A4 scale = 70%
| | A4 scale = 70% |
Cycle transmission notes page 5
In the past, all 'screw-on' freewheels and hubs would fit each other. But they have now been superseded by different designs of 'freehub' and 'cassette' and compatibility has become a big problem. In fact it's a real mess!
There are two main groups of freehub, Shimano types with 9 splines and Campag ones with 8 splines, but there are also variations within these groups. Most makes conform to the standard Shimano 8/9 speed pattern and replacement sprockets are readily available for these.
Alternate sprockets and spacers slide onto freehubs and are usually retained by a lockring. Most sprockets are interchangeable, making it easy to customise your gear ratios and replace worn sprockets.
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Modern freehubs measure 130 or 135mm between their locknuts but, with care and the right tools, most older bicycle frames can be widened to accept them. You can often adjust the hubs themselves by adding or removing spacers from under their locknuts, and the spacers can be moved from the left to the right end to increase chain clearance if your chain rubs your frame in top gear.
The following table identifies some modern freehubs. The precise number of sprockets you can fit on each one depends on your rear derailleur and gear shifter, as explained next under Indexing.
| freehub | splines | body length | sprocket compatibility |
|---|---|---|---|
| Shimano 10 sp (alloy) Shimano 10 sp (steel) Shimano 8/9 sp Shimano 7 sp | 9 deep 9 shallow 9 shallow 9 shallow | 35 mm 35 mm 35 mm 31 mm | x Shimano 8/9 sp Shimano 8/9 sp Shimano 8/9 sp |
| Mavic 10 sp (M10) Profile 6 sp Profile 3 sp | 9 shallow 9 shallow 9 shallow | 38 mm 24 mm 11 mm | Shimano 8/9 sp Shimano 8/9 sp Shimano 8/9 sp |
| Campag 9/10 sp Campag 8 sp | 8 deep 8 shallow | 38 mm 36 mm | x x |
( x : incompatible with anything else )
Many shops only sell ready-assembled 'cassettes' of sprockets but these can usually be broken down and the sprockets mixed as required. Some cassettes are clipped together, some are bolted and some are rivetted. File the heads off rivets and punch them out. The bolts and rivets aren't essential and can be thrown away.
Highpath can supply complete cassettes, individual sprockets and spacers for most common systems.
| © Chris Bell, 2006 | next page... |
| HIGHPATH ENGINEERING Cornant, Cribyn, Lampeter, Ceredigion, SA48 7QW, Wales, UK phone / fax: +44 (0)1570 470035 (UK office hours only) email: 
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