# Roll Rate, Tramp Rate, and Roll Center Location

Branch ID: 220

Request Number: 80000220

Table 1.
.plt File .mr, .abf File Component Unit Comment
F1 RESULT(1) Not Used Not Used Not Used
F2 RESULT(2) Suspension Roll Rate N-m/deg The change in axle moment per change in axle roll angle (excluding tires) or:

track = abs((right wheel center y) - (left wheel center y))

roll rate = track^2/(C(3,3)-C(3,9)-C(9,3)+C(9,9))/rtod/1000

F3 RESULT(3) Total Roll Rate N-m/deg The change in axle moment per change in axle roll angle (tires in series) or:

track = abs((right wheel center y) - (left wheel center y))

deltaz = C(3,3)-C(3,9)-C(9,3)+C(9,9)+2/(tire stiffness)

roll rate = track^2/deltaz/rtod/1000

F4 RESULT(4) Tramp Rate N-m/deg The change in axle moment per change in axle roll angle (tires in parallel) or:

track = abs((right wheel center y) - (left wheel center y))

deltaz = (C(3,3)-C(3,9))*1/(tire stiffness)/

(C(3,3)-C(3,9)+1/(tire stiffness))+

(C(9,9)-C(9,3))*1/(tire stiffness)/

(C(9,9)-C(9,3)+1/(tire stiffness))

tramp rate = track^2/deltaz/rtod/1000

F5 RESULT(5) Not Used Not Used Not Used
F6 RESULT(6) Roll Center Height mm The suspension roll center is found by intersecting the line connecting the left tire patch and the left tire patch front view instant center with the line connecting the right tire patch and the right tire patch front view instant center. The roll center height is defined as the difference between the roll center z coordinate and the average tire patch z coordinate.

ltpdz = C(3,3)-C(3,9) + 1/(tire stiffness)

rtpdz = C(9,9)-C(9,3) + 1/(tire stiffness)

Orientation A:
ltpdy = C(2,3)-C(2,9) + slr*(C(4,3)-C(4,9))
rtpdy = C(8,9)-C(8,3) + slr*(C(10,9)-C(10,3))
Orientation B:
ltpdy = -C(2,3)+C(2,9) + slr*(-C(4,3)+C(4,9))
rtpdy = -C(8,9)+C(8,3) + slr*(-C(10,9)+C(10,3))
m1 = -ltpdy/ltpdz
m2 = -rtpdy/rtpdz
rcy = (ltpz-rtpz+m2*rtpy-m1*ltpy)/(m2-m1)
rcz = ltpz+m1*(rcy-ltpy)
roll center height = rcz - (ltpz+rtpz)/2
F7 RESULT(7) Roll Center Lateral mm The roll center lateral location is defined as the roll center y coordinate. See the comment for F6/RESULT(6) for equations.
F8 RESULT(8) Not Used Not Used Not Used