Dura-ace 10 speed 7800 casette query

[Triskeliongirl]

I just got a new wheelset (Easton EA70). It says its shimano 8/9/10 speed compatable (650c). I went to mount a new Dura-ace 10 speed 7800 casette. When i finished, I noticed an extra thin spacer in a platic bag, with instructions for mounting on 9 spd hubs. Does anyone have any idea if I was supposed to have used this, or is this just for hubs that are 9 spd only?

I guess I'll know when I test the wheel, but wondered if someone knew to save me the time of taking the wheel on and off if I did it wrong.

[dianne_1234]

You need the spacer. It's used on hubs that are 8-9-10 speed compatible, like yours. It goes on the hub first, then the cassette goes on as usual.

If you don't install it, it's likely your cassette will have some axial play that may cause poor shifting and funny noises.

Here are Shimano's Service Instructions explaining it:

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Dura-Ace/CS-7800/1Z80A_EN_v1_m56577569830605972.PDF

According to Shimano the spacer is 1mm thick:
http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/CS/EV-CS-7800-2253_v1_m56577569830608753.pdf

[Triskeliongirl]

Oh thanks...........Too bad I found it after tightening the casette, but better to know before installing the wheel.

I have also installed 9 speed casettes on the same kind of hub, but never noticed an extra spacer. So, can I assume its only required for the 10 speed casette on this wheel type and not 9 spd casette?

[dianne_1234]

Yep.

[TrekWSDmechanic]

Hi sorry, just thought I'd chime in here with some clarification.

The spacer is used if you are running a 9 speed cassette. If you are running a 10spd cassette, you DO NOT need the spacer.

The reason: The extra cog takes up more room across the cassette on a 10spd cassette, yielding a slightly wider cassette overall. Hubs these days can accommodate a 9 or 10 speed cassette, but that minimal difference in width is compensated for by using the spacer if you run 9 speed.

If you are running 9 speed, then as dianne mentioned, you will have play in the cassette if you don't use the spacer. You shouldn't have this issue if you are running 10 speed.

[Triskeliongirl]

I think Dianne was correct, you do need the spacer that is supplied with the casette to mount a 10 speed shimano casette on a wheel that accepts 8/9/10 speed casettes. I found the reason articulated well in this thread from this site http://www.bikeradar.com/road/forums/viewtopic.php?p=14963574&sid=022fc4cfb138d1c041c118b10e2f912b:


If I was going to be pedantic, I'd point out that a 10 speed cassette is actually wider than an 8 or 9 - it's simply that there's a recess in the back of it where it mounts to the freehub body which needs to be filled by a spacer! But of course I'm never pedantic...

Anyway, since this seems to be a bit of a FAQ, I'll have a go at a definitive and comprehensive answer:

With Shimano factory wheels, you never need a spacer to fit an 8-speed or 9-speed cassette. You'll need a thin spacer to fit a 7-speed cassette on any modern 8/9/10 speed hub, since the whole cassette is narrower. For most Shimano wheels you need a thin spacer to fit a 10-speed cassette (which should come with the cassette if bought separately) due to the recess. However the older DA 10-speed wheels and the Ultegra wheels are 10-speed only - they won't take anything other than a 10-speed cassette, and you won't need a spacer for this.

With Mavic wheels you need a Mavic spacer for any Shimano cassette (this is assuming an M10 freehub body, as the cassette won't fit at all on an ED10 Campag body). Additional spacers as above - ie none for 8/9, an extra spacer for 7, a different extra spacer for 10.

Any other wheel with a Shimano compatible freehub, including handbuilts (apart from handbuilts with DA 7800 hubs) as Shimano 8/9/10 wheels - ie no spacer for 8/9, a spacer for 7, a different spacer for 10. DA 7800 hubs are the same as older DA and Ultegra wheels - ie 10 speed only, and no spacer needed.