[DeTomaso] Brake Hoses

[MikeLDrew at aol.com]

In a message dated 6/13/07 11 35 56, JDeRyke at aol.com writes:

First Jack writes:

> Replacing stock 'iron' brake pads with Porterfields will improve braking, 
> as
> will removing the stock non-adjustable prop-valve. This invention of the 
> devil
> limits brake pressure to the two big calipers up front where arguably about
> 70% of the braking will be done.
> 
>>>It doesn't limit the pressure, it reduces it.   There's a difference.


>  Instead, it routs full pressure to the
> toy-sized rear calipers. By adding a gutted stock prop-valve (which is a 
> bolt-in
> conversion indistinguishable from totally-stock), you will get full pressure 
> to
> all 4 calipers. 
> 
>>>Define 'full' pressure.   You will certainly get EQUAL pressure to all 
four calipers.   That may or may not be a good thing, as the front and rear 
calipers are significantly different, and the braking requirements for the front 
and rear of the car are different also.


> The combination of the two makes for a significant upgrade to
> stock brakes. My experience indicates that for a mostly-stock Pantera that 
> is
> not raced, no proportioning valve (manual or automatic) is needed.
> 
>>>I can't argue that directly, as I have Wilwood brakes on my car now.   
However...
> 
> Rule of thumb on any brake mods: if you cannot lock up any tires in
> max-effort-panic-stops, you need more effective brakes. 
> 
>>>Very true.   The stock brakes should be very capable of locking up all 
four wheels, but in many cases they aren't due to long-term neglect, as well as 
poor pad choice by De Tomaso.


> If you CAN lock up tires, you
> need more traction from bigger tires- 
> 
>>>That's a joke of course--more brakes causes more tires causes yet more 
brakes in an endless circle, but eventually you have to settle on a given tire, 
and then your brakes should be able to lock them up (which is not the ultimate 
measure of brake effectiveness by the way).


> and which end locks first dictates
> whether you need to 'proportion' the brake forces (adding force to the end 
> not
> locking).
> 
>>>A-ha.   Therein lies the contradiction.   The factory determined that due 
to the different braking requirements and caliper styles, if equal pressure 
were applied to both the front and rear calipers, the fronts would lock 
prematurely, which effectively eliminates the rear brakes from meaningfully 
contributing to the stopping of the car.   The idea behind the factory proportioning 
valve is to reduce (not limit) brake pressure to the front brakes, which means 
that the rear brakes do more work than they would otherwise, for a given amount 
of pedal pressure.   Presuming they did their job correctly, this results in 
improved braking.

Jack's experience and description are of a car whose front brake calipers are 
suddenly made substantially more effective; this means that for a given 
amount of pedal pressure, there is more braking action sooner, and it 'feels' like 
the brakes are working better.   But in fact, in all likelihood the braking 
SYSTEM is actually performing worse.   

It would be interesting to do back-to-back testing of a car before and after 
this modification is performed.   I suspect that before, as long as the brake 
system is otherwise working correctly (i.e. no stuck pistons in the calipers, 
displaced shuttle valve, etc. etc.), then the front brakes would lock just 
slightly before the rears and the optimum stopping distance would be the result.  
 After the modification, the front brakes would become considerably more 
effective, and would lock up with less pedal effort, which on the surface would 
FEEL like an improvement, but due to the fact that the back brakes are now just 
along for the ride, the actual stopping distance would increase (which is 
bad).

I haven't had the opportunity to dial in my brakes fully yet; I bought a 
'ready-to-wear' brake kit from Pantera Performance Center.   Even with 
substantially stickier tires on the front, my front wheels lock up first (which is good). 
  What I don't know is, how well are the rears working?   I will probably 
introduce an adjustable proportioning valve in the front circuit, mimicking the 
factory's efforts to balance the braking on the car.   I will run tests and 
continue to reduce brake pressure to the front end, until I go too far and the 
rears lock up first, and then I will back up a few steps and call it good.

Oh, and as for the braided stainless steel lines, all the vendors carry them. 
  You shouldn't have to screw around with adapters etc; any quality vendor 
should be able to provide you with bolt-on brake lines that are appropriately 
plumbed at each end for a stock car with stock calipers.   If the one you call 
starts talking about adapters, hang up and shop elsewhere for this particular 
item.   Cost should be in the $100 range I think.

They are a very good idea.

Cheers!

Mike




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