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This entry is a follow-up to a how-to I wrote in 2009 about adjusting the brakes on your John Deere L100 mower. Even if you're planning to do the full rebuild I show here, you should probably read that first. (link)
Back in 2009 when I wrote the original posting, I had no idea that 3 years later I'd still be getting positive feedback from people on it. I'm glad that I've been able to help people get their brakes working right, and I've decided to follow it up with more detail. For me, the adjustment was no longer working. I wasn't getting any kind of useful result any more and thought I'd need to replace pads or something else. I decided to tear into the assembly and see what there was to work out.
* Note: I call the part here a "caliper" which is, strictly speaking, not true. It doesn't move. It does sit very much in the way a typical disk brake caliper would and I just couldn't come up with a better way to refer to the part. If you have a better suggestion, let me know.
To refresh everyone's memory, the first picture here (from the original how-to) shows the brake assembly itself and the adjustment nut. The picture is taken from the "starboard" side (right side, when facing forward) of the tractor, just ahead of the rear wheel. If you want to find out more details about adjusting the brakes using this adjustment nut, please go read the original how-to.
What went wrong with my brakes turned out to be that the small metal rods, or pistons that fit through the outer caliper (pictures below) had gotten some corrosion on them and didn't smoothly fit through their bore holes any more. They were stuck. To get them out, I had to put the outer caliper in a vise, and use a nail set and hammer to gently tap them back out. I did this from the inside thinking that the corrosion was more likely to be thickest on the outside. Once I got them out, I cleaned and smoothed them, as well as cleaned and smoothed out the bore holes. When I re-assembled everything, I coated them liberally with water proof bearing grease. Basically, everything but the pads themselves, and the disk got a liberal coating of water proof bearing grease when I re-assembled the parts. Aside from smoothing the operation of the parts, this should keep the corrosion from coming back so quickly.
Before disassembling the brakes, I strongly recommend you are prepared with the following:
Seen from the top, the center "post" is the threaded bolt that the adjustment screw threads onto when this caliper part is facing out and installed on the mower. Next to it, you see the two small piston rods that should smoothly slide in and out. These take the pressure from the plate that applies the brake, and push against the brake pads. Mine had just enough corrosion on them to prevent them smoothly moving through the bore holes.
This is the same part, the outer caliper, seen from the inside. You can see where the brake pad seats. On this outer caliper, there is a metal backing plate that goes against the back where it can contact the piston rods and evenly distribute their pressure to the pad. The backing plate goes in first, then the pad. I cleaned the backing plate to remove corrosion and applied a very thin later of grease to it. Be careful not to get any grease on the brake pad itself.
Once you have the outer caliper removed, you can easily side the brake disk itself off this axle. You can see that the axle is keyed to prevent the axle spinning independent of the brake disk. What you don't notice right away, is that the key is itself a very small part, and sits in a recess on the axle. Don't loose this little moon shaped key! Also note that the key "rocks" so you may have to work it back and forth a bit as you put the disk back in place to make everything seat right.
This last picture just shows how small the pads themselves are. Mine are worn down about 1/8 inch, which you can tell because the disk is round, so the bottom corners of the pad are not worn. This isn't a problem. That's why the adjustment nut is there.
Once you have re-assembled the brakes, I suggest you quickly read about adjusting the brakes using this adjustment nut in the original how-to.
Finally, I would like to invite you to please leave a comment here if you found anything wrong, have some advice to add, or found this useful. I really do enjoy hearing from people who use these kinds of how-to articles.
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totally convinced that a third grader must have designed it. I cleaned
everything up and adjusted the nut. My first run around the yard yielded a good
trail of smoke as my pads were almost on fire. I loosened the nut some and now
the mower seems better. However, as you mentioned, the brakes don't stop the
mower on a steep hill...which I have. It's a dangerous design for anybody
mowing on a slope, as the mower refuses to stop quickly when moving down a
hill. The braking system will be the first thing I look at when I buy my next
mower, as this one is junk!