What's the rpm difference at 130 km/h in ML320 and ML230?

    ML320    ML230 
 A  5th gear 0.830      0.799
 B  axle ratio   3.70   4.78
  final ratio = AxB  3.071 3.819

Final gear ratio means the tires turn x times less than the engine crank shaft.

  Kilometers per minute 2.16666 2.16666

Here are 130 Kilometers per hour converted to x Kilometers per minute

 tire size   255/65R16   225/75R16
   tire circumfrence in mm   2 251 2268
 wheel rpm @ 130 km/h 962.5 955.3

Note that the tire on the ML320 is slightly smaller than the ML230 tire !!

Dividing Kilometers per minute by the tire circumfrence gives us the revolutions per minute of the wheel

engine rpm  2 956 3 648

Revolutions of the wheel per minute times the final ratio gives us the engine rpm

Difference between ML320 and ML230 is 692 rpm @ 130 km/h

© 1998-99 Harold Pietschmann