Sentence:  These are MPH for Car speed RPM for Engine crankshaft speed R for Rear axle gear ratio W for Tire size Tire size can be determined in several ways but the one that is the easiest and as accurate as any <WSD>is</WSD> by measuring the effective radius of a wheel and tire assembly . 
Meaning of the word marked with <WSD> tags:  be identical to; be someone or something