Does anybody know if Ford ever made different brake proportioning valves for the 93' F250.

We are currently in monsoon season here in BC and I noticed that my 91' F350 CC with worn tires seems to brake a lot better (stop a lot faster) than my 93' F250 with brand new Michelin tires. The 93' has a tendency to lock up the rear brakes really quickly and I was wondering if Ford every offered different styles of propotioning valves for splitting the rear and front braking efforts on the 93' F250.

I do run empty a lot more than loaded so I would much rather have a proportioning valve that favours the front brakes more than the rear.

Note, ABS braking systems on both trucks are disconnected, in my mind the early ABS systems on these trucks do more harm than good, especially on our bumpy roads which seems to trigger them more readily.

Are there possibly any adjustment procedures I could to to my existing proportional valve? Different spring?

Any help on this would be much appreciated. In my mind the lighter truck (93') should be able to stop better than the heavier truck (91') with the proper brake proportioning valve setting.

Finally note, putting new tires on the 93' has helped improve braking; however it is still much worse than the 91' with worn tires. The 91' will spin out easily when too much throttle is applied, yet brakes great without locking up the rear wheels.


Seb....

 

Is there any valve other than the RABS on these things? I've heard of guys buying adjustable valves. What did unhooking the ABS do for it? Mine still works (I think). The only time I feel it work is after a right rear tire burnout and tag the brakes.

 

The ABS systems on these trucks basically reduce braking pressure to rear wheels if the VSS senses that the rear wheels are starting to lock up. Unfortunately on bumpy roads the RABS come on a lot sooner that you want them to and significantly impact your stopping ability. The RABS on the early trucks also did not work well with towing trailers and goosenecks. Many guys started skidding into intersections with there rigs as the ABS would come on as they approached the intersections. Often once the RABS was engaged it would not dis-engage significantly increasing your stopping distance.

To disconnect all you need to do is unplug the ABS module. The 91' has it located behind the dash, above and to the right of the throttle pedal. The 93 has this unit located behind the glove compartment. With the controller disconnected the RABS valve now is dis-abled and the brakes work like they used to in the olden days.

The only thing I would like to know is if you can either adjust the existing proprotioning component of the RABS valve or get an aftermarket adjustable proportioning valve. Clearly there are different setting available seeing how differently the brakes on my 91' vs. 93' perform.

I think I could improve the braking performance on my 93' significantly based on my driving style by letting the truck braking load shift more to the front wheels and not have the rear wheels lock up so soon. It is also easier to keep control of the truck if the rear wheels don't lock up too soon.

Funny enough, keeping the rear wheel from locking to keep control of the truck is the intend of the RABS system, the only problem with the early RABS is they did not do too good of a job, making the RABS more hazardous then beneficial in my mind.

Note, both trucks have identical rotors, calipers, pads, drums, shoes, as well as master cylinders so the only difference I can figure would lie in the proportioning system that sets the front vs. rear brake load.

Any thought or information on an adjustable proportioning valve would be much appreciated.


Seb....

 

Seb, just out of curiosity, do a couple test runs with and without your ABS plugged in. If your ABS works better in this weather [like it was ment to] all the better and unplug it when the weather changes....just a thought.

 

I may fool around with that too. My truck with a load won't stop at all.

 

I know from years of driving, especially in this kind of weather that plugging the RABS back in will increase my stopping distance, especially at bumpy intersections with poor paving and I got lots of those on my way to work every day. Once the RABS engages when you go over bumps it won't let go unless you let off the pedal.

I think the newer ABS systems on the newer trucks have improved tremendously, that said the early ABS systems are more of a hazard than do good under a number of road conditions. Overall I found given my driving style I am better off without the RABS on both trucks. Note, the last owner had already disconnected the RABS on my 91 before I even got the truck last November.

 

Do the 90 model trucks still have the load sensing valve on the rear axle?

Driving on wet roads and the rear brakes locking can be from the brake shoes swelling from moisture. That organic replacement for asbestos does like to swell up.

 

My 87 has RABS, my Dad's 86 has the mechanical valve tied to the rear end.

 

Mine also has the mechanical valve.

I need to remove it, I have so many springs on mine it always thinks it is empty.
It still will lock the rear brakes when the weather is real damp for the first couple of stops.

 

just a thought, could it be as easy as adding one of these?http://www.jegs.com/webapp/wcs/store...10002_25589_-1

 

That would work if you did not haul loads like I do.
I need to get the load sensing valve either recalibrated or removed.
I could deal with locked brakes easier than not enough braking force on the rear axle when loaded heavy. With a couple of tons on the back, I lock the front axle brakes first.

 

Thanks,

I ordered two of the JEG's propotioning valves. For $36 there is not much to loose.

Dave, thanks for the update on the brake shoe linings swelling, I use the non-asbestos "metalic" shoes and front brake pads. They are a little bit more expensive, more abrasive, and wear out faster but sure grab well. They also keep my rotors and drums nice and clean so I never have to bother turning them when I change pads or shoes.

The only problem I had with my factory front rotors on my 93' was they were of a very poor casting and started to get a few deep corrosion pits in them so I ended up replacing them rather than turn them.




Seb....

 

Those metallic's should not swell like the organic non metallic shoes do.
Semi metallic's are somewhere in the middle.

 

I finally did get the JEG proportioning valve installed on my 93' last weekend.

I must say the braking on this truck has improved significantly, especially in rainy or icy conditions.

I installed the valve on the rear brake line right off the Master Cylinder. Supported the valve with a small aluminium bracket off one of the bolts that bolt on the MC.

The JEG valve allows me to reduce the pressure to the rear brakes and I now can step on the pedal harder which provides better braking in the front.

If I am carrying a load or pull a trailer I can adjust the valve to increase the rear braking as required.

For about $40 plus another $40 for shipping and handling this valve is the best thing I have ever done to give me control of my braking based on actual road conditions.

Note, I disconnected the RABS system at the controller behind the glove box. The RABS system in the early trucks was poorly set up in my mind and you did could not adjust it. It always came on too soon when you ran the truck empty as the brake balance always favoured the rear brakes per factory settings.

The adjustment provided by the JEG valve allowed me to significantly reduce my stopping distance on wet and icy roads without loosing control of the rear end.



Seb....

 

glad you have the problem in hand and i like that you opted for the better shoes and pads. i've had alot of rear brake issues with these fords, even 1/2 tons. found that alot had to do with NOT turning the rear drums or at least checking them to make sure they are not out of round, then scuff 'em up real good to help take the glaze off so they will brake-in better and last longer.

i read a break-in procedure from Bendix - 30 stops from 30mph with 30 sec. cooldown interval-works great.
something else i've run into is putting duelly wheel cylinders on a single wheel truck really increases apply pressure and increased lock-up
also contamination makes them want to lock especially when cold.