In reality, the fancier parts aren't always the most suitable, in the same way that a Ferrari, while it is a great racecar, isn't at all as good for daily transportation as a Toyota -- there are practical issues of cost, reliability, serviceability and durability. With bicycle components, the performance gain with higher-end models is often minuscule. Remember, you account for 80 percent of the weight even if you are riding a rather heavy bicycle! Shimano Freehubs dating from the mid 1980s onward have replaceable bodies, held onto the hub shell by screw threads and, usually, splines. This is explained above in the transplant section of this article. With other freewheels, reassembly can be more difficult. In days of yore, there were special bobby-pin-like clips to hold the pawls compressed against their springs while you re-assembled the freewheel. These are no longer available. Long-cage (SGS) derailers have greater takeup capacity, and work with all types of cassettes. Long-cage derailers are commonly called "mountain" derailers currently, though in the past, this style of derailer was known as a "touring" derailer. (The marketeers retired the use of "touring" as a buzzword in the late '80s when mountain bikes became the hot item.) "Road" vs "Mountain" Front Derailers When discussing cassettes, the terms "Road" and "Mountain" are marketing terms, not technical ones.

working on freewheel bodies is generally not worth the trouble. The freewheel bearing gets the least wear of any on a bicycle, since it only turns when it is not carrying any load. Some people will ignore my advice and try to service freewheels (or have no choice). A 5-speed freewheel or Suntour Ultra-6 will work with the 120 mm rear dropout spacing that was usual in the 1970s. A 7-speed freewheel needs at least 126 mm spacing, but only steel frames are likely to have narrower spacing, and they can usually be cold set to spread the dropouts. You also may need to redish the rear wheel-- see article on frame spacing. To convert to a cassette, you would have to replace the rear wheel.

All recent freewheels and threaded hubs, regardless of where made, use ISO threading. The older British and Italian standards use the same thread pitch but a very slightly different thread diameter, and are generally interchangeable. However, for strong riders and on tandems, it is best not to mix and match -- freewheels sometimes do strip the threads of aluminium hubs. A French freewheel may start to thread onto an ISO/British/Italian hub but will soon bind. An ISO/British/Italian freewheel will skim the top of the threads of a French hub and will slip forward if an attempt is made to use it. Do not force a freewheel -- you will ruin the hub. Many off-brand "Shimano type" Freehub bodies are not available, if they're even removable. Many of the off-brand hubs have the body riveted onto the hub shell.

Are the shims trapped underneath the bearing balls? If so, you will have to remove the bearing balls before you can remove a shim, and replace shims before installing bearing balls. You can remove the bearing balls with a magnet, or turn the freewheel over far enough to spill out the bearing balls, while holding the outer body so it doesn't fall off. Mountain" hubs will likely be slightly better sealed against dirt and mud than "road" hubs, but this is rarely an issue in practice. The wider 135 mm spacing will generally result in a slightly stronger wheel due to reduced dishing of the spokes.Shimano lists Freehub bodies as a separate part, or you could cannibalize a hub. Wheels with damaged rims and good hubs are not hard to find.

Campagnolo made a very slight change in indexing in 2001. Supposedly, you need to use 2001 or later shifters with 2001 or later rear derailers, but the difference is so small that it doesn't matter in practice. speed freewheels with 13-15-17-19-21-24-28 teeth are available from Shimano, SunRace and IRD. This is a nice, even progression, or you may choose another -- see list of available freewheels from Harris Cyclery. Modern freewheels have the same easy-shifting features as cassettes. Shown here is an aluminum body that has suffered this sort of damage. Someone has filed down the burrs to make it re-usable after a fashion. Freewheel bodies have a larger diameter than the spoking flange of many hubs. Warning: loosen a freewheel before cutting the spokes to replace the rim, otherwise you may not be able to loosen the freewheel or to replace the spokes on the right side of the wheel. The barrel (between the flanges) of many hubs will break if you respoke only the left side and then try to unscrew the freewheel.Freewheels screw onto the hub without any tools, then, as you ride the bike, your pedaling effort tightens them down.