bicycle freewheel

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    B I C Y C LE FRE E W H E E L

    Practically every bike, trike or quad you will make will require some kind of freewheel in the transmissionsystem. A freewheel is basically a sprocket attached to a ratchet, allowing the transmission to drive the wheelin only one direction, much like a socket wrench. Without a freewheel on a bicycle, you would need to pedal atall times, never able to coast. This type of drive system is called a "fixed drive" or "fixie", and is often used forstrength training on an upright bicycle, where the rider works against the forward momentum in an attempt to

    slow or stop the vehicle. A similar fixed drive system would be found on a unicycle.

    Figure 1 - Some tools you will need

    Removal or repair of a freewheel requires only a few basic tools as shown in Figure 1. You will need twowrenches to remove the axle nuts, and the home made Shimano style freehub removal tool, which we willdiscuss soon. A center punch will also be needed if you plan to take the freehub apart to re-grease the bearings

    or repair the ratchet system. Cone wrenches and professional freehub removal tools are also available at manybike shops, but I can tell you from experience that the simple home brew freehub remover is much better than

    the professional tool and will last forever. I have broken two store bought freehub tools, but have never hadany problems with the home made remover.

    Figure 2 - Cartridge freewheel (left) and Shimano type (right)

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    Before going any further, note that there are two distinct types of multi-speed freewheels and hubs: thecartridge type as shown in the left of Figure 2 and the classic Shimano type shown on the right of Figure 2.

    Only the Shimano type of freehub can be used for trike or quad axle mounting as it can be removed as acomplete working unit by unthreading it from the hub as will be shown soon. The cartridge style freewheel

    cannot be removed from the hub (only the chain rings), as the ratchet system is built into the hub as an integralunit.

    A Shimano freewheel is easily identifiable as it will have a recessed bearing race with two or more small holesin the ring that allow it to be removed. The cartridge steel freewheel will not have a visible bearing race, but

    instead a spline with several inner teeth. Cartridge style freewheels are usually found on expensive wheels andaluminum hubs, whereas the Shimano style is usually used on lower quality department store bicycles, oftenhaving a steel hub.

    Figure 3 - Removing the wheel axle

    Before you can remove a freewheel from a hub, you must remove the axle, as it will be in the way of the innerspline that our removal tool will need to lock with. To remove the axle, place a wrench on the cone nut and

    another on the lock nut on the non-freehub side of the axle as shown in Figure 3. Turn the wrenches in thedirection shown in Figure 3, so that the top wrench removes the lock nut in the counter clockwise direction.With the lock nut removed, the larger cone nut will easily unthread from the axle if the threads are notdamaged. If the threads are in rough shape, you may need to grip the freewheel side of the axle while removingthe nuts.

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    Figure 4 - The hub bearings

    Depending on the manufacturer of your hub, the bearings may fall out individually or be held together by asmall retainer ring. As shown in Figure 4, the bearings in the hub were individual and because the grease wasminimal, they simply fell out. Keep this in mind if you plan to reassemble the hub, and carefully remove the

    last nut so you can catch the bearings because they may fall right out. A bucket over the hub does a nice job.

    Figure 5 - The hub axle hardware

    The complete axle assembly is shown in Figure 5 after removal of the left side nuts and all of the bearings. Thehardware on both sides of an axle are the same, but the spacer on the freewheel side is much longer in order toallow the lock nut to clear the inside of the freewheel. This is necessary because the lock nut must press against

    the inside of the rear dropouts when mounting a rear wheel to a frame.

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    Figure 6 - The inside spline on a Shimano freewheel

    Figure 6 shown the internal spline on the Shimano style freehub, which is where your removal tool must lock

    in order to unthread the freewheel from the threaded hub body. You can purchase a tool from many bike shopsthat will mate with this spline, allowing you to adapt a wrench, but be warned - these tools are easy to strip,and often fail to remove an old freewheel that has been torqued on from years of use. The home built toolshown next is much better.

    Figure 7 - Find a bolt that is slightly too large

    To create your own hub busting tool, start by finding a bolt that is slightly too large to fit into the freewheel

    spline. The tips of the bolt head should sit over the spline as shown in Figure 7. The bolt that I found thatworked well was about 7/8" across from one flat side to the other as shown in Figure 7.

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    Figure 8 - Making the bolt fit into the spline

    The freehub removal tool is ultra simple - a bolt ground to fit into the spline and then welded to a lever with alength of at least 12 inches. As you can see in Figure 8, a little work with the angle grinder on the edges of the

    bolt will make it fit snugly into the freewheel spline. It should be easy to press into the spline, but not so tightthat you need to hammer it in. Just work at the bolt with your grinder a bit at a time until it fits as shown inFigure 8.

    The bolt is then welded to some type of steel rod or arm so that it can be used like a long wrench to muscle off

    the threaded freewheel from the hub. I used a retro crank arm from my scrap pile, as it was easy to weld thebolt into the axle hole. The arm was the perfect length to allow good mechanical advantage.

    Figure 9 - Using the freewheel removal tool

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    To use the freewheel removal tool, press the bolt head into the spline and then crank on the arm in the counterclockwise rotation as shown in Figure 9. This process requires that the wheel still be laced to the hub or you

    will not have any way to hold it in place as you crank on the removal tool. Also, I can almost guarantee youthat banging the tool with a hammer will be the only way to free a well used freewheel from the hub threads,

    so cranking it by hand may be futile. Once you get the freewheel to start turning, it will easily unscrew fromthe hub.

