. :thumb:

Thanks for your replies. There is a 15-year Old Bikeforums Thread (https://www.bikeforums.net/singlespe...ockring-2.html) where someone had a similar problem and reading through it, I couldn't come to a conclusion on whether you could get away with skipping a locking. [MENTION=44824]mihlbach[/MENTION], the rota fix method looks like it will work and with a bit more torque than I'd get with a chain whip, but looks like it might be rough on the bb finish. [MENTION=471203]seamuis[/MENTION] yes, it's a multispeed freewheel hub and yep, that's why the improvised BB lock ring. The ring leaves only a couple threads exposed when cranked on tight (photo below). In the old thread, someone said the Sheldon Brown website had info on cog dimensions. I only found it on the second trip to the site after scrolling down (Sheldon Brown- Chainline). Maybe a pre-2005 Surley would work, but I'm not sure where I could get one to try. I'll go with thread locker blue and avoid skids. [MENTION=251447]ThermionicScott[/MENTION], the hub is a late-model multispeed freewheel, maybe the older ones are threaded to the end. If the fixed gear experiment goes well, I'll build a proper wheel and use a frame without a derailleur hanger.

Thanks for your recommendations. Rota fix with thread locker and no skids.

https://cimg1.ibsrv.net/gimg/bikefor...a2c47584c1.jpg

If your worried about damaging your bottom bracket finish, wrap it in a rag before you rotafix.

Yeah exactly, just throw a rag over your bottom bracket and wrap the chain over it. That's what I do.

That'll be the plan (a rag and some muscle) for the final torque of the cog. I picked up the rear axle spacers this past weekend. My project for the next week will be to re-dish the wheel.

To satisfy some curiosity, I tried the track cog on a multi-speed hub from '70's (Maillard) wondering if there'd be more threads on an older hub. Nope. There is still only, at most, two exposed threads. Maybe an old, pre-2005 Surly cog or a cheap cog that's cheap because it has less threading/ material would do, but I'm going to stick with what I got for now.

two week long weekend project... complete
 

Thanks all for the your input and replies. I re-spaced and re-dished the rear wheel last weekend. I used thread locker blue and put my 200 lbs into the chain whip to snug up the cog. 60 miles so far and no mechanical issues. In the spirit of "didn't happen without a photo," I attach two from my afternoon ride (taken just before the 40 minute delay for a downpour, thunder, and lighting). I've enjoyed my first fixed-gear rides and like the variety it has added to my mileage this week. The rear brake is redundant, but I didn't want to have to re-wrap and shellac the bars if this ride evolves; and it provides some security for my novice fixed-gear skills (descending on dirt roads is gonna take a bit more practice). Cheers.https://cimg5.ibsrv.net/gimg/bikefor...887339b5e0.jpg
drive-side profile
https://cimg4.ibsrv.net/gimg/bikefor...1c0a159c13.jpg

wheel-dish and chainline

looks like it turned out great

I just tried a bunch of cogs (SunTour, Dura-Ace, Euro-Asia, etc.) on a Campagnolo Record road hub and the only two that offered more than a thread or so of engagement for a lockring were both long out of production: an early 1950s Sturmey-Archer cog from before they adopted the splined cogs, and another marked "Reich."

N.B. if you're going to run a fixed gear on a road hub, lockring or not, keep the rear brake and don't use your legs for slowing down or stopping.

For practical road fix gears, older road bikes with horizontal dropouts are the sweet deal. Derailleur hangers don't matter. I go out of my way to find early '80s horizontally dropped bikes using the standards the Japanese used. (English tube diameters and frame threading, metric elsewhere.)

Road dropouts mean you can use a rear brake and have little rim height change if you change cogs and have the wheel a little further forward or back. Road dropouts also make pulling and installing the rear wheel a lot faster; a real blessing if you have to fix a flat in the dark. That all road fix gears marketed now have track ends says a lot about both marketing and peer pressure.

If I had to can the hanger, I'd cut it off. Yes, I know that is a sacrilege but I'd rather do that than be saddled with track ends. (Good thing is my ego can deal with an ounce and a half of useless hanger and I don't have a paint touch-up to do.)

Edit: Bah! Old thread. I hope the OP stayed with this Miyata. Sweet ride! I'd call it a keeper.

Ben

bigbowlcut Thank you. The fixed-gear experiment survived the first summer and it's in the basement for maintenance. I used an old chain that was still in spec. and managed to squeeze the last miles out of it. So this spring, a new chain is in order.

JohnDThompson Oh, I'm keeping both brakes. I'm too old to try to impress. And thanks for verifying the received wisdom of the internet. It is possible to use a lock ring with an appropriately "vintage" fixed gear cog on a road bike; just not with the limited parts in my bin. Other than the risk of "unthreading" the cog from the hub, is there any other reason not to use your legs for slowing down/ stopping? Does changing the direction of the torque applied by the chain lead to a faster fatigue of the hub? I've seen freewheel hubs crack on the shoulder between the threads and the spoke flange.

79pmooney Hear, hear on the re-purposing of older road bikes for fixed-gear/ single-speed (or just riding 'em in general). Paradoxically and presently, my fixed gear ride is the only frame I have with an integrated derailleur hanger and my only bike without a rear derailleur. The 70's Fuji S-10s that I have possess forged horizontal dropouts without derailleur hangars (no modifications required). Now, if I could just find one locally in my size (25" frame).

cheers.

Glad it is working out for you. I have a Miyata 312 that is solely fixed gear and I love it. I've said before it will probably be the last bike I part with when I cannot ride anymore. The frame fits me to a "T" and I kept both brakes just in case, although I keep track of how much I use them sometimes just for fun and I would say 1 out of every 3 rides I never tough them except to rest my hands on the hoods. At that rate, they might last forever!