Re: [AMC-list] brake proportioning valve

[markprice242 <wrambler242@xxxxxxxxxxx>]

You can do some alteration in rear brake action by changing wheel cylinders. Finding one that is larger in diameter slows application due to taking a larger volume to move a stated distance. Smaller cylinders apply faster. The catches are 1. Finding a cylinder that fits 2. Realizing the size swap may also make the pedal lighter or harder to work. The application force is usually not a big change. One reason to swap rears is when you have say a 1+" bore rear cylinder and can not get rear lock up. Swapping down to 1" or 7/8" Should get you a rear lockup and then you can tune from there, either by finding the cylinders gives you the action Frank explains or allowing you to then use the adjustable valve in the rear line to reduce their action. Mark, (wrambler) ----- Original Message -----
> From: "Frank Swygert" <farna@xxxxxxxxxxx>
> To: amc-list@xxxxxxxxxxxx
> Sent: Wednesday, May 16, 2012 5:17:09 PM
> Subject: Re: [AMC-list] brake proportioning valve
> If the brakes work fine you need NEITHER. What you have to do is go to
> a WET parking lot (WET, not just damp... or better yet a dirt road),
> get up to about 40, and slam on the brakes as hard as you can. Observe
> how the rear brakes lock. If they lock immediately with little effort
> then you need a proportioning valve in the rear brake line. If they
> just do lock up with a lot of effort, then you're fine. You want them
> to lock, but only with just about the greatest amount of effort you
> can supply and not right away. If all four lock at about the same time
> you're okay. You mainly don't want the rear locking real easy in a
> panic stop. If they do you could swap ends if the front wheels get
> turned any or the road surface slopes one way or the other -- anything
> to start the rear end sliding sideways.
> I researched how AMC used proportioning valves. They were only used on
> some cars in the mid to late 70s, about a 6-7 year period. Before and
> after they weren't used. That might not be a big deal, except that
> Concords used them for a year or two, then didn't. Hornets didn't have
> them then they did. Apparently there was some experimentation in the
> 70s -- metering valves for the front disc brakes were used a few years
> on all models, then only on the big cars, then dropped along with the
> proportioning valve. Most just copy what the factory did in similar
> cars just to be safe, but testing your brakes is the best way.
> ----------------
> Date: Tue, 15 May 2012 18:09:53 -0700
> From: "Thomas Garner"<Tgarner@xxxxxxxxxxxxxx>
> I have my 1964 Classic. Upgraded the manual brakes to power and front
> disk brakes. Do I need a "brake proportioning valve" for the front and
> rear or just the rear or neither.
> --
> Frank Swygert
> Editor - American Motors Cars Magazine
> www.amc-mag.com
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