Converting 12-27 to 13-30?

Art Harris said:

I have a 12-27 Ultegra 9-sp cassette that I'd like to convert to
13-30. The 13T 1st position cog is readily available, but not the 30T.
Any reason I can't use a 30T sprocket from an 8sp Deore LX cassette?

Thanks,
Art Harris

The Ultegra 9 uses a carrier for the big cogs, and the 8sp Deore does
not (IIRC). I don't know if it is feasible to drill out the rivet for
the big cog on the Ultegra and drop in another, standard (Deore) cog
in its place. I think it would just sit like a shim behind the
carrier. -- Jay Beattie.

No drilling out needed. The 13t 1st pos cog replaces the two existing outer
12t and 13t cogs, and because the new 13t cog has an inbuilt spacer, that
frees up the spacer that was between the 13t and 14t cogs. That spacer goes
between the 30t cog and the existing three big cogs on their spacer.

"Jay Beattie" <[email hidden]> wrote in message
news:[email hidden]...

Art Harris said:

I have a 12-27 Ultegra 9-sp cassette that I'd like to convert to
13-30. The 13T 1st position cog is readily available, but not the 30T.
Any reason I can't use a 30T sprocket from an 8sp Deore LX cassette?

Thanks,
Art Harris

The Ultegra 9 uses a carrier for the big cogs, and the 8sp Deore does
not (IIRC). I don't know if it is feasible to drill out the rivet for
the big cog on the Ultegra and drop in another, standard (Deore) cog
in its place. I think it would just sit like a shim behind the
carrier. -- Jay Beattie.

Jay Beattie said:

Art Harris said:

I have a 12-27 Ultegra 9-sp cassette that I'd like to convert to
13-30. The 13T 1st position cog is readily available, but not the 30T.
Any reason I can't use a 30T sprocket from an 8sp Deore LX cassette?

Quoted message said:

Thanks,
Art Harris

The Ultegra 9 uses a carrier for the big cogs, and the 8sp Deore does
not (IIRC).  I don't know if it is feasible to drill out the rivet for
the big cog on the Ultegra and drop in another, standard (Deore) cog
in its place. I think it would just sit like a shim behind the
carrier. -- Jay Beattie.

I would leave the carrier alone. Since the 9 speed big cogs aren't
dished like the 10, you should be able to reuse a regular 9s spacer
after the carrier, so you'd drop the 12 &13(2nd position) from the
Ultegra and replace them with the 13 (1st position) and the 30.

You'd go from:
12
13(2nd)
14
15
17
19
21-24-27

to:
13(1st)
14
15
17
19
21-24-27
30

Make sense?

Any difference in spacing on that last shift will be negligible, since
it's at the end of the cassette. It would probably be hard to get into
from the big chainring, but you should avoid that combo anyway.

Nick Payne said:

No drilling out needed. The 13t 1st pos cog replaces the two existing outer
12t and 13t cogs, and because the new 13t cog has an inbuilt spacer, that
frees up the spacer that was between the 13t and 14t cogs. That spacer goes
between the 30t cog and the existing three big cogs on their spacer.

Good thinking. I forgot to subtract the 12! Has anyone tried a loose
cog behind a carrier? -- Jay Beattie.

Jay Beattie said:

Nick Payne said:

No drilling out needed. The 13t 1st pos cog replaces the two existing outer
12t and 13t cogs, and because the new 13t cog has an inbuilt spacer, that
frees up the spacer that was between the 13t and 14t cogs. That spacer goes
between the 30t cog and the existing three big cogs on their spacer.

Good thinking. I forgot to subtract the 12! Has anyone tried a loose
cog behind a carrier?  -- Jay Beattie.

I did essentially the same thing on my MTB, where I took a Shimano 105
13-23, replaced the 13 and 14 with a 1st position 14 and added a SRAM
34 on the other end. I've been riding on that for over a year without
any issues.

Hank Wirtz said:

I would leave the carrier alone. Since the 9 speed big cogs aren't
dished like the 10, you should be able to reuse a regular 9s spacer
after the carrier, so you'd drop the 12 &13(2nd position) from the
Ultegra and replace them with the 13 (1st position) and the 30.

You'd go from:
12
13(2nd)
14
15
17
19
21-24-27

to:
13(1st)
14
15
17
19
21-24-27
30

Make sense?

Yep. But I'm not sure about the "new" 30T cog. Will any 8 or 9 speed
Shimano cog fit on the Ultegra freehub? How about an SRAM cog? I don't
currently have a 30T. I'm thinking of maybe picking up a used cassette
just to salvage a 30T cog.

Art Harris

Art Harris said:

Yep. But I'm not sure about the "new" 30T cog. Will any 8 or 9 speed
Shimano cog fit on the Ultegra freehub? How about an SRAM cog? I don't
currently have a 30T. I'm thinking of maybe picking up a used cassette
just to salvage a 30T cog.

Art Harris-

All of the above will work. If you felt like scouring the dregs of
bike shop junk piles, you could probably turn up a Shimano Uniglide
cog- it'd work, too.

