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Re: Rear Brake Swap

To: a roadster list <datsun-roadsters@autox.team.net>
Subject: Re: Rear Brake Swap
From: Toby B <toby@wolfenet.com>
Date: Wed, 24 Nov 1999 12:44:00 -0800
Oh, no, 
        Tom, you're backwards! 
For more rear braking force, use a LARGER cylinder.  
For less, use a SMALLER cylinder.

Think about it this way(I'm exaggerating and rounding numbers for
clarity)- 

you push on the pedal, generating 100 psi of hydraulic pressure. 
There's 100 psi everywhere- in the lines, and in each wheel cylinder. 
Now the pressure against a 1-square-inch piston is gonna be 100 psi*1
inch= 100 pounds of pressure against the shoes.  

But the pressure against a 2-sqare-inch piston is the same 100
psi*2inches= 200 pounds of pressure against the shoes.
So when you make a wheel cylinder bigger, you increase the pressure
against the shoes (or pads).  

But since there is more area that can move, you increase pedal TRAVEL as
the wheel cylinders "expand" in volume internally.

Hope this helps!
More can be found in Fred Puhn's Brake Handbook...
TOby

Thomas Walter wrote:
> 
> This is getting pretty interesting.
> 
> Both Bill and Calvin are correct. Looks like they are saying opposite
> things, but not really.
> 
> If you want the REAR BRAKES to lock up first, use a SMALLER rear wheel 
>cylinder.
> 
> If you want the FRONT BRAKES to lock up first, use a LARGER rear wheel 
>cylinder.

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