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Author Topic:   Brakes
chevelle
Dirt Full Roller

Total posts: 71
posted July 23, 2003 08:13 PM  
I was talking to the tech man at the track I am going to run next year, said they were going to crack down on brakes not working properly. He said to remove the proportioning valve and run straight lines. He said this would give more even braking to all four wheels. I thought the purpose of the valve was to delay braking to the front to avoid nose diving, because discs have more stopping power than drums. Also will I need to run residual pressure valves. Our rules call for stock brakes, master cylinder, etc.
Thanks

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 23, 2003 10:49 PM  
According to my handy dandy repair manual,THE METERING VALVE LIMITS PRESSURE TO THE FRONT BRAKES UNTIL A PRE SET PRESSURE IS REACHED AND THE REAR BRAKES ARE APPLIED.

dilbert
Dirt Full Roller

Total posts: 38
posted July 24, 2003 11:29 PM  
I think even stock 4 disc systems will have a proportioner. I always thought it was because the car gets lighter in the rear when brakes are applied, therefore doesn't need as much pressure. That's also why they put ABS on the rear of most pickups now days.

dragonfly
Dirt Roller

Total posts: 10
posted July 25, 2003 08:51 AM  
we run a stock master cylinder off of a 79 olds gutlass with no power booster or proportion valve, just a line straight to the rear and attach it to the splitter in the rear , and run one off the other side to the front with a tee in the middle to split it off. i also run a shut off valve to my right front brake, .,

hobby39
Dirt Maniac

Total posts: 112
posted July 25, 2003 03:17 PM  
I run a manual brake on a 77 nova, no porpotional valve and get smooth even brakes. I've had no probles at all. I didn't remove the valve the car was already stripped and didn't have one, like the original post my tech guy suggested not replacing it so i didn't. On a previous car i had the valve and don't notice any major differance. So i wouldn't remove it and create the extra work if everything was intact personally. Just my 2 cents.

Hutch5375
Dirt Maniac

Total posts: 123
posted July 25, 2003 08:44 PM  
Approximately 75% of the car's braking is done with the front. This is achieved by the prop. valve. In a dirt more brake is preferable, and removing the prop. valve is an easy way to accomplish this. Another way is to flip the lines connected to the master cylinder, that in effect changes the work done by the rear drums.

SLEEPY GOMEZ
Dirt Freak

Total posts: 295
posted July 25, 2003 11:01 PM  
With your rules, tie the front and rear lines together with fittings. This will assure equal pressure to all four wheels. Because the drum rears are self energizing you will get more braking on the rear which is what you want. Discs need more pressure to achieve the same braking effect. This is not always a perfect proportioning but it is fairly close. You must use both lines (tied together) of a two line master cylinder or one master cylinder chamber will empty and the other overflow. A balance bar with dual master cylinders is the best way but rules and pocketbook don't always agree. SLEEPY

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