About a month ago my wife had a flat tire in the rear pass. She was close to home and got the idea to try and drive on it. Needless to say, the tire was ruined. It was a 315/40/17. Anyway, for the time being I put some stock 16's out back to get by until I can get some new tires, and a new wheel. So I have 17's up front and 16's in back. I didn't think there would be much of a differance when driving, but that's not true. The car now seems to randomly sway from side to side in the rear. It actually feels like the front is trying to go one way and the rear the opposite. I think I have a bad shock in the rear right, the spring is a new OE replacment, but the car sits low on the corner. It was like that before the flat however, and this never happened. It can be really scary at times, such as when it's raining. If I'm on the highway it feels like I'm hydro planing constantly. Is it the bad shock and I'm only now able to feel it with the slimmer wheel? What should I check out? Thanks for any help.

 

smaller tires (diameter or width) should be on front, more importantly the rear tires MUST match each other and the front tires MUST match each other, but the fronts and backs don't have to match just have to be within like 3/8" of the same diameter. please list tire sizes for ALL 4 corners.

 

I'm guessing 275/40r17 on the front and 245/50r16 on the rear? Op was running a tall tire on the rear to begin with. Should be 315/35r17 to keep size close

 

You got it. The rear are 245/50/16, the wheels I took off had 315/40/17. It's just a temp thing for now. Until I can get new tires though I have no choice but to drive it. I can't put the taller/wider tires in back because of the offset. There 17x9.5/17x11 ZR1's. So long as this crap goes away when I get new tires, that's good. Thanks.

 

I mean to keep both tires close to.the same diameter you should run 35 in the back not 40 series. That'll put them the same height as the front.

But yes. Skinnier tires in the back will make the car feel like how you described. The 275s should fit on the rear though just temporarily. The car will feel 100x better