Old Chainrings, New ChainsThere is a lot of confusion about the compatibility of narrow 9- and 10-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9- or 10-speed ones, but then they're all too eager to sell you stuff, whether you need it or not. 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. Except with 11 speeds, cog spacing is different enough from Shimano's that Shimano derailers and shifters may not work well with Campagnolo cassettes, and vice versa. It is possible to fudge compatibility in some cases where cog-to-cog spacing is similar. In general, all Shimano Cassette Freehubs will work with all Shimano cassettes, any number of speeds. There are a very few exceptions:

SRAM "ESP" or "Exact Actuation" derailers and shifters (generally designated by a decimal model number: 7.0, 8.0, 9.0 etc) can only be used if the shifter and rear derailer are both ESP. A Jtek ShiftMate pulley adaptor can make a SRAM shifter work with a Shimano derailer, or vice versa. All SRAM 10-speed derailers and shifters are of yet a third type. Unless you are willing to put up with friction shifting, you need to install new shifters. Indexing handlebar-end shifters, top-mount shifters or downtube shift levers let you know how to shift by feel. Brake-lever shifters return to the same position after every shift, so you don't know what gear you are using. They also tend to be expensive. Brazed-on bosses for downtube shifters on some older frames will not fit today's index shift levers or cable stops, so you will need to use a clamp-on adapter. Campagnolo 8-speed cassettes used a slightly different spline pattern from the current pattern used for 9-and 10-speed systems. Your Sugino may be 110mm bcd, in which case it will accept an inner ring down to 34 tooth. If 130 bcd, then a 38 is available, or 39 if 135 bcd.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. A freewheel that has been ridden for a long time, especially by a strong rider with low gears, may be quite difficult to remove because the threads are so tight. Derailer cage widths differ, but this is most often a concern when replacing pulleys: the bolts may not reach. 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. Long-cage 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.)

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! Within a given brand/style of rear derailer, all "speed numbers" are generally interchangeable. This applies to all indexable models, basically everything manufactured since the late 1980s. There are a few exceptions:

Cassette sprocket-tooth widths

Sheldon's advice makes very good sense for Shimano Freehub bodies, because they are common, and easily replaced. But these days, more surviving freewheels are cherished antiques. Rebuilding them doesn't deserve to be a lost art. Here is how to rebuild one. I (John Allen) especially like old SunTour freewheels, and I use them as examples in this article. Freewheels of other brands are basically the same, but differ in detail. Rebuild the freewheel, so you can clean all the internal parts thoroughly. See our article on freewheel rebuilding. Replacement bodies are not available for these early hubs, which can sometimes be identified by the narrow barrel, without the characteristic bulge on the right end. (The bulge is to accommodate the threading for the hollow bolt used on newer Shimano Freehubs) See the photos below, kindly provided by David Landsberg. FH-7850 and FH-7900 Dura-Ace bodies, which have returned to a splined attachment between Freehub body and hub shell, but it is larger than the usual one. It is similar but not interchangeable between these two models. Shimano information on the 7850; 7900.

To remove some Freehub bodies (or a freewheel), the hub must be spoked into a wheel. However, the most usual kind of Shimano Freehub body can be removed from a bare hub if a cassette is installed. The fixing bolt which holds the FreeHub body can't be fully tightened when replacing the body, though, unless the hub is spoked into a wheel.Do you need to replace an older, threaded rear hub to update to a modern, index-shifting drivetrain? Narrow chains bring other problems, though. They are usually more expensive and -- with 10 or more speeds -- don't last as long -- even when used in the intended system.