BFGoodrich G-FORCE WINTER 2 is a winter tyre made in total of 107 sizes, ranging from R14 to R14 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 275/50 R20 is 120mm wider than the narrowest dimension (155) and 0mm narrower than the widest one (275). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (275mm), which results in 137.5mm sidewall height.