ditch 50/50 weight distribution for better rear traction?
03-02-2003, 11:38 PM
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ditch 50/50 weight distribution for better rear traction?
I've come to the conclusion that I need to change the suspension settings in the rear to aid my traction problems. I have already placed an order for softer rear springs as was recommended by a friend. However, before I go in swapping springs, I'm going to try a few things.
I can't get power down exiting turns b/c the car wants to oversteer. I've tried many lines and still suffer from the rear end stepping out. I'm running some toe and camber to help the bumpsteer problem (1/4" toe in, ~3 degrees of camber) springs are 10kg front and rear which is about 560lbs. First thought that came to mind was to lower the rear end, but that would throw off the 50/50 front to rear. I just need to get the left and right side to be equal, front to rear can be off. The car sits right now with the front slightly lower due to corner weighting. This gives a raked stance that I also think might be my problem. I played around with compression and rebound settings by raising one and lowering the other to see how the car responded to steering imputs. It seems as though with the tires I was running (victoracers) the handling was best with higher rebound than compression.
any other advice besides lowering rear and/or installing softer springs?
tia
-ardy
I can't get power down exiting turns b/c the car wants to oversteer. I've tried many lines and still suffer from the rear end stepping out. I'm running some toe and camber to help the bumpsteer problem (1/4" toe in, ~3 degrees of camber) springs are 10kg front and rear which is about 560lbs. First thought that came to mind was to lower the rear end, but that would throw off the 50/50 front to rear. I just need to get the left and right side to be equal, front to rear can be off. The car sits right now with the front slightly lower due to corner weighting. This gives a raked stance that I also think might be my problem. I played around with compression and rebound settings by raising one and lowering the other to see how the car responded to steering imputs. It seems as though with the tires I was running (victoracers) the handling was best with higher rebound than compression.
any other advice besides lowering rear and/or installing softer springs?
tia
-ardy
03-03-2003, 02:23 AM
#2
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Why not change the front swaybar? That adds roll stiffness to the front, reducing oversteer and keeping the chassis flatter which reduces inside tire spin caused by that tire becoming unloaded. Much easier to change and there are several adjustable versions to choose from with a wide range of prices.
03-03-2003, 06:12 AM
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VaporS2k,
Do you have any pictures of your car and a list of your mods? Very curious to see what you've done to it.
As for the oversteer problem, I also would try a different front sway bar. However, when you compare your spring rate ratios to the stock ratios, you will find that you have stiffened up the back of the car relative to the front and this will lead to an oversteer condition. So, bringing the rear rates down will help quell the problem.
You want to leave a slight rake in the stance of the car as this helps high speed stability, I would not suggest lowering the back relative to the front.
Maybe you can also go with wider rear tires?
Do you have any pictures of your car and a list of your mods? Very curious to see what you've done to it.
As for the oversteer problem, I also would try a different front sway bar. However, when you compare your spring rate ratios to the stock ratios, you will find that you have stiffened up the back of the car relative to the front and this will lead to an oversteer condition. So, bringing the rear rates down will help quell the problem.
You want to leave a slight rake in the stance of the car as this helps high speed stability, I would not suggest lowering the back relative to the front.
Maybe you can also go with wider rear tires?
03-03-2003, 03:09 PM
#4
Lowering the rear won't shift weight to the rear. The weight is where it is.
By lowering the rear, you will be more likely to hit the bump stops under acceleration, which will create instant loss of traction.
Lowering the rear will change the height of the roll axis in the rear, and that may have some effect on handling but I haven't thought enough about how the roll axis affects handling to tell you how. I don't think that it will be a big effect, and it probably has more to do with how much the body leans than how much weight shifts left to right in turns.
By lowering the rear, you will be more likely to hit the bump stops under acceleration, which will create instant loss of traction.
Lowering the rear will change the height of the roll axis in the rear, and that may have some effect on handling but I haven't thought enough about how the roll axis affects handling to tell you how. I don't think that it will be a big effect, and it probably has more to do with how much the body leans than how much weight shifts left to right in turns.
03-03-2003, 07:13 PM
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Please explain why lowering the rear won't shift weight to the rear. Last time I checked, as I lifted up the handles of a wheelbarrow (essentially lowering the front), I noticed distinctly that the barrow's weight moved forward.
The weight stays in the same locations in the car, however, how it is distributed on the ground does in fact change.
The weight stays in the same locations in the car, however, how it is distributed on the ground does in fact change.
03-04-2003, 12:30 AM
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If there is any change in weight distribution caused by altering the car's rake angle, it's pretty insignificant.
A loaded wheelbarrow is top-heavy. It's center of gravity is located fairly high above the pivot point, so altering the wheelbarrow's rake angle will horizontally shift the CG a significant amount.
A loaded wheelbarrow is top-heavy. It's center of gravity is located fairly high above the pivot point, so altering the wheelbarrow's rake angle will horizontally shift the CG a significant amount.
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03-04-2003, 07:06 AM
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The CG of a loaded wheelbarrow is high, and you raise the wheelbarrow by maybe 30 degrees, which is enough for the geometry to shift the CG forward.
Lowering the rear of the car will change the angle by only 1 degree or so. Lowering the rear 1 inch shifts the CG down 1/2 inch, but if the CG is 6 inches above a line through the suspension pickups, it will shift rearward only 0.06 inches. For a 2700 lb car that's a weight shift of 1.7 lb from front to rear. A gallon of gasoline would make more difference.
If you are oversteering and wheel lifting you don't want to shift weight rearward anyway. Not only will rear weight increase oversteer, but it will also increase wheel lift, since it moves weight transfer from front to rear. Heavier front bar (or lighter rear bar) is absolutely the textbook approach, since either move weight transfer from rear to front, addressing both your proiblems.
[QUOTE]Originally posted by S2kRob
[B]Please explain why lowering the rear won't shift weight to the rear.
Lowering the rear of the car will change the angle by only 1 degree or so. Lowering the rear 1 inch shifts the CG down 1/2 inch, but if the CG is 6 inches above a line through the suspension pickups, it will shift rearward only 0.06 inches. For a 2700 lb car that's a weight shift of 1.7 lb from front to rear. A gallon of gasoline would make more difference.
If you are oversteering and wheel lifting you don't want to shift weight rearward anyway. Not only will rear weight increase oversteer, but it will also increase wheel lift, since it moves weight transfer from front to rear. Heavier front bar (or lighter rear bar) is absolutely the textbook approach, since either move weight transfer from rear to front, addressing both your proiblems.
[QUOTE]Originally posted by S2kRob
[B]Please explain why lowering the rear won't shift weight to the rear.