[CR] Re: Dura-Ace brakes...

(Example: Racing:Jacques Boyer)

To: classicrendezvous@bikelist.org
From: "Grant McLean" <grant.mclean@sympatico.ca>
Subject: [CR] Re: Dura-Ace brakes...
Date: Tue, 30 Oct 2007 08:44:46 -0400


shimanophiles...

Just to clarify, there is no 7401 caliper. the reason is that the 7401 aero lever is not SLR, it has no return spring, so it used the 7400 caliper. It's a little confusing, because shimano did change the pads.

The evolution went: 7400 caliper with alloy pad holders and non aero 7400 levers 7400 caliper with molded pads and 7401 aero lever (no return springs) 7402 caliper (still single pivot) SLR spring and 7402 SLR lever with spring 7403 dual pivot caliper - came out with STI, but still works with 7402 SLR lever

Grant McLean Toronto, Canada

Date: Mon, 29 Oct 2007 15:40:40 EDT From: Stronglight49@aol.com Subject: [CR] Re: Dura-Ace brakes...

Tom Dalton noted a goof in my notes, one perhaps worth mentioning as an example of the continued R&D which Shimano poured into their products. The 10% commitment of their resources to development was noted as one factor in their defeat of Suntour.

Thanks Tom! - You're absolutely right. Good call:

The 7400 was from 1986 and it's the 7402 specs dated 8/88.

The only difference I can see between the two is the addition of a nylon or plastic cylindrical anti-friction "sleeve" on the end of the return spring for the later model - just as you'll find carried over onto the 7700 & 7800 series well into this century (perhaps even the current models, but I've not checked them).

The 7400 had similar "U" shaped inserts on the caliper arms, but these were open. I think the enclosed sleeves actually produce a "self-cleaning" effect where the others could still allow build-up of grit at these pivot points - just the same as bare alloy against the steel springs of the very oldest side-pulls had permitted. And I think the friction at this point is the main reason why single pivot side-pulls always seem to go out of adjustment and ultimately cause one pad to touch the rim slightly before the other.

The Model 7403 was issued in late 1989... these were first Shimano "Dual Pivot" style calipers.

BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA

------------------------------------------------ tom_s_dalton@yahoo.com writes:

BR-7400 Brake calipers --- Last single pivot brakes [08/88]

There was a model with an improved brake pad (7401?) and then a later version with the SLR spring, called 7402, I think. That was the last single pivot. As a friend called it, "The ultimate evolution of the side-pull caliper."