iRacing Street Stock JR Motorsports User Manual
- June 4, 2024
- iRacing
Table of Contents
STREET STOCK
USER MANUAL
Street Stock JR Motorsports
DEAR iRACING USER,
We hope you enjoy the Street Stock, one of the many free cars that comes with
your iRacing subscription.
From all of us at iRacing, we appreciate your support and your commitment to
our product. We aim to deliver the ultimate sim-racing experience, and we hope
that you’ll find plenty of excitement with us behind the wheel of your new
car!
When it comes to grass-roots racing, it doesn’t get any more “rooted” than
Street Stocks. Although there are (nearly) as many different variations on
Street Stock rules as there are quarter- and half-mile race tracks around
America, the common thread is the use of an older American street car as the
basis of the Street Stock race car.
Depending on the race track and its rules (and your budget), Street Stocks
range from little more than a street car with its interior gutted, its windows
removed and a rudimentary roll cage installed to a full-on race car with a
highly-tuned engine, upgraded suspension and plastic bodywork conforming to
the shape of the original street car. (iRacing’s Street Stock is built to the
full-on race car rules).
Regardless of the specific rules, turning a street car into a Street Stock is
not only less expensive than buying a purpose-built race car, but the process
of building a race car from a street car also helps wanna-be race drivers and
mechanics learn the fundamentals of race car construction, maintenance, and
setups. And learning is what it’s all about, for Street Stocks is the class to
learn the basics of stock car racing.
The following guide explains how to get the most out of your new car, from how
to adjust its settings off of the track to what you’ll see inside of the
cockpit while driving. We hope that you’ll find it useful in getting up to
speed.
Thanks again for your continued support, and we’ll see you on the track!
TECH SPECS
Introduction
The information found in this guide is intended to provide a deeper
understanding of the chassis setup adjustments available in the garage, so
that you may use the garage to tune the chassis setup to your preference.
Before diving into chassis adjustments, though, it is best to become familiar
with the car and track. To that end, we have provided baseline setups for each
track commonly raced by these cars. To access the baseline setups, simply open
the Garage, click iRacing Setups, and select the appropriate setup for your
track of choice. If you are driving a track for which a dedicated baseline
setup is not included, you may select a setup for a similar track to use as
your baseline. After you have selected an appropriate setup, get on track and
focus on making smooth and consistent laps, identifying the proper racing line
and experiencing tire wear and handling trends over a number of laps.
Once you are confident that you are nearing your driving potential with the
included baseline setups, read on to begin tuning the car to your handling
preferences.
GETTING STARTED
Once you load into the car, select 1st gear. Slowly release the clutch while applying the throttle to drive away. The Street Stock features a four-speed manual transmission that can be shifted without the use of a clutch, but it is faster to do so. To upshift, let off the throttle and depress the clutch, then select the next higher gear. Once the next gear is selected, release the clutch and apply the throttle. Upshifting is recommended when the red shift light on the dash illuminates at high RPM. To downshift, depress the clutch while selecting the next lower gear. If downshifting quickly, it is recommended to blip the throttle just prior to releasing the clutch to prevent a mismatch of engine and wheel speed, which can lead to wheel hop and a spin.
LOADING AN iRACING SETUP
When you first load into a session, the iRacing Baseline setup will be automatically loaded onto the car. If you would like to try any of the other iRacing pre-built options, you may select it by going to Garage > iRacing Setups > and then selecting another option that fits your needs. Because this car uses slightly different chassis and body configurations on different types of tracks, it will be necessary to load a setup from the same track type to pass tech inspection. For example, a setup for Talladega will pass at Daytona but likely will not pass at Bristol. If you would like to customize the setup, simply make the changes in the garage that you would like to update and click apply. If you would like to save your setup for future use click “Save As” on the right to name and save the changes. To access all of your personally saved setups, click “My Setups” on the right side of the garage. If you would like to share a setup with another driver or everyone in a session, you can select “Share” on the right side of the garage to do so. If a driver is trying to share a setup with you, you will find it under “Shared Setups” on the right side of the garage as well.
