b'TECH TIP PAGETech Tip 60:Tuning mechanical grip versus aero grip. First, we need to be clear on thedifference. Mechanical grip is tire grip created by the chassis, geometry, suspension &steering with no aerodynamic aids to create grip through downforce.The chassis part is weight, distribution, center of gravity, track width, etc. The suspension partis springs, sway bars, shocks, control arms, stiction, etc. The geometry includes dynamic front& rear roll centers, camber & caster gain, anti-dive, anti-squat, etc. The steering part includestoe settings, bump steer, Ackerman, steering input, etc. All of these components contribute tothe raw handling of the race car & the net result we call mechanical grip.Aero grip, is additional grip we create by adding aerodynamic aids to create downforce on thecar & therefore on the tires. Wings, spoilers, air dams, splitters, diffusers, smooth belly pans,canards, etc. all combine to create downforce in some quantifiable amounts, front, rear & total.Which do we tune first?This answer should make it clear. Think of the grip in layers. Themechanical grip is the bottom layer & the aero is the top layer. In running your race car, youALWAYS have the mechanical grip, but you dont always (at lower speeds) have aero grip. So mechanical grip is your FOUNDATION. Aero grip adds a LAYER of GRIP on top of themechanical grip in the higher speed corners, where you need it, to create more TOTAL GRIP. Design your cars front aerodynamic aids to create maximum downforce in the front & leave italone. We dont tune to reduce the front downforce in full bodied, front engine cars. We want all we can get up front. Then we balance the aero at the rear of the car. Design & adjustyour cars rear aerodynamic aids to create a measure more downforce than youll ever need. While driving & tuning for the slower corners of the course, we dont want to crash the car in the faster corners. So, to be safe, we always adjust the rear aero in the shop for more reardownforce than we need. This way, if we start to over drive the fast corners, the car will push& let us know to back off, instead of the rear end stepping out at high speed & ruining our day.Plan your tuning sessions this way. Start in the slower corners, 40-70 mph, to dial in thesuspension to make the race car handle optimum here. We need the mechanical gripfront &rearto be both maximized & balancedto be fastest in these slower corners. Ignore totallap times. Utilizing segment timers, as well as driver feedback, is the best method here.Then we move on to trimming out the rear aero to achieve the most BALANCED total grip wecan get in the fastest corners. Trimming out means to take out rear downforce a step at atime. All wise racers & teams that run aero, set the rear aero to create a slight aero push inthe high speed turns. Then they trim it out a step at a time. This is the safe way.Starting with the car aero loose is fu@#ing dumb & a great way to crash the car. Whentesting a brand new car, always start with max rear downforce & trim it out when tuning.Lastly, and this is KEY, aero downforce is not an absolute. Airflow is a variable. If we have a headwind, well have more downforce. Tail wind? Less downforce. Crosswind? Who knows! Hang on!A wheel jerking Driver can make downforce disappear long enough to crash. Withsignificant aero, the Driver HAS TO BE SMOOTH as glassor bad stuff will happen. 531'