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Brake System

Welcome back to the My Street Car project and Stage 2 of this build up where I will be concentrating on the braking system upgrade. If there was ever one down fall to our early Commodore models, it would have to be the vehicles braking system. For years Commodore drivers were screaming out for Bigger Brakes…!!! Yet, it wasn't until 1998 that Holden answered the call with the release of the all new VT model which featured an improved braking system including a twin piston front brake caliper, improved rear brake caliper and essentially a major overhaul as compared to previous models. The VT Commodore was a significant step forward and finally we had a vehicle that had stopping power and a solid foundation for further modification.

Whether you are driving a standard domestic vehicle or a high speed racing car, brakes are critical...!!! When it comes to vehicle safety systems, the brake system is at the top of the list.

I was very tempted to commence the build up with the brake system upgrade being Stage 1 of this project, simply as a means to strongly emphasis the extreme importance of the braking system on modified cars. It was only my eagerness to have a crack at the V6 engine and the fact that I knew the car would be limited to minimal driving until I commenced the brake upgrade that I elected to modify the engine first.

A critical element of this build up was SAFETY SAFETY SAFETY...!!! From the beginning, it was always my intension to improve the overall performance of My Street Car in every aspect with strong emphasis on under car systems.

If you are modifying your engine for more power, be sure to have a plan in place to match this power increase with a suitable performance brake upgrade.

Most modern brake systems are more than adequate in their performance for normal road use. However, problems start arising when a vehicle must stop from a high speed then do it continuously over and over again. It is during this aggressive adverse condition that the performance of a brake system can be truly measured.

All brake systems, being either disk or drum use friction to stop the vehicle. Friction is the resistance to sliding created when two surfaces are rubbed together. With a dick brake system, there is friction between the stationery brake pad and rotating brake disk (rotor) and with drum brakes, the friction is between the stationary brake shoe and rotating brake drum. Friction from the brakes creates heat. Technically, a moving vehicle is basically now an energy source. To slow a moving vehicle, this energy must be converted to another form. The brake system of the motor vehicle converts the energy from the moving vehicle to a heat energy via the friction created from the braking system.

The heat generated from continuous brake operation is a major concern in brake design and must be addressed with any performance brake modification. A specific brake system and impaticular brake friction material will have a maximum operating temperature. Once this temperature is reached, the brake system must have the opportunity to be cooled off to avoid dangerous brake operation and component failure. The consequences a driver will face with brakes that have exceeded there maximum operating temperature range is brake fade. Brake fade is loss of braking due to overheating. Brake fade will result in you requiring increased brake pedal force to stop your vehicle. If the brakes are not cooled at this point and you continue to drive with brakes exceeding this temperature threshold, you will eventually loose all braking power and if the brake fluid starts to boil off you will loose your brake pedal. Brake fade usually occurs at the worst possible time, such as braking heavily on a descending road with a heavy load (towing) or on some vehicles may even occur after a series of higher speed brake applications using only moderate brake force. Driving a vehicle that is experiencing brake fade is not a place you want to be and is a very dangerous situation.

To further explain the results of brake fade, I wish to share a real life experience with you. Several years ago I was towing my ski boat down a very long hill that had several hair pin turns that seemed to go on forever. At that time, I was driving a VN Commodore V6 with a 5 speed manual transmission. This particular hill was really steep and required constant braking in a low gear just to maintain safe cornering speeds. After a few minutes braking, I noticed excessive amounts of smoke starting to billow out from the front wheels. Shortly after this I found myself pushing harder and harder on the brake pedal only to find that I was rapidly running out of braking force. Whilst I still had a full pedal, the brakes simply no longer worked and I knew I was in trouble as I simply could not stop...!!! I only managed to escape from this dangerous situation by forcing the gearbox into first gear (Thank god it was a manual) and just holding my foot as hard as I could on the brake pedal whilst carefully applying the handbrake. Fortunately the road did start to straighten out and I was soon out of the danger zone. I certainly attracted plenty of attention as the car really did look like it was on fire with the amount of smoke these brakes were producing. This was a really scary experience that really rammed home the importance of good brakes.

This is just the very basic fundamentals of a braking system...!!!

For My Street Car I feel I have significantly enhanced the vehicles brake performance with just a simple upgrade program. In fact the upgrade was so quick and easy that I feel I am going to struggle to make much of a story out of it. However, the reality is that the brakes feel amazing and the upgrade was carried out at a very low cost.

