I currently have factory Berlinetta rims on the car, which limits me to 14" tires. Due to various circumstances, I've been doing two tires at a time, starting with a pair of Cooper 235-60x14's. The next pair was a Discount Tire no-name brand same size. Up to this point, no problem. The Coopers, which were on the back, wore out this summer, so I picked up a pair of BFG TA's, same size.

Suddenly the car started having a lot of trouble with jerking side to side in truck-rutted roads. I discovered they only put 28 psi in them when they mounted them, so I upped that to 32 psi. That helped, but it was still pretty bad, so I went to 35 psi. It's almost tolerable, but still not good.

I had the same issue when I mounted 245-50x16 GSC's all around.

Can't blame alignment, since the tires went on the back. Can't air them up any higher, 35 psi is the max.

Any ideas?