Brakes

[Doug Gould]

Brakes 101

Brake pad area has nothing to do with stopping power. Braking force = friction co-efficient times applied force.

Increased braking force needs a bigger lever arm (ie bigger diamter discs), higher friction co-refficient pads, and / or higher clamping pressure (bigger caliper pistons, smaller master cylinder or push harder). I am using rear pads from a Nissan GTR on the front, which are the same as the Alfa pads, but not as deep which theoretically gives greater braking force and some cost to pad life.

Nearly all the enegry from a stop goes into the brake discs as heat. The bigger the mass of the brake disc the more capacity the system has for braking. Getting heat out of the discs prepares them for the next stop, so heavier, vented rotors are better. Open spokey wheels help and so does ducting.

Alan is correct about caliper flex, but my pads wear evenly, so I don't care. I'm one of the few who stick to road tyres and my experience has been that when I ran Ferodo DS3000 pads I could lock a front wheel at any time at any speed. So I reckon there is enough stopping power available in the standard  GTV6 system unless you are in Allan, or Robin or Victor & Mary's league.

I have proper ducting for the front, vented rotors at the rear, use Motul DOT3 fluid (I think DOT3 gives better feel and less caliper drag than DOT4 or DOT5), Endless type R pads on the front and Pagid on the rear. The car has more braking than I have willpower, but my next project is better coling for the rear. I get through a club sprint with as good a pedal at the end as the start, but the pedal started to get low in my stint at the Malalla 6 hour, so cooling the rears is going to get more attention.

Doug

[Victor Lee]

Hi Andrew,

They are AP Racing 4 pot calipers on 330mm vented rotors.  You may recall that I had the Group A double caliper set-up.  At the time it was going to cost about $700 each for new rotors (old ones worn out...ran them for 8 years!) because they were some unique size.  Also the roll center mod had been done but not the extended stub axle mod done (Hugh would not let me modify the existing ones..got some Group A historical value).  So bit the bullet and changed the entire front end.

Result?  Bloody fantastic!  Still need a bit of fine tuning with the brake bias...the back brakes just seem to be locking up.  The brakes felt as good on Sunday afternoon (minus engine power obviously) as they did Saturday morning.  They've got lot more "feel" than the old set up, not forgeting I'm using a pedal box and therefore no power-assistance.

This should keep us out of trouble for next few years! 

[BradGTV]

Hi Guys,
thanks for all your replys!
this is all very helpful information,

what model or year volvo does the 4 pot brakes come from?
and what mods are required to fit them?

cheers brad

[alfagtv152]

Hi Brad,
I believe mine came from something like a 1986 Volvo 264,just be sure they come from vented discs and are Girlock not ATE.The only mod for the calliper is to turn it from 2 input lines to 1,you can do this by drilling the calliper internally to common the inputs and plugging one threaded hole,you will need to change the nut on the end of the alfa pipe to suit the Volvo calliper.Alternatively you can use a little brass block to put the 2 Volvo lines into and the one Alfa pipe as I did(see earlier pictures).The calliper bolts straight on to the standard upright.
For the the disc you have 3 choices I know of,#1 is use the gtv6 disc and redrill it 4 stud but you will waste the top 10mm or so of the pad.#2 is use the Volvo disc and machine a little off the outside of your hub until it fits inside the Volvo disc then redrill 4x98mm pcd and use the wheel to hold the disc on.
#3 requires a bit more machineing,use a 164 disc,redrill it 4x98 and bore the center out to suit the hub,then machine a spacer 9mm thick(i think) off the front of some old 4 stud discs,Put the studs through the 164 disc then the spacer and then the hub to give the correct offset.
You will probably have to run 15 inch wheels after.
Cheers
Andrew

[BradGTV]

thanks andrew,

i will go down to u-pull-it and see what volvos thay have,
im intrested in the volvo calliper with the volvo disc,
my mate has a small engineering shop so machining shouldnt be a problem.
also was the brass brake line adaptor fabricated or off another car?
i already run 15 inch v4 simmons so they should fit?
cheers, brad,

[alfagtv152]

Hi Brad,
I bought the brass T and all the necessary fittings from Auto Brake services and they made up my pipes for the calliper and changed the nut on the Alfa brake pipe.
Cheers
Andrew

[BradGTV]

hi guys,
finally my brakes have been drilled, machined and are ready to go,
i was lucky that the volvo i got the brakes off was sitting next to a bmw at u pull it,
bmws have a t-piece at the rear that takes volvo pipe and alfa pipe,
so do not need to get them made or adapted to the alfa pipes ect.
cheers for ur help andrew
brad

[BradGTV]

some more,
this is of the t-piece - alfa pipe and volvo pipes.

[BradGTV]

and all the fittings and pipes for the the volvo 4 pot brakes,
i tried fitting them on my parts donor car and just like andrew said they fit straight up!
this is a great mod and is highly recomended,
in background you can see my v4 simmons, they have just been pulled apart and restored (new zinc plated SHS with new nylock nuts and dad painted them in 2-pac metalic grey) and should look sweet
cheers, brad

[alfagtv152]

Hi Brad,
Dont you love it when it all comes together,good work.
Cheers
Andrew

[MD]

Brad,

If that's a Volvo rotor you are using, what diameter is it please?

[BradGTV]

hi MD,
the diameter of the volvo disk is 260mm,
cheers, brad

[MD]

Thank you.