Engine Speed
Tire Size Gear Ratio Final Drive

ENGINE SPEED. Measured in revolutions per minute. BMW decided that the redline of the 2.5 and 2.8 liter engines is 6200 rpm; the redline of the 3.0 liter engine is 6400 RPM. If you are using this calculator to determine the top road speed of your car, you should understand the difference between a rev-limited car and a drag-limited car.

TIRE SIZE. The three specifications for tire size, printed on the sidewall of your tire, are width (in millimeters), sidewall height (measured as a percentage of the width), and tire diameter (in inches). Unfortunately, these figures probably do not represent the actual overall diameter of your tires. (See Technical Drivel for details.)

GEAR RATIO. If you have a stock four-speed manual gearbox, then your ratios are:

  • 1st gear (3.85:1)
  • 2nd gear (2.08:1)
  • 3rd gear (1.375:1)
  • 4th gear (1.00:1)
  • (5th gear [0.82:1]; optional)
  • Reverse (4.13:1)

Stuck with an automatic? If you're not quite ready to perform that five-speed conversion, then:

  • 1st gear (2.50:1)
  • 2nd gear (1.52:1)
  • 3rd gear (1.00:1)
  • Reverse (2.00:1)

FINAL DRIVE. I included final drive ratios that one might encounter on an E3. The 3.64 is the standard ratio for all U.S.-spec E3s; the 3.45 is apparently common on the Euro-spec 2800, 3.0s, and 3.0si; the 3.25 is found on the high-end Euro coupes (3.0 CSi and 3.0 CSL); the 3.07, standard on the 635 CSi, has been transplanted to at least a couple of Bavarias; and the 4.10 rear end, normally associated with the 2002, is rumored to have been attached to at least one of Bill Proud's E3s.

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