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Setup Dev 08 - Gearing

rFactor setups, GTR2 setups, GTL setups, RACE setups, Sim Racing setups
Gearing is our first "black art" subject. Proper gearing is often overlooked to the point of blatant neglect by many sim-racers. We usually set our top gear to what is needed for the longest straight and evenly gap the remaining gears. This will do the trick of course, but without optimizing your gearbox for the track you are losing time.

The first step in the process is to determine the RPM range at which the engine is at peak power. “Power” is usually defined by the common term “horse power”. But, horse power is a fictitious number based off torque and RPM. It should not be used as the sole rating of power. You must also look at the Torque numbers of a motor. Torque is what propels the wheels. Horse power simply maintains that motion.

What truly creates forward motion is the torque to the drive wheels. This torque is transferred through the tires to push the racing surface backwards. Since the racing surface itself happens to be fixed to this huge ball of dirt we call Earth it can not be pushed backwards. In turn, it pushes back with equal force (Newton’s Law) propelling our vehicle forward. The more torque you can deliver to the drive wheels, the greater the force in which you will be propelled forward. The engine torque will always remain the same between all gears, differing only with RPM. Yet, the rear-wheel torque will change with gearing.

An example I have used in the past; Remember your old 10-speed bicycle in the garage? Put it in first gear and pedal away as fast as you can… you shoot off, right? Now place it in the 10th gear and try again… much slower, right? The engine (your legs) are producing the same amount of torque no matter what gear you are in, but the gearing has changed the amount of torque being delivered to the rear tire causing faster acceleration. 1st gear will always deliver more torque to the rear wheels then 2nd gear even though the engine is not delivering any addition power. This is why it is much easier to accidentally spin your tires in a lower gear then in other gears.

So now that we know what we are looking to optimize, we can set out to do just that. Start by setting your top gear to the longest straight on the track. Set it to a point that maximum engine RPM, just before braking, is right at (or just beyond) the point of maximum horse power.

You will now have to decide what purpose 1st gear will have for this race. Does the track have a hairpin turn that may require a super-low gear selection? Standing or rolling start? Are pit stops required? These questions will help determine the use of 1st gear. Generally, if you car is going to be at a stand still for any reason and you will be accelerating from that stand still, you will want to reserve 1st gear for that reason alone. This stand still could be a standing start or pit stops.

If you are lucky enough to not have to deal with your car being at a stand still, then tune that gear to the slowest corner of the track, or the speed of your formation lap pace speed of a rolling start. You are looking to have your engine RPM just below the point of maximum torque at the exact time you are planning to accelerate from those low speeds. If you are already in 2nd gear, you are not using the full potential of the torque that can be delivered to your drive wheels. If you are already near maximum engine RPM in 1st gear, you will be forced into an instant gear change costing even more time. If your peak torque is at 5500 RPM, then 4500-5000 RPM is a good target to shoot for as you are exiting that slowest corner. The goal is to exit the corner fully and still have a few RPM left to accelerate in a straight line before changing gears.

All gears in between need to be optimized for each corner in which that gear will be used. You are looking to avoid any unnecessary gear changes, and especially looking to avoid any gear changes while cornering or accelerating out of a corner. By this time you know what gear you will be using in each corner of the track. Set each of those gears to be at peak Torque (or slightly below) just as you are finishing your track-out portion of the turn. Ideally, you will have another second or so of maximum torque prior to changing to the next gear. This will maximize your acceleration out of the corner and onto any straight following it. You may not have "even spacing" between gears any longer, but you will be accelerating faster out of each corner and lap times will drop.

Note: You may need to revisit your gearing setup after any significant setup changes that may alter your cornering or straight line speeds.