SCToy

I had a set of carbotech bobcat compound pads made for my truck and they work ridiculously well. I don't let people drive it because if you panic stop you will lock up, which isn't good. Remember sliding friction is a lot less than static friction, so if you lock up your brakes, your stopping distance will be greatly increased. This isn't to say that being able to lock up your brakes is a bad thing, but not being able to modulate them so they don't lock up is. That said, not all pads are not created equally. You need a quality pad, they need to be bedded properly and you need to be sure the system is entirely bled with no water in the lines. Sounds like you have most of this covered except the quality pad, so i would start looking there.

Harvey Wheeler

Just a few thoughts because I have had the same problem with my 88. When you said that that moving the PV in both directions it didn't make any difference. If the PV is working it should always make a difference one way or the other. My first guess would be that the valve inside the PV is stuck. Mine was (too many Michigan winters) I removed it and removed the return line. But if you want to try to save the PV I think it also has a bleeder on it? Its been a while since I took mine off but I remember trying to bleed it first and it had a lot of rust and junk in it.
My second idea is did you check the rear brakes for proper drag/adjustment? If they are out of adjustment your peddle will travel far and make the brakes harder to lockup because you run out of peddle travel before you hit the floor board. Take a jack and a set of jack stands support the rear axle so both rear tires are in the air and spin the rear tires. They should not make a full rotation if spun.

TurboKH

Rears are new, like most everything else, and are adjusted properly. I got the new calipers, just waiting for he new (again) rotors and pads. Hopefully thursday. I bought drilled Brembos and ATE ceramic pads. This truck will stop like a race car. Too bad it's got an engine smaller than my lawn tractor.

Kiroshu

Are both the front calipers bleeder valves at the top? If not theres your problem.

TurboKH

Oh God, yes.

Kiroshu

Hehe =P

Harvey Wheeler

One other thought I had you may want to check. I know you mentioned that the brake lines are new but are the rubber brake hoses that go to the front calipers and rear axle new? My brothers 85 had soft brakes until we replaced the front and rear rubber hoses with new stainless steel ones. One of the old rubber hoses (25 + years old) where ballooning up when he pressed the brakes. Just thought I would mention it if you have not already checked them.

skypilot

iTrader: (1)

Perhaps you should zip tie the P/V up in the chassis for more rear brake pressure. Have you used the bleeder valve on the P/V yet? You might have air trapped since the P/V is pretty high in the chassis.
I replaced my rear flex hose with one from Marlin Crawler and it made a big difference in pedal feel and travel (might have been shot after 23yrs?) so the front's are next up.

angrybob

From this:

and this:

Your truck now has a 1" master cylinder and the stock booster. Originally, it had a 13/16" m/c. The difference in m/c area is now about 50% larger with no additional boost. Line pressure = master cylinder input force from the booster rod / master cylinder area. You are now making that same 50% LESS line pressure than you did with the 13/16" m/c.

Think about all of your comments - new parts, proper adjustments, PEDAL FEELS FINE, booster has vacuum. You are just not generating enough line pressure.

The fix - get the original size 13/16" master cylinder or get the tandem booster thats matched to the 1" master cylinder and you will be fine. You can return the ceramic pads and brembo rotors you bought if not installed (seriously, stick with the OE stuff you already have)...at least don't throw any add'l money at it.

Good luck.

NicCantDecide

I agree with this. If you don't match the booster to the master cylinder you can get bad side effects. If your booster is too big it can lock up your brakes without you even being on them (I've had that happen, it sucks). If your booster is too small, you'll never get enough pressure to the calipers.

angrybob

Just curious if this ever got resolved and how. If so, you should close the loop for future reference.

TurboKH

Sorry to keep you in suspense.. yeah it all works now. (I did add the double diaphram booster a while back, by the way.) It all turned out to be a bad PV. It was NEW, but not working right!! I put another new one in place and it works like it should.. the brakes are awesome now! I guess things don't always operate like the should just because they are right out of the box. As a result of this, I now have all the parts from a 91 3.0 truck plus some crazy drilled Brembo rotors and pads. Way over kill for a truck that gets driven maybe 3 times a month, but.. oh, well.. it works! Next I need to build a stroker for more power...

Thanks to all who contributed to keep the ideas flowing. I really appreciate it!
-Karl
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