TeamGP:
Yes we did this many times over the past few years and again with the FK05.
Like polesitter61 indicates theoretically a stiffer chassis should work better, but this is like saying that theoretically less chassis roll will mean more grip. Both true and both essentially useless statements when we look at the dynamics involved in real life.
On the track less chassis roll means more grip, but that doesn't give you anything if the additional grip is insufficient to cope with the additional force put on the tires during cornering. If the additional grip is insufficient the car will slide out. So you change to softer springs, softer damping, more droop or change a host of other setup options to dampen the force put on the tire at the expense of some of the grip the tyre will give. Result, less theoretical (!) corner speed, but better laptimes overall.
A similar argument goes for chassis flex. Theoretically stiff is better. But who cares if you are sliding of the track loosing many seconds each time?
Polesitter61:
While 1:1 setup theories in general apply, we allways need to take into account a couple of important facts. For one thing the track surface is not to scale. We race on the same asphalt the 1:1 cars race on, except our cars are ten times smaller. I.e. bumps, cracks etc have a ten times bigger effect on our cars than on their 1:1 counterparts. Also, on many corners we have corner speeds in excess of 30kph (tight corners) up to 50kph or more (fast corners). I have yet to see 1:1 cars drive through tight corners at 300kph and faster corners at 500kph (ok, Indy cars may come close).
Screswel:
1) Not sure I understand what you are asking here. If you mean what has the biggest effect on torsional stiffness I am not sure I have a clear answer. I'll try anyway. Generally the chassis is the bigger change if only because it takes a lot of time to make the change. So which chassis you run is one of the first choices you need to make. With the chassis change you change torsional flex at both the front and the back. Next comes the top deck. Using the front-posts you can reduce chassis flex at the front of the car and similarly the rear posts have the most effect on the rear of the car. Both we generally use more as fine tuning options, BUT the actual effect can still be fairly large on the car's handling.
2) This is difficult as there are a lot of variables involved. The answer is that it depends. Both if you have too little flex and too much flex you can have a car that feels like it has too little grip. With too much flex this is often augmented by an unstable and especially unresponsive feel to the car while with too little flex the car will feel great until it suddenly breaks traction either at the front, the rear or both. Be carefull though as there are multiple things you can change to get the car to work better that influence the same basic paramenters on the car.
As to the priorities, they are mostly the result of practicality. The choice for a chassis comes first. Once this choice is made you can optimize the setup for that chassis. Next comes tires and tire treatment as these have the biggest influence on grip. After that comes springs and damping.
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