Street-tire class tires, stickiness & usefull life Options

[airsix]

For a couple of years I've been autocrossing in street-tire class with my 1.7 and I've always done ok - no wins, but no embarasments either. Until now...

This is my third year running these Dunlop SP8000 Sports - sizes 225/55-16 and 245/45-16 on 7" and 8" wheels. I know the tires are a little too wide for the wheels, but I bought them off a 944 and they came that way. I've just been using them up. I also know that this is an awful lot of rubber for a 1.7 - well I fully expected to have a fire-breathing six by now but you know what they say about best laid plans (let alone mine).

So there's the background. I've been running these tires for three years and they are close to being used up but they are not quite on the wear-bars yet. But... Either I don't drive like I used to, or these things just don't stick any more because I can't keep the car planted. I spun three times at the last autocross and I normally spin maybe once a year.

So my question: Do street tires "go away" just like race rubber after too many cycles? I don't want to blame the tires if it's me or something else wrong with the setup, but I'm trying to look for the most likely cause. Of late I have found that I can't even moderately trail-brake without losing the back-end. When I say loosing I don't mean it wiggles. I mean it's greasy.

Your musings will be considered and appreciated (even if the answer is "No man, tires are fine, you just suck"). (IMG:style_emoticons/default/laugh.gif)

-Ben M.