How to Make a Fixed Gear with J.B. Weld

I’ve gotten a lot of google hits for “fixed gear” and “JB Weld,” so I thought I’d write up a bit more detailed post on converting a road bicycle to a fixed gear for $20. I have to caution everyone that I do this only because I’m slightly crazy and very thrifty. I can take no responsibility for any catastrophic failure associated with this conversion process: employ it at your own risk.

I'll assume you’re moderately handy and have a basic ratchet set, household tools, hex wrench set, and the desire to spend about 4 hours restoring a bike (on the first go-round) because you want to experiment with fixed gear riding. If you know something about basic bicycle repair/maintenance, this is a snap. If not, your local library or used bookstore will have a book or two on bicycle repair. The books can be intimidating, but don’t worry, you won’t need special tools (one exception) for a conversion, and much of the information won’t apply.

I’m going to make this as non technical as I can. Bike geeks should be able to follow along, the laypeople will also hopefully be able to get a handle on the process.

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Selecting Your Victims

The first thing to do is find your patient: a “tag-sale bike,” preferably a road bike from the 70s, 80s, or 90s. The best bikes for conversions have these qualities:

The frame should be stiff and strong – look for extended lugs (the little cap like things that hold the individual frame tubes in shape), and should have long horizontal drop outs. Drop outs are the little slots that the rear wheel fits into. If they go up and down, that’s no good, you won’t be able to use the frame. You want drop-outs that are at least an inch long and would let the wheel (if loosened) slide “forward and backward” on the bike. (An angle, any angle, is OK, so long as the wheel can move forward and backward for an inch or more.)

Other than that you want to look for aluminum. Lots and lots of aluminum – generally aluminum components are lighter than steel and are found on the more recent higher-end bicycles, for example, aluminum wheels are much lighter and nicer than steel wheels. I’d try to convert a decent bike rather than a complete clunker. But if you have an old 10 speed in the attic or shed, you might want to simply roughly convert that one, just to get the feel of a fixed before deciding to spend the time converting a nicer bike.

You also want to look for a bike that has adjustable crank sets. Look at the big gears the pedals/cranks are attached to. The individual gears (2/3) should be held on to the crank with hex nuts (older steel bikes are sometimes bolted.) If the cranks/gears are one piece or are riveted together, you might want to keep looking – unless you really love the bike, in which case you can buy two bikes and swap the crank/gears one to the other. That requires a special $15 “crank puller” tool though (read the bike repair book). One thing to watch out for is “sharked” gears. If the gears look like little sharkfins, that’s no good for the conversion bike. Sharking happens when, over time, sand/grease grinds away the inner surface of the large gears. It depends on the metal, the riding habits of the former owners. Most likely you’ll be using only the small gear (or middle gear). That’s the one to look at.

(In fact, if you’re handy, it’s probably best to get 2 or 3 very cheap/partially broken “donor” bikes and combine the best components from each. Find a totally rusty, seatless bike with good aluminum wheels, tires, tubes (which don’t rust). Find another with great handlebars, seat, rack, and reflectors. Find a third with the perfect frame and a completely useless set of wheels and busted tires. $5 each, you end up with 1.5 workable bikes.)

That’s about it. Most road bikes made in the 80s and 90s fall into this category. Church tag sales, local tag sales, the roadside/dump, thrift stores: all good candidates to find this type of bike.

General things to watch out for – rust spots on the tubes, dried rubber components (such as brake pads and tires – any cracks you can see are bad), ovalized/off true wheels, stiff cables (brakes that require you to pull hard), rusted chains, rusted derailleurs (you’re not going to use them but watch for them anyway), bent front forks. Basically, the bike should be rideable as is – if it’s not, don’t hesitate to point these flaws out to the seller, and don’t offer more than $10-20 for it unless you know that there’s a specific thing about the bike which you want which is worth more than $10. There’s no point in getting a “fixer upper” for $40, then going to the bicycle store and spending another $60 on cables, tubes, tires, and a seat. A professionally made fixed wheel will only cost you about $150 or so. If you want to spend the cash, go that route.

**

So – you have the bike (or bikes) at home. I’ll approach this from the perspective of “one good bike,” although if you have two, figuring out what to swap won't’ be that hard.

Wear latex painting gloves or mechanic’s gloves. Awkward at first, but your nails will thank you for it later.

First thing to do is to take off the shifting/gearing system (i.e., the shifters, the derailleurs, the cabling). You won't need them. Use the appropriate tools to take them off – wrenches, screwdrivers. Be careful (as always) not to scratch the frame. If you’re building a bike stable, save them (actually, it’s always good to save good components). If they’re junky/rusted/discardable, and you’re cutting shifter cables, etc. remember to take the tension off them before applying the cutters.

