In this second part of our feature, we look at the very important, yet often overlooked areas of suspension and brakes.
This is a big one! It is quite amazing how many people will spend big dollars on shock absorbers, but then think that it all stops there. The bottom line is that for the car to be fast the vehicle dynamics will have to be absolutely correct and this involves many facets. For example when you lower a vehicle you may change the whole geometry of the suspension and unless you check this, your vehicle may never perform at its optimum level.
Spring rates are another area that will need careful scrutiny. Cars running on slick tyres as a rule will require much heavier spring rates than cars running on semi slicks. Sway bar sizing is also a critical factor. Generally speaking, the best solution to suspension tuning is to find an expert in the field and confer with them before spending your hard earned cash. As every vehicle is different it may pay to shop around and find someone that is experienced in your make and model. This can potentially save a bundle as they already have the data you require to get you very close to your goal right from the outset.
It will also pay to find someone that may accompany you to the track to fine tune your suspension. At the high end of the spectrum you will find a majority of Pro Class cars use completely custom-made suspension more often than not with blade-style sway bars that are adjustable from inside the cabin, infinitely adjustable arms and top level dampers that could be found on any world-class race car. In fact, the coilovers on the Sierra Sierra Evo were actually the units originally used on their Indy Car that were adapted to fit!
Most of the high-end shock absorbers are expensive for a reason and at the top level are a fine investment – but just like anything at that level, they are only as good as the tuner!
Brakes are another area that requires careful planning on your time attack project and once again, getting the right advice early in the piece can be the difference between wasting a stack of money and getting it right. It is often thought in racing circles that when it comes to braking that “bigger is always better” but in time attack racing this may be questionable for many reasons.
Firstly – weight. The bigger the brakes the heavier they are and as they are a part of “unsprung weight” it has an even greater effect on vehicle dynamics. Now I am not saying for a second that bigger rotors won’t have better stopping capacity as this is obvious through their greater moment of inertia. However, once you have an optimum size brake rotor – going any bigger may adversely affect the handling, which would offset any better stopping power. And remember, unlike many other forms of motorsport we are only after one lap.
It is interesting to note that the Cyber Evo won the WTAC 2010 event with standard size brake rotors and standard callipers! In 2011 they came back with bigger rotors, 6 piston callipers, a much faster engine and aero package and shaved 2 seconds off their lap time.
Again, this will depend on the vehicle as well. You will certainly not be able to achieve this with standard callipers on an R34 GTR as they are much heavier and therefor will require a much bigger brake to give the equivalent stopping power. The brakes on the Advan/Hi Octane GTR are Alcon units designed for a V8 supercar and are massive, but they are necessary to give the R34 a similar stopping power to the Cyber Evo and overcome the large weight difference between the two cars.
Pad material is another science that must be addressed with the correct pad selection. Wrong pads can make an enormous difference to your car’s braking capacity. Just as important is the fluid selection. Remember that most of the racing style brake fluids (high boil point) are traditionally very hygroscopic, (which means they absorb water) and must be changed regularly.
In the next instalment we take a look at the final three fundamentals – tyres, aero and the driver. Stay tuned.