By James Andrew
20 July 2005
Q) "The car snaps away when I accelerate out of a corner"
Try adjusting the differential power locking or increasing the preload. If that doesn't help, revert to the old setting and try reducing the rear bump damping. Alternatively try increasing the rear toe-in but don't exceed +0.5 degrees.
Q) "The car slides sideways or becomes twitchy when I lift off the accelerator"
Increasing the differential coast locking percentage or preload will help eliminate this problem. Decreasing the front negative camber will also help.
Q) "I keep spinning off" or "Too much oversteer"
Decrease the rear anti-roll bar or increase the front anti-roll bar. If the problem is only in slow corners, reduce the front negative camber. If the problem is only in fast corners, increase the rear wing angle.
Q) "The front tyres seem to be sliding all the time" or "Too much understeer"
Reduce the front anti-roll bar stiffness or use a stiffer rear anti-roll bar. Alternatively, increase the castor angle. If the problem is worse in slow corners, increase the front negative camber or reduce the rear toe-in. If the understeer is worse in fast turns, decrease the rear wing angle.
Think of the tyre pressure as the stiffness of the tyre; lower the tyre pressures and the tyres will flex more and the more the tyre flexes, the more heat is generated in the tyre. Increasing the tyre pressures will make them stiffer and therefore won't build up as much heat.
The pressure at which a tyre provides most grip is known as its 'optimum' pressure, usually the tyre temperatures recorded from a session will indicate whether the tyre is above or below the optimum pressure. If you take the average temperature of the two edges of the tyre and compare it to the temperature of the middle of the tyre and the values are identical, this usually means that the tyre pressure is the optimum. If the middle of the tyre is hotter than the edges, the pressure is above optimum. And, if the temperature of the middle of the tyre is less than the edges, the tyre is below its optimum pressure.
However, pressure is not the only thing that matters about the tyre. The temperature of the tyre is just as important if not more so: a racing slick tyre is designed to adhere to the track surface much better when it is hot, although if the tyre overheats it becomes less efficient and wears out very quickly. The optimum tyre temperature doesn't really have an exact value, but it is a 'window'. This window in which the tyre provides most grip is from around 85-105 degrees but varies a bit between compounds and tyre manufacturers. As a general rule the hard compound tyres work best at a slightly lower temperature window of around 75-95 degrees. In professional motor racing it is common practice to run each tyre at a different pressure in an effort to keep all the tyres within the optimum temperature window. For instance, if your right front tyre is only reaching 75 degrees and your left front is reaching 90 degrees, reducing the pressure of the right front tyre would really help increase its operating temperature and result in an overall improvement in front end grip.
Finally, I just want to say that soft compount tyres aren't always the quickest, even for a hot lap. The tyre temperature is much more crucial than the compound, so always pick the compound that keeps the tyre inside the optimum temperature window.
Adjusting the suspension can fundamentally change the way the car feels.
The main adjustments of the suspension are: spring stiffness, damper rates, ride height and anti-roll bar stiffness. Adjusting these affects the handling in both lateral (mid corner) and longitudinal (braking and accelerating) at both low and high speed cornering. The springs carry the weight of the car, so if you go too soft the car will 'bottom out' easily, forcing you to raise the ride height or use bump stops. Go for too stiffer spring and the tyres won't be in contact with the road 100% of the time and the grip level will therefore be lower unless the track surface is perfectly smooth (which is never the case).
Dampers are not shock-absorbers! It's really the spring that absorbs the 'shocks'. The damper provides a resistance to spring movement which helps the spring to settle after hitting a bump. Without them the car would just continue bounce up and down after hitting a bump in the road. Using very weak dampers will give a similar effect and will tend to make the handling inconsistent, often leading to a car that you have to ‘fight' through a corner. Running the dampers too firm will stop the spring from absorbing bumps in the road. However, running the dampers a bit firmer than normal can make the transitions from braking to accelerating (and vice-versa) smoother with more predictable handling. Essentially in this case you are trading grip for driveability because using too firmer damper is just like stiffening the spring. If the car does not feel 'alive' on it's suspension, chances are the dampers are too firm.
Dampers in GTR can only be set properly by trial and error. In earlier ISI based games such as F1C, the damper resistance was shown as an actual figure which made it easy to guess what settings to use to sort out a particular handling problem. In GTR the numbers in the damper settings relate to the actual settings for the valve adjustment nut. The numbers in the setup screen don't mean much at a glance. A setting of 1 means the damper will provide the lowest amount of resistance it can, allowing the spring to compress or recoil quicker. But how do you know the relationship between a setting of 1 and the maximum setting of 16? Racing dampers offer a maximum bump to rebound ratio of approximately 1:2. On that basis it's fair to assume that a damper setting of 16 (the maximum in GTR) offers twice as much resistance as a setting of 1.
Increasing the percentage of power locking will give you better traction when going in a straight line but tends to make the 'rear try to overtake the front' when accelerating whilst turning. If you have 100% locking, both rear wheels will recieve the same amount of torque when you accelerate which means that the outside wheel will be more likely to lose grip during cornering. Decreasing the power locking will cause more wheelspin in a straight line but you won't get as much power-oversteer because the lions share of the engine torque will be fed to the inside (unloaded) wheel causing it to spin. This doesn't always result in oversteer since it is the outside wheel that is doing most of the work. Beware of setting the power locking too low as this will cause wheelspin.
The theory for coast locking is the similar but when coasting there is nowhere near as much torque for the diff to transfer to the wheels, only the effect of engine braking. If you encounter oversteer when lifting the throttle, such as when braking, increase the coast locking. If you set the coast locking very high or even 100% you may find that the car becomes unstable when downshifting. Decreasing the coast locking frees up the car when decelerating and will help turn-in, though setting the coast locking too low will give you lift-off oversteer.
Preload is what it says: it applies load to the diff even before torque is tranferred and affects power, coast and neutral throttle (neither accelerating nor decelerating). You have to have enough preload to takeup the play in the bearings so if you set this too low the diff will be 'loose' and the diff will slip and never lock-up fully. Too much preload will make the diff 'tighter' and lockup very suddenly when power is applied. If you were thinking of increasing both power and coast locking, you should try increasing preload instead as this gives you more locking overall.
Thanks to our guest author, James Andrew for this set-up guide.