Tires: new tires causing front end control issues, rim diameter, street tires

Question
I had new tires put on the back of my Toyota Tundra. The tires that were replaced were regular street tires but I asked to have road grippers put on because I don't get much traction in the rain or on hills on dirt roads. since the new tires have been put on I lose front end control at intermitent moments while driving. Very scary feeling. The tires have been exchanged for two new ones, air pressure has been adjusted, and tires have been rebalanced. Even though the tires are supposed to be the same size my husband noticed the front tires have 16/75 on them and the back ones have 16/45. Curious if this is an issue. Desperate for resolution a.s.a.p. because we have scheduled a 2000 mile trip for the 24th of June.

Answer
Patsy,

If what you have said is true, then you have HUGE!!! problems.

But first we need to be sure of the tire sizes involved.

The pattern is PXXX/YYR16

Where the letters in front of the tire size are either "P" or "LT", XXX would be the width of the tire (which you didn't tell me!), YY is the aspect ratio (which you said was either 75 or 45, and that is what is alarming!) R = Radial, and 16, the rim diameter.

BTW is this a 4X4 - if so, all 4 tires should have been changed at the same time.

Post back with the tire sizes involved and let's see where that takes us.