I have a 2016 Volvo R-Design. We purchased a set of aftermarket wheels and tires for my car hoping to prevent the factory wheels from being scratched during mounting and dismounting. I was sold an 18" wheel and learned that my factory wheels are 20".... Is this going to cause any problems for the transmission, or brakes? I am worried...

 

with AWD cars, you want to use the same size tires at all four corners to avoid different rotation speeds. Its not uncommon for a model of car to offer different wheel sizes by trim package (For example a standard car may have 17s, but the sport trim has 18s or 19 (even 20) The key is the tire profile varies with the rim size. Example, say your S60 came with 235/45-17 tires. If you decided to upgrade the wheels to 18s, you'd run 235/40-18 tires (and so on...). Its not uncommon to run one size for summer tires and another for snows as well, but again if you have AWD you should run the same size at all four corners. Note, its ok to run a different size rim for a short time provided the tires have the same circumference (ie a "donut" spare is a different size, but its only intended for up to 50 miles.

 

Thank you so much for your input! All 4 tires are the same!