Bicycle Freewheel - Page 1 of 6
Figure 1 - Some tools you will need
Practically every bike, trike or quad you will make will require some kind of freewheel in the transmission system. A freewheel is basically a sprocket attached to a ratchet, allowing the transmission to drive the wheel in only one direction - much like a socket wrench. Without a freewheel on a bicycle, you would have to pedal at all times, never able to coast. This type of drive system is called a "fixed drive" or "fixie", and is often used for strength 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.
Removal or repair of a freewheel requires only a few basic tools as shown in Figure 1. You will need two wrenches to remove the axle nuts, and the home made Shimano style freehub removal tool, which we will discuss 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 many bike 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 had any problems with the home made remover.
Figure 2 - Cartridge freewheel (left) and Shimano type (right)
Before going any further, make note that there are two distinct types of multi-speed freewheels and hubs; the cartridge 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 a complete 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 integral unit.
A Shimano freewheel is easily identifiable as it will have a recessed bearing race with two or more small holes in 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 more expensive wheels and aluminum hubs, whereas the Shimano style is usually used on lower quality department store bicycles, often having 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 inner spline 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 the direction 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 not damaged. If the threads are in rough shape, you may need to grip the freewheel side of the axle while removing the nuts.
Figure 4 - The hub bearings
Depending on the manufacturer of your hub, the bearings may fall out individually or be held together by a small retainer ring. As shown in Figure 4, the bearings in the hub were individual and because the grease was minimal, 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.
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You can build it yourself from our easy to follow DIY plans!