I guess the best sign would be excessive floatiness over big dips on the highway. My Tokico Illumina 2s were getting like this after about 90,000 km of hard usage, including about 6 or 7 days of open-track events with R-compound tires. I found the rear of my car to be getting soft and taking too long to settle down after going over large dips, esp. at 75 + mph. So I've changed the rars for a pair of Konis for now, that fixed a lot of it. The fronts aren't so bad, so I'll wait until winter to do them. Scott, figure that if your car has original shocks, and more than about 120,000 km, they're probably due for replacement. Springs don't generally need to be replaced as soon, however, I've seen T-Birds with busted coil springs here in Toronto. But that's likely due to corrosion caused by winter road salt, they just use sand where you are, don't they ?
cheers
Ed Nicholson
SCCoO