Dash Configuration
The dash in the Street Stock is straightforward and conventional, featuring only three gauges and a shift light. Listed from left to right on the dash:
DIALS & GAUGES
TACHOMETER
Displays Engine RPM in 1000rpm increments. Above and to the left of the
tachometer is the shift light, which will light up when the engine is at the
ideal RPM for upshifting.
OIL PRESSURE
Displays the pressure in the engine oil system in pounds-per-square-inch. This
should be between 45 and 65 psi during normal operation.
WATER TEMP
Displays the temperature of the water in the engine coolant system.
ADVANCED SETUP OPTIONS
This section is aimed toward more advanced users who want to dive deeper into
the different aspects of the vehicle’s setup. Making adjustments to the
following parameters is not required and can lead to significant changes in
the way a vehicle handles. It is recommended that any adjustments are made in
an incremental fashion and only singular variables are adjusted before testing
changes.
Tires & Aero
TIRE SETTINGS
COLD AIR PRESSURE
Air pressure in the tire when the car is loaded into the world. Higher
pressures will reduce rolling drag and heat buildup, but will decrease grip.
Lower pressures will increase rolling drag and heat buildup, but will increase
grip. Higher speeds and loads will require higher pressures, while lower
speeds and loads will see better performance from lower pressures. Cold
pressures should be set to track characteristics for optimum performance.
HOT AIR PRESSURE
Air pressure in the tire after the car has returned to the pits. The
difference between Cold and Hot pressures can be used to identify how the car
is progressing through a run in terms of balance, with heavier-loaded tires
seeing a larger difference between Cold and Hot pressures. Ideally, tires that
are worked in a similar way should build pressure at the same rate to prevent
a change in handling balance over the life of the tire, so Cold pressures
should be adjusted to ensure that similar tires are at similar pressures once
up to operating temperature.
TIRE TEMPERATURES
The amount of tread remaining on the tire once the car has returned from the
pits. Tire wear is very helpful in identifying any possible issues with
alignment, such as one side of the tire wearing excessively, and can be used
in conjunction with tire temperatures to analyze the car’s handling balance.
These values are measured in three zones across the tread of the tire.
STAGGER
Stagger is the difference in circumference of the left- and right-side tires
with both front and rear stagger available as an adjustment in the street
stock. Increasing the front stagger will increase the size of the right-front
tire and add understeer on deceleration and turn-in. Increasing the rear
stagger will increase the size of the right-rear tire and add oversteer
through the center and on throttle out of the corner. Stagger can be set
independently between front and rear to suit various driving styles.
Chassis
FRONT
CROSS WEIGHT
Cross weight is the amount of weight on the car’s Left-Rear and Right-Front
tires relative to the entire weight of the car, displayed in percent. This is
adjusted via the corner Spring Perch Offset adjustments as well as Front ARB
preload. For an oval car, Cross Weight is one of the most influential settings
for grip level while the vehicle is turning. Higher Cross Weight values will
place more weight on the left rear and right front, both stabilizing entry and
helping drive-off on corner exit, but excessive cross weight could prevent the
car from rotating through the center. Lower Cross-Weight values will help the
vehicle rotate and keep it “free” in the corner to prevent speed from being
lost, however too low can result in unstable entry and exit.
TOE-IN
Toe is the angle of the wheel, when viewed from above, relative to the
centerline of the chassis. Positive toe-in is when the front of the wheel is
closer to the centerline than the rear of the wheel, and negative toe-in (toe-
out) is when the front of the wheel is farther away from the centerline than
the rear of the wheel. On the front, toe-out is generally preferred. More toe-
out typically provides better turn-in and straight-line stability due to
increased slip angle, but at the cost of increased tire temperature and wear.
STEERING RATIO
The Steering Ratio is a numerical value for how fast the steering response is
in the vehicle’s steering box. This ratio can be thought of as the degrees of
steering input needed to produce one degree of turn on the steering box output
shaft. For example, a 12:1 steering ratio will require 12° of steering input
to rotate the steering output shaft 1°. A steering box with a lower ratio will
feel more responsive to steering inputs and will require less steering input
to reach the amount needed to navigate a corner. A steering box with a higher
ratio will feel less responsive and will require more steering input to reach
the amount needed to navigate a corner.
