I have a 09 Lapierre Zesty, When taking off the standard shimano 9 speed cassette off the Mavic Crossrides on the biek, I noticed that there is reasonbly thick spacer behind the cassette. Never noticed that before on any other bike or any other wheelset. Is the spacer specific to the wheels, the bike or the cassette ? Anyone know ?

specific to the mavic wheelset

+1 TR, I have one on my Mavic Aksium wheelset as well 🙂

specific to the mavic wheelset

Wonder why its there ? why havent they made the cassette body the right length ? If I swapped wheels on the bike to a different set of a different make without the need for a spacer, would the cassette be similarly aligned etc

Probably narrower hub and longer freehub body? Not sure why – I am sure someone knows 🙂

on the Aksium, It's there for 10 speed cassettes. Surprisingly, the 8/9 speed cassettes are actually wider than the 10sp!

I imagine it's something similar with 9/8 speeds on the MTB wheelsets.

why havent they made the cassette body the right length

When I got a set of those wheels I was told the spacer was there to allow for 10 speed cassettes. HOwever I understand 10spd is the same width as 9 speed – maybe it's for 11 speed? Future proffin, anyway 🙂

Never worried about this before, but having read this thread I may have been doing this wrong for years on Mavic / Shimano combinations.

For Shimano 9 speed cassettes use the Mavic spacer.

For Shimano 10 speed use the Mavic spacer plus the Shimano spacer supplied with the cassette.

Never had any problems, but any thoughts appreciated.

Is it a Shimano – Mavic compatability thing, if I go to a different 9 sp cassette (i.e SRAM) I assume I still need the spacer just the same

Coleman that sounds right to me

By using the spacer it means that Mavic are avoiding any infringements and therefore royalty payments to Shimano for exactly copying the Hyperglide freehub body.

It's simple. Mavic make their own 10 speed cassettes (M10) which don't have a dished largest sprocket and as such, don't fit on a standard 9/10 speed shimano freehub body. So, if you use a Mavic wheel with a Shimano 9 or 10 speed cassette, you need the spacer to take up the extra space.

HTH

Never worried about this before, but having read this thread I may have been doing this wrong for years on Mavic / Shimano combinations.

No, you're right, there's other folk doing it wrong!

10 speed cassettes are narrower than 9 speed, so you use the 0.75mm Shimano spacer in conjunction with the Mavic one. For 8/9 speed (which are exactly the same width) you just use the Mavic one.

colnagokid and njee – Thanks for feedback.

Interestingly… SRAM 10 speed cassettes don't have the spacer, you'd think there'd be spacing issues using a SRAM cassette/Shimano mechs, but seemingly not. I guess the sprockets are slightly offset or sommat.

I've found, although not with a Mavic wheelset, that I needed a spacer behind an XT cassette as the carrier that the largest ring is bolted to fouls the spokes.

Interestingly… SRAM 10 speed cassettes don't have the spacer, you'd think there'd be spacing issues using a SRAM cassette/Shimano mechs, but seemingly not. I guess the sprockets are slightly offset or sommat.

The sprockets are indeed offset. Not the SRAM ones though but the Shimano ones! The thing is, the business side of a 10 speed cassette is actually slightly wider than a 9 speed. The only obvious reason for the offset cogs (and hence need for a spacer) is that they made the splines on first generation DA 10 speed hubs narrower, so you used a 10 speed cassette without a spacer and a 9 speed cassette didn't fit at all – though the splines on a 9 speed cassette wouldn't fit on those either. Deliberate incompatibility which doesn't exist any more, but the feature is retained on cassettes so that they all work on that generation of hubs.

As regards the spacer on Mavic hubs, that's mainly so that you can use a Campag spaced cassette (which is wider). Presumably it's easier for them to use the same cassette body on all hubs rather than have something different on their MTB hubs where there's no particular need to use a Campag cassette.