Your bike should be looking remarkably cleaner now, even though the chain is droopy.

LEAVE THE BRAKES ON. Yeah, it’s cool to go brakeless, but this isn’t a professionally built bike, and you're not a fixed gear god (if you were, you'd have a professionally built bike). On my 3 fixeds, I’ve left the front brake on all of them, and the rear brake on 2.

**

Next, take the rear wheel of the bicycle. You’ll want to take apart the cluster of gears (cogs/freewheel/freehub) on the rear wheel and replace it with something that won’t spin. (This is where most of the work/time comes in.)

I’ve found that the older 70s/80s freewheels are easiest to bond together, and many are not “twisted” which helps insure the chain will remain on its single ideal gear (more on that later) which, I suppose, is another benefit to using multiple bikes: swiping a freewheel from a steel 70s wheel, then slapping it on a aluminum racing wheel.

I’ll be assuming you have a freewheel hub on the bike. (Consult that bike book for an explanation of different gear clusters.)

The freewheel has 3 main parts. There’s a lockring on the front face of the freewheel (unscrews clockwise) with two little dents in it. The lockring holds the spinning outside gear cluster onto the inner part (on which the cluster of gears spins) which is firmly screwed to the wheel itself. In between the two are lots of free (and tiny) ball bearings and two little ratchety things (should be held in place when you open the freewheel) called “prawls.” The prawls let the wheel spin free in one direction (when you coast – they make the click click click noises) and lock up in the other direction (when you pedal.)

Opening/Removal of the Freewheel from the Rear Wheel

BTW – this is so not the correct way to work on a freewheel, but given the generally adhered state of these older freewheels, and the bonding we’re going to be doing, I have found that these removal steps in this order work the best for me.

Work over an old t-shirt or garbage bag to catch the bearings. To open the freewheel, get yourself some PB Blaster or Liquid Wrench and spray the lockring. Tap the whole thing a bit with a hammer or a screwdriver handle to work the solvent in. Usually you’d use a special tool to open the ring at this point. El Cheaparinos like myself put their knees on the wheel and use a very large nail (or several soft nails that won’t hurt the hub but do tend to bend) and a hammer to tap tap tap the ring open. (Put the point of the nail in one of the indentations, hold at a 45 degree angle.) Sometimes, it helps to tap the ring tighter then reverse direction.

Unscrew the ring. Lift the outer cluster off the inner bit. Let the bearings fall into in the bag/shirt below. Some may stick to the outer bit or the inner bit. Shoo them in with their buddies. Make sure you get them all into the catch area before you begin looking at the mysterious innards of the freewheel.

The two little hinged things sticking out of the side of the inner part are the prawls. Leave the prawls where they are. They’re a headache to put back.

Now you have to get the inner bit off the rear wheel hub. (The wheel has been on its side, under your knees throughout all this.) Since we’re going to mess with the freewheel any way, get a plumbers wrench or some large vise grips, and turn the inner bit counter- clockwise to loosen. (Gripping with vise grips and a few gentle hammer taps should loosen it.) Be careful when you do this though – you don’t want to damage the prawls, and you don’t want to damage the top threads which held the lockring on (it, and the bearings, are going back on later). There should be plenty of gripping area on the bottom of the inner bit (down close to where it attached to the wheel. Some inner bits have slots on top for special wrenches to aid in their removal. But we’re keeping it cheap. Remember that – cheap.

Cleaning/Prepping the Freewheel

This takes the longest, but do it well – you only get one shot at this.

Now that you have your 3 components, you have to clean them. I’d use Simple Green, or the dishwasher. Steel wool and a wire brush works nice. So does a steel brush on a drill or dremmel. You have to get the “inner surfaces” where the parts meet very clean and prevent outer gook from getting on them through casual handling. Generally, I’ll wash all three parts in soapy water with a brush to remove general sand/gook. Then I’ll scrape it with a selection of scraping tools (old screwdrivers, etc.) to remove the more wax like deposits, then I’ll Simple Green/wire brush it. It does not really matter how you do it. The inside is more important than the outside. But BE CAREFUL with the prawls.

To clean/degrease the bearings, simply roll them from the catching cloth into another smaller cloth or doubled paper towel. Fold it over and rub them so they roll inside. Then roll them into a sandwich bag with a teaspoon of Simple Green in it. Roll again. Roll them back into the cloth, roll them dry. Easy. If fumble fingered – do all this over the catching cloth so you won’t lose any.

