AWD Understeer
08-28-2009, 01:40 AM
#16
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If a car understeers, the faster you travel around a given turn, the more you have to turn the steering wheel to maintain the same turn. If neutral steer, you can steer the same amount regardless of speed. If oversteer, the faster you travel around a given turn, the less you have to turn the steering wheel to maintain the same turn. I think understeer is more stable and predictable; oversteer is unstable and the car suddenly spins out; a slight amount of understeer to neutral steer is ideal to maintain control.
If the car is front heavy, more cornering force occurs on the front tires in a turn, they slip more as speed increases, and the car would understeer. A rear engine car would tend to oversteer. Too much understeer or oversteer would limit how fast you can corner since either the front or rear would slide out first.
The FM platform moves the front wheels forward and engine rearward to better distribute weight closer to 50/50. I think the AWD is slightly more front heavy and would tend to have slightly more understeer.
When you accelerate in a turn with RWD you generate traction force and cornering force on the rear tires so the rears will slip more and reduce understeer. I think the G AWD would do the same thing since it defaults to RWD unless you lose traction -- correct? Unfortunately, I don't drive my AWD car hard enough to offer any advice on how best to do this.
I don't know what happens if you decelerate with RWD vs. AWD when turning.
If the car body rolls or leans, more force ends up on the outside tire and the tires lean, reducing the amount of cornering force they can generate -- this probably creates more understeer and limits the speed you can corner regardless of steering. Stiff springs, low cg, and anti-roll bars help this. Wide sticky tires also --
Another issue is how quickly you can change into and out of turns. Stiff springs, anti-roll bars, quick ratio steering, and stiff tires (low profile) help this.
If the car is front heavy, more cornering force occurs on the front tires in a turn, they slip more as speed increases, and the car would understeer. A rear engine car would tend to oversteer. Too much understeer or oversteer would limit how fast you can corner since either the front or rear would slide out first.
The FM platform moves the front wheels forward and engine rearward to better distribute weight closer to 50/50. I think the AWD is slightly more front heavy and would tend to have slightly more understeer.
When you accelerate in a turn with RWD you generate traction force and cornering force on the rear tires so the rears will slip more and reduce understeer. I think the G AWD would do the same thing since it defaults to RWD unless you lose traction -- correct? Unfortunately, I don't drive my AWD car hard enough to offer any advice on how best to do this.
I don't know what happens if you decelerate with RWD vs. AWD when turning.
If the car body rolls or leans, more force ends up on the outside tire and the tires lean, reducing the amount of cornering force they can generate -- this probably creates more understeer and limits the speed you can corner regardless of steering. Stiff springs, low cg, and anti-roll bars help this. Wide sticky tires also --
Another issue is how quickly you can change into and out of turns. Stiff springs, anti-roll bars, quick ratio steering, and stiff tires (low profile) help this.
08-28-2009, 11:45 AM
#17
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Ok ,thanks everyone. I guess I will have to do some trial and error in the turns to see how the car feels. Throttle definately helps, but I am still nto sure when and how much to apply...
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