[DeTomaso] removing second set of stock rear brake calipers?

Julian Kift julian_kift at hotmail.com
Sun Mar 7 15:32:08 EST 2010


IMHO the necessity for the proportioning valve depends on your aftermarket master cylinder and the volume ratios front to rear (assuming you have a tandem M/C). There are spreasheets available on the web that calculate various aspects of the braking system; recommended M/C bore size and front to rear braking bias, based upon vehicle weight, C of G, wheel rolling radius (tire width doesn't come into it), disc size, pad contact area etc. I would recommend anyone upgrading or modifying brakes to obtain such a spreadsheet for guidance.

 

Most modern braking systems have the proportioning valve in the rear line, but as said if you have far more front than rear that's not going to do much good.

 

Julian
 
> From: guson at home.se
> To: pantdino at aol.com; detomaso at realbig.com
> Date: Sun, 7 Mar 2010 19:38:29 +0100
> Subject: Re: [DeTomaso] removing second set of stock rear brake calipers?
> 
> The stock prop valve is there to prevent premature front wheel lockup. With
> dual rears it may not be necessary. If you remove the extra set the valve
> should go in again. That said, the dual calipers are not likely the cause of
> your drag. I have dual calipers per side (one stock, one other) on my car
> and the drag is not notably different from one caliper per side. Your drag
> should go away with a general overhaul.
> 
> Tomas
> 
> -----Original Message-----
> From: detomaso-bounces at realbig.com
> [mailto:detomaso-bounces at realbig.com]On Behalf Of pantdino at aol.com
> Sent: den 7 mars 2010 19:11
> To: detomaso at realbig.com
> Subject: [DeTomaso] removing second set of stock rear brake calipers?
> 
> 
> When I got my car 20 yrs ago the PO had installed a second stock caliper on
> each rear wheel. I suspect as a result the car has always had more brake pad
> drag, evidenced by resistance to rotating the wheel by hand or pushing the
> car. (The rotors are not warped-- the resistance is steady.)
> I believe the cars came with a brake proportioning valve, which was removed
> when the aftermarket (GM I think) master cylinder was installed. (Again, by
> the PO). My understanding is that said proportioning valves are to prevent
> rear wheel lockup.
> I would like to remove the redundant rear calipers to eliminate the extra
> drag, and my question is whether I have to reinstall a proportioning valve
> if I do that.
> I am running 285/40-17 and front 215/45-17 front tires, Goodyear Eagle F1.
> Looking at that puny rear pad I find it hard to believe that it will lock up
> that wide tire before the larger front pads will lock up the much narrower
> front tire.
> So I'm thinking removing the extra rear caliper will not require a
> proportioning valve.
> 
> I'll disassemble the calipers also to check their condition after 20 yrs of
> silicone fluid use.
> 
> Jim Oddie
> 
> 
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