Miele Man

A friend of mine wants to build an ultra-cheap fixed gear bicycle. His plans?

Use a rear wheel designed for a thread on freewheel and use a Uniglide 14 teeth cassette cog and a bottom bracket lockring screwed directly to the rear hub.

I told him that there's a good chance that the cog and lockring could unscrew and that fixed gear hubs have opposing threads to prevent that.

He also thinks that he might decrease the spacing in the frame because he wants to remove spacers in the wheels and center the rim over the hub.

What are the opinions here if he does all this? Do you agree with me that he'll be creating "an accident looking for a place to happen"?

Cheers

dabac

Ah, a ”suicide fixie”.
IME, for a rider that comes from a solid background of freewheeling bikes, and ISN’T trying to skid, they can be an acceptable risk.
Red Loctite may be a good idea.
An Uni-Glide sprocket is thinner than a regular fixie sprocket and may strip the threads.
Squeezing a frame together is a so-so thing. On a stiff frame, it can flex the axle bad enough to cause noticeable drag and uneven wear on the bearings. It’s probably not a great idea for the frame either, but I have no personal experience of that.

For a rider that wants to skid, a ”leftie” might make more sense. Swap things around to put the drivetrain on the left. Mount pedals TIGHT, with loctite. Ride until something breaks.

veganbikes

It sounds like a bad idea. It is not like fixed gears are ridiculously expensive and even doing a conversion on an old road bike can be done pretty cheaply without resorting to bad ideas.

If you have to Loctite a cog on you are probably in trouble. All my cogs are greased and use a lockring which is also greased and it doesn't come loose on me. Granted I like my undies clean so no skids but still if properly torqued down I don't really worry about it. When you are putting something on wrong such as using a uniglide sprocket and a bottom bracket lockring on a hub not designed for either you should worry.

Miele Man

It's amazing what some people will try on a bicycle. I was helping a guy fix a bike and noticed that somehow he'd managed to thread a right pedal onto a left crankarm. When I asked him if he noticed that it was hard to get that pedal on, he said yes and that he had a LOT of trouble getting it on.

Cheers

acoustophile

I knew a few guys who ran suicide hubs with locktite and/or jbweld and it worked perfect. This was back around 2008 when fixed hubs were harder to come by or were expensive. Doesn't make sense nowadays with with the high availability of ss/fixed wheels on the market for cheap.

79pmooney

So the cog is not threaded? Just slipped over the hub threads like a washer, then secured by a bottom bracket lockring serving as a nut?

One real issue is going to be that this "washer" is not going to stay centered. It will get pulled out of center by the chain. Once that happens, the chain will go alternately tight and loose as the hub rotates; I'm predicting a lot. He will not be able to set his chain slack to be not too tight at the tightest and not too loose at the loosest. Also the splines of the cassette cog will tear up the FW threads and probably kill the hub.

Note also that nowhere will you find a lever supplying torque slipped over an axle and secured by just a nut with no mechanical connection at all. I cannot imagine he will be able to get up any kind of hill without it slipping to much to be ridable.

Now if his wheel is headed for the trash and he just wants some close to home fun destroying it, sure, try it. Stay away from cars, keep the brakes and not go any faster than he is willing to throw the chain and lock the rear wheel, damaging spokes and chainstay paint (with deep gouges; better be steel)..

Edit: I don't know the Uniglide cassette cogs. Are they threaded? Standard freewheel threading? As said above. fix gear cogs and bottom bracket lockrings on standard road hubs has been done for many years quite successfully (without skid stops and using regular brakes). Got my start that way without issue. If threaded, was this Uniglide designed to thread onto aluminum or steel. The Uniglide I remember was long before cassettes and all freewheel bodies were steel. Running a narrow intended steel o n steel cog on an aluminum hub sounds to me like a formula for destroyiny the hub and walking home.

Miele Man

Only the last cog on a Uniglide cassette is threaded. You screw that cog onto the freewheel hub and then screw the bottom bracket lockring tight against it. The potential problem is t hat both cogs screw onto a freewheel hub clockwise and thus there's a chance that a skid-brake might unscrew both the lockring and t he cog.

Cheers

AnonymousPython

subbed

jack pot 

RED LOCTITE

Happy Feet

Depends.

Does the friend just want the experience of riding a FG but isn't going to push the limits ie. no brakes, skid stops, hard riding? If so, it will probably do. It's a cheap way to try riding FG casually before investing in it whole hog. When I started the first thing I did was throw a front brake on and avoid hills until I worked up the muscle skill to slow down.

If they know they are going to be more aggressive with the riding or go no brakes then I would do it right. FG is fun but also unforgiving.

I think I get the rationale for going cheap at first. About 10 years ago a friend came by with his FG bike and asked if I wanted to try it. It was bonkers and I wondered why anyone would want to ride something like that. At that time, if someone suggested investing in a dedicated FG bike, I would have passed. Years later I picked up an FG conversion with a good flip flop hub cheap of CL and tried again (after adding a front brake). The time was right I guess because it stuck and now I couldn't see a stable without a decent FG.. but it took time and exposure. The first couple of rides were like "I'm either going to get this, or die".

Miele Man

I appreciate all the responses and advice.

My buddy had recently watched the movie QUICKSILVER and thought he'd like to try a fixed gear bike just for fun. He wouldn't b e riding it much (unless he finds he really likes it) and wanted to try riding the bicycle backwards*. That's where I think the greatest risk of the cog and bottom bracket lockring unscrewing lies.

He has an old frame without any braze-on bits that he thought he'd use.

* I told him to look closely at the bikes in the film t hat were used to ride backwards and especially the bike used in the open concept apartment scene. I told him not only were those fixed gear bicycles but they were dedicated trick riding bicycles.

I often wonder how many takes it took to do those scenes.

Cheers

c_m_shooter

Permanent locktite and a bottom bracket lockring. Will work if tightened down good. I use that method for a fixed cog on both side of my flip flop. Don't narrow the hub, move the spacers to the other side to get your chainline right and then dish the rim to center. I have done that on a couple single speed conversions.