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Discussion Starter #1 (Edited)
I've seen a few variations on how to plot the neutral line. Top of front tires. Front tire x axis with CG y axis. And a few others.

My question is why aren't we using the CG for both x and y axis? Wouldn't the force vector of acceleration (Bottom of contact patch through the instant center) in relation to the CG (both x and y axis) determine how the rear of the car reacts? Wouldn't that be a better way to calculate antisquat?

The way we do it now doesn't seem to take into consideration where the cg is compared to the wheelbase. Unless I am missing something.
 

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Seems that the X CG could be calculated using the wheelbase and the front/rear weigh bias, I think the older Chris Alston method used something like that. Could swear I have heard of guys balancing the car on two jackstands in the middle of the car also, that might be something Billy Shoppe has wrote about.
Using the camshaft height on the centerline of the front wheels is the most common I have seen. I still figure AS the old school way with everything layed out full scale on my garage wall and use strings to find the points. 馃 If you project a line from the contact patch thru the instant center all the way to the front wheel centerline, the AS is the ratio of the difference between that point (pitch center) and the vertical CG.
 

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Discussion Starter #3
Seems that the X CG could be calculated using the wheelbase and the front/rear weigh bias, I think the older Chris Alston method used something like that. Could swear I have heard of guys balancing the car on two jackstands in the middle of the car also, that might be something Billy Shoppe has wrote about.
Should they not get the same result?

Using the camshaft height on the centerline of the front wheels is the most common I have seen. I still figure AS the old school way with everything layed out full scale on my garage wall and use strings to find the points. 馃 If you project a line from the contact patch thru the instant center all the way to the front wheel centerline, the AS is the ratio of the difference between that point (pitch center) and the vertical CG.
Yes it seems common, but front to rear bias plays no role in the calculation. Yet it does in reality. Two identical cars except for a vastly different front to rear bias, but the same calculated AS%. One might squat, the other may go the other way. Am I wrong?
 

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The AS is a fixed point, I think the difference in weight bias may lead to different settings to make a particular car work? I thought about this same shit, but my shits working so good now I tried to stop over thinking it, 馃槂 The only method I can remember using the weight bias to determine anything is the Chris Alston "percentage of rise" formula, but that's old school shit and probably has no meaning in the radial world or with today's power levels. Could be wrong on that, just my opinion,
 

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My thought is that it should be calculate on actual C/G. Think about it. Two cars. One is 120" W/B the other is 100" W/B. Assume both chassis 100% stiff for this question. Both have the C/G 25" up and 50" out. Why would either car react any differently with the same percentage of anti squat? Why does the wheel base have any affect? With the front wheels off the ground there would be no difference.
Doug
 

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I kinda like the old Alston "Percentage-Of-Rise" thinking more than the "squat/anti-squat/neutral line" deal. My opinion is because "POR" just gives you a basic/simple percentage reference number directly related to the C/G's height, with no reference to a neutral line (and no reference to if the car "should" squat or separate) like the S/AS/N does.

The reason I care less about the "magical" neutral line is because over the years I have seen some cars that did exactly the opposite of what the neutral line theory says they should have done. Some either (A) squated even though their I/C was well above the neutal line, or (B) they separated even though their I/C was below the neutral line. IMO this is because the neutral line theory doesn't/can't factor in the additional effects the engine's power/torque numbers also has on a car ability to squat or separate at launch.

POR doesn't make any claims about if the rear suspension will squat or separate, it just gives you a simple reference number 0 to 100 to try out, kinda like bumping the volume up/down on the TV.
 

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My thought is that it should be calculate on actual C/G. Think about it. Two cars. One is 120" W/B the other is 100" W/B. Assume both chassis 100% stiff for this question. Both have the C/G 25" up and 50" out. Why would either car react any differently with the same percentage of anti squat? Why does the wheel base have any affect? With the front wheels off the ground there would be no difference.
Doug
This seems to go with Shoppes theory of. It doesnt matter the hieght and length of IC as it will act the same at the same giving AS%.
 
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