Chev P3 chassis poor brakes

[ALO]

I have a 1990 P3 class A 27' Coachmen. This thing is nasty to stop. It has hydro-boost brakes on it, disk front. Both front brakes will lock up if I apply any amount of solid pressure. The rear are ajusted as tight as I dare, all the brakes do function. In the rain it's impossible to stop, I can't trust it at all. If I tow my 4800 lb trailer, well forget it. The front is doing all the work even though the entire braking system is serviced.

[Max Hubrich]

AlO,

I feel for you-- I had the same problem with my old, P-30, tag axle, 33' HR coach. My rig had a second master cylinder mid way down the coach, underneath, near the steps-- It needed service badly. It acutated the tag axle's Ford F-350 drum brakes- never figured out why GM used Ford components in those days.

Having gone through changing all brake items (except the master cylinder), including wheel brake hoses, it still didn't stop good until I installed a brake buddy in my towed Saturn-- That helped more than anything.

I now have a gas W-22 (Workhorse) chassis with great brakes-- The best stopping I've ever seen in a large vehicle.

A post on the vintage RV site here on iRV2 might bring more advice---

Good luck,

[rvten]

Have had 3 MH's on the P chassis. All were a PITA with poor braking. One reason we went with W-20 chassis on 4th MH.

[Brazels RV Performance]

ALO,

Take your coach in to someone who can measure the brake pressure output to each wheel. I think you may have a proportioning valve the is either defective or off center.

[ALO]

I have considered the proportioning valve as a problem. I am looking for an adjustable one that will fit in there, maybe I can equalize the system. Usually the brake warning light would come on if the valve kicks one way, at least that's how a car system would work. I'd just a soon through a part at it considering the cost of labour on these things. Some of this work I can do myself as I'm a car technician.

[ALO]

Would anybody know the PSI rating on this RV braking system? I have found an adjustable valve that is rated up to 3000 lbs.

[mike brez]

Everyone I talk to has poor braking in their older P3. lets face it they were ment to be a potato chip truck not a MH.

[ALO]

That is so funny, ,,,,,,but true. Had I known better I never would have bought it.

[-Gramps-]

Is it true that a potato chip truck weighs less when its full than when its empty?

[mike brez]

Actually mine was a bread truck because on a bright sunny day you look down the side of mine you can still see in big letters WONDER