STEERING OFFSET
Degrees of steering wheel offset, achieved with a combination of installing
the steering wheel into the quick release mechanism off-center and adjusting
front tie-rods. This can be used to compensate for chassis settings which
place the wheel off-center and is primarily a driver comfort adjustment.
Positive values will rotate the steering wheel to the right, negative values
will rotate the wheel to the left.
BRAKE BALANCE BAR
The Brake Balance Bar adjustment controls Brake Bias, or the percentage of
braking force that is being sent to the front brakes. Values above 50% result
in more pressure being sent to the front, while values less than 50% send more
force to the rear. This should be tuned for driver preference, track
conditions, and also may need adjustment during a race to get the optimum
braking performance for a given situation.
SWAY BAR SIZE
The Sway Bar Size is the outer diameter of the front sway bar and affects the
roll stiffness of the front suspension. Increasing the diameter of the sway
bar will result in a higher roll stiffness on the front suspension, helping to
keep the chassis flat relative to the racing surface, but can also increase
understeer. Smaller bars will reduce the roll stiffness of the suspension but
can increase mechanical grip in the front end, increasing oversteer.
LEFT BAR END CLEARANCE
The Left Bar End Clearance sets how far the left-side sway bar arm must travel
before engaging the suspension and loading the sway bar, as in the case of a
“slapper”-style bar. A positive clearance signifies a gap between the
suspension and the sway bar arm, meaning the suspension must move freely
before loading the bar. A negative value signifies the bar is in contact with
the suspension and is being loaded, thus giving the bar a static preload.
Positive clearances can be used to reduce bar load, especially on the
straights to keep the front end lower, while negative values (bar preload) can
be helpful in preventing the bar from unloading in situations where that is
not desirable.
ATTACH LEFT SIDE
When checked, the Attach Left Side option will place a solid connection
between the left-side sway bar arm and the suspension, loading the bar in all
situations. When unchecked, the bar behaves as a “slapper”-style bar, and will
only load in left-hand turns.
BAR PRELOAD
The Bar Preload is the static load in the sway bar while the vehicle is in the
garage. Preload adjustments can be used to alter the dynamic loads in the bar
while on track, and can be used to remove or add bar load in the corners and
on the straights.
SKIRT CLEARANCE
The Skirt Clearance is a representation of how far the bottom of the front
valence is from the ground. This value is essentially a fifth ride height
requirement and must be above 5 inches to pass tech inspection.
FRONT CORNERS
CORNER WEIGHT
The weight underneath each tire under static conditions in the garage. Correct
weight arrangement around the car is crucial for optimizing a car for a given
track and conditions. Individual wheel weight adjustments and crossweight
adjustments are made via the Spring Perch setting.
SKIRT CLEARANCE
The Skirt Clearance is the distance from ground to the bottom of the door
panel, or skirt. Rear heights are measured just in front of the rear wheels at
the lowest point on the door. Since these values are measured to a specific
reference point on the car, these values may not necessarily reflect the
vehicle’s ground clearance since some components may be lower, but instead
provide a reliable value for the height of the car off of the race track at
static values. Adjusting Skirt Clearance is key for optimum performance, as
they can directly influence the vehicle’s aerodynamic performance as well as
mechanical grip. Rear heights can be increased to produce more aerodynamic
downforce at high speeds, while lowering the rear heights can help with
traction in slower corners.
SPRING PERCH
Spring Perch is used to adjust ride height (skirt clearance) and corner weight
by changing the preload on the spring under static conditions. Decreasing the
value increases preload on the spring, adding weight to its corner and
increasing the ride height at that corner. Increasing the value does the
opposite, reducing height and weight on a given corner. These should be
adjusted in pairs (left and right, for example) or with all four spring
preload adjustments in the car to prevent crossweight changes while adjusting
ride height.
