Bad coupling from the steering wheel to the rack & pinion or steering gear. Faulty steering gear
If everything was fine prior to the new tires and If the tires were balanced correctly then you have at least 1 defective tire rotate the tires to identify where the culpret is.
I've heard unevenly worn tires may cause death wobbles. if the tires are worn unevenly, look for the cause of uneven wear and rotate/replace bad tires. if the truck has a lift then maybe it wasn't tightened down to specified torques or may require re-alignment. worn out steering and steering stabilizing components may also cause death wobbles.
You may need a new steering shock, rotate tires or need new tires. A new steering dampner shock, or front break rotars.
Your tires would definitely have to rotate if you are speeding !
In my area it costs $20-$32 to rotate and balance the tires.
Rotate tires 2 front 225 and 2 back 245
Sure, you can balance the tires. Any place that sells tires can balance your tires. You cannot rotate the tires as you have already stated they are not the same size. Balance but do not rotate.
More than likely your tires are out of balance. Have your tires rotated and balanced. Make sure they check for a bent wheel.
Most common cause is warped rotors.
There could be several reasons why the steering wheel in shaking when you are coming to a stop. Below are some things to check for: 1.You may have a knot in the side wall of one or more of your tires. 2.If you have recently had your tires rotated, this may cause your steering wheel to shake. This is because you have waited to long to rotate your tires. Put the tires back to their previous location, however, this may not correct the problem. 3.Check to see if all of your tires are wearing evenly. If they are not, take your vehicle to a certified auto shop to have the alignment corrected.
On average you should rotate your tires every 6000 mile or 6 months.
It's a good idea to rotate your tires every so often.