Ok, I'm not one to go around correcting spelling/grammar all the time but at least in the track forum we can get this right. Chord = something you play on a guitar Cord = stuff that shows through the rubber on a tire when you've killed it
If I owned a tire shaver I wouldn't shave used tires. Too easy to mess up the blade with rocks and nails and stuff. Shaving won't bring your rears back if they're heat-cycled out, which they might be. Get some formula V or other tire softener and use that if you're worried, probably cheaper than shaving and won't be a waste of time and rubber. I would definitely go to the 285's in front if I were you.