275/65 R18 doesn't belong to the most popular dimensions for summer tyres - there are 7 tyre models available, which can be compared to
155/60 R15,
160/60 R18,
165/60 R14. Let's break down the sizing - 65 is height of the tyre, which is calculated as 65% of the tyre width (275mm), which means the sidewall height has 178.75 mm. The wheel diameter is R18, which means it fits to a 18 inch/457.2mm diameter wheel. The total circumference of the tyre is 2559.46 mm, which is very similar to 255/70 R18
(2557.88 mm), 235/85 R16
(2531.81 mm), 265/75 R16
(2525.53 mm), 265/70 R17
(2522.07 mm), 285/65 R17
(2520.5 mm), 265/65 R18
(2518.61 mm), 285/60 R18
(2510.76 mm). There are multiple speed indexes available for summer tyres in 275/65 R18: H
(210km/h), K
(km/h), S
(180km/h), T
(190km/h). The same goes for weight indexes: 113, 116, 123.