    Figure 10 - The threaded hub

    The threaded hub body is shown in Figure 10 after unscrewing the freewheel using the home built removaltool. These threads are 1.375 inch by 24 TPI for a distance of about 3/8 inch along the hub body. These threads

    are the same for multi speed hubs as well as single speed BMX style hubs. The hub body shown in Figure 10 isthe cheap steel type, which is great for using in your own projects as it can be cut and welded with ease.

    Figure 11- A typical Shimano freewheel

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    The typical Shimano freehub is shown in Figure 11 after removal from the threaded hub body. This unit hassix chain rings, but they are often available with as few as five rings and as many as nine rings. The ratchet

    system is built into the body of the freehub, so this unit can easily be adapted to any hub or axle with therequired threads.

    Figure 12 - The threaded body of the ratchet system

    The threaded part on the underside of the freehub (shown in Figure 12) is actually the built in ratchet system,allowing the chain ring to turn freely in the counter clockwise rotation and lock to the hub in the clockwise

    rotation. Because the inside diameter of the splined area is greater than 3/4 inch, it is easy to adapt thesefreewheels to a variety of axles for trike or quad usage. A cartridge freehub cannot be adapted to an axle.

    Figure 13 - Removing a BMX freewheel

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    Although a BMX (single speed) freewheel has the same type of threaded mounting system, it cannot beremoved by the home built removal tool because there is no internal spline. A BMX freewheel will often only

    have two small holes on the face, so you will need a center punch to tap off the freewheel.

    Place a punch in one of the holes and tap it so the freewheel can be unscrewed in the counter clockwiserotation. It will take awhile to remove the freewheel using this method, and many small taps should be used

    rather than powerful hits or you may damage the hard surface or break your punch. Switch between the holesoften while removing the freehub.

    Figure 14 - Two types of threaded freewheels

    Figure 14 shows both the multi-speed freewheel as well as the single speed BMX freewheel after removal fromthe hub. Besides having only a single chain ring, the BMX freewheel also requires a larger width chain thanthe multi-speed freehub. Other than that, the ratcheting operation is identical.

    Figure 15 - Removal of the top bearing race

    Chances are you will never have any need to take a freewheel apart, but I am going to rip one open so you cansee what makes it tick. Because all of the parts inside are made from extremely hard steel, there is not much

    room for modification or welding, so hacking a freehub into something new is probably not a good idea.

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    Freewheels contain many tiny free floating bearings on the top and bottom, so you will need a bucket or clothunder the freewheel when you are taking one apart as the bearings are only slightly greased (if at all), and will

    fall all over the place. As shown in Figure 15, the top bearing race is tapped off in the clockwise rotation byusing a center punch in one of the small holes on the face. Tap lightly, switching holes as you work so you do

    not damage the hard steel ring.

    Figure 16 - Removing the ratchet body

    The ratchet body will fall out of the freewheel once the top bearing race has been removed. Along with theratchet will come many small bearings and a few washers, so keep note of where they were installed.

    Figure 17 - All of the internal ratchet parts

    Once you remove all of the internal ratchet parts and clean the loose bearings, you will have what is shown inFigure 17. The two small bits that were held to the body with the small retaining ring are called pawls, and

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    their job is to lock to the ratchet inside the freewheel body. It is the pawls that make the clicking sound againstthe ratchet teeth when you spin your freewheel in reverse.

    Figure 18 - The ratchet teeth and pawls

    The ratchet teeth can be seen on the left of Figure 18, and the pawls are shown connected to the ratchet body(right side) by the small retaining ring that makes them spread outwards.

    Figure 19 - Putting the freewheel back together

    To reassemble the freewheel, you will have to place all of the bearings back on the top and bottom just as theywere before they fell out all over your garage floor. To make this job easy, find some grease and collect all of

    the bearings so you can place them back into position. The grease will be used to stick the bearings in placewhile you put the freewheel back together.

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    Figure 20 - Bottom bearings installed

    By using your finger to run a small bead of grease around the bearing race, it's easier to then drop the bearings

    in place as shown in Figure 20, sticking them to the grease. Once you have an entire ring of bearings stuck inplace on the lower race, drop the ratchet body (with pawls installed) back where it came from as shown inFigure 20.

    Figure 21 - Top bearings installed

    Installation of the top ring of bearings is the same - add the grease, then place them in one at a time until they

    stick into position. If there seem to be two or three bearings short on the top, don't worry; this is actually howthe manufacturer built the freewheel, often with a gap of two or more missing bearings on the top. There is

    almost zero force on these bearings since they are only in use when the wheel is coasting, so a few missingbearings is unimportant. Also, remember that that top race has reversed threads, so it will screw back on in thecounter clockwise rotation.

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    Figure 22 - A threaded freewheel on a trike

    Because these Shimano type freewheels are a complete working unit, they can easily be adapted to a trike axleusing a threaded part like the one shown in Figure 22. Almost all of the trike or quads on this site use this typeof mounting system because it is inexpensive and extremely robust. On this particular trike, a disc brake

    adapter has also been added to the freewheel adapter.

    Figure 23 - The Kyoto Cruiser Tandem Trike

    OurKyoto Cruiser Sociable Tandem Trikeshown in Figure 23 uses two freewheels adapted to each rear axleso that both riders have their own independent transmission and can be in whatever gear they like. This

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    independent transmission system was easy and inexpensive to create due to the threaded freehub adapter thatallows the Shimano style freewheels to be adapted to the axles.

    The next time you see a bent, discarded rear wheel at the dump, pick it up and salvage the freewheel, as these

    are useful building blocks for any multi-speed vehicle, especially a delta style trike.

    Free bike building tutorials:

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