Brakes: Part 1 - The rear rotors
It's been some time since I last made an entry into my Endless Corrado project. Soon after my update in October, my wife and I purchased a second house in the nearby mountains. My efforts have therefore been redirected on a number of projects, including refurbishing a house, rather than rebuilding my car. However, that does not mean the Corrado project is forgotten. As I drive up the windy mountain roads on my way to the new cabin, I often find myself imagining myself on the very same roads behind the wheel of my Yellow corrado. I can feel the tight handling, the positive feedback through the steering wheel and the roar of the G60 as it forces the thin high altitude air into the combustion chambers of the PG motor. It's the balance of this FWD
automobile that the automotive press praised in the late 1980s--some calling it the best handling front wheel drive automobile available. It is these same twisty mountain roads that makes ownership of this automobile worth the unreasonable investment that Corrado enthusiasts often heap upon these aging automobiles.
As most will agree, the Corrado has decent power, handles very well, and possessed formidible stopping power when necessary. All of these traits when balanced equally makes for an exciting driving experience. The corrado has all of these characteristics and performs them equally well. So I thought I would turn my efforts towards one of those essential traits--braking.
In my opinion, Braking is as (if not more) important than acceleration. The ability to decelerate effectively , especially under extreme driving conditions, increases control, improves safety, and enhances driver confidence. My particular model was manufactured in August of 1989 and was therefore one of the least complex of the Corrados released in the United States. Although all Corrados were equipped with four wheel disc brakes, 11" vented discs up front and 8.9" solid rotors in the rear, most were also equipped with Anti-lock Braking systems (ABS) My particular model was the more simplistic power assisted hydraulic system very similar to those found on MKII GTIs with the exception of the larger diameter rotors and calipers up front. No ABS.
For this entry, we will focus on the rear disc brakes only. Roughly 30% of braking takes place in the rear wheels and therefore most owners will service the front brakes 2 or 3 times before it becomes necessary to refresh the rears. That was my case and since this was an extensive refurbishment project, I thought I would upgrade the entire braking system.
In this world of hot hatchbacks, It is fashionable to enlarge the brakes with colorful aftermarket brake kits. However, in my opinion, the stock brakes are more than adequate for street driven automobiles. If one were to take their car to the track, then I would consider larger brakes can calipers. Larger after-market brakes are expensive and can add to unsprung weight negating some of the balance I mentioned earlier. The hardened metallic brake rotors have a substantial amount of weight and mass. It is this mass of the brake rotors that absorbs the heat generated by the friction of the pads. Theoretically, the larger the mass, the more heat energy that can be absorbed and dissipated. However, the larger mass also adds to unsprung weight making suspension duties handled by the shocks and springs more difficult and therefore less effective.
So I'll opt for maintaining the stock size but make enhancements in other areas.
The rear brake rotors are originally solid discs. There is no ventilation cast into the rotors. In addition, the rear wheel bearing races are pressed into the rear rotors. It is highly recommended to replace the rear bearings when replacing the rear rotors. One will also need the bearing cap, cotter pin, locking nut, and bearing grease which can usually be purchased as a kit.
I opted this time for PowerSlot rotors. This particular manufacturer uses Brembo Rotors which are German made and of very high quality. Brembo is the OEM manufacturer for many high performance European manufacturers. Powerslot then machines small slots into the rotors braking surface. The theory is that brake pad material under extreme heat expel gases which can act as a cushion between the pads and the rotor stopping surface. By slotting the surface, it allows a path for expelled gases to escape creating better stopping adhesion. It's probably functional on the track but in normal everyday street driving, it's likely overkill. BUT it is visually impressive!
In addition to the PowerSlot rotors, I also installed Steel Braided brake lines from Autotech. These steel braided hoses are lined with teflon and the steel braid jacket prevents any flexing under pressure. The result is a more positive and solid feeling brake pedal.
I chose Mintex Redbox pads which are good performance brake pad for street use. My experience is that they don't require a warm up like some other performance pads, do not wear down my rotors, and they leave little dust on the wheels during use.
I will not cover the step by step because anyone doing modifications to a Corrado should have a Bentley Manual which will detail everything from part numbers to torque specs. However, when installing PowerSlot rotors, the slots are directional and it is imperative that the slots are oriented in the correct direction. There is a left and a right rotor and they are stamped on the disc. See the [R] on the disc illustrated below. The left rotor will have an [L]
One suggestion: I ordered my rear rotors , rear bearings, and bearing cap kit from the same retailer. I requested the bearing races to be pressed into the rotors prior to delivery which they did free of charge. This can save you time and frustration--especially if you don't have a hydraulic press or a bearing installation kit in your arsenal of tools.
Lastly, in order to retract the pistons in the rear caliper, one will need a special tool. Keep in mind, the rear piston has to be compressed and rotated back into the caliper to accomodate the new pads and rotor. I used a brake tool purchased from my local auto parts store which costs around $5. This little universal brake tool is a cube and there are four tabs on one side that will match two notches in the VW rear brake piston. There are four tabs on the universal tool so I found the one that is the best fit and I ground the other two diagonal tabs off-- leaving just the two that I need. See illustration below.
I can now use this tool with a C-clamp to twist and compress the caliper until it is fully compressed. The brake tool is utilized with a 3/8" ratchet which insert into the square opening in the center.
The procedure is to first open the cap on the brake master cylinder to allow hydraulic fluid to flow back into the reservoir. Then back at the rear caliper, compress the piston lightly using the C clamp. Then with the tool inserted into the two notches in the piston-- turn the ratchet spinning the piston back into the caliper. Repeat this process little by little until the pistion is completely recessed back into its bore. You will now have enough clearance to fit the new pads into their place and reposition the caliper back onto the new rotor. Repeat on the other side.
Next time I'll detail the procedure on the front brakes.
Dedication: Many of the parts for my Corrado --including the parts above-- were acquired from Virtual World Parts at www.parts4vws.com
Mike Potter-- is knowledgeable and enthusiastic about VW/Audis and has always been a knowledgeable VW/Audi resource. Without his help, the Endless Corrado Project would have not progressed. Unfortunately, in 2010, the economy took its toll on Virtual World Parts and his business is no longer. The VW Community will miss Mike & Kristin Potter and Parts4VWs
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