Read on …!!!

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Photo 1: This photo displays the front brake components for VT-VY Commodore. Pictured is the twin piston brake caliper, 300 mm standard brake rotor, heavy duty brake pads and brake hose.

 

As mentioned earlier, the VT onwards Commodore featured a much improved braking system. Fortunately, us earlier model Commodore drivers are blessed with the fact that these components are interchangable onto early models with the retrofit basically just bolt on. I was attracted to this option simply because of the fact that these components are simple to fit, there is an abundant supply of these brake parts in the market place, the conversion will yield great results and the parts are very low cost. The main advantage of this conversion is the fitment of the twin piston front caliper. This brake caliper, its design, appearance and just shear size makes the early single piston caliper look sub standard by comparison. The main advantage of this brake caliper is its capacity to fit a larger brake pad with the twin piston feature allowing more uniform / even force being applied to the brake pad.

A significant disadvantage of the single piston caliper is its inability to apply uniform force across the brake pad due to brake pad deflection under severe operating loads. Whilst the centre section of the brake pad which is making contact with the brake piston receives full piston pressure, the pressure applied to the outer edges of the brake pad is greatly reduced due to deflection of the brake pad. This situation reduces the efficiency of the brake pad in a single piston caliper.

Photo's 2 & 3: These photo's display the completed fitment of the twin piston front brake caliper.

 

 

 

 

 

What a transformation...!!! This brake set up looks amazing with all this new gear just being a basic bolt up. The 300mm rotor is a floating type unit that fits straight up to the wheel hub and the brake caliper bolts directly to the existing brake caliper mounting points. The only modification required involved the cutting and grinding of the brake rotor dirt/dust shield. As the twin piston brake caliper is a much larger unit, it fouls with the existing shield in its original form. To allow fitment and prevent component fouling the shield must be reworked. To achieve this I simply bolted the brake caliper onto the wheel hub and then using a permanent marker traced over the shield using the caliper as a template. Once I had made my markings the brake caliper was removed and the dust shield was cut back using an angle grinder with the final finish and shaping carried out using files and a die grinder stone. This operation was a little messy and time consuming as the modification needs to be carried out on car as the shield is riveted onto the wheel hub. All that is needed is a littler patience and care. To complement this fitment, new brake hoses were also fitted. A mandatory requirement with this brake upgrade is you must have/or fit minium 15 inch diameter wheels to allow brake caliper running clearance from the inside of the wheel rim.

My brake pad selection was Bendix Heavy Duty. For some time now I have aligned myself with Bendix products as I feel their products have provided me with excellent quality as part of my workshop operation. Having said this, I also believe there are several good quality brake brands in the market place. I have always remained open minded to the use of any products and maintain the philosophy that I will use anything if it works well for a particular application. The Bendix Heavy Duty brake pad is a relatively new product that features a titanium strip that eliminates the need for brake pad run in. (a real workshop plus when your in a hurry). I am very impressed with the performance of this brake pad. I have recently been fitting this brake pad to several cars that come through the workshop, mainly targeting the more aggressive driver or customers who are regularly towing heavy loads. So far I have had no complaints and a real plus with this brake pad is that they work well cold. A common problem with many performance style brake pads I have fitted in the past relates to their poor braking performance at cold temperatures. I believe this is a safety hazard for a road going car and can be very dangerous for the unaware driver. There is nothing worse than pulling out of your driveway then hitting the brakes at the first corner only to find you have a hard pedal with no stopping power. (This experience will kick start your heart as you grip the steering wheel and attempt to push the brake pedal through the firewall). The Bendix Heavy Duty brake pads feature a maximum continous working temperature rating of 450 degrees Celsius. To conclude brake pad selection, there is no argument that there are several good quality brake pads and options available. Optimum brake pad selection will depend on specific vehicle operating requirements. I feel the Bedix Heavy Duty brake pad was suited to this application based on the intended vehicle usage once this project is completed and also consideration was given to value for money.

Photo 4: This photo displays the standard VS Commodore rear brake caliper set up.

 

The only modification carried out to the rear brakes included the fitment of Bendix Heavy Duty brake pads. The brake calipers were assessed for condition with the only service operation required being the cleaning and lubricating of the brake caliper guide pins.

All that was left to do at this point was bleed the brakes. As part of this operation I bleed off approximately 300-400 ml of brake fluid from each brake caliper to ensure the brake hydraulic system was completely flushed from old brake fluid.

