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|Cassettes for sale from Harris Cyclery|
This article is your guide to work on Shimano and Shimano-compatible 8-speed cassettes (sprocket clusters) -- how to find replacements for worn sprockets, make substitutions, and build custom combinations. The tables below list current models from major brands, and some discontinued models.
If you're not sure whether your bike has a cassette Freehub or a thread-on freewheel, we have a separate illustrated article explaining how to tell them apart.
Another article on this site gives more general information about cassettes.
More sprockets must be better, right? Not necessarily! The trend toward more sprockets is driven largely by spec hype. A second or third chainwheel adds much more than one more sprocket.
7- and 8-speed systems use a relatively wide, and almost identical, spacing between sprockets. With 9-speed systems -- and even more so, 10-speed systems -- index shifting becomes more finicky as sprockets crowd closer together. The newer, narrower chains are weaker and harder to service.
Though shifters are different for 8, 9 and 10-speed cassettes, the same rear derailers index properly with 7- through 10-speed Shimano cassettes. Most Shimano-compatible freewheel bodies accept 8-speed cassettes.. Note the following exceptions:
Many Shimano sprocket combinations are identified by one-letter or two-letter codes such as "W" or "ab".
In the Shimano table, model numbers covered in current (2010) Shimano product literature are in boldface, like this: CS‑HG30‑8I. Older model numbers are included to help you choose replacements.
Some Shimano flat steel sprockets and spacers are in bolted or riveted assemblies, indicated by tooth counts in italics in the table below. The bolts or rivets only serve to keep sprockets and spacers in order when the cassette is not installed on the freehub. They can be removed to replace sprockets or build up custom combinations..
The Shimano parts lists linked below will help you identify models and order replacement parts.
Shimano-compatible 8-speed cassettes are available from SRAM, IRD and SunRace -- see additional sections below the Shimano section. Miche sprockets are available individually in all sizes, also useful in building up a custom progression. Taking all of these options into account, there is plenty of variety available to keep an 8-speed system going.
|CS-HG60-8I, CS-8G50-8I 8-speed, an group
CS-HG50-8I 8-speed, aw group
CS-8G50-8, S/T/U/V/W group
|CS-HG40 8-speed, an/aw group
CS-HG40-8i 8-speed, ao group (Megarange)
CS-HG30-8i 8-speed, an/aw group
Model numbers ending in "I" have Interactive Glide thicker sprockets and thinner spacers, and should only be used with Interactive Glide chain.
|XTR, XT R/ah (New code: bf)||11||12||14||16||18||21||24||28|
|ak/ (new code: an)
XTR, XT Q
|XTR, XT P||12||14||16||18||21||24||28||32|
|Sprockets shown in color are interchangeable with other same-size sprockets shown in the same color.|
|SRAM cassettes and individual sprockets are compatible with Shimano. SRAM sprockets have ramps and shaped teeth but shifting will not be as smooth when mixing brands in the same cassette.|
|IRD cassettes and individual sprockets are compatible with Shimano. Shifting will not be as smooth when mixing brands in the same cassette.|
When these cassettes skip the same sprocket sizes, it is fair to assume that the sprockets are interchangeable while maintaining smooth shifting.
SunRace also makes 8-speed cassettes with 9-speed spacing and a spoke protector in place of the innermost sprocket, like Shimano Nexave.
|SunRace cassettes and individual sprockets are compatible with Shimano. Shifting will not be as smooth when mixing brands in the same cassette.|
Shimano wants you to use one of its standard combinations, and offers a wide-enough choice to suit the needs of most cyclists, but you don't have to if you don't want to! It is not difficult to customize Shimano cassettes. If you substitute an un-approved cog, Uniglide or Hyperglide, SRAM, IRD, Miche, or some other brand, it will still work, but the shift to/from that cog will probably not be as smooth as a Hyperglide shift normally is. Since people managed without Hyperglide for several decades, this shouldn't scare you off. In particular, if you substitute the top or bottom sprocket, you will only have one shift that isn't HG; shifts to or from the extreme sprockets tend to be less troublesome than intermediate shifts anyway.
Generally, the smallest sprocket needs to be one with a built-in spacer, designed for the top-gear position. While you can't insert or remove a sprocket within a spider module, you can add sprockets on either side of these modules.
For example, if you want a 13-34 8-speed, you can start with an 11-28 -- the stock HG-50 13-15-17-19-21-24-28 has a sweet sequence of gears just as it is -- but to use a larger chainwheel or get a lower bottom gear, you might make this modification:
There is no problem mixing, say, thinner 9-speed speed sprockets into an 8-speed cassette. You might use a thicker, 7-speed spacer to compensate for a thinner, 9-speed sprocket (see spacing cribsheet). The smaller sprocket sizes (11, 12, 13) that have built-in spacers should ideally be matched, but even this isn't generally a problem in practice.
Sprockets are available individually, too:
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