We used to have some Goodyear Wranglers on my beater BroncoII - got them as new take-offs from a Jeep for a price that was hard to refuse. They transformed the Bronco into a scary nervous mess at highway speeds. Just too much sidewall flex - tall squishy tires combined with the bronco's short wheelbase and you'd get into a sort of feedback loop with it if you tried to correct the gentle swaying too much. I think it was more of a sensation of an impending loss of control than a reality, but it was hard to untrain yourself to counter steer when you felt the tail waggling around a little. Never could cure it, finally got rid of the dreaded cheap Wranglers and put on a nice set of Michelin SUV tires and it tracks straight as an arrow now.

Similarly, I once temporarily ruined the handling on the Miata i used to have when I replaced the *excellent* original set of Bridgestones with a set of Pirelli's. Instanly, the same thing - a squirmy unsettled feel at highway speeds, that couldn't be 'tuned' away by altering the tire pressure.

Which brings up the final point - tuning the feel with tire pressure. Altering the pressure will make some subtle (and sometimes not so subtle) changes in the way the sidewalls deflect. (This is in addition to the why it changes how the tread sits on the pavement for better or worse). Generally speaking, more air pressure results in a stiffer tire. This has more to do with the transient feel as the tire goes from straight ahead to cornering, and not quite as much when in a steady state pull, but often the small things that happen in transition affect what the car does a little later - a little tail wag in transition can result in a full on slide once the car has started to rotate that way. So (within reason) you can tweak the handling from under to oversteer and back again by varying the pressures front to rear. The Miata was very sensitive to this - moving from predictable understeer to exciting voersteer within a range of only about 5 psi differential from front to rear. My suggestion to you would be to try a good 4 to 6 psi more in the rears than in the fronts (like 30/36) and see how that feels. If still a little to squirmy, try moving all the pressures up slightly (32/38) - until you hit the max pressure. Of course, at some point you might slightly reduce the traction by overinflating the tire relative to the load it is carrying - but generally I think you notice the feel of the tire a lot more than you notice the absolute grip.
--
I'm JohnMc, and I approved this message.