Rear Commodore Disc Brake conversions
If it wasn’t good enough to have disc brakes added to the front of your EJ/ EH, then consider this. Disc brakes on the rear! It may not sound like your cup of tea, but to most modifiers it is essential. Nothing makes people want to look under your car more than when you say it has four wheel discs. The stopping advantages are tremendous. Virtually say goodbye to brake fade, adjusting drums, changing shoes and no handbrake in reverse.
First of all you will need complete rear brake assemblies off a VN Commodore. You will need everything, caliper mounts, backing plates, calipers, slide brackets, rotors and handbrake cable. You will also need a VH40 or VH24 Brake booster if you plan on running a second booster for the rear. If you are not running a tandem brake system, then you will also have to convert to this. You cannot legally run four wheel discs on a single system. It would be ludicrous to do so. If you need it done, and it is very tricky, I suggest you speak to Alex at The Brake Shop Melbourne Mob. 0408 12 1964.
You can do most of the work, and the assembly yourself, but you will possibly have to get an engineer or fitter and turner to make up a couple of small components for you. The components that you need made up, first of all are the pre-load retainers for the axle bearings. Remembering that the caliper mounting plate is thicker than the original drum backing plate, you will need to get a spacer ring made up to compensate for this difference. It goes between the bolt-on plate on your axle and your wheel bearing, and creats the same pressure that your original bolt-on plate supplied. The other component is two rings that go on the hub at the end of your axles to allow for the larger diameter of the hub hole in the Commodore disc rotor. It needs to fit solidly on the end of the axle, by either pressing it on, or heat shrinking. It must then fit very snugly inside the rotors.
if your car is lower than standard height, you may have some clearance problems with your calipers near the back chassis rails. If this is so, all you need to do is do a dummy fit, and locate the area that the calipers would hit. Then you need to make a small box section that travels about 20mm in to the chassis rail, 60mm long and 60 mm high. It is not as painful as it may sound, and with a dummy fit, and a few hours , you will have it worked out. The boxed section can even be pop riveted in, as it is not cut into a sructual part of the vehicle.
The handbrake cable will have to be modified. You will need to supply your original EH cable, and your Commodore cable to Alex from The Brake Shop, and he will modify the assembly as required. It is then a case of making sure all components are in serviceable condition. If in doubt, get your calipers overhauled or new rotors or new brake pads if required. Use only quality rotors, not Taiwanese units. If using cross drilled rotors, you must use standard pads, not metal or race pads. Last bit is to get the new brake lines made up. If you make a template with some wire, straighten it out and take it to a brake shop they will make them for you. Make sure, and it is very important that you tell them it is going from EH body to Commodore calipers. If you want to make sure, take your old lines and the calipers with you.
You should be ready for assembly now. Get a friend to help you with bleeding the brakes. You may wish to consider coverting to silicon brake fluid if you whole system is empty and rebuilt. It is about $50 a litre, but it does’nt eat through paint.
The approximate cost of the job. Second hand parts $200-$250, new rotors $200 pr, new pads $40, rebuild calipers $40 ea, handbrake cable $80, brake lines $40, Brake fluid $50, box sections by custom panel beater $200-$300, box sections by friend $slab, retainer rings x4 $60-$200 (ring around), convert master to tandem brakes $200-$600, engineers report $250-$400. So you can see it may cost as little as $400 not including an engineers report all the way up to a staggering $2000. I am being realistic here, as it all depends on how good, safe or legal you want your conversion to be. I support the use of automotive engineers in all modifications. They are there to make sure the conversion is above all safe and legal.