With such a low aspect ratio side wall your going to have a lot stiffer tire. Also when you changed springs did you change the spring rate? The tire pressure maybe to high, when my father and I set up our cars we took them out on the highway for 30-40 mins. to get the tires warm. And then checked the tire temps with a pirometer, outside tread, middle, inside. What you want is equal temps across the tire, if the middle temp is higher than the other two the tire has to much air pressure. What you might find is your tire is rated for a lot more load than your putting on it. You tire might say 35 psi max load 1650lbs, you should not be at 35 psi in your tire on a tiger. Over inflated is going to give a smaller contact area, which gives longer braking, less traction and a harsh ride (great gas mileage).