ordered new wheels and want to put 285 35 tires on because the 20s were to harsh. the tire shop is telling me that it wont fit and i should use 275 30
the wheels are 19x9.5 et 25

 

Most people here run 275/30/19 on the rears to avoid any rubbing issues.
That is the exact setup i just ordered for my 19's.

Try searching at the top right Google Toolbar.

This exact topic has been talked about in length on this forum.

 

With ET25 in the rear on 9.5" rim, you can run 285/30/19 if you want to. The 285/35 isn't as ideal but it would work. The problem is that your front rim has to be 245/35/19...which would put you way "off spec" on a 285/35 rear.

 

285/35/19 on 166M rims work fine. I think the offset is 28?? but I don't remember.

The problem is the front. You have to run a 245/40/19 (not 35) to match the circumference. On a 166m rim with a 12mm offset that is a problem. You need a higher offset to move the rim inward.

The safer bet is to run a 285/30 or 275/30 in the rear. Both will work, allowing you run a 245/35 in the front.

I just like the look of the bigger tires, but they are a bit more challenging.

 

From my last reply, the 285/35 with the 166m offset is fine. You need to verify the offset which I think is 28mm. A 25mm offset would push the rim outward by 3mm which is a little bit less than 1/8". From looking at my wheels, it is close but may work. You will be right on the border line, but the rear fender lip can be rolled (unlike the fronts).

 

with 19s in those sizes, recommended size is 275/30/19. with an offset of ET25, you will be fine. you can even run a spacer if you would like as the offset for that size wheel with the recommended tire size and having them flushed is about ET16, but Id suggest putting the wheels on first and seeing how you like the stance it will give your car.