[DeTomaso] rear brake options?

Thomas Tornblom Thomas.Tornblom at hax.se
Wed Mar 24 14:19:35 EDT 2010


Ken Green skrev:
> Front calipers generally have larger pistons to provide greater braking, so generally, you don't want to use front calipers on the back, or you may have to excessively restrict the flow to the rear calipers.  We did a back of the envelope analysis a while back and I think we concluded that the weight distribution shifts from 40/60 to about 60/40 under 1 G braking.  So with a single tandem master cylinder you'd want the rear pistons to be 2/3s the area of the front (or less) to avoid locking up the rear wheels first.  We compared this estimate to the areas of Porsche 996 turbo (has about the same 40/60 weight dist) caliper pistons and it came out very close.  

This is why you want to have a prop valve plumbed into the *rear* 
circuit, not the front.

You want to have the brake balance set up to match the static weight 
distribution, and then handle weight transfer with a prop valve.

Remember that the prop valve initially doesn't reduce the pressure, but 
after reaching a certain pressure (when weight transfer starts to become 
significant) it reduces the output pressure compared to the input 
pressure, which makes the idea of having a prop valve in the *front* 
circuit totally backwards.

Thomas

>  
> I don't know if there are stepped brake master cylinders?
>  
> Ken
> 
> --- On Wed, 3/24/10, Rob Dumoulin <rob at dumoulins.net> wrote:
> 
> 
> From: Rob Dumoulin <rob at dumoulins.net>
> Subject: Re: [DeTomaso] rear brake options?
> To: pantdino at aol.com
> Cc: detomaso at realbig.com
> Date: Wednesday, March 24, 2010, 10:03 AM
> 
> 
> About a year ago, I installed a Brembo Grand Turismo big brake kit on my
> 350Z.  A friend of mine that has a auto repair shop saw my stock Pantera
> rear calipers. and suggested I put my old stock 350Z front calipers on the
> Pantera rears.  I'm confident they are superior to the stock Pantera ones,
> maybe too good.  Anybody done retrofits with other applications?
> 
> On Wed, Mar 24, 2010 at 12:20 PM, <pantdino at aol.com> wrote:
> 
>>
>> Sounds like the stock rear brakes on a Pantera are too small.
>> Putting in a pressure control valve just limits the fronts so they don't
>> lock up too soon
>>
>> Have people put a different kind of caliper on the "extra" mounting points
>> and kept the stock one for the hand brake?
>>
>> I see Wilwood calipers are actually pretty cheap (($125 for the caliper
>> itself).  Would that make sense?  I haven't paid much attention to those
>> because I believe they don't have dust seals at the pistons.
>>
>> I'm afraid to even ask Steve Wilkinson if stock rear calipers (to replace
>> my frozen "extra" ones) are available and how much they cost. But I guess
>> I'll summon the courage.
>>
>> Jim
>>
>>
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-- 
Real life:   Thomas Törnblom             Email:  Thomas.Tornblom at Hax.SE
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