Do not under estimate the importance of brake fluid. Brake fluid doesn't last for ever...!!! More and more now vehicle manufactures are placing strong emphasis on brake fluid changing. In fact every vehicle manufactures service book that I know of makes clear and concise instructions for the changing of brake fluid at intervals not exceeding 24 month's (2 years). This fact alone confirms the importance of brake fluid service and maintenance. The most critical property of brake fluid is its ability to resist boiling at high temperatures. However, the quality of brake fluid soon deteriorates due to moisture absorption. Old brake fluid or fluid that has absorbed high moisture content will have a considerably lower boiling point. On road, this could result in disaster as brake fluid that has boiled creates small gas bubbles within the brake pipes. Because these gas bubbles are compressible, this will result in a low or spongy brake pedal.

Well, that’s it...!!! The brake upgrade is complete. On road, the car feels great and the brake performance strong which really does provide a greater level of driver confidence. More importantly, My Street Car now has the capacity to handle more punishment ensuring greater braking power and efficiency during continuous high brake loads and operating temperatures.

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Conclusion notes:

  1. The brake parts for My Street Car were purchased from Hoppers Stoppers in Melbourne. I found Hoppers Stoppers whilst surfing the internet for brake parts and information as part of the project research. I was very impressed with their web site and the huge range of brake upgrades available for many vehicles and in particular all Holden Commodore models. This web site is truly worth a look if you are sourcing brake information, upgrade components or complete brake kits at very reasonable prices.

    Hoppers Stoppers are at:
    Web: www.hoppers.com.au
    Address: 9 Nevada Court, Hoppers Crossing, Victoria 3029
    Ph: 03 9748 6950
  2. Hoppers Stoppers do advise as part of their fitting instructions that if a firmer brake pedal is desired then a VT 1 inch / 1 1⁄4 stepped bore master cylinder may be adapted to the VS booster. When fitting the VT style twin piston caliper onto earlier Commodores it is strongly recommended that a 1 inch bore master cylinder be fitted to ensure a firm high brake pedal is achieved. Consult Hoppers Stoppers for further information
  3. A personal observation I have made during this project whilst assessing various cars and components is a variation in the brake pipe flare where the flexible brake caliper hose connects to the fixed steel pipe connection on the vehicles inner guard. I have found some steel pipes feature a double flare (Which I think is the most common) and also other applications that feature a raised dome type flare. The brake hoses WILL NOT interchange. At the time of this report preparation I do not have the support information to provide specific vehicle model to brake pipe identification data. Just be sure to check and confirm correct brake pipe connection relationship before fitment.
  4. Whilst I understand that this brake upgrade is minor in comparison to the unlimited brake options and components we have been blessed with in the after market, I do feel this upgrade is credible for consideration as it will work, provide a worthy increase in braking power and safety and is very low cost. Considering we have the weight saving of a V6 engine and a limited budget, this conversion fitted the build criteria for My Street Car perfect in every as aspect.
  5. My recommendation for any persons contemplating a brake performance upgrade is just consider your options first, do some forward planning taking into consideration the vehicles intended usage and your desired outcome.

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Hear are some helpful hints:

  • Select a brake system that will provide the greatest coefficient of friction for the intended application. Bigger brakes and greater the braking surface area is usually best.
  • With brake pad selection, my recommendation is just give some thought to the intended vehicle usage and select a brake pad type based on that information. The brake pads and associated hard ware must have the capacity to quickly absorb and dissipate heat energy with the friction material (brake pad) remaining stable at expected operating temperatures. Modifications to increase brake cooling capacity for racing or severe operating conditions should also be considered. Eg vented, cross drilled and slotted rotors, ducting to increase air flow cooling capacity etc
  • Use good quality and appropriate grade / specification brake fluid. Ensure brake master cylinder caps and seals are in good condition for the prevention of moisture absorption and foreign particle contamination. Due to brake fluids rapid moisture absorption characteristics it is strongly recommended that only new brake fluid from an unopened container be used. (The half used brake fluid bottle that has been sitting on the garage shelf for 12months........ Get rid off it...!!!)

The internet is a great source for information with most brake manufactures hosting very detailed and informative sites relating to their products including related technical data.

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Stage 1
Engine & drive line

Stage 2
Brakes

Stage 3
Steering & suspension

Stage 4
Wheels, body & accessories