Locking disc brakes

I was going to wait until I could do more testing on this but I'm home sick in bed, the ground is muddy and I probably won't get back on the tractor for a bit, so:

I read in the archives something about adding springs to fix a locking brake problem. Didn't really understand where these springs were being added but it got me wondering.

When my brakes lock they usually stay that way, though the brake pedal and linkage all the way to the threaded adjuster rods return to the normal unlocked position, with the adjuster rods remaining out in the locked position. Long story short, I rigged up some external springs that push against the adjuster nuts. I've only been able to test it once, and it seemed to work on one side, the other still locking. I was planning on increasing the spring pressure, but with only a rudementary understanding of how everything is connected inside, i'm wondering if I'm just wasting my time with this? I only use this tractor to move the backhoe from place to place on loose soil so the locking brakes are not a big issue at this point, but it would be nicer if they didn't.

TIA,

Paul

Hi Paul,
You don't say what the tractor is but I'm guessing that its a MF 65 or industrial version or possibly a 165. Hope you get better soon. The attached photos show the setup from a tractor with oil immersed brakes but the principle is the same.
Grabbing or jamming of dry disc brakes is a constant problem reflected by the number of postings on the forum.
Its an interesting experiment to attempt to return the actuator discs by applying external spring pressure. The discs have tapered tracks with the balls in between. When the brakes are applied the discs turn in opposite directions and consequently expand outwards causing the brakes to be applied. When you release the pedal the springs should pull the discs back together and the friction discs be released. There are several causes for jamming. Small wear pockets can occur at the point where the brakes are applied on the ramp. In effect then the ball has to go over a step to release it. A build-up of dust can cause much the came problem. Lastly the discs must be free but not loose in the location points in the axle casing. Too loose and the actuator can 'kick' and jam on. In adding your external springs I think that you might be adding an external force that may interfere with the equally spaced return springs in the actuator. We are talking fine lines here so its really only conjecture.
On several MF and Leyland tractors in the past I have cleaned the bearing areas of the actuators and the points of contact in the casing with a small sanding disc and emery. I have applied a small amount of copper grease to these points.
There has been a great improvement in all tractors but it has to be realised that this is a relatively short term solution. When the grease dries up the problem may well return.
Please let us know how you get on if you go any further with the springs.
DavidP, South Wales

Hi David,

Thanks for the great operational description and photos. I agree the springs I added could be introducing some additional and unwanted forces. It is definitely working on the one side though, it's the first time since I bought the tractor that there has been any progression in braking, it's always been instant lock up with the slightest pedal pressure. The other side is unfortunately still locking up immediately, but it's a simple matter to increase the spring pressure and see if that helps. The foot boards on my tractor (MF40) run closely under the adjuster rods, I just bolted L brackets to them with compression springs over the adjuster rods, pushing against the adjuster nuts.

I'll post a photo if I get both sides working properly and report back if I can't.

Paul

Wanted to report back on this. Here is a photo of the auxiliury springs I added to stop my rear brakes from locking. Happy to report it's working. Took a bit of adjusting of the springs, jack bolt and brake adjustment to make sure the rod always returned but still a darn sight easier than pulling it apart. I know, it's ugly...

Paul