SPRING RATE
Spring Rate changes how stiff the spring is, represented in a force per unit
of displacement. Primarily responsible for maintaining ride height and a good
attitude under changing wheel loads, stiffer springs will maintain the car’s
attitude better while sacrificing mechanical grip. Softer springs will deal
with bumps better and increase mechanical grip, however this could cause the
chassis to pitch and roll too much, hurting aerodynamic performance at faster
tracks.
LEAF ARCH & BLOCK
The Leaf Arch & Block adjustment is used to change the preload on the rear
springs, and thus change the ride height on either rear corner. Increasing the
size of the Leaf Block will lower that corner’s ride height and reduce spring
preload, while reducing the size of the Leaf Block will raise that corner’s
ride height and increase spring preload.
LEAF SPRING RATE
Leaf Spring Rate changes how stiff the spring is, represented in a force per
unit of displacement. Primarily responsible for maintaining ride height and a
good attitude under changing wheel loads, stiffer springs will maintain the
car’s attitude better while sacrificing mechanical grip. Softer springs will
deal with bumps better and increase mechanical grip, however this could cause
the chassis to pitch and roll too much, hurting aerodynamic performance at
faster tracks.
CAMBER
Camber is the vertical angle of the wheel relative to the center of the
chassis. Negative camber is when the top of the wheel is closer to the chassis
centerline than the bottom of the wheel, positive camber is when the top of
the tire is farther out than the bottom. Greater camber angles will increase
the cornering force generated by the tire, but will reduce the amount of
longitudinal grip the tire will have under braking. Excessive camber values
can produce very high cornering forces but will also significantly reduce tire
life, so it is important to find a balance between life and performance. For
ovals, set the left side positive and the right side negative.
CASTER
Caster is how much the steering axis is leaned back (positive) or forward
(negative), which influences dynamic load jacking effects as the car is
steered. More positive caster results in a heavier steering feel but decreases
dynamic crossweight while turning by loading the inside front tire with
steering input, as well as adding straight-line stability. Running less caster
on the left-front than the right-front will cause the vehicle to pull to the
left, a desirable effect on ovals.
REAR CORNERS
CORNER WEIGHT
The weight underneath each tire under static conditions in the garage. Correct
weight arrangement around the car is crucial for optimizing a car for a given
track and conditions. Individual wheel weight adjustments and crossweight
adjustments are made via the Spring Perch setting.
SKIRT CLEARANCE
The Skirt Clearance is the distance from ground to the bottom of the door
panel or skirt. Rear heights are measured just in front of the rear wheels at
the lowest point on the door. Since these values are measured to a specific
reference point on the car, these values may not necessarily reflect the
vehicle’s ground clearance since some components may be lower, but instead
provide a reliable value for the height of the car off of the race track at
static values. Adjusting Skirt Clearance is key for optimum performance, as
they can directly influence the vehicle’s aerodynamic performance as well as
mechanical grip. Rear heights can be increased to produce more aerodynamic
downforce at high speeds while lowering the rear heights can help with
traction in slower corners.
LEAF ARCH & BLOCK
The Leaf Arch & Block adjustment is used to change the preload on the rear
springs, and thus change the ride height on either rear corner. Increasing the
size of the Leaf Block will lower that corner’s ride height and reduce spring
preload while reducing the size of the Leaf Block will raise that corner’s
ride height and increase spring preload.
LEAF SPRING RATE
Leaf Spring Rate changes how stiff the spring is, represented in a force per
unit of displacement. Primarily responsible for maintaining ride height and a
good attitude under changing wheel loads, stiffer springs will maintain the
car’s attitude better while sacrificing mechanical grip. Softer springs will
deal with bumps better and increase mechanical grip, however this could cause
the chassis to pitch and roll too much, hurting aerodynamic performance at
faster tracks.
REAR
FUEL FILL TO
This selects the amount of fuel in the fuel tank when the car leaves the
garage.
REAR END RATIO
The Rear End Gear Ratio is the ratio between the driveshaft pinion and the
differential ring gear. Higher number values produce better acceleration but
reduce top speed, lower number values reduce acceleration but result in a
higher top speed.
STREET STOCK
USER MANUAL