GEAR HEAVEN!. An important principle.

I've been doing my own mechanics on bikes for 20 years, building wheels, assembling whole bikes etc.
I learnt this principle for the first time the other day, and it's terribly simple and maybe
everyone else knows it, but I've never seen it stated, AND it certainly is not known by many
manufacturers who assemble bikes.

The problem.

A bike which no matter what I did, did not index properly.

I had replaced all the cables and wires without success, replacing all the cable housings with
identical lengths of proper Shimano index housing. No good.

I had a look at it and thought. What would happen if I made the last cable housing (the one into the
derailleur) a couple of inches longer, making a long lazy loop.

I'll tell you what happened.

Gear heaven.

The tightness of this loop was the major cause of friction, obviously.

I now have completely frictionless perfect indexing.

 

> The tightness of this loop was the major cause of friction, obviously.

Garry, you forgot those long, lousy looking, loops in the early seventies? The housing was not
stainless steel, nor was there any teflon lining to make it smoother, shorter and ... lighter. We
used to un-peal a generous length of brake cable housing, have it chrome plated and install it for
frictionless-smooth downtube friction shifting.

Still works that way, with my bikes.

Sergio Pisa

 

Gearóid Ó Laoi, Garry Lee wrote:
> I've been doing my own mechanics on bikes for 20 years, building wheels, assembling whole bikes
> etc. I learnt this principle for the first time the other day, and it's terribly simple and maybe
> everyone else knows it, but I've never seen it stated, AND it certainly is not known by many
> manufacturers who assemble bikes.
>
> The problem.
>
> A bike which no matter what I did, did not index properly.
>
> I had replaced all the cables and wires without success, replacing all the cable housings with
> identical lengths of proper Shimano index housing. No good.
>
> I had a look at it and thought. What would happen if I made the last cable housing (the one into
> the derailleur) a couple of inches longer, making a long lazy loop.
>
> I'll tell you what happened.
>
> Gear heaven.
>
> The tightness of this loop was the major cause of friction, obviously.
>
> I now have completely frictionless perfect indexing.
>

I've seen 2 things that could be happening here. 1 is the less curved loop lets the cable move more
freely -- did you try teflon cable? 2 is the tight housing acted like a spring and pulled the
deraileur away from the gear cluster which made the shifting sloppy. On and XTR deraileur (and
probably others), you can play with the "b" adjustment screw to get the DR closer to the cassette
(or further away if it's too close).

David

 

Garry-<< I had a look at it and thought. What would happen if I made the last cable housing (the one
into the derailleur) a couple of inches longer, making a long lazy loop.

I'll tell you what happened.

Gear heaven.

We normally take the piece supplied by shimano and chuck it and replace it with a longer and 5mm
piece of der housing back there- We called shimano and asked if they could make it a few cm
longer...you can guess what the reply was....

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

"Gearóid Ó Laoi, Garry Lee" <[email protected]> wrote in message
news:<[email protected]>...
> The problem.
>
> A bike which no matter what I did, did not index properly.
>
> I had replaced all the cables and wires without success, replacing all the cable housings with
> identical lengths of proper Shimano index housing. No good.
>
> I had a look at it and thought. What would happen if I made the last cable housing (the one into
> the derailleur) a couple of inches longer, making a long lazy loop.
>
> I'll tell you what happened.
>
> Gear heaven.
>
> The tightness of this loop was the major cause of friction, obviously.
>
> I now have completely frictionless perfect indexing.

You are not the only one that learned this. Even some pro bikes set up with too short of a loop. 1'
rule applies here (I use slightly longer than 1' myself). I even use the 4mm housing that some has
said is dopey (plastic Shimano ferrules and all! I just take out the little O-ring/donuts inside).
It works great and looks neat!

 

I've always used teflon lined cable since it became available