Bob the easy way to see if it's on the bump stop is to simply check the top of the stop/chassis..........likely have a 10-20mm shiny spot.


See if this sounds familiar:

My Showroom Stock class 1990 Miata (MX-5) would in a banked right hander , Turn 2 LVMS outside road course, corner on the bump stop. If I progressively unwound the wheel off the apex, the car would jibe to the left and get the back weaving around like the wheels bearings were loose but only for about 30-40ft. After that it would exit the corner normally. For this corner I'd wind the wheel in just past a 90 degrees. When unwinding the wheel if I paused at about 45 degrees for a split second then kept unwinding, no problem. I finally figured it out my third race with the car: I was being greedy and did a slide job on 3 spec RX7's from a 100ft back (oops). Well needless to say as the car slid up the baking I heard a light bonk, even though I'd already unwound the opposite lock the rear end snapped round to the left...........after being plucked out of the gravel trap I looked at the bump stop and sure enough the left one was slightly polished. Being a Stock class car I had to live with it.

Basically the bump stops have a much greater spring rate and as soon as the load came off the rubber, it would shove the back end up 1/4 inch or more.......creating a sort of crack induced weight jacker making the car weavy in one section of one corner. Also becuase of instructing at track days I end up in a lot of cars, some with goofy set ups.........usualy the rebound cranked way stiff (car jacks down in long sweepers with pavement undulations) so your plight sounded familiar.

I know I trimed the stops in the coupe when we lowered it.

Tom