The next thing to do is to prepare the “inner surfaces” of the freewheel for the JB Weld. JB Weld is a kind of metal epoxy. It bonds best to very clean surfaces, something that does not usually describe a gear cluster. I take no chances (ha!) and try to expose new, rough metal for the JB Weld to bond to. That means using files, sand paper, or some non-residue abrasive to score and deface the inner mating surfaces. No need to be pretty here. I’ve had my best luck with a dremmel and a oxide sharpening stone. You can get everything down to bright shining metal in about 5 minutes. You’ll want to delicately score the prawls as well as the bearing channels. You’ll certainly want to clean/score the area behind the prawls, the area they normally recess into.

But, again, do not mess with the lockring threads (except to degrease them, as you have.) Also, when cleaning the inner hub, don’t overly mess with the ratcheted surface (you’ll see it) that the prawls move against. Score it, don’t destroy it.

Bonding It Together – Let’s Stay Fixed Forever

So- now we’re ready to put the freewheel back together lock the whole thing forever. This is the easy part. All the hard work is in preparation.

WEAR GLOVES! (painting gloves are fine) Mix the JB Weld according to instructions. One standard packet (two tubes) will be enough for 2/3 wheels. I generally mix it on newspaper and apply it with an old nail.

We’ll want to use the bearings because we don’t want to end up with a lopsided ring.

I smear a generous amount of weld on the inner (prawled) part of the freewheel, right in the channel where the bearings will go. You should keep this part vertical – i.e., stand it up on the paper. The JB Weld has a consistency somewhere between heavy grease and toothpaste. It will hold the bearings. I then touch the goopy nail tip to my pile of dried, clean bearings. Some stick and are easily transferred to the freewheel. When I have a ringd of bearings on the bottom, nesting in their bed of weld, I then work my way up the freewheel. It’s like frosting a cake. Make sure you fill in the space behind the prawls with BJ Weld.

I then put the top part (gear cluster) of the freewheel back on. Holding it together with my hands, I spin it a bit to make sure the Weld is distributed, and the bearings even, then I turn my attention to the top. You should be able to look down and see the prawls (on most models). Make sure you turn the wheel clockwise a bit so that the prawls are “engaged” - we want them to lock that way. Putting in the rest of the bearings to fill the upper area is easy – just sprinkle them in and herd them with the nail. Put in a lot of JB Weld – enough to make sure the prawls are backfilled and the bearings are covered.

Then you put the lockring back on. I make sure the inner threads of the ring and their matching threads on the freewheel are very clean. I use more JB Weld (it should be oozing out the top when done) to “lubricate” (and subsequently lock) the threads together.

Use the hammer/nail trick to get the ring on as tight as it can possibly go. If the ring does not tighten up all the way (if the outer gear cluster “wobbles” the slightest bit, you have a bearing playing hooky (normally on the top area.) Unscrew the ring, adjust the bearings, tighten again.

Wipe off any excess JB Weld, perhaps using some to “lock” the top gear in place (depending on freewheel models – if you see any kind of thread visible, JB it.) You don’t want anything to ever possibly move again.

Let it solidify over night.

The one place you don’t want JB Weld on (during this stage) is the inner threads of the freewheel – the ones that screw onto the wheel itself. Obviously, you want those clean and ungooked so you actually put your new locked up freewheel back on the rear wheel itself.

***

Basically, all we’ve done in the above step it to “replace” any oil/grease areas in a freewheel with scored metal and JB Weld.

You could accomplish the same kind of immobility by taking the freewheel to a welder and having him braze or weld the freewheel immobile. Muffler shops are particularly good for doing this kind of work for next to nothing. If you do that, soak the whole thing (spinning now and then) in Simple Green to get all the grease out. Fires are bad. A bit of wire alternated with Simple Green soaked twine is the ideal way to "floss" between the gears of these old and crusty freewheels.

***

When the freewheel is dry, you use the JB Weld (new small batch) to lube up the rear wheel threads and the inner matching threads, then screw the freewheel onto the hub. Use a hammer/dead-screwdriver to tighten the freewheel as much as you can. The JB Weld should be retained inside the threads as well as gooping up “inside” the freewheel body and outside it, bonding it more firmly to the hub.

***

So that’s basically it. All the hard work is done. You should have an immobile gear permanently fixed to the hub. If you break spokes, you obviously can’t take the wheel apart and fix them, but hey, we’re staying under (or damn close to $20, depending on the tools – so what do you want?)

