

Hmm, had the exact same problem too with ace 250. As mentioned above, i'm pretty sure that heat of the day plus friction, makes the cuffs very weak.
So after 4 breaking on me i decided that was enough!
I made my own. Get down to Homebase and buy a 4" pvc wastepipe bend. look for the one that has the last 3 inches flared.(guess why you want the last 3"?)
I chopped that piece off, chopped off the top leaving a more profound and tighter circle than the original armcuff.
Get your old cuff and snap off the remaining half leaving you with the bottom portion that is moulded to fit the shaft.
Drill through the new cuff with 2 holes into the old shaft clamp, add some glue and put 2 large self tappers through it all. make sure you countersink them!
A series of holes drilled and filed into shape for the velcro strap done the trick.
The sticky foam.... i was lucky and the last cuff i used broke, but was left hanging by unbroken foam,so i peeled that off and used it.
I stuck the original 2 halves of the yellow cuff around the new one for decoration and to hide the grey pipe.
Sounds tricky writing it out, but the whole thing took me less than 20 minutes.... And it isn't EVER gonna break again!!!
It's tighter, stronger and you can wave the detector about like it's Harry Potters wand. Cost... $10.95