How to find your CG height. - Suspension and Brake Forum

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How to find your CG height.
Sunday, March 26, 2006 12:48 AM
Ever want to know your CG height for your car (useful when used in conjuction with the roll axis)?

This is best done with a solid rod in place of the struts.

1) Get your car on some scales
2) Weigh the car (total weight, and front weight)
3) Jack the rear of the car 10"
4) Weigh the front weight again.


CGH = [ WB * FWc ] / [ TW * tan x ]

Where:

CGH = center of gravity height
WB = wheelbase
FWc = Change in front weight (jack weight - level weight)
TW = total weight
HT = height
tan x = HT / sqareroot( HT^2 + WB^2 )


The higher you can jack, the more accurate it will be, but I wouldn't recommend over 20 inches.



Re: How to find your CG height.
Monday, March 27, 2006 8:43 PM
it is good information, but i doubt anyone will use it



Re: How to find your CG height.
Monday, March 27, 2006 9:07 PM
where is the CGH as you have found it? What is your ride height? Im glad to see the start of more technically in depth discussions on suspension. The usual "where did you get your struts" and "can I lower my car on stock struts" droning gets tiresome after a while. Still...ya have to start somewhere I suppose.



02 LS Sport http://www.cardomain.com/ride/2135396
68 Firebird http://www.cardomain.com/ride/2135556
56 GMC http://www.cardomain.com/ride/2135587
66 Suburban http://www.cardomain.com/ride/2135589
Re: How to find your CG height.
Tuesday, March 28, 2006 5:44 AM
ah yes. I had seen that before but could not remember where. Nice to see it again.

If I wasnt about out of time working on stuff this winter I would try that out since I have my buddies corner weight scales at the house right now....

Maybee next fall.


Dan


YEP, my 60' times suck

247HP/267ftlbs at 13psi with built motor

Project updates and stuff: www.clubhousecustoms.com
email: dan@clubhousecustoms.com
Re: How to find your CG height.
Tuesday, March 28, 2006 5:57 AM
I haven't calculated my CG yet, as the motor and transmission are currently removed


Re: How to find your CG height.
Tuesday, March 28, 2006 6:12 AM

1) Weigh your car at all 4 wheels. We're looking for the weight at each wheel.
2) Throw some metal rods in place of the front shocks
3) Jack up the rear 10-20" or so
4) Weigh the front wheels


Now:

CGH = Center of Gravity Height
CGwb = Center of Gravity in wheelbase (from behind the front wheel centerline)
CGtrw = Center of Gravite in track width (from left side of track width)
WB = Wheel Base
TrW = Track Width
HT = Height Raised
FW1 = Front Weight before jacking
FW2 = Front Weight after jacking
RW = Rear Weight
RtW = Right Side Weight
TW = Total Weight



Having said that:

tan x = HT / squareroot( HT^2 + WB^2 )
FWc = FW2 - FW1
CGH = ( HT * FWc ) / ( TW * tan x )
CGwb = ( RW / TW ) * WB
CGtrw = (RtW / TW ) * TrW




That's how to find your CG point.


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