Re: [CR]brake caliper tension.


In-Reply-To: <000001c33644$42214ae0$6501a8c0@megaroad1>
References: <000001c33644$42214ae0$6501a8c0@megaroad1>
Date: Thu, 19 Jun 2003 11:22:11 -0400
To: "matt yee" <mattmatthew@hawaii.rr.com>, <classicrendezvous@bikelist.org>
From: Sheldon Brown <CaptBike@sheldonbrown.com>
Subject: Re: [CR]brake caliper tension.


At 11:22 PM -1000 6/18/03, matt yee wrote:
>Hi all -
>
>I was just curious bout something. I noticed that older sidepull brake
>calipers have a ton more spring tension than, say, newer dual pivot
>brakes. My friend has some old Modolo calipers - and without the correct
>tools they were not FUN to put on at all. At least the dual pivots were
>fairly easy to do with very rudimentary tools. Wondering though why
>there's so much more tension on the springs than the new stuff? Are
>there differences between the old Italian stuff and other contemporary
>component manufacturers?
> In the late '80s, there was a major change in brake design, initiated by DiaCompe, then copied by Shimano, and later by all other brake manufacturers. Instead of a very strong spring in the calipers/cantilevers, they installed a very weak spring, so weak that it could not reliably retract the brakes by itself.

To help the weak spring out, they added a new, also weak spring to each brake lever. Thus the cable was both pushed and pulled back to the rest position when you released the brake lever. As a result of this design, they were able to make the total sproinginess of the two combined springs very much lighter than the stiff springs needed for the older one-spring system.

This was also accompanied by various friction reducing features, including lined housing and nylon spring pads, ball-bearing caliper action, plus the improved cable routing of "aero" levers.

This system was called "BRS" (Balanced Response System) by DiaCompe; "SLR" (Shimano Linear Response) by Shimano.

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