I third that on the Michelin XGT's...I've run them for years
Up to a few months ago, I was running Michelin XGTV4's on my T-Bird and XGTZ4's on my '91 535i. I loved them. They were a great combination of many things. They handled and stopped great, were above average in the rain, offered some traction in the snow, and were fairly quiet too. I've run Michelins for about the past 15-20 years now and have never had a problem with them going out of round, developing tread bubbles, or going out of balance. Michelin builds quality tires if you ask me.
I recently put BF Goodrich Traction V's on my T-Bird. It was just my beater car for when I didn't want the 535i in the rain or snow. The Tractions are supposed to get about 60,000 miles, which is about double what you can expect out of XGT's. They were also quite a bit cheaper and have turned out being pretty decent tires. So far, I'm pleased with them.
When the XGTZ4's are done on the 535i, I may be looking at the Bridgestone G009's or RE950's. I'm also considering the Pirelli P-Zero Nero M&S, which has been getting rave reviews on the Tirerack site. The main reason I'm going away from Michelins is simply price. For 235/45-17's, they are around $200 per tire. The Bridgestones and Pirellis are just too much cheaper to ignore. Also,we have Bridgestone Turanza LS-H's on my wife's V-6 Camry. If those weren't so much for the 235/45-17's, I'd put them on my 535i in a second. They are GREAT all season, grand touring tires. We love them!
Well, there's more info for you to think about. Hope this helps some. I'd also suggest reading the reader reviews of tires on Tirerack's site. Lots of great info there.
Grace and peace,
Robert K
1991 535i