I will be buying 17's soon
when I do... if I get a flat... can I still use the donut, or does it become useless???
thanks

 

doesn't matter at all. so long as you use it on the front of the car, or else it will damage the differential.

 

so if i get flat in rear.. i put 17x7.5 on rear and donut on front??

thanks

 

yes.

 

What schatten said is fine, as long as the rolling diameter of the front and rear wheel/tire combo are (very) close.

 

This is very interesting.
A thought just came to me while reading this that our front and rear hubs are different diameters! If the aftermarket wheels have specific hub rings for the front and rear, simply switching the front to the rear so you can put the donut on the front is not a correct fitment anymore.
Does this mean that our stock wheels are not hubcentric specific to the front and rear?

 

It just came to me that the front hub diameter is larger than the rear.