This is weird, but my 2003 5-speed Cooper does not feel as "stable" on the road as I'm accustomed to. The car will zip a little toward the left at times. Not so much that it's gonna send me into oncoming traffic, but enough to notice. It's kind of a 'feel' thing, if you know what I mean.
In the last month I had the snow tires removed and the original 16" run-flats put back on and they replaced the steering rack (although this current problem does not seem to be steering related).
Any suggestions or have I finally gone mad?

 

I think the first problem is you're just getting your snows off?!

Are you sure you're not just experiencing "tramlining", where the tire is following the contours of the road? Does it do this on all road surfaces, and have you hit anything "typical" in Detroit lately (you know, the pot-holes and assorted obscene undulations)?

 

I thought that Memorial day was the traditional time to remove your snows, when do they go back on, labor day?

Other than tramlining, which the 16" rf tires will do more than the narrower snow tires, I would have the alignment and tire balance checked. When they replaced the rack on our MINI, they did an alignment, but I noticed some shake and saw that somehow all the wheel weights have fallen off.

 

I thought I read somewhere that you're not supposed to rotate the tires on a Mini due to them wearing differently in the front than in the back. Maybe your runflats were mixed up when they put them back on, and you're noticing the difference?

 

I had my tires rotated at the dealer at 20K miles,the car feels and handles
exactly the same.now 90% of that is straight prairie highway.not to hard on the tires.In the twisties it feels the same also.

 

Detroit probably has the worst roads I've ever seen. I live in MN now and the roads here suck, but not the same way the the roads in MI suck. Probably because MI has like 50 freeze/thaw cycles over the winter, and MN seems like it only has one - one BIG one that is.

Anyhow, as for the ON topic stuff, you might want to make sure your wheels are still balanced. Maybe a weight fell off or something over the winter, although it sounds more like alignment to me.