Crashton

I don't believe they put any more stress on the diffs. All 4 tires are the same size, if they weren't then yes they'd stress the diffs. I am running 34 pounds pressure in them.

I believe that radio will fit just fine. There is a guy that goes by the name of Juice who posts on Edmund's all the time that has put one in his wifes Outback. I have the same radio in my Forester & it's great.

I don't have the Optima in there yet. I'm waiting for the oem Panasonic to die first. The Optima 75/35 & the 34/78 both should fit just fine. You will need to get a longer positive battery cable. The dimensions of the oem Panasonic are L 9" x W 6 3/4" x H 8". I just measured it. Chuck

I bought a set of Yokohama Advid Touring tires for my 2000 Forester L. I went up one size to 215/65/15. They are about the same height & 10mm wider than the stock tires. The fit is great with no clearance issues. Very nice tires IMHO. Can't comment on their snow performance, I use Blizzak's when the snow flies. I'm still on my original battery, but when it goes I'm buying a red top Optima. It will fit, but you will need to replace the positive cable with a slightly longer one. At least that's what I read on NASIOC.

I would have your mechanic check the runout of the front rotors. If your ABS light has stayed off that probably rules that out as a cause.