Custom Shimano cassettes

I think you'll need a spacer of a different size in order to make it
fit right, see sheldon's site: http://sheldonbrown.com/k7.html#spacing

Also, the shifting from 14 to 17, 17 to 18, 18 to 19 may be somewhat
less smooth. Apparently the ramps are specifically designed to shift
to and from specific sprocket sizes. I haven't tried this, don't know
how much of a problem it is...

Zog The Undeniable said:

I know this sounds like a slightly weird thing to do, but can I lose the
15T sprocket from a 13-14-15-17-19-21-23-26 8-speed cassette and
substitute an 18T sprocket from a 7 speed cassette? I spend all the
time flicking between the 17T and 19T sprockets, and I happen to have an
unused 11-28 7 speed cassette in the garage.

Then you may find you'll miss the 15, that 17-14 jump is NASTY.

You can do this. I believe the 11-28 is an IG cassette, which uses
slightly thicker sprockets and thinner spacers, so you should use one of
a thinner spacer betwixt the 18 and the 19. Probably a 9-speed spacer
would be best for this application.

Quoted message said:

I'd rather lose the 13T or 14T, but the way the cassette is made
prevents this.

I don't think so. I checked one out from our stock. The 14 can be
removed, and would be probably missed less than the 15.

Quoted message said:

Sheldon's site says I can put 8 or 9 speed sprockets on
a 7 speed cassette,

Right.

Quoted message said:

but the other way round?

Did I say that? Where?

It would be better to get an HG 18 instead of the IG one, but since
you've already got the IG you might as well give it a try.

Sheldon "Occasionally Misquoted" Brown
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Harris Cyclery, West Newton, Massachusetts
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Sheldon Brown said:

Zog The Undeniable wrote:

Quoted message said:

Quoted message said:

Sheldon's site says I can put 8 or 9 speed sprockets on a 7 speed
cassette,

Right.

Quoted message said:

but the other way round?

Did I say that? Where?

I was asking whether it does work the other way round. Must be a strage
British grammatical construction that doesn't travel well ;-)

The 7 speed is a Hyperglide-C cassette.

I'll see if I can remove that 14T.