Skip Barber Tips and Techniques 2
These are old articles
for previous models of iRacing cars that may have changes significantly. This
was all designed for a TNT Racing app in 2015, but is now free to the public as
a general guide. Some links may be broken and can no longer be updated.
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The brakes in any race car are biased toward the front as weight transfer forward occurs every time you step on the brakes. The brakes on the front are usually bigger (physically more capable and larger with better cooling options) to cope with the tremendous loads put on them. In iRacing, there is currently no model for brake wear, so that discussion is removed and will be re-instated upon inclusion into the service. What racers should focus on is the shortest stopping distance coupled with proper apex timing and the weight transfer relationship discussed earlier. When discussing maximum braking effort and minimum distance, the idea is to gain the entire grip available out of both the front (and in some cases the rear as well).
When you brake too much, the tires at the front or the rear lock up. If the rear locks up, the rear of the car becomes unstable at times, resulting in oversteer and possibly an out-of control situation. Front lockups generally result in an inability to turn the car, longer braking distances, and missing the entry point. Optimal braking occurs just prior to wheel lockup. At this point, the wheels are rotating slightly slower than a one-to-one relationship of the distance traveled as the car slows. This can be found in telemetry when looking for lockups and partial lockups within the "wheel deceleration" diagrams (See Picture).
When you find wheel-lock in telemetry (or in the car), try to recognize the instantaneous braking percentage to use as a guide for brake application the next time you brake at that corner (Figure XYZ). It’s acceptable to have partial lockups. This means you are trying to get that perfect wheel-speed, but are slightly over, though not fully locking up the tire. Typically, the inside tire will lock up first if you have any cornering weight applied (as in trail-braking). The partial lockup may occur over bumps which at times may be unavoidable when achieving optimal braking. All corners are different. Let us assume that we are entering turn 1 (T1) at Lime Rock Park (LRP). This corner is unique in that it requires quick braking application and a slight trail-brake for the quickest sector time. The corner is also a “decreasing-radius” turn. The first half of the corner has a specific turn radius and the second half has a turn radius slightly that is slightly lower. In other words, the second half of the corner requires a slightly tighter turn based on geometry alone. This is the first thing that should be studied when dissecting cornering options. It is important to understand how a corner is designed and what the fastest way through the corner would be in a theoretical sense. As an example, let’s assume that after T1 at LRP there is a long straight (which, obviously, there isn’t). In this case, the proper line would be one that maximizes exit speed. If the following section was a slow-speed chicane, perhaps the best line would be one that minimizes time in the corners versus the previous example of generating exit speed. The next important aspect is to find the proper braking marker to use to begin braking.
In real-world racing, a driver that has no experience at a particular circuit would brake early on the first attempt to try to find the correct spot to begin braking. Lap after lap, the driver would attempt to brake later as he or she found that later braking was optimal. IRacing has the added benefit of not having to pay for mistakes, so the ability to test and acquire the optimal braking zones happens faster. Initial braking technique should be to max-perform the available tire grip all the way to any weight transfer required by turning the car. Using the “speed-delta,” in iRacing, you can find optimal times which roughly equates to optimal performance in a specific sector. It is usually best to use all the grip available to slow down, transition immediately from brake to throttle (using left-foot brake and right-foot throttle to quickly transition), and use throttle for as much of the corner as possible. Occasionally, trail-braking makes for optimal sector times.
Previous braking technique (straight-line) prior to turn-in works great, but in cases such as decreasing radius turns and various other types of corners trail-braking is optimal. Trail-braking simply means that the driver is using the brake during weight-transfer in corner entry to modulate grip levels and oversteer/understeer. As you begin braking, it remains imperative to reduce speed as quickly as possible as late as possible to arrive at corner entry with the correct speed to begin cornering. As you begin cornering, trail-braking technique is applied to continue to slow the car down while maintaining the perfect line to an apex. As you are able, transition from the high level of braking to no braking at the rate that allows maximum cornering G (if required) such that you can pick up throttle and use it to push to the exit point. There is an option to not trail-brake, but rather to use excessive amounts of oversteer to slide the car around a corner, slowing down in the process, but to understand how this works best, weight transfer must be discussed in detail. Click on "weight transfer" below to continue.