rear drum brake improvement?....Nice!....I agree, mine is pretty worthless, too. It appears the shoes make contact with the drum on only a very small portion of the braking material. I like your idea to get around this by shaving down part of the material.
How did you cut those grooves? and was there a reason for the shape and spacing of them?
The timing of your post is great..I have a new set of EBC rear brake shoes out in my garage waiting to be installed on my scoot. Mine isn't due to worn out brakes (2900 miles on scoot) but due to terrible pulsation in the back brake. I've pulled the wheel and cleaned the brake shoes and drum and the first time the pulsation went away for a short time. The second time I did it the pulsation didn't change at all. (really irritating to apply rear brake and have it pulsate)
I'm hoping a cleaning and new shoes will solve the issue because the other alternative is that the rear drum is warped and if that's the case I'm screwed because I don't want to spend the money on a new rear wheel.
The rear drum brake was pretty useless on my Agility as well. Quite dangerous actually - my driveway is quite steep and when the scooter has been rolling backwards the rear brake never worked at all. And when I was pulling the front brakes (while rolling backwards on the steep driveway) the front wheel always tend to lock. Then the scooter started sliding backwards and I had to do some gymnastics to keep the scooter upright.
I almost gave up all hope to get the drum brake work properly, but fortunately stumbled across some Youtube videos about drum brake modifications. Some owners cut grooves at a 90 decree angle - others cut grooves at an angle as shown at my photo. I could not find any comments about the best way to cut the grooves - I just thought the way I cut it might help to direct brake dust to the open (outlet) side of the drum.
I just used a sharp knife to cut the grooves. Was planning to use a hacksaw, but could not find it. The grooves were widened with folded sandpaper. The pads are quite soft - so it's quite easy to cut the grooves.
I just cut 3 grooves on each pad - one groove has been cut halfway between the top an bottom part. The other two have been cut toward the top an bottom end.
I noticed some people cut 4 grooves on each pad. The grooves on my pads are quite long - if it was shorter I would probably have cut a 4th groove as well.
The wear on my scoot's pads were uneven as well. I don't think there is any reason to worry about a warped drum on your scooter. I think the way the brake pads work is actually the cause of uneven wear.
I think the slightest uneven wear actually prevent the brake not to work properly. That's part of the reason why I decided to shave the pads down at the opposite side where most wear usually seem to take place.
This mod actually improves the riding experience on my scoot completely. Stops suddenly became much quicker and i think a lot safer. We often have loose gravel on our tar roads and I was always dead scared of the possibility of pulling the front brake on loose gravel....
Anyway - should you decide to try this mod, it will be interesting to hear about your experience.