paulnptld Posted September 1, 2014 Share Posted September 1, 2014 On my way to Burning Man I had two frightening incidents, both involving front brakes locking up. The bias adjustment was made last year, so there's not much more to do on that front. I was heading down a 6% grade going slowly (though clearly not slowly enough) when around a corner the front brakes locked up and kept me moving in the direction of the skid. Unfortunately, the skid was taking me to a lethal drop off. Fortunately I was able to correct. I had a similar incident on the way home, this time going even slower. A pothole triggered this skid. Is there anything more that can be done to shift the brake bias to the rears? And please don't answer 'drive slower.' I was doing 20mph on a 45mph turn when the first incident happened. Quote Link to comment Share on other sites More sharing options...
linda s Posted September 1, 2014 Share Posted September 1, 2014 Have you adjusted your rear portioning valve to max yet. It delivers more braking to the rear. Look here post #6 has picture and clearly describes it. http://toyotamotorhome.org/forums/index.php?showtopic=4321&page=1 My front brakes locked up recently and it appears it was just a complete break down of the fluid. Might have been in there since new. Cleaned out the system and new fluid and no troubles since. I did clean my master cylinder and bench bleed it too. Linda S Quote Link to comment Share on other sites More sharing options...
paulnptld Posted September 1, 2014 Author Share Posted September 1, 2014 Unfortunately, they're adjusted as far as they will go in favor of the rears. The fronts still lock well before the rears. In fact, the rears have never locked on me. Quote Link to comment Share on other sites More sharing options...
WME Posted September 2, 2014 Share Posted September 2, 2014 Forget the adjustment, bend the long rod so that the valve is full on. Or remove the adjustment end of the rod and bolt it full up to the chassis Quote Link to comment Share on other sites More sharing options...
linda s Posted September 2, 2014 Share Posted September 2, 2014 You could also try tightening the brake adjuster on the rear wheels. Little place you stick a small screwdriver in behind the wheel. I did that too. Helped even it out some more. Linda S Quote Link to comment Share on other sites More sharing options...
zero Posted September 2, 2014 Share Posted September 2, 2014 On my way to Burning Man I had two frightening incidents, both involving front brakes locking up. The bias adjustment was made last year, so there's not much more to do on that front. I was heading down a 6% grade going slowly (though clearly not slowly enough) when around a corner the front brakes locked up and kept me moving in the direction of the skid. Unfortunately, the skid was taking me to a lethal drop off. Fortunately I was able to correct I'm assuming the brakes unlock when you take your foot off the pedal? I'm trying to ascertain if you have a brake equalization problem or something else? Some brands of semi-metallic brake pads will "grab" and hang on - causing lock-up that has nothing to do with pressure-equalization. Did this problem start after getting new brake pads? If all you have is a brake-pressure-equalization problem - spend $40 and install a manual proportioning valve. Easy to mount under the hood next to the master cylinder. I have one on my Toyota Chinook. Quote Link to comment Share on other sites More sharing options...
paulnptld Posted September 2, 2014 Author Share Posted September 2, 2014 I'm assuming the brakes unlock when you take your foot off the pedal? I'm trying to ascertain if you have a brake equalization problem or something else? Some brands of semi-metallic brake pads will "grab" and hang on - causing lock-up that has nothing to do with pressure-equalization. Did this problem start after getting new brake pads? If all you have is a brake-pressure-equalization problem - spend $40 and install a manual proportioning valve. Easy to mount under the hood next to the master cylinder. I have one on my Toyota Chinook. That looks like a solution that makes sense. Yes, the brakes release just fine. I've not had them done recently, but they were inspected and at roughly 30%. Either way, I was white knuckling it for the rest of the trip. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted September 2, 2014 Share Posted September 2, 2014 I think there's maybe something else wrong. I'm not saying a manual proportioning valve might not improve things, but I've never heard of anyone else having to install one to make it safe to drive. Quote Link to comment Share on other sites More sharing options...
Maineah Posted September 2, 2014 Share Posted September 2, 2014 Unfortunately, they're adjusted as far as they will go in favor of the rears. The fronts still lock well before the rears. In fact, the rears have never locked on me. Likely as not you'll never get the rears to lockup.The majority of the weight is in the rear of the truck it does not get the weight shift as a car or empty truck would (the rear does not lift) the fronts lock because of this lack of weight. Not so many years ago larger trucks such as dump trucks had no front breaks at all it was not until they were controlled by antilock system that they used them. The valve on mine at the rear was totally by passed full breaking, they would not lock unless they had very little traction. This is not saying you don't have an issue with front breaks they really should be looked at but these things do not stop well. Quote Link to comment Share on other sites More sharing options...
DanAatTheCape Posted September 3, 2014 Share Posted September 3, 2014 because of the weight of these units, it is possible to lock up the front wheels on inclines & declines - especially when backing up & when on loose gravel. a technique that works for me in those situations is to use the parking brake - I also use it on long grades when down shifting is not enough. On long grades I might use the hand brake a few times then alternate to the pedal brakes. The hand brake operates only the rear brake shoes while the pedal brakes will primarily use the front disk brakes. One other word of caution - NEVER forget you are driving a relatively heavily truck and not a family car. I have learned to slow down - way down while maneuvering on gravel. If you look at how much rubber is actually in contact with the road service then look at what is pushing that little bit of contact service..... well I am sure you get the idea. Quote Link to comment Share on other sites More sharing options...
Vanman Posted September 3, 2014 Share Posted September 3, 2014 While you are replacing the brake fluid it might be time to replace also the rubber hoses on the front brakes. I don't know how old mine were, but they looked OK from the outside but I had everything changed anyway. Cut it in half and boy it sure didn't look too good from the inside. Was going to keep them as spares but threw them away. john Quote Link to comment Share on other sites More sharing options...
DanAatTheCape Posted September 4, 2014 Share Posted September 4, 2014 flexible brake lines do go bad. when they do they can restrict brake fluid pressure getting to the front brakes and/or restict the return of that fluid. They are not very expensive - I would change both at the same time. Quote Link to comment Share on other sites More sharing options...
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