Tires?

Will 205/70R15's work on a 99 Grand Am?

It should but it is going to be very close not sure if it is going to work on bumps. I suggest ask them just to mount two on the front and try. let me guess tired of bad roads :), I felt the same way nothing worse than not keeping distance from the car in front of you, and then when you see that the car in front hits the path hole hard it is already late. (damaged 4 rims on mine didn't have more than 5K on tires) since then never wanted to buy anything bigger than 15.

if original is 195/65/15 it is just one size bigger (195x65)/100=126mm hight
(205x70)/100=143.5mm 143.5-126=17.5mm or just bit more than 1/2 inch taller

in general you should not go more than +/- 4mm in difference or your speedometer in this case will show slower speed but you top speed will be higher. Think about bicycle gears :)

HELLO. We have run the 205/70/15 size on my daughter's "96" grand am ever since the original 195 s wore out. No problems. Do account for speedo error however. Just drive a mile or two under the posted limit.

NOVAZ27