Rear disk breaks? How did that turn out?

[Case500D]

Hi Guys,



I have gone back to the drum brakes on the W-250 now. Was wondering about something. Can any of you with the disc brakes lock the rear wheels up in a hard stop? I know that the discs I had on sure wouldn't. Just curious.



Jeremy

 

[PPeters]

I don't think I ever did, disk or drums. I'll say one thing, after converting to disk I could feel RWAL valve working throught the pedal on hard stop. Don't ever recall having that happen with the drums. Problem is I can lock the fronts up with no trouble, so antilock is not much help when the steering pair are not turning



Pat

 

[HFletcher]

PPeters' point seems good. Granted, two wheels skidding is better than four, but how much value, practically speaking, has RWAL if the front brakes lock up? Opinions, men?

 

[cerberusiam]

It is Rear Wheel Anti Lock not All Wheel Anti Lock after all. Without the RWAL system and good rear brakes even light braking would lock the rears. The 4x4 are considerably worse than the 2x4 but it still makes a difference especially on slick roads. If you are at the point braking is locking the fronts you are either going too fast or too following too close. "Aw s#$t, this is gonna hurt!" is about all that is left to say. There is a lot of weight in the front with the motor there and with weight transference it is even more so you have a choice, lock em and slide or back off the brakes and dodge the obstacle.



Pat, would you qualify the conditions you are locking the fronts? Panic stop or hard braking? Loaded or unloaded? Trailer or box load? Did you do the fronts with the EGR brake also and what pieces did you use?



Going to a better brake pad in the front will help with stopping loaded but you run the risk of over applying the brakes empty and locking the brakes. There is a point at which a certain weight can be stopped in a certain distance while still maintaining control and the only way to reduce the distance is larger brakes and larger tires. We can put better parts in and gain efficiencies but we can't get around the laws of physics.

 

[PPeters]

Cerberusiam:



I know it's not 4 wheel anti-lock, should have used the sarcastic smilie in my post. No, I've got the stock Bendix setup on the front. Lockup I am talking about is in testing, unladen, doing a panic stop on pavement. Hard braking (not panic, unladen) on other road surfaces (tar and chip or dirt) will easily lock the fronts. Throw the gooseneck trailer on with 4 ton of hay in tow and the rears pick up a little of the slack, but I'm not following close or speeding doing this, I can assure you. Overall, I feel that the braking with the disk conversion improved the stopping capability of the vehicle over the stock drum setup.



I use NAPA lifetime pads, and keep the calipers serviced (read lubed) to ensure reliable operation. The brake system was completely overhauled a little over a year ago, new master cylinder, hard lines and stainless braided to all 4 corners, and the TSM rear disk kit. As previously stated, just replaced the ebrake cables, now that is operating satisfactorily. I'm happy with the brakes, and understand the limitations. But your recommendations are sound, and mean old Mr. Gravity is always waiting for you to FU



Pat

 

[cerberusiam]

Pat, I think that means I need to do major brake work on mine then. I cannot lock the front brakes on a rough chip road even with a panic stop from 75 mph empty. The truck just stops straight true and quick with no lockup front or rear. I know my rears are only about 50 or 60 percent effective so the bulk of stopping is happening on the front. Replaced the rotors a little over a year ago and used good NAPA pads. I know there are rear issues cuz the front rotors are starting to warp again. About the only time I can get a squeak out of the fronts is a panic stop on hot slick asphalt or a heavy trailer with the brakes not working. I think I spent too much time making it go fast and not enough making it slow down. Was wondering whether you used EGR's front rotors and or special pads as they are supposed to give better bite and thought that might account for tendency to lockup fronts. I guess I have been lucky so far as the only incident I have had to stop fast was pulling thru Seattle with a loaded trailer and the traffic went from 65 to 0 in a hurry. I got stopped fine but brother inlaw in my suburban with empty trailer had to take the shoulder to miss the truck in front of us.

 

[bvanetten]

Has anyone removed the stock proportioning valve and replaced it with a "T" fitting for the front and a adjustable proportioning valve for the rear? The more research and studying I do about brakes the more I think stuff needs to change. Who on the list is a wiz with hydrolic theory? In the end it's all in the math as far as getting these conversions to work their best. Master cylinder piston size, caliper piston size front to rear, hard line diameter. It will work if all the parts work together mathmaticlly. I was told by a hotrod custom shop that if we were to remove the brake lines at the right front and rear wheels and put a pressure gauge on them that with 100 ft lbs of pressure at the peddle we should see between 1200 and 1500 ft lbs. Has anyone tried this? I got to get this worked out before I pull heavy.

 

[bvanetten]

Ok. I just replaced the stock pads with ceramics on the rear and an agressive semi metallic on the front, and I bled them again. Totally different truck! Stops much better. I think I still want to put an adjustable proportioning valve in for the rear. Jeg's has one that you can run into your cab. It has a lever that you can switch at will for different ratio's. It would be cool to set it up with two settings, one for pulling heavy and one for empty. Maybe later...

 

[Wayno]

Originally posted by bvanetten

Has anyone removed the stock proportioning valve and replaced it with a "T" fitting for the front

I took the valve out years ago and put a T fitting in place of it for the front and rear lines and have had no problems at all . I have done this to just about every vehicle I have ever own . You can get enough fittings to do each line without having to cut any lines .