Thomas-
So I am thinking that the tandem master cylinder (like on my '70 2000)
provides a balance between the front and rear brake; that is, the two circuits
(or whatever) are sized to compensate for the difference in slave (wheel)
cylinder diameters and therefore displacement volume, front and rear ; allowing
balanced braking (per the design intent of the engineer who laid out the
braking system). Have I got that right?
Gary McCormick
San Jose, CA
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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.
>
> For you engineering students out there, still in school, have a little
> fun with your MATLAB program. MATLAB provides a can routine to you can
> see the static and dynamic results in the brake pressure.
>
> The early (single) and later (tandem) brake master cylinders both have
> a single pressure point on the pedal. For racing, it is best to use
> an adjustable ballance bar and two seperate master cylinders (I think
> Bill Kenyan has such a set up on his vehicle... been a while since I
> have seen it -- or was that on Ralph's?).
>
> QUICK CHECK: Step on the brake pedal... feel how far it goes to the
> floor; Now pull up on the handbrake, and try again! If you feel a big
> difference... you need to adjust the rear brakes. Obviously the pressure
> was the same in both cases, yet the brakes would behave different under
> braking... hint, displacement does play a big part of this.
>
> Carrol Smith has a pretty good write up in one of his "... to Win" books.
>
> Cheers,
>
> Tom Walter
> Austin, TX
>
> P.S. For you engineering students: Front pistons are 2.125" diameter.
> Master cylinder is 3/4". Rear wheel cylinders can be 11/16" , 3/4",
> or 13/16". You'll always find the LARGER rear wheel cylinder will have
> more STATIC pressure... but add displacement volume, and observe the
> dynamic results.
>
> >From: "Calvin Grandy" <cmgfam@sover.net>
> >
> >When considering fluid power (hydraulic brakes) The work is done by
>pressure not by distance. This is not the true definition of work i.e. Force
>X Distance, but is what we are considering. If the small cylinders move out
>more rapidly under pedal application, so what! The resistance to movement,
>when the shoes hit the drums, will result in a build up of pressure that will
>extend any sluggish members (front caliper pistons perhaps). When all the
>free play is taken up, then the real pressure will build, and the work of
>stopping can be done.
> >
> >If the wheel cylinders are smaller, the resulting braking force may be
>smaller (do not neglect the self energizing effect of the leading shoe) and
>there will be less pedal travel before the brakes start to "bite", A higher
>pedal action.
> >Mechanical adjustment of the pedal linkage can reposition the pressure point
>of the pedal if desired.
> >
> >Please do not construe this as an endorsement for the exchange of wheel
>cylinders! I do not know what the results will be. I just want to make clear
>the nature of the system.
> >Regards
> >
> >Calvin Grandy
> >Vermont
> >
> >----------
> >> From: SRL311KA@aol.com
> >> To: toby@wolfenet.com; datsun-roadsters@autox.team.net
> >> Subject: Re: Rear Brake Swap
> >> Date: Tuesday, November 23, 1999 10:24 PM
> >>
> >> Hey list,
> >> Pistons in smaller rear wheel cylinders will move further than larger
> >> cylinders with the same amount of pedal depression. Think about it!
> >>
> >> Bill Kenyon
> >> SRL311 KA
> >
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