There will be a slight change to the system but should not be a huge problem. I offer a product called the Recalibrator from AutoTrans that corrects the signal sent to the speedo and ABS computer for accurate displays and function - $149. Stopping can still be compromised due the addtional weight of the tire.

285 is the max width you would want to put on a 7" wide rim and is actually wider than most tire manufacturers advise. You will get more wear down the center of the tire but it is worth it IMHO as the tire looks SOOO much better on the VX.