Re: [CR]weinmann vs. universal centerpulls - Toe-in

(Example: Production Builders:LeJeune)

Date: Thu, 7 Jul 2005 22:12:37 -0700 (PDT)
From: "r cielec" <teaat4p@yahoo.com>
Subject: Re: [CR]weinmann vs. universal centerpulls - Toe-in
To: HM & SS Sachs <sachs@erols.com>, Classic Rendezvous <classicrendezvous@bikelist.org>
In-Reply-To: <42CDBEBA.7020401@erols.com>


Ahoy !

RE: Toe-in of Universals

If caliper cannot be bent without high risk of breakage, is toe-in accomplished by reshaping the pad by cutting or filing or making tapered shims between caliper and pad holder ?

Richard Cielec Chicago, Illinois

HM & SS Sachs <sachs@erols.com> wrote: It happens that a few years ago I actually measured the lever movement and cable pull for some levers. The results, as a ratio of lever throw per unit of cable take-up, are below. What you will see is that the Universal has a very low ratio. Roughly speaking, moving the lever 2 mm shortens the cable ~1 mm. In contrast, with the Weinmann "red-dot" of the early 60s (a personal favorite), it takes 3 mm of lever travel to pull a mm of cable. As Joe B-Z says, the Universal has uncommonly low mechanical advantage. Lots of cable pull, very little force transmitted. It is not "powerful," but it is very direct since it takes up slack amazingly quickly and then has full contact. Then it is up to brute strength to get it to convince the pad and rim to get intimately acquainted.

Ratio, lever 3.2 DiaCompe 3.9 Weinmann Delta 3.0 Weinmann Red-Dot 2.1 Universal 61/68 4.2 Sachs "Ergo" 2.4 Shimano 105 Road (not sure which one)

AT the other end, the caliper, you can do the same sort of measuring. Let's ignore the straddle cable geometry for now, and just think about the relative lengths of the lever arms (pivot is the fulcrum). It's roughly 2:1 for the CP-61 and 1:1 for the SP-68. So, a mm of cable pull moves the brake pad roughly 1/2 mm with the 61 and 1 mm with the 68. That is one heck of a big difference. So, all other things being equal, the 68 SP calipers are easier to modulate and require less pressure than the 61 CPs.

My Hetchins came with Universal 61s. Even with the original pads, they inspire confidence by their combination of good feel/modulation and adequate power with the force my 60 year old fingers can maintain. Last week, I set up 68s on my NOS Weigle, which wants longer sidepulls than the modern fashion, with Universal levers. It was a bit scary, and I will change to levers that need more lever travel to take up cable, so they have more mechanical advantage.

Like most of us, Universals are quirky. In this case, great when set up right, impossible to adjust toe-in (guaranteed to break), lousy hood rubber but fine pads, poor chroming on the CP hardware... My own quirks are somewhat different.

harvey sachs mcLean va Met a smiling chap on my morning commute today, at Key Bridge, NoVA. He gets to ride his only bike, a '72 chromed paramount, to work. My commuting bike would have a half-life (before theft) measured in hours parked outside where I work...

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