I have a 93 NX2000 with 97,000 miles. The car rides harshly. At times the steering wheel shakes. Also I get a lot of noise from the rear of the car when traveling at expressway speeds. The tires have good tread, but are older. The shocks and struts have been replaced recently. The rear brake rotors are also new. What else could make the car ride harshly? Thanks.