This article was first published in 2001.
You'll often hear blokes around the pits of club days saying "Brakes? They just make you go slower!"
Well, that may be true but in the complete performance equation, brakes play a big part. And with Australia's own modified Commodores and Falcon becoming more and more powerful with three, four and five hundred horsepower(!) not uncommon on streetcars, brakes become pretty damn important!
In the late 1980s, HSV went looking for a better braking solution for its high-performance 200kW road cars. Holden had introduced a four-wheel disc brake system with 290mm front rotors and a reasonably stiff sliding caliper on the VL Turbo (and later, the V8). However, HSV deemed this braking system not up to the standards it required for its premium SV5000 and VN Group A models.
The result was an exclusive brake package whose main feature was larger front rotors and new calipers with greater pad area than the Holden system. More recently, Ford's performance partner Tickford adopted an almost identical system; first for its EL GT Falcon, and then for its premium AU T-Series cars. Both brands' packages offer braking benefits by using a larger-diameter rotor (330mm vs. 290mm) and a larger brake pad located by a larger, stiffer caliper which features two pistons, rather than the standard single piston.
Fade occurs when the pad material gets so hot it begins to degrade. This reduces brake effectiveness by over-heating the friction material to the point where it simply doesn't work as well as it should. Also, escaping gasses (usually from the burning of the binding glue which holds the friction compounds together) actually cause the pad to 'aquaplane' or 'skate' over the surface of the disc, like an ice cube or a pat of butter being fried in a saucepan.
With greater initial retardation (thanks to greater pad contact and more leverage due to the larger diameter of the rotor) and greater resistance to the usual underpants-filling brake fade (more brake material to soak up and shed heat), these HSV- and Tickford-style braking packages make a great upgrade for a fast road/occasional track use Commodore or Falcon.
Brakeboyz dealers Australia-wide offer these brake packages for just about every street car you can name - here's a look at what's involved in fitting big brakes to a Commodore.
The new 330mm rotors dwarf the original units. Not only are they larger in diameter, they're thicker, too. More material allows more heat energy to be absorbed before fade sets in. Better cooling (through greater internal surface area) allows the rotor to ultimately shed heat quicker, too.
Same deal with the calipers. The new caliper has a larger pad area (more bite) and is pressed upon by two, smaller pistons compared with the original single large piston.
This two-point contact spreads the load over a wider area, which reduces pad flexing (increasing 'bite') and gives a better-feeling brake pedal.
A new, longer brake line is also required.
Fitting the Discs
This V8 VP Calais had been previously upgraded with DBA's excellent cross-drilled and slotted rotors and Bendix Ultimate pads which had improved things over standard immensely. But luxo-barge weight, modified V8 engine and 50,000km of um, enthusiastic driving (plus towing) had taken its toll. Time for some big ones! The first step is to put the car on stands and remove the wheels.
It's not essential but it makes for a less messy job if the brake line is clamped before removing the original components. The clamp stops brake fluid leaking everywhere when the caliper is removed and its hydraulic line disconnected.
The two bolts holding the original caliper in place are removed and the caliper released from its hydraulic line. The grease cap is removed from the hub and the nut holding the wheel bearings removed. On later models (VR onwards) the disc is 'hubless'; in other words, it locates over a hub which contains sealed-for-life bearings -the disc is removable without the need to repack the wheel bearings.
With the old disc rotor removed, the original backing plate (why do cars have these?!) is removed. For good - it won't be going back on! Three bolts locate it to the strut. Now both backing plates, and their six bolts, are located in the bin...
The new slotted 330mm rotors are given a clean with thinners to remove any grease or rust preventative that may be present before the wheel bearings are repacked and dropped into place. This set of bearings, with 50,000km on board (they were renewed when the last set of rotors went on) were inspected and found to be suitable for repacking with grease and reinstallation.
The calipers originally used on the Holden Commodore and Ford Falcon use a single-piston caliper which is located to its mount via rubber-shrouded pins. The pins allow the caliper to compensate for pad wear by moving in relation to the edge of the disc. These high-performance pad-guided calipers actually use the brake pads' backing plates to hold the caliper over the disc. The caliper 'floats' over the pad. Benefits? There are no pins to lubricate (or seize if not lubed!); easier manufacture, less risk of brake noise/squeal and easier pad replacement.
Then it's back onto the stub (with the grease seal in place, of course) outer bearings in (after repacking with grease) tightening and pinning.
Final rotor installation step is to replace the grease cap.
Using a big socket and a hammer isn't a bad idea to ram the cap home square.
Fitting the Calipers
Attention now moves to the calipers. The PBR twin-piston jobbies have a mounting cradle with two mounting bolt holes; however for many cars (such as Commodores) another adapter bracket must be used to mount the caliper to the strut. Brakeboyz supplies brackets to suit many stove-hot street cars.
With the caliper mounted to its adapter bracket, the caliper cradle assembly is bolted to the strut using the original mounting bolts. These must be tightened to specifications: tight-as, then a bit more.... A new, longer brake line is also required. Gavsport makes these on-site and of course includes them in the installation.
Then the caliper, loaded with pads, is itself loaded onto its cradle. The pad-guided design (see breakout) of the PBR twin-piston calipers means the pads and caliper are 'dropped on' to the cradle assembly as one unit and a single pin locates both pads and caliper. Put another way, future pad replacement is just a matter of removing the pin, lifting off the caliper and allowing the old pads to simply drop out of the caliper.
Final assembly step is to bleed the brakes. Gavsport did it the easy way with an air-sucker bleeder; if you're at home by yourself the trick is to fill your master cylinder to the top with brake fluid; crack open the bleeder nipples slightly, put some newspaper on the floor (to soak up any brake fluid) and leave for several hours. Gravity does the rest... With evidence of fluid dribbling from the bleeder nipples, simply tighten them up and you're done.
GavSport 02 9673 0988 for info on all BrakeBoyz conversions
The slots in the DBA-manufactured discs improve braking performance in two ways: 1) The slots form an escape path (to the edge of the disc) for gasses which may be released by an almost-overheated brake pad, eliminating the 'fried ice-cube' effect and 2) the edge of the slots works like a knife to constantly clean and 'dress' the pad, ensuring a fresh friction surface is always present. One downside is reduced pad life; however this is usually of little concern to a performance enthusiast. The standard-sized rotors fitted to the VP shown in this article 'ate' three sets of pads in 50,000km - less than one set of pads per year.