Michelin PILOT ALPIN 5 is a winter tyre made in total of 107 sizes, ranging from R16 to R16 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 305/30 R21 is 100mm wider than the narrowest dimension (205) and -20mm narrower than the widest one (285). This tyre profile of 30 means the sidewall height of the tyre is 30% of the tyre width (305mm), which results in 91.5mm sidewall height. In 305/30 R21, there is only one possible speed index for Michelin PILOT ALPIN 5 - "V", which is good for speeds up to 240 km/h. In 305/30 R21, PILOT ALPIN 5 usually competes against UltraGrip Performance 3, which is a tyre from GoodYear with a rating of 96%, compared to 99% of the Michelin in question.