I’ve done three wheels this way and they’ve all held up thus far. I think the main benefit of the design is that you’re using a tried and true geometry – when pedaling forward this design does not seem any more likely to fail than a regular freewheel would, as the prawls are still taking most of the force (they’re just locked in place.) When pedaling “backwards” or resisting the forward motion, I’m careful to also use the brakes on steep descents, or whenever the resisting force moves above a certain level – I don’t try for long skids or anything crazy. I’m very comfortable with the risks as I figure that any failure could be compensated for by the brakes – after all, two brakes are enough to slow down a regular road bike with no backpedaling force (plus I’m not going to end up going all that fast on a fixed anyway).

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Wheel on the Bike, Bike on the Road

The last bit is putting the wheel on the bike and adjusting the chain. (You can use quick-detachable wheel threads if you want, but I use a solid bolt for extra strength. A bike book can show you how to rebuild a wheel – very easy, 10 minutes.)

It’s important to get your chainline absolutely straight. You don’t want the chain to be bent at all, rubbing the other gears – if the chain jumps gears, you’re screwed. If it jumps up, the whole drive train will “lock” and if it jumps down, the whole train will loosen (probably before wrapping around something and locking). Another reason to use “non-twisted,” widely spaced, 70s/80s freewheels.

That means you can use the big front gear and a small rear gear, or the small front gear and a larger rear gear.

I go for the more moderate gearing – small front gear and large rear gear. It’s like locking the bike in 3rd/4th gear all the time. Since I swap freewheels between different bikes, I can play with the ratios somewhat.

To remove the extra gear, from the front cranks, use the hex wrench (or ratchet set, depending). If both gears are held on by a single set of hexes (usually 5), you’ll have to go to a bike shop and get spacers to compensate for the missing gear. Basically, they’re just thick washers.

I normally remove the big gear, then switch the smaller gear over to the outmost side of the cranks. That lets me get a bit higher gear out of the bike. Plus it looks cooler. If you want an easier gear (especially on a trial bike) put the smaller gear back on the other side of the cranks, closer to the bike, and your “perfect gear” (see below) will move up a notch to an easier pedaled gear.

I then line up the chain with the ideal gear in the back. Look at it from different angles, make sure the chain does not bend. There will be one gear that it bends the least for. That’s you’re perfect gear. Sorry you can’t choose the gear - $20, remember, $20.

Now you need your one special tool: “The Chain Breaker” (bicycle tools have such cool names.) A chain breaker is basically a tiny vise that pushes one of the chain pins out from a bicycle chain. You then take out links (or put in links) and turn it around to push the chain pin back in. It’s very easy to use - the Bike Repair Book will show you, if you’ve never used one before. You can get one for $10. You can also get a mobile multi-purpose bike tool containing a chain breaker (an Alien, or Alien-clone) for $30 which is a very good investment for even the casual bicyclist.

Use the chain breaker to shorten the chain so that (eyeball, overlap the chain so it looks shorter) it will be tight on that ideal gear with the rear tire axle resting about a ½ inch from the furthest point of those long dropouts you noticed when you got the bike. It may take you 2 tried with the breaker to get the ideal length.

The extra space allows you to pull back on the wheel and tighten the chain (might take a few times till you discover your own perfect system for doing so). Since the chain takes force both ways on a fixed, you want this as tight as possible without binding. Say, maybe a ¼ to a ½ inch of flex on the chain? You’ll see what I mean more effectively than I could explain it. Just use that space to make the chain as tight as you reasonably can.

BE CAREFEUL when working on the chain. If you have a a fixed gear off the ground and start it spinning (say to check the brakes), the inertia of the rear wheel will cause the chain (and front cranks) to keep moving. This force, so effective on the road, can and will take off your finger if it wanders too close.

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And that’s it. You’re ready to hit the road (hopefully not literally). Please read up on fixed gear riding. Sheldon Brown has a great website on it (search for "Sheldon Brown" and "fixed gear".

Again, the above conversion is a moderately risky thing. You can fuck it up, and if you do, the bike can crash, which can either hurt or kill you. So don’t do any of the above unless you’re comfortable with the risks involved and want to assume the responsibility for them yourself. It’s like doing a brake job on your car. Some people can, some can’t.

***

Final $ tallies – say $10-20 for the perfect one-shot conversion bike, or up to $40 for multiple, flawed bikes. $10 for the chain breaker. $15 for the crank puller (any semi-serious biker will want both for all other kinds of use, including properly maintaining geared bikes.) $1 for the spacers. $5 for the JB Weld.

