Cassette compatibility

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ugo.santalucia
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Cassette compatibility

Postby ugo.santalucia » Fri Feb 15, 2013 14:40 pm

As requested by our host, a little digression about cassettes, number of speed and freehubs/freewheels.

The older 5-7 speed systems are typically screw on freewheels, which include the sprockets and the freewheel mechanism. 5 speed fit 120-126 mm rear dropouts, while 6-7 speed will only fit 126 mm rear dropouts or wider. Italian and British thread are pretty much interchangeable... I use them indifferently. 5-7 speed freewheels are cross compatible between brands.

With the advent of 8 speed, the rear dropouts became wider at 130 mm, which is still the standard for road cycling, while MTBikes use 135 and cyclocross are moving in that direction too (often using 132.5 to be compatible with both systems). At the same time, they introduced the freehub/cassette system to replace the screw on freewheels.
There are 7 speed cassettes, they are becoming a bit of an oddity in road cycling, but they are still there. They are fitted with Shimano splines and can go on modern Shimano HG freehubs 8-9-10 speed with the addition of the appropriate spacer (4.5 mm). 7 and 8 speed Shimano have the same spacing between sprockets, which means indexed systems for 8 can be used for 7 speed with a spare click.
9 speed shimano cassettes will only work with 9 speed Shimano STI levers, although there are devices to make them compatible with Campagnolo Ergo levers (see below). 9 speed cassettes go on a Shimano modern freehub without the need for spacers.
Shimano 10 speed cassettes are actually smaller than 9 speed, as the spacings are narrow and go on a Shimano 8-10 speed cassette with a spacer, which is provided with the cassette (Tiagra does not use the spacer). They also go on the newer 11 speed Shimano freehub, as long as the 1.8 mm spacer (as included with the hub) is used in combination with the tiny spacer provided with the cassette. Also 9 speed Shimano cassettes and 8 speed will go on an 11 speed freehub using only the 1.8 mm spacer.
If you have an 11 speed Shimano cassette, this will only go on the new wider 11 speed freehub.

For Campagnolo things are simpler as 9-11 speed cassettes go on the same Campagnolo splined freehub.

Mavic use their own freehub size, which is wider than a normal 8-10 speed one. This means all 8-10 speed cassettes need the Mavic spacer which is provided with the wheels, while the 11 speed Shimano cassettes don't need it.

Shimano and SRAM compatible cassettes have splined designed to go only on the Shimano HG and the SRAM freehubs, which are interchangeable, in the same way Campagnolo cassettes are splined to go only on a Campagnolo compatible freehub.
To move from one system to the other, there are typically 3 possible ways
1) replace the freehub with one compatible with the new system
2) get hold of a cassette spaced with your new groupset but splined to go on the older freehub (Marchisio for instance only for 10 speed)
3) get a pulley device that converts the levers pull ratio i.e. the Shiftmate

Typically the three solutions have similar cost... it is down to what is available, option 1 being the most sensible

A few golden rules

1) When fitting a cassette, the last sprocket needs to engage with the splines, but not entirely as the lockring needs to sit on the last sprocket and not on the freehub body. If that happens, you are missing a spacer.
2) When tightening a lockring, manufacturers advise to use 40 Nm torque... I find it excessive, there is no need for such a torque, which can damage soft alloy threads and might result in the lockring seizing. Do it tight, don't overtighten it
3) Chainsets are pretty much interchangeable across the range... you only have to make sure your chainset matches the bottom bracket type and has 2 or 3 rings, according to the shifters compatibility. 9-10-11 speed chainsets are just marketing, they are virtually the same thing.
4) Chains all have the same pitch, but have different width, according to the number of speed. 5-8 speed chains are the same, but 9 onwards are speed specific. In an emergency, you can use anything, but best to stick to the correct chain of the correct brand/compatibility

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