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6-speed, 7-speed, 8-speed, 9-speed, 10-speed, 11-speed?
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by Sheldon "7-11" Brown
revised by John "I'm All Sept, Thank You!" Allen
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Bicycle Gears: 6-speed, 7-speed, 8-speed, 9-, 10-, 11-, ...?

Component manufacturers like to sell you lots of new parts, even if you don't need them. This has led to much confusion as various parts are labeled as if they are incompatible with other parts even though they are actually usable with little or no problem. Also, design often is churned by spec hype, and "keeping up with the Joneses," as in more sprockets, lighter weight, higher-priced components must be better. "Jones" is also a slang term for a drug addiction!

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 minusucule. Remember, you account for 80 percent of the weight even if you are riding a rather heavy bicycle!

There are, on the other hand, some real compatibility issues.

The following parts only are "speed specific":  

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But What About...?

Derailers -Rear

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:

Derailers-Front

Front derailers don't generally care how many gears you have in back, though models designated for higher numbers of speeds may have slightly narrower cages , so they might be a bit more fussy in adjustment/trim when used with wider chains.

Front derailers are generally 2- or 3-chainring specific.

Different seat-tube angles and chainwheel sizes also may require different front derailers. See my Front Derailers Article and Derailer Adjustment Article for more detail. Also see "Road" vs. "Mountain" comments later on this page.

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Wheels/Hubs

There's considerable interchangeability among hubs . If you're upgrading from a system with fewer than 8 rear sprockets to one with more, you may need to concern yourself with the frame spacing. See my Frame Spacing Article for details on this.

Old Style Thread-on Freewheel Systems

The freewheel threading on these older hubs is generally interchangeable except for some very old French units. If you go from a 5-speed freewheel to a 6- or 7-speed freewheel, you will usually need to add some spacers to the right end of the axle between the cone and the locknut. Once you have done this, you'll also need to re-dish the wheel to bring the rim back to the centerline. You may need to re-space the frame if you have added spacers to the axle. See my Frame Spacing Article for details on this.

Shimano 5-speed and 6-speed shifters are made to index with the 5.5 mm spacing between sprockets on older 5- speed and 6-speed freewheels (or even, some new freewheels made as replacements). Without indexing, and because chains with protruding rivets are no longer widely available, it is possible to shift partway between sprockets and for the chain to "skate" along one side of a sprocket and on top of the teeth of the next smaller sprocket. On the other hand, old SunTour "Ultra" and modern 7-speeds have 5 mm spacing and will index with Shimano or SRAM 7-speed shifters, or 8-speed shifters with alternate cable routing. On an older freewheel without Hyperglide (or similar) shaped sprocket teeth, shifting will not be as clean as on a modern freewheel or cassette, but the indexing will work.

Cassette sprocket tooth widths

Up through 9-speeds, all cassettes use very nearly the same wdith of sprocket teeth, and will work with 7/8 or 9-speed chains. Old Uniglide 6-speed cassettes have larger spacing between sprockets, and like older freewheels, have the same shifting issues.

10-speed sprocket teeth are narrower, to cram in one more sprocket. As a result, 10 speed sprockets do not wear as long. The structural strength of 10 speed sprockets also can be a concern; some have bent, a problem unheard of with other cassettes. Manufacturers have come up with clever ways to strengthen a cassette by riveting several sprockets together or machining them out of one piece of metal, but generally at the cost of increased expense, and of having to replace several sprockets at a time when only one is worn.

Campagnolo Cassette Systems

Campagnolo 8-speed cassettes used a slightly different spline pattern from the current pattern used for 9-and 10-speed systems.

8-speed Campagnolo cassettes will not fit on newer "9-speed" and "10-speed" hubs.

9- and 10-speed Campagnolo cassettes will not fit on 8-speed hubs.

It is theoretically possible to upgrade Campagnolo 8-speed hubs with newer cassette bodies, but in practice the parts don't generally seem to be available.

Shimano Freehub Cassette Systems (and copies)

In general, all Shimano Cassette Freehubs will work with all Shimano cassettes, any number of speeds. There are a very few exceptions:

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Chainrings/Cranks

Old Chainrings, New Chains

There 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.

These chainrings have the teeth slightly farther to the right than the older chainrings to work a little better with the narrower chains. There is no difference whatever in the crank spiders.

The manufacturers also are concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) [Not with a 9- or 10-speed cassette, to be sure -- John Allen] If you do shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.

In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.

New Chainrings, Old Chains

Going the other direction, using wider chains with chainrings intended for narrower chains is not generally a major problem if there's only a one- or two- generation difference. The only problem you might run into is that the chain will be more liable to rub on the inside of the bigger chainrings in the small/small crossover gears, gears you shouldn't be using in any case.

"Road" vs. "Mountain" Cassettes, Derailers and Hubs

When discussing cassettes, the terms "Road" and "Mountain" are marketing terms, not technical ones.

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Spacing Cribsheet --dimensions of hubs and sprockets

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See also my article on Derailer Adjustment on this site.

Britain's Cyclists' Touring Club Website has a good article on derailer gearing.

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