Posted on , by Rob

Racecar gear ratio selection

gears

The old theory for gear ratio selection went something like:

  1. Pick the ratio for your top gear by aiming to hit the rev limiter when about to brake first the first corner immediately following the longest straight.
  2. Pick the ratio for your first gear that will maximise your start line getaway.
  3. Distribute your other gears evenly between first and seventh

 

There are however other factors to consider. Sebastian Vettel showed us at the recent 2011 Italian GP at Monza that top speed is less critical to success. The commentators made a point of expressing how Vettel had gone with a different set of gear ratios than traditionally would be selected, and than what the majority the other competitors selected.

First gear is important because positions are hard to come by and it's easiest to make up positions when the cars are closest together. This is obviously at the start. To increase torque and reduce wheelspin a high first gear is desired. spacing 2nd through 6th evenly toward 7th isn't the correct way to go though.

In most cases you can consider 1st gear as the starting gear and then ignore it altogether. Gear 2nd gear significantly lower than 1st, so that off the line there's maximum torque, but once second gear is engaged, there's maximum power and you're in the upper rev range before quickly shifting to 3rd.

Gears should be selected based on the circuit and the ratios should be kept close together and correctly selected to leave the engine in the best power generating rev range. You can short shift where extra traction is required.

Ideally 1st and 7th should be two taller bookends either side of your ratios, with 2nd through 6th closely together. Having a much tighter gearbox should provide better corner speed and as Sebastian Vettel provide, a faster lap time.

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