I had to use a 3mm spacer up front to make my wheels clear the caliper, but i did not put a 3mm in the rear as I did not need to. The X is my first AWD car, so I was wondering if this will cause any issues with the AWD system. Thanks!

 

no it won't

i drove around on 16mm spacers up front for a week before having the rears installed. No adverse affects. And people who track their cars will often run spacers on the rear only.

 

I thought that it was in the front to widen for turning?

 

Ya, people put it in front so they can rotate better, I believe.