Bridgestone Alenza 001 is a summer tyre made in total of 57 sizes, ranging from R17 to R17 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 315/35 R21 is 100mm wider than the narrowest dimension (215) and -40mm narrower than the widest one (275). This tyre profile of 35 means the sidewall height of the tyre is 35% of the tyre width (315mm), which results in 110.25mm sidewall height. In 315/35 R21, there is only one possible speed index for Bridgestone Alenza 001 - "Y", which is good for speeds up to 300 km/h.