265/40 R17 doesn't belong to the most popular dimensions for summer tyres - there are 2 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. Let's break down the sizing - 40 is height of the tyre, which is calculated as 40% of the tyre width (265mm), which means the sidewall height has 106 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 2022.56 mm, which is very similar to 235/45 R17(2020.99 mm), 215/55 R16(2019.73 mm), 265/35 R18(2019.1 mm), 235/40 R18(2026.96 mm), 265/30 R19(2015.65 mm), 215/50 R17(2031.98 mm), 190/55 R17(2013.13 mm). There are multiple speed indexes available for summer tyres in 265/40 R17: Y(300km/h). The same goes for weight indexes: 100.