master cylinder size choice?? - TenTenths Motorsport Forum

Goran Malmberg

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Racer

Join Date: Mar

Stockholm Sweden

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Quote:

sihorton

Originally Posted by

Aft All

Also how do u choose the correct clutch master cylinder size?

Simon

You will get efficient and thoughtful service from MOTEC.

I suggest an total pedal to pad ratio of about 200:1 for a manual system. This means that if we have the front cylinders with a total piston area of mm^2 and a brake pedal ratio of 6:1 to become a master cylinder area of 300mm^2 quite right. Ratio = (/300) * 6.

The system is obviously heavy pedal and does not really fit street cars, about 50-75 kg pedal to lock the wheels. But gives a good braking feel.

The main problem concerns the rear brakes which may not be locked before the front wheels. Here we probably need a ratio of 100:1. To work out the details we need to know the car's weight, weight distribution, CGH, wheel base, tire sizes o rubber friction coefficient, all caliper piston areas, brake pads, disc dimensions and A Few more things like downforce and its distribution.

This is probably too complicated so I suggest 100:1 theory and then very careful braking tests and replace the master cylinder until you have found the right one. Brake balance bar must be at the center position all the time. You peel NOT use the balance bar to adjust the errors in the hydraulic relationship.

Myself I use 3/4" front master and 8x1,3/4 " caliper, 5/8"rear masts and 4x2" caliper. But this is a mid engine car that has 60% rear weight.

This I can write a book about, so you have to understand that this is rough guidelines.

kind regards.
Goran

Hi Simon.I suggest an total pedal to pad ratio of about 200:1 for a manual system. This means that if we have the front cylinders with a total piston area of mm^2 and a brake pedal ratio of 6:1 to become a master cylinder area of 300mm^2 quite right. Ratio = (/300) * 6.The system is obviously heavy pedal and does not really fit street cars, about 50-75 kg pedal to lock the wheels. But gives a good braking feel.The main problem concerns the rear brakes which may not be locked before the front wheels. Here we probably need a ratio of 100:1. To work out the details we need to know the car's weight, weight distribution, CGH, wheel base, tire sizes o rubber friction coefficient, all caliper piston areas, brake pads, disc dimensions and A Few more things like downforce and its distribution.This is probably too complicated so I suggest 100:1 theory and then very careful braking tests and replace the master cylinder until you have found the right one. Brake balance bar must be at the center position all the time. You peel NOT use the balance bar to adjust the errors in the hydraulic relationship.Myself I use 3/4" front master and 8x1,3/4 " caliper, 5/8"rear masts and 4x2" caliper. But this is a mid engine car that has 60% rear weight.This I can write a book about, so you have to understand that this is rough guidelines.kind regards.Goran

McLeod Hydraulic Throwout Bearing Conversion Kit

Hydraulic clutch throwout bearing conversion kits deliver smooth action, improved header clearance, and reduced free travel. Available for many popular applications, from Ford Model A to late-model muscle, they require a few modifications and work with stock and aftermarket transmissions. Where there&#;s no bolt-on option, there are still plenty of clutch master cylinders, hydraulic release bearings, and slave cylinders to accommodate most vehicles with a little ingenuity. Matching the right components will not only give you the best pedal feel, but also prevent clutch mechanism damage.

Let&#;s look at several key points for understanding proper pedal ratio, bore sizing, travel, and mounting angle.

Pedal ratio is the amount of leverage your clutch pedal exerts over the master cylinder. On average, clutch pedal ratios range from 5.0-7.0:1. To determine the pedal ratio, measure the pedal pad to the pivot, then measure from the master cylinder rod mount to the pivot and divide the second measurement into the first. The higher the ratio, the more leverage you will have over the clutch. This will decrease pedal effort and increase travel; the opposite will apply to lower pedal ratios.

Master cylinder bore size determines the amount of fluid that will be displaced as the clutch is depressed. With equal travel, a 7/8-inch master moves more fluid than a 3/4-inch master. While a larger-bore master cylinder displaces more fluid, it takes more pedal force to create the same pressure as a smaller-diameter bore.

Master cylinder travel is the distance the master cylinder piston can travel before it bottoms out. A pedal stop must be used to limit stroke to prevent clutch, release bearing, and transmission damage.

Mounting angle is critical to smooth operation and master cylinder longevity. Mount the master cylinder so the pushrod maintains a straight approach into the master cylinder throughout the pedal&#;s range of movement. Excessive angles can cause binding and premature wear; the exception to this would be a master cylinder that pivots on its mount like a Tilton 78-series.

Always follow master cylinder sizing recommendations for the hydraulic throwout bearing or slave cylinder. The goal is to have a balanced system that uses the majority of the master cylinder stroke with a pedal that comfortably disengages the clutch.

If you want to learn more, please visit our website Auto Clutch Cylinder Manufacturer.