With tools and the perfect bike – $10-$30
Without tools – $35-$50
Without tools and getting a pile of decent and junky bikes to play with: $55-70 (but you may get 2 fixeds out of it. You can certainly get two (for you and a friend) for under $100)

It’s really cost- effective to get several bikes, if you have time to steal parts from them. I’ve bought $10 bikes for the sake of a rack that would normally cost $40, then found I could use the cables, one tire, one tube, etc., as well.

Or for a totally “ride it for a few weeks just to see what it's like” ugly/experimental bike, you could use somebody’s old, totally steel, rust spotted, 10-speed bike that you or some extended family member has kicking around in the shed or garage. Just put the chain on one of the front gears, take off the derailleurs, fix the hub per any of the above methods, shorten/tighten the chain, hit the whole with soap and water, oil the chain and brake cables and go. In this case you’re looking at only $10 for the chain breaker and $5 for the weld.

Timewise, you’re looking at shopping for the bikes, ½ hour to strip the shifting system, ½ hour to remove the freewheel(s), an hour to clean the freewheel, a ½ hour to bond, a ½ hour to adjust the rear wheel and set your saddle/handlebar positions. So, X hours shopping, 3 or 4 or 5 hours converting.

If you have a weekend to shop, the conversion process is something you can do in easy steps throughout the week.

Scoplaw

PS – Scoplaw’s 3 secret weapons for restoring old bicycles are:

Simple Green
Clear Spray Paint
Bicycle grease and oil

It’s amazing what happens when you clean/degrease a bike, grease and oil all the moving parts, then hit the whole with clear spray paint, which restores luster, at least slows rust you’ve scoured off, and can be used “over” stickers.

Comments

[charles]

Great article, but isn't there some way you can show some pictures? With technical ideas such as these, it is a shame to try to understand this without pictures.

[Scoplaw]

Hey Charles -

This was pre-digital camera I'm afraid. Also, since it's probably not the safest project in the world, I don't want to encourage people to actually do this themselves.

[mike]

good stuff, thanks. pictures would be nice though.

[Scoplaw]

See above.

[Danny]

I have read numerous articles on how to convert a road bike to a fixed gear, and many folks have covered very simple and quite obvious subjects such as "horizontal dropouts" and "Chainline".Any idiot can figure these issues out by trial and error in my opinon.Now for a real topic.How to detrmine pitch in the frame threading in order to install a cotterless bottom bracket.If you can help please e-mail me.

[Scoplaw]

Well, to email you, I'd need your email - my psychic powers aren't what they once were.

Or you could just go here - http://www.sheldonbrown.com/bbsize.html

Sheldon's one of the best free and public resources out there.

[paula]

I've been wanting to use JB Weld on a project I'm doing (art related) and was fearful of it because of the one time I tried to use a regular epoxy it was a disaster.

This time I'm using jb weld and already hated using acetone to clean the steel so today I googled simple green and jb weld and found this post. You seem to be well versed in using this stuff and I wonder if you can tell me do you use it on both sides of whatever it is you are epoxying?...and you use a good amount?

I know with the runny liquid epoxies you are supposed to use a dab, I used a good amount of jb weld and couldn't help but test it after 4 hours by gently moving the objects I welded together. they weren't even close to be welded. so i waited the 15 hours and see the two pieces are together but I get the feeling I could easily separate them. (right now they are still taped together they are long thing steel pieces)

I'm excited to think simple green is good enough to use, do you dilute it with water?

If this weld doesn't work I think it's because I didn't roughen the steel up enough and/or used too much. Appreciate any thoughts.

paula

[Anon of Florida]

I would like to mention a way of customizing the gears used:

http://forums.mtbr.com/showthread.php?t=373319

[Scoplaw]

Well, go ahead and mention it then.

[Ron]

I did something like this with a cassette hub - brazed the freehub body where it ratcheted to seize it permanently. But with a cassette hub you can use spacers and a single cog. Problem you have - as you note - is chain jumping, because with a screw-on, one-piece freewheel, you still have the other cogs to catch the chain. It's a real bad problem. I would suggest chucking the freewheel in a lathe and slowly grinding off the teeth on the cogs adjacent to the cog you want to use. Or something like that, such as dremeling them, or even breaking them off. Maybe even grind/break down TWO cogs on either side of the one you want to use, to make it difficult for the chain to jump.

[scoplaw]

Yep. Eventually came to that conclusion myself. If you line it up right and use a skinny chain, it's not so bad. But getting rid of the adjacent cogs is probably the safest thing to do.

Now that fixed gear cogs and hubs are so cheap, this mod is a bit outdated, but still fun to fool around with.

[Aaron]

This is truly an amazing blog, it was a great help in fixing up my gears. If you've any other guides, I'd be greatly interested.

Thanks!