Originally Posted by
caltek1
Hello Martin,
What about hints and tips for setting up FWD cars. I find that they can be the hardest to get right and not all want to share the results.
Some ideas would be for understeer and oversteer. The rear end suddenly letting go mid way through the corner,etc
Regards,
Calvin.
First let me say, I have never worked on a front wheel drive setup before, so what I suggest, has no basis in actual front wheel drive experience. With the FWD cars, the fast majority of the cars weight is at the front of the car, which should translate into the car pushing while entering the corner because the front of the car wants to keep going straight due to the extra weight at the front of the car. I would imaging however that as the car starts to scrub speed to a point where the grip on the front tires is enough to overcome the lateral forces due to weight, and the vertical weight over the front tires could actually start to give the front tires more grip than the rear, then this could cause the snap oversteer. I would guess you don't experience this in a high speed constant speed sweeper, but more in the tighter corners that require you to decrease speed.
Assuming I am on the right track here in terms of the cause, and this typically happens at the apex of tight corners likely in an off power situation, we need to figure out a way to decrease the steering at that point of the corner.
If you increase your ackerman (i.e. the outside tire does not turn as much at full lock) this would help cause the car to push mid corner, which would likely help reduce the snap oversteer.
Next I would make sure I have a low roll center on the front of the car, as this can help with initial turn-in but induce push mid corner, which again could help reduce the snap oversteer.
Next I would think about the spring rates. If the realized spring rate at the front is much stiffer than the rear when you compare pushing the back and front of the car down into the driving surface. This could also be contributing to the snap oversteer as well as contributing to the push on entry. I would strive to find a balanced suspension that feels the same front and rear.
Last I would make sure you have a health amount of droop in the front and rear of the car...likely 3mm above ride height in the rear and 2.5mm above ride height in the front. This will smooth out the car in the corner and help prevent snap oversteer as well.
Again...I have not worked on FWD cars, so I could be out to lunch here. Give these ideas a shot and let me know how they worked.
Cheers.