Archive-URL: http://search.bikelist.org/getmsg.asp?Filename=tandem.10207.0780.eml
Date: Wed, 31 Jul 2002 16:25:07 -0700 (PDT)
From: Brian Jenks <tech(AT)hubbub.com>
Subject: [T(AT)H] Part 2 - Mix Campy Shimano

Part TWO

At 01:09 PM 7/31/02 , Robert Adelman wrote:
>Just to take a step backward, I'm curious about the conventional wisdom that
>Campy shifters and Shimano RD/cassettes don't mix well. Is the thought that
>the Campy shifter pulls the RD a different distance per shift than a Shimano
>shifter?

Yes.  I have written an explanation a few times and will eventually 
supplement the existing article:

Please keep in mind that the "advantages and disadvantages" are entirely 
subjective and, for the purposes of the explanation, we are going to assume 
that we actually WANT to combine Campy Ergo-controls with a Shimano 
drive-train.

A few years ago I experimented with Campy and Shimano 8 and 9-speed 
integrated controls (before 10spd) just to learn exactly what the 
differences were in the indexing rings and ratchets.  I had received a few 
requests to combine the two and thought an in-line cam-like device (similar 
to the Travel-Agent) might do the trick.  In order to design one I needed 
to know what the relationship was between the indexing points and the cable 
displacement.  After plotting the results I found that, not only did 
Campy's line have a much steeper slope but it had a distinct 
curve.  Shimano's line was shallower and, actually, much closer to actually 
being linear.

What this means:  Each time you move the shifter one indexing point, Campy 
moves the wire some CHANGING multiple of Shimano's relative 
displacement.  As I recall, the multiple starts out around 1.4 and 
increases to around 2.1 (The numbers may only be close and/or the direction 
of the curve may be reversed, I don't remember).

There were a couple possible solutions I could think of.  One was what 
Erickson did and the other was to modify the indexing ring in the Campy 
control.  Before I succeeded in pulling that one off, Campy released the 
10-speed levers.  Understanding the differences between Campy's 9-speed and 
10-speed systems led me to think that the 10-speed lever came closer to the 
action of the STI.  So I tried a Shimano RD, hub and cassette, in 
combination with a 10-speed Ergolever.  It did not work.  The action was 
slow in the high gears, nearly perfect in the middle gears and fast in the 
low gears - as described in Part ONE.  In mathematical/graphical terms this 
phenomenon is due to the differences in curvature between the two 
functions.  (The 10-Ergocontrol function has a similar slope to the Shimano 
9-speed STI but still the same curve as the 9-speed Ergocontrol.)  This 
curvature is accounted for in Campy's RD design so the actual RD movement 
across the cogs is linear.)  So I tried to come up with a way to speed up 
the RD's response in the high-gear positions, keep it about the same in the 
middle-gear positions, and slow it down in the lower-gear positions.  One 
way was to extend the point of wire-attachment.  I tried turning the 
"hooked washer" and, to my surprise, it worked.  I put it though a few 
paces to make sure I wasn't dreaming and couldn't make it NOT work.  I have 
since installed, converted a couple singles and several tandems.  One 
single was finicky and a couple tandems have required slight adjustments 
but all, to my knowledge, have met or exceeded the expectations of 
experienced riders (with high expectations).

Whew!  I'll keep working on simplifying that explanation so that it is 
suitable for an article.

Best regards to all,
Brian
tech(AT)hubbub.com
HubBub Custom Bicycles
Cleveland Heights, Ohio