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Date: 08 Jun 2007 01:10:07
From: damyth
Subject: Mod Shimano 9s 12-27 cassette to 13-30?
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There is a century coming up this weekend with some gnarly climbs, and
I'd like to modify my Ultegra 12-27 9 speed cassette to 13-30.
Happily there is a shop here that sells loose Miche cogs.
In order to do this, what width spacer do I need in the last position,
since the largest cogs on the Ultegra cassette are on a spider? In
other words, do I need a "special" spacer to account for the little
protrusion of the spider? I suppose I would also need a 13t first
position and the corresponding lock-ring, or can I get away with just
using the existing (non serrated) 13t?
Sheldon, if you are reading this, some guidance would be appreciated!
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Date: 08 Jun 2007 10:29:45
From: damyth
Subject: Re: Mod Shimano 9s 12-27 cassette to 13-30?
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Sheldon Brown wrote:
> Someone wrote:
> > There is a century coming up this weekend with some gnarly climbs, and
> > I'd like to modify my Ultegra 12-27 9 speed cassette to 13-30.
> > Happily there is a shop here that sells loose Miche cogs.
> >
> > In order to do this, what width spacer do I need in the last position,
> > since the largest cogs on the Ultegra cassette are on a spider? In
> > other words, do I need a "special" spacer to account for the little
> > protrusion of the spider? I suppose I would also need a 13t first
> > position and the corresponding lock-ring, or can I get away with just
> > using the existing (non serrated) 13t?
> >
> > Sheldon, if you are reading this, some guidance would be appreciated!
>
> That's how we make our Century Special. You do need a top position 13
> for most newer hubs. It's less about the serrations than it is about
> the built-in spacer. If you use a flat 13 it is not likely to engage
> the splines on the Freehub Body.
>
> The spacer betwixt the 21-24-27 module and the 30 sprocket is the same
> spacer that was behind the flat 13.
>
> So, all you need to make your own Century Special is a top 13 and a
> flat 30 (plus your 12-27.)
>
> You will also need a longer chain.
>
> Sheldon "Trade Secret?" Brown
> +-----------------------------------------+
>
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Date: 08 Jun 2007 09:50:20
From: Sheldon Brown
Subject: Re: Mod Shimano 9s 12-27 cassette to 13-30?
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Someone wrote:
> There is a century coming up this weekend with some gnarly climbs, and
> I'd like to modify my Ultegra 12-27 9 speed cassette to 13-30.
> Happily there is a shop here that sells loose Miche cogs.
>
> In order to do this, what width spacer do I need in the last position,
> since the largest cogs on the Ultegra cassette are on a spider? In
> other words, do I need a "special" spacer to account for the little
> protrusion of the spider? I suppose I would also need a 13t first
> position and the corresponding lock-ring, or can I get away with just
> using the existing (non serrated) 13t?
>
> Sheldon, if you are reading this, some guidance would be appreciated!
That's how we make our Century Special. You do need a top position 13
for most newer hubs. It's less about the serrations than it is about
the built-in spacer. If you use a flat 13 it is not likely to engage
the splines on the Freehub Body.
The spacer betwixt the 21-24-27 module and the 30 sprocket is the same
spacer that was behind the flat 13.
So, all you need to make your own Century Special is a top 13 and a
flat 30 (plus your 12-27.)
You will also need a longer chain.
Sheldon "Trade Secret?" Brown
+-----------------------------------------+
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Date: 08 Jun 2007 08:18:20
From: bfd
Subject: Re: Mod Shimano 9s 12-27 cassette to 13-30?
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On Jun 8, 1:10 am, damyth <mdk.10.dam...@spamgourmet.com > wrote:
> There is a century coming up this weekend with some gnarly climbs, and
> I'd like to modify my Ultegra 12-27 9 speed cassette to 13-30.
> Happily there is a shop here that sells loose Miche cogs.
>
> In order to do this, what width spacer do I need in the last position,
> since the largest cogs on the Ultegra cassette are on a spider? In
> other words, do I need a "special" spacer to account for the little
> protrusion of the spider? I suppose I would also need a 13t first
> position and the corresponding lock-ring, or can I get away with just
> using the existing (non serrated) 13t?
>
> Sheldon, if you are reading this, some guidance would be appreciated!
>From Sheldon's cassette article:
Building Custom Cassettes
Shimano wants you to use one of their standard combinations, and
they offer a wide enough choice to suit the needs of most cyclists,
but you don't have to if you don't want to! It is not difficult to
customize Shimano cassettes. If you substitute an un-approved cog,
Uniglide or Hyperglide, it will still work, but the shift to/from that
cog will probably not be as smooth as a Hyperglide shift normally is.
Since people managed without Hyperglide for several decades, this
shouldn't scare you off. In particular, if you substitute the top or
bottom sprocket, you will only have one shift that isn't HG; shifts to
or from the extreme sprockets tend to be less troublesome than
intermediate shifts anyway.
For example, Shimano doesn't make any true "corncob" (one-tooth-
jump) cassettes for time-trialists or flatland riders. In 7 speed, the
closest is the J (13/14/15/16/17/19/21).
If you remove the 21 tooth sprocket from a J, you can make it into
a 13-19 corncob by buying an 18 to put between the 17 and the 19.
Altenately, you could make it into a 12-18 by removing the 19 and the
21, and buying a 12 and an 18.
Similar modifications can be done with other ratios. Generally,
the smallest sprocket needs to be one with a built-in spacer, designed
for the top-gear position. While you can't insert or remove a sprocket
within a spider module, you can add sprockets on either side of these
modules.
For example, if you want a 13-32 9-speed, you can start with a
12-27:
* Replace the 12 and 13 with a top-position 13.
* Add a spacer and a 32 after the 27
(you don't need to buy the spacer, because you can use the
spacer that came between the original flat 13 and the 14.)
Shimano cassettes that don't use spiders have most of the
sprockets held together by 3 small bolts, or, in some cases, 3 long
rivets. These bolts/rivets are not essential. Their function is
convenience, in allowing the cassette to be installed slightly more
easily. To make a custom cassette, you will often need to remove the
screws or rivets. Just discard them, they are un-necessary in
practice.
* Some cassettes use screws have a 4 mm hex head. These can be
removed with an adjustable wrench.
* Some cassettes use screws with a 2 mm Allen head. These are
frequently mistaken for rivets.
* In the case of cassettes that are actually rivetted
together, the easiest way to remove the rivets is to grind off the
heads where they protrude from the largest sprocket. I generally do
this on a bench grinder.
There is no problem mixing, say, 9-speed or 8-speed sprockets into
7- or 8-speed cassette. The smaller sizes (11, 12, 13) that feature
built-in spacers should, ideally be matched, but even this isn't
generally a problem in practice.
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Date: 09 Jun 2007 12:06:40
From: John Henderson
Subject: Re: Mod Shimano 9s 12-27 cassette to 13-30?
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bfd wrote:
> * In the case of cassettes that are actually rivetted
> together, the easiest way to remove the rivets is to grind off
> the heads where they protrude from the largest sprocket. I
> generally do this on a bench grinder.
Thanks for that. I've been trying to simply push those pins
out. Easy when you know how - I just used a file and it took a
minute or so.
John
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