9 FRONT ANTI-ROLL AND ROLL PRE-LOAD
You can use each of the Belleville stacks with or without pre-load. There are two types of
pre-load, described in detail here below. The limit of the system is the rocker touching the
magnesium support when moving laterally.
Double stiffness pre-load
•Within the pre-load range, the stiffness is double the stiffness of one stack, both stacks are
working
•Passed the pre-load, the stiffness gets back to the nominal stiffness of one stack
Infinite stiffness pre-load is accomplished with an additional nut and a counter nut
•Within the pre-load range, the rocker doesn’t move at all
•Passed the pre-load, the stiffness gets back to the nominal stiffness of one stack
•The choice of a pre-load setting, or the non pre-loaded setting might be based on the car’s
balance exigencies, tyre wear, drivers’ preference etc…. Pre-load settings generally help for
sharper turn-in characteristic.
•Clearance between the platform and the rocker (B) shall not be more than 6.5mm when
platform just touches the Belleville stack, with no pre-load.
•The amount of pre-load is the difference between the current and the free length of the
Belleville stack.
•For any Belleville stack, in running condition, rocker lateral motion and the chosen pre-load
must never reach the "Maximum Deflection" (see Table 6), to avoid a sudden lateral locking
of the rocker.
•Once the rocker overcomes the pre-load, the total stiffness reduces to the nominal stiffness
of one Belleville stack. You may like to work within the roll pre-load range under certain
conditions (turn-in…) and wish to pass over the pre-load range in some others (mid-corner,
curbs…). Set accurately the transition point (pre-load level) between the two conditions, since
the stiffness change is sudden and affects transient car behaviour.
You can achieve a progressive load / displacement characteristic by combining in series two different
stacks or a regressive load / displacement ratio by fitting an appropriate pre-load. Total length of
any stack should be maximum 34 mm.
BELLEVILLE STACK CONFIGURATIONS (Belleville thickness 2.0mm)
Stack configuration Max deflection
mm Stack width
mm Nominal stack stiffness
Kg/mm (no pre-load) Maximum
notches
<<<<>>>> 1.12 17.50 2504 8
<<<>>> 1.12 13.50 1796 8
<<<>>><<< 1.69 20.25 1197 12
<<>><< 1.69 14.25 761 12
<<>><<>> 2.25 19.00 571 17
<<>><<>><< 2.81 23.75 457 22
<>< 1.69 8.25 362 14
<><> 2.25 11.00 272 17
<><>< 2.81 13.75 218 22
<><><> 3.37 16.50 181 26
<><><>< 3.93 19.25 155 28
<><><><> 4.50 22.00 136 34
<><><><><> 5.62 27.50 109 44
Note: the front rocker lateral movement has been increased from the previous (F399-301) maximum
6mm to about 10mm on the F302/3/4 car.
