[DeTomaso] Wilwood Brakes WTF????

Thu Apr 18 02:17:48 EDT 2013

I find this residual valve discussion interesting. Through last 15 years 
I've been into the hobby, I've seen it come up in several discussions 
and it's always the same. Some people are very strongly opposed to using 
any in disc brake systems unless the master is below calibers. Although 
the only real life case against it, that I've ever seen anyone report, 
is the one where somebody installed one in series with existing drum 
prop valve which has residual valve already, and got the brakes sticking.

I wonder where the strong opinions come from? Maybe it's not needed if 
everything comes together, but what is the big deal against? I'd really 
like to hear from someone who actually installed one and can trace pad 
wear or other bad behavior to it. Until that I'll personally treat this 
as "You should always eat your vegetables" type of discussion and feel 
sorry for anyone who dares to publicly confess using RPV with disc 
brakes with normal master location.

I actually bought RPV's for my mustang (with 4 wheel Baer discs and 
aftermarket distribution block), when I wanted to increase pedal ratio, 
but not have any extra pedal movement to be able to still heel and toe. 
Fiddling with pedal ratio (one pre-defined, easy to use, alternate 
setting for pedal ratio) I noticed that when you set up the pedal 
pushrod to give zero lash or minimal preload in the pedal, the vacuum 
booster actually provides a little residual pressure in the system. If 
you preload little too much with engine off and brakes not dragging, 
when the booster kicks in, you suddenly have drag. At least in my case. 
Perhaps the vacuum seal in my booster is less than perfect over time. 
The car had been standing for a long time when I made the initial 
adjustment.

Then I noticed that the higher pedal ratio still let the pedal too far 
down to mess my heel and toe and so I went back to old ratio and 
adjusted slightest preload without drag.

I did not come to think of checking if it was only front wheels 
dragging, as I have prop valve to the rears reducing pressure there. If 
that was the case, then maybe RPV in the rear circuit could have gained 
me little something...

-Janne

4/18/2013 3:45 AM, richard bosch kirjoitti:
> So what keeps the pistons from retracting too far?
> Just curious how it is designed without the valves.
> --- On Wed, 4/17/13, Tomas Gunnarsson <guson at home.se> wrote:
>
> From: Tomas Gunnarsson <guson at home.se>
> Subject: Re: [DeTomaso] Wilwood Brakes WTF????
> To: theemonkey at yahoo.com
> Cc: detomaso at poca.com
> Date: Wednesday, April 17, 2013, 2:08 PM
>
>
>
> No, I have disassembled both master cylinders and calipers down to bare castings and there are no valves.
>   
> Tomas
>
>
>
> <-----Ursprungligt Meddelande----->
>
> From: richard bosch [theemonkey at yahoo.com]
>
> Sent: 16/4/2013 10:52:14 PM
>
> To: Tomas Gunnarsson
>
> Cc: detomaso at poca.com
>
> Subject: Re: [DeTomaso] Wilwood Brakes WTF????
>
>
>
>
>
>
>
>
>
> It could be that only the American cars have the valves in the master cylinders.
>
>
>
> Maybe Europeans have them in the calipers or distribution block?
>
>
>
> They have to be somewhere in the brake system or else you have a delay in the brakes being applied as the pistons would have a much longer area to traverse before they contact the rotor.
>
>
>
>
>
>
>
>
>
>
> --- On Tue, 4/16/13, Tomas Gunnarsson <guson at home.se> wrote:
>
>
>
>
> From: Tomas Gunnarsson <guson at home.se>
>
> Subject: Re: [DeTomaso] Wilwood Brakes WTF????
>
> To: theemonkey at yahoo.com
>
> Cc: detomaso at poca.com
>
> Date: Tuesday, April 16, 2013, 6:06 AM
>
>
>
>
>
>
> Must be an American thing. Euro master cylinders I've come across have no valves built into them.
>   
> Tomas
>
>
>
> <-----Ursprungligt Meddelande----->
>
> From: richard bosch [theemonkey at yahoo.com]
>
> Sent: 16/4/2013 1:10:46 AM
>
> To: detomaso at poca.com
>
> Subject: Re: [DeTomaso] Wilwood Brakes WTF????
>
>
>
>
> Disc brakes require 2 psi residual pressure valves.Drum brakes have 10 psi. valves.
>
> Most master cylinders have them under the flare seat  where the brake lines are screwed in thats why you do not normally see them or think about them.
>
> Without the residual pressure the pistons retract much further in the caliper and there is a delay while the piston has to travel further before it contacts the rotor.Not good as seconds count in braking distance!
>
> Mike's valves are "add ons" because his master cylinder does not have any valves built in.His valve pressure is correct as the pads did not drag on the rotors before the pad wear/cocked pad happened.
>
> Just what i have learned from playing with lots of cars  :  )
>
> _______________________________________________
>
>
>
> Detomaso Forum Managed by POCA
>
>
>
> DeTomaso mailing list
>
> DeTomaso at poca.com
>
> http://poca.com/mailman/listinfo/detomaso
>
> _______________________________________________________________
>
> Annons: Skaffa Spray Mail du också - Gratis, enkelt och säkert!
>
>
>
> _______________________________________________________________
> Annons: Skaffa Spray Mail du också - Gratis, enkelt och säkert!
> _______________________________________________
>
> Detomaso Forum Managed by POCA
>
> DeTomaso mailing list
> DeTomaso at poca.com
> http://poca.com/mailman/listinfo/detomaso
>
>