Frankenstein - Jug Jr.

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Forget Regrets

SiCCMADE
Dec 18, 2010
3,468
83
48
Santa Ana
Question for you guys. When im going through a whoop section then go to flat, i have to pump the brakes. Driving on street is fine but sometimes if the truck idles for a bit in drive then go to drive it gets soft again. I have wilwoods on all 4 corners, not leaking any fluid (anymore), and running stock master/ booster. It was suggested to me by a friend that i need to run a wilwood master cylinder. Is it a pressure issue due to having a total of 16 pistons stopping the truck?

This is all from todays experience in barstow. Oyherwise the truck did really good.


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Do Dah

Senior Member
May 13, 2012
375
212
43
Question for you guys. When im going through a whoop section then go to flat, i have to pump the brakes. Driving on street is fine but sometimes if the truck idles for a bit in drive then go to drive it gets soft again. I have wilwoods on all 4 corners, not leaking any fluid (anymore), and running stock master/ booster. It was suggested to me by a friend that i need to run a wilwood master cylinder. Is it a pressure issue due to having a total of 16 pistons stopping the truck?

This is all from todays experience in barstow. Oyherwise the truck did really good.


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Combination of flanged axles and solid mounted calipers.
The axle flange flexes and pushes the caliper piston away from the rotor.
You can try a 2lb residual valve on the rear brake line to keep some pressure in the line.
 
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84projectford

Senior Member
Sep 8, 2010
2,160
1,927
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Phoenix Az
Do you have a lot of pedal travel to lock up the brakes even when the brakes work correctly?

If the master is too small, the brakes will work very easily but requires far more pedal travel. It also means (like do dah said) that when you have axle flex and solid calipers, it requires even more pedal travel to now fill and tighten up the pads before braking starts as the rotor pushed the pistons back in a bit.

You need a larger master but the residual valves might help mitigate the issue for now.
 

Forget Regrets

SiCCMADE
Dec 18, 2010
3,468
83
48
Santa Ana
Combination of flanged axles and solid mounted calipers.
The axle flange flexes and pushes the caliper piston away from the rotor.
You can try a 2lb residual valve on the rear brake line to keep some pressure in the line.
Would having a portioning valve help with this; that i have.


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Forget Regrets

SiCCMADE
Dec 18, 2010
3,468
83
48
Santa Ana
Do you have a lot of pedal travel to lock up the brakes even when the brakes work correctly?

If the master is too small, the brakes will work very easily but requires far more pedal travel. It also means (like do dah said) that when you have axle flex and solid calipers, it requires even more pedal travel to now fill and tighten up the pads before braking starts as the rotor pushed the pistons back in a bit.

You need a larger master but the residual valves might help mitigate the issue for now.
Between the floor and stationary id say the pedal travels half way before i can lock them up if i need to. I almost thought it was a vacuum issue because of when i have to pump them. For example, I didn’t lose them in the whoops but when i was driving or coasting on pavement. It did it again when i was coasting down a hill and had to “build pressure” with a couple pumps. Then another time in a parking lot it went soft and had to pump. So it feels like to me its only happening under coasting and not under power, if that makes sense.

I called my fabricator and he said the same thing happens in his ranger. He has wilwoods in the back and stockers up front and only has to pump in the dirt, not the street.


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84projectford

Senior Member
Sep 8, 2010
2,160
1,927
113
Phoenix Az
That issue means your booster is at full power (engine goes into vac, booster gets full vac, most power applied to the brakes). If your booster is leaky or some other reason, brakes will feel stiffer till it gets full power but what you are feeling is exaggerated big time due to a smaller master cylinder. Your booster may be just fine

I just went through this whole issue on mine and reduced the rear cylinder size to get my brakes back. You either have to reduce the slave aide (calipers) or increase the master size. Using half your brake travel before any lock up occurs is too much imho.

You need more master cylinder and the master should match the caliper sizing.
 
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Forget Regrets

SiCCMADE
Dec 18, 2010
3,468
83
48
Santa Ana
Decided i wanted to buy some more shocks for the pre runner. Ive been working on a mock up shock for the front bypasses. Gonna be a 3.5x10” 3 1” tube, piggy back bypasses, fin reservoirs, with robby gordon port, and prerunner dimensions. Mocked it up with race dimensions and its about 1” too long. Could maybe get away with a welded rod end. Pics just show the layout ill be doing. Tubes and sharpie holes are NOT to spec. Need to cycle it once with the prerunner dimension to make sure everything clears.

Today 5/11/21 i picked up some black cerakote, green anodized race series 3.0x16” coilovers with fin reservoirs. Aside from tubing and all the misc stuff for a back half; i have what i need to link the truck. Still need to do the cab cage, engine cage, then back half, add rear bypasses, and that’ll basically be it for a bit.







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