Sunrader brakes

[Guest Guy]

I have an 86 21 footer with a 1 ton axle. Having problems with the rear brakes. They don't want to work very much. Most of my braking is coming from the front. On a slick road the fronts lock up and it feels like the rears are doing almost nothing.

I have had the rear brakes replaced, shoes, cylinders,hardware,turned at a reliable shop. I have since taken it to 3 other mechanics. They've bled the brakes again, manually adjusted them, and in the end don't know what's wrong or how to fix it. No one seems to know any thing about how the proportioning valve works, which I am guessing is the problem. The vehicle has air bags. I let all the air out and there might have been a minor improvement but still totally insufficient. I bent the arm up to hold the proportioning valve piston in the up-most position which also seemed to have a minor effect.

Can I by-pass the valve? Is there a replacement that is made for the rv? Any suggestions?

Thanks, Guy

[Gulfstream Greg]

You don't want to bypass the valve. What it does is when you brake in a normal truck the rear rises and the front dives. This takes the weight off the rear wheels. The arm on the valve moves when the rear rises and reduces braking to the rear wheels so that they will not lock up. My guess is the arm is way out of adjustment or the valve is bad. I really don't know which way the lever is supposed to move for increased braking. An 86 probably originally had the bad axle and the one you have now was installed at a later date and there is a good chance the linkage to the valve was not configured correctly. It might be beneficial to take it to a Toyota dealer and explain all this to them as they supposedly should have the technical ability to make it right. With the motorhomes heavier rear weight, the rear angle change really does not happen.

So long story shortened that valve needs to be in the correct position to balance the front to rear braking. Its repair needs to be approached technically with its intended design. Guessing how it should be set will / can make the system to be unbalanced.

I have an 86 21 footer with a 1 ton axle. Having problems with the rear brakes. They don't want to work very much. Most of my braking is coming from the front. On a slick road the fronts lock up and it feels like the rears are doing almost nothing.

I have had the rear brakes replaced, shoes, cylinders,hardware,turned at a reliable shop. I have since taken it to 3 other mechanics. They've bled the brakes again, manually adjusted them, and in the end don't know what's wrong or how to fix it. No one seems to know any thing about how the proportioning valve works, which I am guessing is the problem. The vehicle has air bags. I let all the air out and there might have been a minor improvement but still totally insufficient. I bent the arm up to hold the proportioning valve piston in the up-most position which also seemed to have a minor effect.

Can I by-pass the valve? Is there a replacement that is made for the rv? Any suggestions?

Thanks, Guy

[Shoprat]

Howdy...

I will have to dissagree with Greg. I bypassed the leaking proportional valve on my rig and the braking improved. There is so much weight on the rear wheels that the valve actually is not needed. After bypassing mine, I took it out on a gravel road and at about 45 miles per hour, hit the brakes. The Toy stopped in a straight line with no adverse effects. I am well preased with the results.

[motoyhomme]

Guy,

The by-pass doesn't do any good on a 21 footer. Somewhere on this site is a tutorial with pictures on how to by-pass it. There is a sweet spot when it comes to setting the rear brakes. It took me all day to adjust my rear brakes after replacing the shoes. Normally the handbrake is off, the back wheels off the ground. Adjust the brakes until you can't turn the wheels by hand then back off the adjustment until they turn with just a slight drag , not too much, and then off one more notch. Do both sides the same. Then pull out the handbrake, it should go 7 clicks and the rear brakes are locked. You may have to adjust the handbrake cable to insure you get the 7 clicks. With the handbrake all of the way off, the wheels should turn freely again. That is textbook. What really happens is that you have to keeping playing with the handbrake adjustment until you find a sweet spot where the handbrake will work and it may be more than 7 clicks and the brakes don't drag while you going down the road. After adjusting them you have to drive a few miles then feel of the rear wheels to see if they're heating up, if they are, back off another notch with the handbrake adjustment. It is possible that the new shoes are not set close enough to the drums in the replacement adustment, but that handbrake is very important. Also make sure that the handbrake equalizer (photo) is not binding. I need to get mine cleaned up very soon. Good Luck.

Allen