ditch 50/50 weight distribution for better rear traction?
03-04-2003, 09:40 AM
#12
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Originally posted by S2kRob
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.
I've been wondering about all those 10KG spring kits out their... Sounds *way* to stiff to me.
03-04-2003, 01:26 PM
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Originally posted by pfb
Yes, but I don't think that lowering the rear suspension a half inch or inch is going to shift a significant percentage rearward. When corner weighting, it's more about balancing the diagonals, recognizing that it's difficult to shift any significant percentage left/right or front/back. Or actually shifting around movable components (like ballast weight or batteries) to achieve a better balance.
I've been wondering about all those 10KG spring kits out their... Sounds *way* to stiff to me.
Yes, but I don't think that lowering the rear suspension a half inch or inch is going to shift a significant percentage rearward. When corner weighting, it's more about balancing the diagonals, recognizing that it's difficult to shift any significant percentage left/right or front/back. Or actually shifting around movable components (like ballast weight or batteries) to achieve a better balance.
I've been wondering about all those 10KG spring kits out their... Sounds *way* to stiff to me.
this is a dated corner balance, I had this done several months back and since (I estimate) that about 50-75lbs has been shaved.
The wheelbarrow is a tough comparison to the s2k when raising and lowering the legs. The CG is pretty low on the s2k and the slightest changes shift the weight by at least 15-30lbs a corner. Ideal set-ups get within 5lbs, but I'm not club racing.
-ardy
03-04-2003, 02:25 PM
#14
Sorry S2kRob, but what happens when you corner balance a car is that you shift weight off one diagonal and place it on the other diagonal. The front/rear and left/right distributions do not change.
Say that your weight distribution is
100 100
100 100
Then you lower the perch on the left rear. Now your weight distribution is
105 95
95 105
If you then lower the perch on the right rear, you do not get
105 105
95 95
You are back to
100 100
100 100
There is a second-order effect due to the CG shifting forward/back relative to the axles. The distance that the CG moves is equal to the height of the CG above the pitch axis of the car, divided by the wheelbase, times the amount that the rear is lowered relative to the front. To calculate the change in weight on each axle, multiply the weight of the car by the amount that the CG moves, and divide by the wheelbase.
Formula: deltaW(f) = W * deltaH * D / L^2
Where W is the weight of the car
deltaH is the change in height of one end relative to the other
D is the distance from the CG to the pitch axis
L is the wheelbase.
Since L is about 100 inches and D and deltaH are each a few inches, the weight shift is a few percent of a few percent...estimate D at a generous 10 inches and each inch you lower the rear will shift 0.1 percent of the weight from the front to the rear (3 pounds on a 3000 pound car).
Cross-balancing, on the other hand, is far more sensitive to changing the perch height of one corner. If your wheel rate is 50 pounds per inch and you adjust the spring perch such that the wheel would be 1" higher, you shift 50 pounds off one diagonal onto the other.
The claim that changing one spring perch height to shift weight to that corner (corner weighting) generalizes to changing both spring perch heights on a side to shift weight to that side just isn't valid. It's a false analogy, similar to the claim that if one swaybar reduces the grip on the front, then a matched set of swaybars reduces the grip on the front and rear. In both cases, you're only thinking about what happened at that corner/end of the car, and not considering what's going on at the other corners/end.
If you think carefully about it, in corner balancing you raise one corner of the car to increase the weight on it, but to shift weight to one end of the car, you lower that end. If that's not a big clue that those are two different mechanisms, then I don't know of any way I can convince you.
Like I said before, if there's a handling effect due to raising/lowering one end of the car, then it's far more likely to be due to a change in the roll axis, camber curves, and suspension geometry effects than due to any weight transferred.
Say that your weight distribution is
100 100
100 100
Then you lower the perch on the left rear. Now your weight distribution is
105 95
95 105
If you then lower the perch on the right rear, you do not get
105 105
95 95
You are back to
100 100
100 100
There is a second-order effect due to the CG shifting forward/back relative to the axles. The distance that the CG moves is equal to the height of the CG above the pitch axis of the car, divided by the wheelbase, times the amount that the rear is lowered relative to the front. To calculate the change in weight on each axle, multiply the weight of the car by the amount that the CG moves, and divide by the wheelbase.
Formula: deltaW(f) = W * deltaH * D / L^2
Where W is the weight of the car
deltaH is the change in height of one end relative to the other
D is the distance from the CG to the pitch axis
L is the wheelbase.
Since L is about 100 inches and D and deltaH are each a few inches, the weight shift is a few percent of a few percent...estimate D at a generous 10 inches and each inch you lower the rear will shift 0.1 percent of the weight from the front to the rear (3 pounds on a 3000 pound car).
Cross-balancing, on the other hand, is far more sensitive to changing the perch height of one corner. If your wheel rate is 50 pounds per inch and you adjust the spring perch such that the wheel would be 1" higher, you shift 50 pounds off one diagonal onto the other.
The claim that changing one spring perch height to shift weight to that corner (corner weighting) generalizes to changing both spring perch heights on a side to shift weight to that side just isn't valid. It's a false analogy, similar to the claim that if one swaybar reduces the grip on the front, then a matched set of swaybars reduces the grip on the front and rear. In both cases, you're only thinking about what happened at that corner/end of the car, and not considering what's going on at the other corners/end.
If you think carefully about it, in corner balancing you raise one corner of the car to increase the weight on it, but to shift weight to one end of the car, you lower that end. If that's not a big clue that those are two different mechanisms, then I don't know of any way I can convince you.
Like I said before, if there's a handling effect due to raising/lowering one end of the car, then it's far more likely to be due to a change in the roll axis, camber curves, and suspension geometry effects than due to any weight transferred.
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CrimsonCore (04-09-2018)
03-04-2003, 03:23 PM
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Note to self: don't get into a geometry debate with a guy named Orthonormal. His angle is always right.
Get it?
Sorry....
Less weight is more speed. Take out all you can and tune around that.
Get it?
Sorry....Less weight is more speed. Take out all you can and tune around that.
03-04-2003, 10:25 PM
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you mean ORTHOGONAL
vapors
you can do the following to reduce your [understeer](correction, the following 4 items are to reduce OVERSTEER; thanks pfb
1. get a bigger front swaybar
2. RAISE rear ride height
3. increase tire stagger to rear(best to get fatter rear tires, )
4. decrease rear camber to -2.00, no greater than -2.50{doing # 2 will help get this}
try 2 + 4 = faster
do all and you'll be euphoric
n.b. the Weigert-Meyer Rule: the obstructed upper pole moiety inserts into the ECTOPIC URETEROCELE, the unobstructed lower pole into the ORTHOTOPIC URETEROVESICAL JUNCTION. ha, just a little pecker-checker humor....you know, human pathophysiology
can be loads of laughs....remember when you peed and it felt like razor blades coming out....what was that skank's name...nevermind.
vapors
you can do the following to reduce your [understeer](correction, the following 4 items are to reduce OVERSTEER; thanks pfb
1. get a bigger front swaybar
2. RAISE rear ride height
3. increase tire stagger to rear(best to get fatter rear tires, )
4. decrease rear camber to -2.00, no greater than -2.50{doing # 2 will help get this}
try 2 + 4 = faster
do all and you'll be euphoric
n.b. the Weigert-Meyer Rule: the obstructed upper pole moiety inserts into the ECTOPIC URETEROCELE, the unobstructed lower pole into the ORTHOTOPIC URETEROVESICAL JUNCTION. ha, just a little pecker-checker humor....you know, human pathophysiology
can be loads of laughs....remember when you peed and it felt like razor blades coming out....what was that skank's name...nevermind.
