What is Anti-Roll Bar (ARB) Asymmetry?
In an effort to increasingly make the stockcars in iracing
as close to their real world counterparts as possible iracing added an
additional tuning parameter to the three top NASCAR stockcars – front and rear ARB asymmetry.
Every race weekend NASCAR race teams try to decide on how best to set up their front and rear suspensions with configurations that
will allow for maximum front end travel, control body roll and have good handling. To accomplish this, in addition to springs and
control arm geometry, ARB arm geometry is today an integral part. As these cars are setup asymmetrically from side to side with
suspension geometry, springs, shocks, tires and weight distribution on ovals it also probably comes as no surprise that ARBs can also
be setup to work asymmetrically. This means their arm geometry from one side of the car to the other differs by some margin
(differing motion ratios) and controls how much the anti-roll bar diameter impacts either side. For example even a perfectly
symmetrical car one will notice that under heavy straight-line braking the left side will travel more than the right side with large
front ARB arm asymmetry. What is happening is the asymmetry is essentially tricking the ARB into thinking there is some amount of
roll in the car to the right, while there is actually none, and engages the bar which in turn rolls the car to the left! What this
can do in the front is help control how the splitter travels relative to the race track surface. Say if the left side is higher than
the right side, or rolled up, more front ARB asymmetry will ‘pull down’ on the left front and ‘pull up’ on the right front and flatten
the splitter out with respect to the track. Vise versa as less front ARB asymmetry will help solve a left front over travel problem
by allowing the left front to travel less.
In the rear, more bar asymmetry can help replace large spring differences and effectively hold up the right rear end during hard
cornering, but quickly disengage while driving off the corner, as load and roll drops off, helping turning in the middle and
stabilizing exit drive off.
iracing decided to allow the members 6 different levels of asymmetry to allow custom control of their ARBs. Choosing how much
ARB asymmetry you need or want (if any) is dependent on the rest of your setup, but it can be used to fine tune how and how much the
anti-roll bars engage.
Please note that rear ARBs are not allowed on the Impala B as the real Nationwide Series
disallows the use of a rear anti-roll bar
Axle/Truck arm assembly preload
Axle/Truck arm assembly preload is the amount of torsion loaded into the axle and truck arm suspension assembly. As the assembly is
oriented by different tire sizes left to right and truck arm mount positions twisting load is introduced. The adjustment in the garage
is meant to represent a way to relieve that torsion with changes akin to changing pinion angle shims installed between the ridged
connection of the truck arms and the axle housing.
Sim Racing Realism
iRacing hosted its first-ever Pro Race of Champions
on December 14th, 2011. Twenty seven real world pro drivers raced for top honours
in two disciplines, first on an oval at Charlotte Motor Speedway, and then on a road course at Watkins Glen International. Enjoy
this short recap of the two races and make sure you watch next year's race, it is sure to be another multi-discipline racing battle!
There was also The iracing Daytona 500
Learning to drive fast at Oulton Park with Jackie Stewart as your instructor
Learning a New Track
Is Smooth Fast?
Racing in the Rain
Focus and Concentration