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A note about range:Rear derailers are often differentiated into "road" and "mountain" models. This is actually a false distinction based on marketing hype. A more meaningful distinction would be:
Generally, in the Shimano line, the wide-range models will handle up to a 34 tooth sprocket; medium-range models will handle up to 30 tooth sprockets, and narrow-range models will handle up to 28-30 tooth sprockets. Wider range models also have more chain takeup capacity, which makes them more compatible with wide range (triple) chainwheel sets.
SGS 86 mm center-to-center If you want to use a rear sprocket bigger than 30 teeth, this is the type you must have.
The marketeers call this a "mountain" size, but that's a bogus designation. This is what you want for most touring applications.
GS 74 mm center-to-center Erroneously called "long cage" in "road" contexts, this is actually the medium length cage.
It is, however the longest that has the marketing designation "road."
SS 50 mm center-to-center Road racing. SS cage derailers are not recommended for wide-range cassettes or triple cranks.
A note about capacity:Manufacturers have to assume that their customers are clueless, and will expect the chain to have some tension on it even in the bad gears where the chain is using small chainrings with small rear sprockets. Thus, the rated chain-wrap capacity is very conservative. A competent cyclist who uses the gears properly can generally exceed this by several teeth with no problem.
Most derailleurs also specify a maximum size rear sprocket. This is often a pessimistic value, based on the largest sprocket that is normally provided as part of that group.
How Many Speeds?Rear derailleurs often are referred to as "7-speed", "8-speed" or "9-speed." This is not as important a distinction as it might appear. Current model derailers are pretty much interchangeable within brands. A "7-speed" or "8-speed" designation generall just indicates that the derailer is an older design, or a cheaper model. They'll all work with all 3 systems, though the models marked "9-speed" will generally be slightly better (whatever cluster you use.)
|Shimano Rear Derailleurs|
(Work with most shifters. Check with us if you're not sure.)
|Wide||RD0776 $129.95||36||45||235 g||RD-M772|
|Wide||RD6030 $89.95||34||45||260 g||RD-M662|
|Wide||RD7592 $62.95||34||43||300 g||RD-M591|
|Wide||RD7590 $62.95||34||43||300 g||RD-M591|
|Acera SGS||Wide||RD8789 $27.95||32||38|
|Tourney MegaRange||Wide||RD8154 $19.95||34||40|
|Tourney MegaRange||Wide||RD8153 $18.95||34||40||With|
|Tiagra SS "Double"||Narrow||RD4600 $59.95||30||N/A||N/A||RD4600 SS|
|Tiagra GS "Triple"||Medium *||RD4404 $56.95||27||37||280 g||RD4500 GS|
|RD-2300 SS "Double"||Narrow||RD2300 $29.95||26|
Will accept 28t.)
| For More Rear Derailers, Check the QBP Catalog Here |
Many newer bicycles have built-in but replaceable hangers. There is a bewildering variety of types of these, with limited interchangeability. See our:
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|Articles by Sheldon Brown and others|
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