Brakes

[Kirby]

OK, let me start with how much I have enjoyed my 84 Sunrader. I bought it less than 6 months ago. We replaced the axle, tires, belts, shocks, fluids, etc. immediately. It runs great and gets 16+ mpg average.

It has taken me kiteboarding, to parties, weddings, camping, etc. I think I am drinking more because I don't have to drive home from late-night parties! Most recently, it was the rig that brought my future wife and the bridesmaids out to the ceremony site at our wedding this July- driven by my father-in-law!

Here's the situation: Backing down a slight hill on gravel or wet pavement...Hit the brakes and the front wheels lock and slide- the rig keeps moving backwards with little hope of stopping. If you use the E-brake, the rear tires grip and the rig stops as it should. I feel like its an accident waiting to happen. This morning we bled and adjusted the brakes and looked everything over. It is pretty much the same. My mechanic says it is because there is so little weight on the front tires when in that situation. This also sometimes happens when moving forward and coming to a stop if there is any gravel/loose material on the pavement.

Is there something that I should check? It seems like the balance between the front and rear brakes is not correct. Any comments/suggestions?

Thanks...

Kirby

[WME]

Most of the time the factory rear brake bias controller is still set at the factory setting for an empty pickup. Air shocks make it think your an empty truck because your M/H is setting level.

You need to adjust the bias lever an far as you can to make the controller think you have a heavily loaded pickup and shift more brake effort to the rear brakes.

I removed the lever from the axle and bolted it to the frame so I have max rear brakes, works good for me. If that's to drastic then adjust the mounting bolt as far up as you can.

[Bodybagger]

My mechanic says it is because there is so little weight on the front tires when in that situation.

On one of the threads here, someone told about how their mechanic (that specialized in motorhomes) checked the stopping torque of the wheels with an expensive high tech device and adjusted the rear brake adjusters until they provided the right amount of stopping power...

in fact they adjusted them so tight that they burnt the rear brakes and drums up.

Real pros, huh? If only they knew about that simple little brake proportioning valve on Toyota trucks. Luckily, your mechanic thought it was due to a light front end and didn't go screwing things up.

See this post:

http://toyotamotorhome.org/forums/index.php?showtopic=1313&view=findpost&p=5783

[turtle]

I removed the proportioning valve entirely on my 1981 diesel when I installed the 1 ton axle (14 years ago). Brakes worked GREAT with the same pressure going to front and rear

On the Sunrader I replaced the "automatic" proportioning valve with a Wilwood "manual" proportioning valve.

THIS IS NOT A RECOMMENDATION THAT YOU SHOULD DO THIS!

Messing around with how you vehicle's brakes operate is one of the most dangerous things you can do if you do NOT know what you are doing!!!!!

[Kirby]

Thanks for the replies!

The proportioning valve makes perfect sense...when we replaced the axle, my mechanic said we did not need to put the arm back on that connects the axle to the valve. Hmmm....I'm starting to question his judgement. So, what is the best way around this? It seems like an unnecessary part considering the weight that will always be on the rear tires.

Can / should I remove it and bypass it altogether? The nipple that connects into the valve appears to be the same size as the one one that conects into the rubber hose with bracket. That seems easy enough. See pic.

Or, should it be adjusted / tricked to think there is weight on the rear?

Should the current setup be considered dangerous? I am planning on taking it to the Oregon coast tomorrow.

[Bodybagger]

Can / should I remove it and bypass it altogether? The nipple that connects into the valve appears to be the same size as the one one that conects into the rubber hose with bracket. That seems easy enough. See pic.

Or, should it be adjusted / tricked to think there is weight on the rear?

Should the current setup be considered dangerous? I am planning on taking it to the Oregon coast tomorrow.

It's easiest to just wire tie the lever in the fully loaded position to trick it into thinking you have a full load on the rear end. Well, actually, you're not tricking it... more like smacking it upside the head and telling it there's MH coach sitting on its back. But if there is no lever on it, I think it will sit in the low pressure proportion position which is not where you want it.

Your stopping distance will be significantly increased if the rear brakes are not seeing much pressure. Is that dangerous? Well, it's better than no brakes... But keep in mind that if you go down long steep grades and your front brakes fade, you'll need downshifting and pulling your E-brake for any real braking power. Yeah, I guess that's dangerous.

You either want to replace the arm and attach it in the loaded position, or *MAYBE* do away with the proportioning valve altogether.

Here's the big question mark... I have had good results with the proportioning valve wire tied, but I don't think this position actually applies full pressure to the rear brakes. I think there is still some pressure reduction. You DONT WANT YOUR REAR BRAKES TO LOCK UP. I don't know if they will lock up or not when the proportioning valve is bypassed. If they do, well, imagine your rear end passing you up shortly before rolling over. Rear skids are very bad.

I vote for tricking your proportioning valve. If you bypass it, be sure to thoroughly road test it under controlled conditions including wet pavement to be SURE you never get a rear-only lock up. And of course, if you bypass it, you will need a little bit of custom brakeline and bleeding both rear brakes.