12-25 to 12-27 install?

Alan Hoyle said:

Hey all,

I recently purchased a 12-27 cassette (dura-ace, heavily discounted) to replace the 12-25
(ultegra) that came on my road bike. I have a few questions about installation before I go and do
something that will damage my bike. I've only got 400 miles on the bike so far, so it's not worn
out, I just want a slightly lower gear, which isn't used very frequently....

First thing I did (after buying a chain whip and lock-ring tool) was go to sheldonbrown.com
and found:

sheldonbrown.comderailer adjustment.htmlOpen ↗

1. The standard "short cage" ultegra RD has enough capacity for this, right? I'm running 53-39
double in front...

That'll work fine. Standard short cage Shimano rears generally work fine up to 30 teeth, as long as
the range in front isn't excessive.

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2. I know I'm going to need to adjust the derailler angle (b-tension).

Maybe, maybe not, it's only 2 teeth.

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Will I have to worry about the top/bottom limits or the indexing adjustment?

No.

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3. Will I be able to use the same chain?

Depends how short the original chain was cut.

If the original chain has more than a few hundred miles on it, I'd adise replacing it anyway when
installing a new cassette, especially a fancy-scmancy Dura-Ace one.

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The cassette is coming with a DuraAce chain too, but I thought I might save it for later if I
didn't need to install it now.) I could just change both in case 400 miles of wear is significant
enough....

4. I also bought one of the SRAM "gold" power links to make it easier to remove and clean my
chain. Looking at my old chain, I see one link that's labelled differently than the others:
"2L". is that the one I should replace? The pins don't look noticably different.

Does'nt really matter.

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5. When dealing with these 9-speed chains, can I use the same chain tool that I bought in '95
with my 8-speed mountain bike? I think the answer to this is "yes", but I'm just making sure.

If it works, it works.

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6. Should I be concerned with the durability of the titanium cogs if I spend less than 1/10th of
my time running in them? (I only got the Dura-Ace because I got it about the same cost as
Ultegra would have been.)

Probably not.

Sheldon "Never Used Ti Sprockets" Brown +-------------------------------------------------------------------
+
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| history of the human race, a way of | securing a more abundant life which does not simply
| consist in | taking away from someone else. -- Karl Taylor Compton, 1938 |
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Alan Hoyle said:

I recently purchased a 12-27 cassette (dura-ace, heavily discounted) to replace the 12-25 (ultegra)
that came on my road bike. I have a few questions about installation before I go and do something
that will damage my bike. I've only got 400 miles on the bike so far, so it's not worn out, I just
want a slightly lower gear, which isn't used very frequently....

First put on the new cassette. Put the wheel into the frame. On the stand, check if the existing
chain will shift smoothly and run the
53/27. If it does that, the length is correct. If not, you need a chain that is 1 link (2
pins) longer.

With the proper length chain, shift to the 39/27. If the derailleur pulley touches the 27, you need
to screw in the 'b' tension screw.

Titanium cogs are both lighter and less durable.

Thank you for all of the effort you've put into posting useful bike information on the web and in
groups like this!

Quoted message said:

Sheldon "Never Used Ti Sprockets" Brown +-------------------------------------------------------------------
+
| In recent times, modern science has developed to give mankind, | for the first time in the
| history of the human race, a way of | securing a more abundant life which does not simply
| consist in | taking away from someone else. -- Karl Taylor Compton, 1938 |
+-------------------------------------------------------------------+