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Indexed rear-shifting systems from Shimano, SRAM, Campagnolo and SunTour have different amounts of
On the other hand, 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:
Other options are to use cable-travel adaptor pulley -- or re-route the cable at the rear derailer to increase or decrease its motion.
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.
Harris Cyclery can supply the Problem Solvers Travel Agent. The Travel Agent is intended mostly to make direct-pull brakes work with ordinary brake levers, but it also works with derailers.
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.
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 10-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 or 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.
This article links to tables showing combinations of shifter, rear derailer, sprocket spacing and adapter (if used) which achieve correct indexing. Here's how to use the tables.
The settings in boldface with no adapters are as intended by the manufacturers. How dlose to these does indexing have to be? I have had good indexing using a Shimano 8-speed shifter (4.80 mm sprocket spacing) with a 7-speed cassette (5.00 mm). The tolerances in the tables are tighter. In a few cases, I have allowed loose tolerances where no other available combination would even be close. You could try combinations with loose tolerances if you like. The tables list all possible combinations.
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.
You may be able to adjust indexing slightly on any derailer by making slight changes in the cable attachment location.
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. JTek Engineering and Quality Bicycle Products have been very helpful in providing technical data on their products.
I have built on all this work, developing a step-by-step approach, and covering many additional freewheels, cassettes, shifters and derailers. I think that the information is mostly correct, though its development has been mostly a math exercise based on manufacturers' specs, collected data and a few measurements. Results are not guaranteed, but I will take responsibility for correction of any errors. Please write in to let me know of what succeeds and what doesn't.
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