Jeff

Art Harris said:

Hank Wirtz said:

I would leave the carrier alone. Since the 9 speed big cogs aren't
dished like the 10, you should be able to reuse a regular 9s spacer
after the carrier, so you'd drop the 12 &13(2nd position) from the
Ultegra and replace them with the 13 (1st position) and the 30.

Quoted message said:

You'd go from:
12
13(2nd)
14
15
17
19
21-24-27

Quoted message said:

to:
13(1st)
14
15
17
19
21-24-27
30

Quoted message said:

Make sense?

Yep. But I'm not sure about the "new" 30T cog. Will any 8 or 9 speed
Shimano cog fit on the Ultegra freehub? How about an SRAM cog? I don't
currently have a 30T. I'm thinking of maybe picking up a used cassette
just to salvage a 30T cog.

Art Harris

Just about any cog should do, Shimano or SRAM, 9 speed, 8
speed...heck, even a 7 speed should work because you don't have to
shift beyond it. S9 is 1.78mm, S8 and SRAM 7, 8 and 9 are 1.8. S7 is
1.85. Only the spacer will matter. I don't remember if the CS-6500's
2nd position cogs have built-in spacers, but if it uses a separate
one, go ahead and use that. Otherwise, a spacer that's roughly 2.55mm
is called for. Shimano 9s are 2.56, SRAM's are 2.54.

Hank Wirtz said:

Art Harris said:

Hank Wirtz said:

I would leave the carrier alone. Since the 9 speed big cogs aren't
dished like the 10, you should be able to reuse a regular 9s spacer
after the carrier, so you'd drop the 12 &13(2nd position) from the
Ultegra and replace them with the 13 (1st position) and the 30.

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

Make sense?

Yep. But I'm not sure about the "new" 30T cog. Will any 8 or 9 speed
Shimano cog fit on the Ultegra freehub? How about an SRAM cog? I don't
currently have a 30T. I'm thinking of maybe picking up a used cassette
just to salvage a 30T cog.

Art Harris

Just about any cog should do, Shimano or SRAM, 9 speed, 8
speed...heck, even a 7 speed should work because you don't have to
shift beyond it. S9 is 1.78mm, S8 and SRAM 7, 8 and 9 are 1.8. S7 is
1.85. Only the spacer will matter. I don't remember if the CS-6500's
2nd position cogs have built-in spacers, but if it uses a separate
one, go ahead and use that. Otherwise, a spacer that's roughly 2.55mm
is called for. Shimano 9s are 2.56, SRAM's are 2.54.

I tried this with a Shimano 10s cassette this afternoon. I took a
12,13,14,15,16,17,19,21,24,27 and removed the 16, which gave the same
gear lineup as a Shimano 9s 12-27, then I added a 30 from an HG-50 8s
cassette. I ended up using a 9s spacer and the small spacer ring that
Shimano provides with the 10s cassettes to approximate the spacing,
because there's an indentation in the back of the 10s carrier. It
shifted quite smoothly in the workstand, though it had a little tooth
interference with the 10s road derailleur.

I think this setup would work nicely with an SRAM PG-950 30 or 32 cog
(reasonable cost vs weight compromise) and a Deore XT or XTR medium cage
(GS) rear derailleur to clear the large cog. Coupled with a 50-34
compact on the front, you'd have a really nice climbing bike with a 10s
drivetrain.

Here's how the gear inches work out (taken from Sheldon Brown's gear
calculator):

+---------+---------+---------+
| 50 | | 34 |
+----------+---------+---------+---------+
| 12 | 109.5 | | 74.5 |
+----------+---------+---------+---------+
| 8.3 % | |
+----------+---------+---------+---------+
| 13 | 101.1 | | 68.7 |
+----------+---------+---------+---------+
| 7.7 % | |
+----------+---------+---------+---------+
| 14 | 93.9 | | 63.8 |
+----------+---------+---------+---------+
| 7.1 % | |
+----------+---------+---------+---------+
| 15 | 87.6 | | 59.6 |
+----------+---------+---------+---------+
| 13.3 % | |
+----------+---------+---------+---------+
| 17 | 77.3 | | 52.6 |
+----------+---------+---------+---------+
| 11.8 % | |
+----------+---------+---------+---------+
| 19 | 69.2 | | 47.0 |
+----------+---------+---------+---------+
| 10.5 % | |
+----------+---------+---------+---------+
| 21 | 62.6 | | 42.5 |
+----------+---------+---------+---------+
| 14.3 % | |
+----------+---------+---------+---------+
| 24 | 54.8 | | 37.2 |
+----------+---------+---------+---------+
| 12.5 % | |
+----------+---------+---------+---------+
| 27 | 48.7 | | 33.1 |
+----------+---------+---------+---------+
| 11.1 % | |
+----------+---------+---------+---------+
| 30 | 43.8 | | 29.8 |
+----------+---------+---------+---------+

Or with a 32:

+----------+---------+---------+---------+
| 18.5 % | |
+----------+---------+---------+---------+
| 32 | 41.1 | | 27.9 |
+----------+---------+---------+---------+

That low gear with a 30 is comparable to the 29.2 gear inches you'd have
with a road triple 52-42-30 and a 12-27 cassette, without the added
weight and shifting complexity and blow to the roadie ego. ;-)

Mike Johnson