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Brake Master Cylinder (Part 2) - obp Motorsport Tech Session

American Government Special Collections Reference Desk

Brake Master Cylinder (Part 2) - obp Motorsport Tech Session

Grant Loc
May 19, 2012

Hello, how are you today?

Ok lets do Part 2 about brake master cylinder sizes and basic info on Master Cylinders and getting great race brakes.

The general idea and rule is to be able to alter and modify the brakes so you can get the best brakes for your racing style, every one has a different race style so it is very important to be able to alter balance and force required to achieve the ultimate brake system that fits you specific needs. A great way to achieve this is to use a bias / balance controlled brake pedal system.

Using a small bore sized master cylinder will provide a harder pedal and ultimately will deliver a 25mm to 40mm movement before full lock up. The smaller the pedal movement the better, again this will be determined by condition of the hoses, pivot points, calipers etc.

The most common master cylinder sizes are .625 / .7 / .75. From our experience we have found that a good starting point to good brakes is .625 Front, .7 Rear and .75 or .7 on the Clutch.

Check the brake line pressure in each instance, you are looking for between 1100 psi - 1200 psi. If you are achieving this required pressure and the brakes are still not up to standard then you will need to check all the hard wear and hoses are in good working condition. If all the equipment is in good working order then you will need to increase the size of the caliper and rotors, this will improve the brake efficiency.

The object is to achieve the brakes full operation with 25mm pedal travel and delivering the target of 1100 psi - 1200 psi of brake line pressure being generated by the driver. This is all achieved my a correct combination of brake cylinder piston bore size, brake pedal ratio, correct fluid, no air in the lines, non-ballooning brake lines, minimum component wear anywhere in the braking system and the drivers ability to deliver the required force on the pedal consistently in race conditions. All this is not easy to achieve, but it is the aim.

The maximum brake line pressure ever likely to be realised is approximately 1400 psi - 1500 psi, and the driver will be a bit of a Hulk to reach these psi pressures.

If the brakes are still not up to the required stopping efficiency when all of the above specifications have been attained then you will be looking into upgrading the rotors, calipers and pads. Increasing the brake friction area will increase the brakes effectiveness.

I trust this has been an interesting and informative article for you.

Grant Loc has been involved with Motorsports for over 15 years and the Director of obp Ltd. obp Ltd is a major player in Manufacture and Supply of Quality Race Car Products and provides most of the leading Motorsport distributors all over the World. obp manufacture Race Pedal Boxes, Handbrakes, Alloy Dry Oil Sump Tanks, etc. www.obpltd.com

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