OK I've tried all sizes and here is the scoop...
both cars the rear brakes lock up too soon , (if the brake all the way
around are in good stock condition) the 1600 needs 3/4 inch, and the 2000
needs 11/16s . the 3/4 inch can be found (btw stock on the 2000), but are
more $$ than the stock 13/16, the 11/16 are harder to find .
Mike Kerr
Roadster Restoration
3730 Todrob LN.
Placerville CA. 95667
Ph.# 530-644-6777
Fax# 530-644-7252
E-mail: mikekerr@innercite.com
Web page : http://www.innercite.com/~wolfgang
Visa & master card
-----Original Message-----
From: Calvin Grandy <cmgfam@sover.net>
To: datsun-roadsters@autox.team.net <datsun-roadsters@autox.team.net>
Date: Wednesday, November 24, 1999 2:39 PM
Subject: Re: Rear Brake Swap
>The only thing I will agree on is there are good references out there.
>
>I would not agree that a smaller wheel cylinder will give greater braking
force than a larger wheel cylinder compared to system in the front that
remains unchanged. In fact the force generated at the cylinders will be
proportional to the cylinder area. Larger area means greater force P=F X A.
>
>BUT!
>
>In the real world the braking force generated is a function of: coefficient
of friction X swept area X radius.
>If the rear brake friction material generates sufficient friction to self
energize the leading shoe, the brakes will lock at very small pedal/ wheel
cylinder pressures. The real world case of rusted drums serves as example.
>
>The designer had something in mind when the components were originally
sized. Modern friction materials could alter these factors. Dual brake
master cylinders, (not tandem!) can serve to refine brake balance as can
proportioning valves. Drum brakes have a much different performance curve
for than do disc brakes, so no one setup can work for all speeds and
conditions.
>
>In the case of a modern day performance motorcycle, maximum braking effort
will result in 100% weight transfer (a stoppie). When the rear wheel is in
the air, the best and worst brakes perform the same!
>
>Regards
>
>Calvin Grandy
>Vermont
>
>----------
>> From: Thomas Walter <walter@omni.sps.mot.com>
>> To: datsun-roadsters@autox.team.net
>> Subject: Re: Rear Brake Swap
>> Date: Wednesday, November 24, 1999 2:03 PM
>>
>> 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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