Tim Wright

I received a lot of good feedback on my original post about my 89 Toyota Dolphin's front tires skidding on wet roads, gravel , and especially going downhill in reverse. Looks like the culprit is the load sensing proportional brave valve. From what I've gathered it sences the ride height of the vehicle and adjusts braking from rear to front depending on how much of a load it thinks the vehicle is carrying. The problem is with the Airbags lifting the rear of the vehicle up , the device thinks it's an unloaded vehicle and shifts most the braking to the front , causing poor braking and the skids. I really appreciated the help with some options of alleviating this problem and useful tips like using your parking brake if skidding backwards down a hill to keep things in control. So now my question is , " How much air should you put in your airbags " They say 90 psi max and I assumed the more the merrier. Since stumbling upon this phenomenon with the airbags I've lowered it to around 50. Still doesn't seem to do anything to the braking and some have spoken of these proportional valves getting stuck in the upward position , lending to most the braking coming from the front , when I need more in the rear. So any thoughts of a good psi for a fully loaded trailer ? I also drive on windy coastal / mountain roads and I'm pretty sure it cornered better with the higher PSI. Also , is this something a RV shop would tackle ? Is there replacement proportional valves available if mine is just stuck ? Anyone know of any shops who deal with this type of thing around Northern California / Southern Oregon ? Thanks for any help , I just want this thing to stop like it should.

Thanks for your reply. Now that I'm beginning to understand how this setup actually works there's hope of this thing actually stopping like it should. Got to get under there and see what position it is in now and where my airbags have it setting. Definitely not gonna max out the airbags any more . Are most RV places aware of this phenomenon ? The tire shop I brought it to has a very experienced mechanic working there and he had no idea about this scenario . I'm probably gonna have someone with knowledge of this situation help me remove the force arm and just bolt if to the frame in the upward position. I definitely think the more brakes in the rear the better. Thanks again.

Thanks for your reply. I just assumed there was a preset proportional valve somewhere on the MH. I had no idea it adjusted with the ride height and am gonna have to crawl under there and look at the unit to grasp how it knows where the motor home is sitting on the springs/ride height. As a coincidence I had a guy at the tire place add some air to my airbags the other day. He totally over inflated them rising the camper way up , then let some air out to achieve desired PSI. Shortly after , the first gravel pull off on road with cliff to ocean , it seemed to skid really easy to my surprise. I wondered if it had something to do with adjusting the airbags as my recent brake inspection/ adjustment seemed to of helped with the problem a little. So my question is , are they now set to the height the MH was when he over inflated the airbags or the current height of max pressure for the airbags. It says 90 psi max so that's what I put in. I definitely noticed it was stopping better before the added air. It was as 60 psi before adding the air. If I return to that psi setting will the PV automatically adjust to the new ride height or is it stuck at the height it was overinflated to. Also is 60 psi enough for the airbags or should they be maxed out. Thanks ahead of time for any response , as I've learned so much already about the proportional valve and see hope of this thing stopping better.

Front tires wanna skid whenever I'm on gravel. Especially if I'm going downhill in reverse. Tire shop guy says brakes look good and he adjusted em. Is there a proportional valve that could be sending too much braking to the front or is it just because there's so much weight in the rear. It's also skidded through an intersection in the rain. I'd be terrified to drive this thing in the snow or a city with steep wet hills. I've talked to another Dolphin owners who said his did it backing out of his garage. I can't imagine this could be normal because it's definitely dangerous. I've been driving it for a few years and it might of gotten slightly better after the alleged adjustment. I really don't know how my girlfriend drive this thing for years and isn't dead. She drives it with no concern and I grew up driving old vehicles without brakes and severely over loaded trucks , run equipment for a living and just know it's not right. Front rotors are slightly pitted with rust. But no wobbles when you brake so I think they're in pretty good shape. Any thoughts would be appreciated.