We'll start by saying that the basic physics are fantastic. Every external and internal force that acts on the car at speed, under braking, or during accleration is modeled. Jump in and smash the accelerator to the floor and you'll be spinning the tires and out of control almost instantly. Get into a turn too hot and you'll either mush right off the track with the wheels turned as far as they'll go, or you'll spin. Which way you crash is dependent upon what you are doing with the throttle/brakes at the time. For example, if you panic and lift the throttle you'll probably spin as weight shifts to the front of the car. Too much throttle and the result will likely be the same as you break loose the back wheels. To get through a turn as quickly as possible requires a deft touch on the throttle. In fact, the physics are so accurate that you will actually use the throttle as you go through the turn to help you control the car. For example, if you find that you're too close to the edge of the track, a slight increase in throttle will help push the car to the outside of the turn. Reducing throttle has the opposite effect, acting to put a little more weight on the front wheels and moving the car towards the inside of the turn. These are very subtle movements of the throttle - too much throttle input can completely break the wheels loose and result in a spin or off-track excursion, neither of which will help you win races.
It's an absolute requirement that you be smooth on the controls, and that you understand the relationship between throttle, brake, and weight transfer. Another thing to be conscious of is down shifting. Downshifting without controlling the rpm of the engine is a recipe for a spin. You want to make sure that the rpm is nicely matched with the rpm you will be going to in the downshift. If you get it wrong, the downshift will act to lock up the rear wheels, almost guaranteeing a spin.
Simbin's GTR Racing is not the first or only PC-based simulator to model these effects, although it is the best implementation I've seen. What sets GTR apart from the pack is that it also models irregularities in the track surface itself. Does this matter? You bet it does! Consider the case of the Rivage turn on the Spa-Francorchamps course in Belgium. This is a 180 degree right turn, requiring strong braking and downshifting of at least a couple of gears. The braking area is a straight piece of track, so this should be pretty easy. What complicates matters is that it is also a very bumpy piece of track. As you get into the heavy braking zone, you will notice a distinct loss of braking efficiency and a skitterish steering feel as the tires and suspension deal with the bumps. This is a single example of a phenomenon you will find on every track in the series, and it adds a level of realism found in no other simulator. If that's not enough, GTR also models weather effects (rain!) and track surface degradation resulting from the rubber "marbles" that build up on the outside of the turns during a race. Oh, you think you will save some time cutting the corner and going across the curb and/or rumble strips? Careful there, fella. Get those wheels bouncing too much and your short cut will end up being the fastest way to lose the race. The surface of any given track and the cars reaction to bumps/curbs is something that has to be dealt with by both the driver and the technical team setting up the car.
Speaking of car setup, this is another area in which GTR shines. It seems that it if can be adjusted on the real car, it can be adjusted on the GTR simulated cars. Tire pressures, spring rates, wings, camber, toe-in, gear ratios, weight balance, brake bias, and many other aspects are fully adjustable. To aid the very knowledgeable car set-up folks, GTR uses the same MoTec data acquisition and analysis package used by real-world race teams. Fortunately, it is not required that you learn to use all of this stuff if you don't want to: the default set-ups are good enough to compete, albeit at a lower competitor skill setting. For those that choose to, though, there is enough complexity in this area of the game to satisfy any would-be crew chief. Personally, we found that minor adjustments to gear ratios, fuel load, and pit strategy were enough to get by and be at least somewhat competitive.
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