Stopping distance ? ? ?
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Post Fiend
Joined: Jan 2003
Posts: 10,323
Likes: 2
From: Montana Territory
Stopping distance ? ? ?
Alright, I just went to rear disk brakes on my 79 2wd F150. I didn't have the chance to test the stopping distance when I had drum brakes, but they weren't working correctly anyway.
So I tried to be unbiassed in the stopping test, my rear brake pressure is completely adjustable from 20-800 PSI, the manual recommended starting at 50%, I ended up with an acceptable stopping distance and rear brake lockup at about 60% of the metering valves setting.
I found a big empty parking lot and started at one light pole, and hit the skids when I got to a white painted line. That ended up being about 50 MPH, and the stopping distance I paced off at 24 paces, almost 75 feet. I didn't jam the brakes, I tried to stop normally. I imagine that I could try the test again and really just get on the brakes, but I wanted a real world test.
I can tell that the rear disks stop better than the old drums did (they were the factory 1979 drums and shoes, still stamped FoMoCo.
So I tried to be unbiassed in the stopping test, my rear brake pressure is completely adjustable from 20-800 PSI, the manual recommended starting at 50%, I ended up with an acceptable stopping distance and rear brake lockup at about 60% of the metering valves setting.
I found a big empty parking lot and started at one light pole, and hit the skids when I got to a white painted line. That ended up being about 50 MPH, and the stopping distance I paced off at 24 paces, almost 75 feet. I didn't jam the brakes, I tried to stop normally. I imagine that I could try the test again and really just get on the brakes, but I wanted a real world test.
I can tell that the rear disks stop better than the old drums did (they were the factory 1979 drums and shoes, still stamped FoMoCo.
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Post Fiend
Joined: Jan 2003
Posts: 10,323
Likes: 2
From: Montana Territory
I made a white mark on the body and **** so I could go back to the original setting, and had thought about being able to turn the rear brakes down in the winter, but turning them up whenever I haul a big load will be something to try.
What did you use for a setup?
I'm using GM calipers, re drilled GM 4wd truck front rotors, and custom brackets with Jegs proportioning valve.
What did you use for a setup?
I'm using GM calipers, re drilled GM 4wd truck front rotors, and custom brackets with Jegs proportioning valve.
More Turbo
Joined: Apr 2007
Posts: 614
Likes: 92
Instead of readjusting your PPV with every change in loads you might try finding a valve that was on an 88 E350 I had,It had levers from the body cross member to a valve in rear brake line mounted on the axle tube.As it was loaded the levers compressed and turned the valve to allow more pressure to the rear brakes.
Freshman User
Joined: May 2007
Posts: 43
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Matt, I did the exact same setup as you. Same proportion valve and everything. I bought mine as a kit that came with loaded calipers, rubber lines, rotors, brackets, and hardware. The price was good and the parts and service is great. Got it from a shop in eBay called Hard On/Off Road.
My F250 had the single piston calipers and light duty front end. I ended up swapping that out for the heavy duty setup off an F350 and got new dual piston calipers. I also upgraded to the 8" dual diaphram vacuum brake booster and the 1 1/4" bore master cylinder. I got rid of the factory proportion valve since it has a front brake delay built in it. Took a bit of work to custom bend all the lines, but the line locks work better than I expected and the system is fabulous now. In the future, I do plan to upgrade to a hydroboost unit for top notch performance.
Here's some pictures of the system. No laughing at my truck.
Rear Disc Setup:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/FinishedDiscConversion3.jpg
Hydraulic Lines From Master Cylinder to In-Cab Controls Under the Dash:
http://i147.photobucket.com/albums/r...cPlumbing1.jpg
Hydraulic Lines in the Engine Bay:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/BrakeHydraulicPlumbing2.jpg
Closeup of In-Cab Controls:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/CabBrakeControlsLabeled.jpg
My F250 had the single piston calipers and light duty front end. I ended up swapping that out for the heavy duty setup off an F350 and got new dual piston calipers. I also upgraded to the 8" dual diaphram vacuum brake booster and the 1 1/4" bore master cylinder. I got rid of the factory proportion valve since it has a front brake delay built in it. Took a bit of work to custom bend all the lines, but the line locks work better than I expected and the system is fabulous now. In the future, I do plan to upgrade to a hydroboost unit for top notch performance.
Here's some pictures of the system. No laughing at my truck.
Rear Disc Setup:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/FinishedDiscConversion3.jpg
Hydraulic Lines From Master Cylinder to In-Cab Controls Under the Dash:
http://i147.photobucket.com/albums/r...cPlumbing1.jpg
Hydraulic Lines in the Engine Bay:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/BrakeHydraulicPlumbing2.jpg
Closeup of In-Cab Controls:
http://i147.photobucket.com/albums/r320/etachell/76%20Ford%20F250/Four%20Wheel%20Disc%20Brakes/CabBrakeControlsLabeled.jpg
Last edited by etachell; Sep 26, 2007 at 09:09 PM.
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