235/40 R17 doesn't belong to the most popular dimensions for tyres - there are tyre models available, which can be compared to 325/30 R21, 155/60 R15, 155/65 R13. Let's break down the sizing - 40 is height of the tyre, which is calculated as 40% of the tyre width (235mm), which means the sidewall height has 94 mm. The wheel diameter is R17, which means it fits to a 17 inch/431.8mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 225/35 R19(2010.93 mm), 285/50 R20(2491.28 mm), 225/50 R17(2063.4 mm), 295/35 R19(2164.87 mm), 225/60 R17(2204.77 mm), 305/30 R20(2170.84 mm), 235/35 R19(2032.92 mm).