345/25 R21 doesn't belong to the most popular dimensions for summer tyres - there are 0 tyre models available, which can be compared to
155/60 R15,
170/60 R17,
160/60 R14. Let's break down the sizing - 25 is height of the tyre, which is calculated as 25% of the tyre width (345mm), which means the sidewall height has 86.25 mm. The wheel diameter is R21, which means it fits to a 21 inch/533.4mm diameter wheel. The total circumference of the tyre is 2217.65 mm, which is very similar to 245/35 R21
(2214.51 mm), 275/45 R18
(2213.88 mm), 225/55 R18
(2213.88 mm), 285/30 R21
(2212.94 mm), 215/70 R16
(2222.36 mm), 285/35 R20
(2222.68 mm), 245/40 R20
(2211.68 mm). There are multiple speed indexes available for summer tyres in 345/25 R21: Y
(300km/h). The same goes for weight indexes: 104, 105.
