All 4 tires are 275? Most 20” 6 series wheels are staggered where the fronts are 8.5” wide w/33mm offset/rears are 9” wide w/44mm offset…and the fronts tires are 245/rears are 275. The square 20” setups are usually 245 tires on all 4 corners & the wheels are the 8”.5 width wheels w/33mm offset. Did you or a previous owner change the 20” wheel setup?
Before buying tires…make sure you accurately know what your wheel’s specs are as well as the tire’s specs are, too that are mounted to the wheels.
If you don’t have much knowledge about the type of tires you want..I highly recommend browsing the
www.TireRack.com website. They offer lots of info about the tire sizes for your car, and information, tests, surveys, comparisons, etc of many tire brands. They also have a tire decision buying guide that can help select tires that fit your personal criteria.
You don't have to necessarily purchase from them…you can use their site for knowledge alone…then order from a local tire store. Tire purchase is very personal. A person that lives in another part of the country from you may have a totally different tire that fits their driving style and location.