Indexed rear-shifting systems from Shimano, SRAM, Campagnolo and SunTour have different amounts of

• cable travel per click,
• derailer movement for a given amount of cable travel, and
• sprocket-to-sprocket spacing.

(Almost any cassette which fits a Shimano cassette body, though, will have the Shimano spacing).

It's often useful to mix and match components to keep an old wheel in service, if you like a particular kind of shifter, etc. etc.

Some nonstandard combinations work with components right out of the box. To achieve a working combination, you also could change the derailer, shifter -- or sprocket spacing:

• There are two common thread-on freewheel sprocket spacings. Most 7-speed freewheels are compatible with Shimano 7-speed spacing, and most 6-speed freewheels, with Shimano 6-speed spacing. For details, see the sprocket spacing cribsheet on this site.
• Almost all Shimano cassettes with 8 or more sprockets fit the same hubs: inter-sprocket spacing decreases with the number of sprockets. The shorter sprocket space of a hub made for a 7-speed cassette will accept 8 sprockets of a 9-speed cassette, or 9 sprockets of a 10-speed cassette. Instructions are here. You usually can also replace a hub's shorter 6- or 7-speed cassette body with an 8-9-10 speed body. Instructions are here.
• There is some compatibility among Campagnolo cassettes with different numbers of sprockets.
• IRD sells cassettes to fit Shimano hubs, but with Campagnolo inter-sprocket spacing.

Other options are to use cable-travel adapter pulley -- or re-route the cable at the rear derailer to increase or decrease its motion.

These adaptations are described next, followed by links to tables listing combinations that work.

Jtek Shiftmate adapter installed on Shimano derailer

Cable-travel adapters use a double, side-by-side pulley with grooves at two different diameters. The cable enters at one diameter, and exits at the other. An adapter can be installed either to increase or to decrease cable travel.

Harris Cyclery does not sell JTek Engineering's Shiftmate cable-travel adapters, due to the several different kinds and low demand -- order these direct.

Correct ratio does not guarantee success. There also are placement issues; and an adapter may run out of cable travel. JTek does not recommend use of Shiftmate adapters with some derailers, including Shimano XTR derailers. Ask, before you buy.

Most of the JTek Shiftmate adapters are available either angled, for use at the rear derailer, or straight, for use in mid-cable or at a cable stop.

Harris Cyclery can supply the Problem Solvers Travel Agent, which is similar. The Travel Agent is intended mostly to make direct-pull brakes work with ordinary brake levers. It is not intended to solve derailer cable-travel issues. It is very useful to reduce the amount of friction where cables in housing go around corners. For this, use only the Travel Agent's larger pulley diameter. The cable housing fits into one end or the Travel Agent. The other end must fit into a cable stop.

Most pulleys used on bicycle cables, including those in shifters, are small enough that the cable will eventually develop metal fatigue (like a paper clip being bent back and forth), fray, and part. This problem is generally tolerated in shifter cables -- but carry a spare cable. A pulley-type adapter adds one more place where this can happen.

Two alternate cable routings for Shimano derailers adapt them for use with nonstandard shifters or cassettes.

Shimano has publicized an alternate cable routing which places the cable slightly closer to the pivot, making the derailer move slightly farther for each click. This adaptation makes newer Shimano derailers work with older Dura-Ace shifters, but it is also useful (though nonstandard and not as accurate) when you want to use a 9-speed cassette with 10 speed shifters, or 8-speed cassette with 9-speed shifters, or a 7-speed cluster with 8-speed shifters.

The other alternate cable routing, suggested by Brian Jenks, proprietor of Hubbub Cycles, decreases the derailer travel for each click. This makes some Shimano derailers and shifters compatible with Campagnolo cassettes. It is also useful when you want to use a 10-speed cassette with 9-speed shifters, or 9-speed cassette with 8-speed shifters, or an 8-speed cluster with 7-speed shifters. You will lose the use of one sprocket, unless you are using a shortened cassette such as a Shimano Linksys cassette, an 8 of 9 on 7, or 9 of 10 on 7. Note the two tabbed washers in the drawing below -- one to change the cable routing, and the other (with its tab facing to the right in the picture) to secure the cable. You may be able to get by without the second washer.

Unlike the JTek Shiftmate adapters and the Dura-Ace modification, the other alternate cable routings are not standardized. To get the indexing to match the sprocket spacing, you will have to check and readjust the place where the cable attaches.

This article links to tables showing combinations of shifter, rear derailer and sprocket spacing and adapter (if used) which achieve correct indexing. Here's how to use the tables.

1. Measure the sprocket spacing of the cassette or freewheel you intend to use, or look it up in the sprocket-spacing cribsheet.
2. Preferably, use a derailer and shifter which are designed to be compatible with the cassette or freewheel.
3. If you need to mix and match, go to the page at Iridocyclectomy or Chris Juden's page at CyclingUK to look up which combinations might work. Also consider using a JTek Shiftmate adapter.
4. Sprocket spacing is narrower as the number on a cassette increases, and with 9-speed on up, the sprockets and chain also become narrower. A rear derailer's chain cage must be wide enough for the chain which is to be used. This can be a problem when using a derailer for a cassette or freewheel with fewer sprockets than it was designed for.

How close to these does indexing have to be? Try and see. You could try combinations with loose tolerances if you like, but shifting is likely to worsen more quickly with wear.

Combinations with longer cable pull at the shifter are likely to work best. Combinations with no adapter or a decrease-ratio adapter are likely to work better than ones with an increase-ratio adapter. Combinations using Shimano derailers with the "Hubbub" cable routing are likely to be less accurate than others.

Sheldon Brown, founder of this Web site, compiled the table of sprocket spacings on which much of the work here is based. He also described some nonstandard combinations. Chris Juden, of the Cyclist Touring Club (U.K.), explored nonstandard combinations systematically, and has published information about them, as has Art's Cyclery. JTek Engineering and Quality Bicycle Products (available through bike shops) have been very helpful in providing technical data on their products.