2008-2013 Cadillac CTS General Discussion Discussion, Tires in Cadillac CTS Second Generation Forum - 2008-2013; Can I put tires on the back of my CTS SPORT WAGON AWD that are larger than the front tires ...
Check the outside diameter (all tires of the same rim size do not have the same outer diameter). If different than stock, it could cause a problem with speedometer calibration. If different than front it could cause a problem with the ABS.
You also have to be concerned about the effect on your AWD. If you are going to the same wheel tire combination, only wider in the rear, you should be good. As mentioned above, different diameters could have the ability to cause a host of problems.
I have the cts-v rims on my AWD sedan, which the rear rims are wider than the front. The only tire sizing that was suggested to be safe for me was 245/50/19 and 275/45/19 for the same diameter in the front and back and to ensure an equal spin.