C3 Corvette chassis upgrade 2021

Integrate C5 front suspension and C4 rear suspension to an upgraded frame for C3 Corvette

1. C3 Corvette Chassis Upgrade (revised 03JUL21)
General Suspension
http://en.wikipedia.org/wiki/Automotive_suspension_design
http://www.carbibles.com/suspension_bible.html
http://auto.howstuffworks.com/car-suspension.htm
https://bndtechsource.wixsite.com/home/fundamental-vehicle-dynamics

Automotive suspension design is an aspect of automotive engineering
http://www.absoluteastronomy.com/topics/Automotive_suspension_design#encyclopedia
The process entails:
 selecting a system architecture
 selecting the vehicle suspension targets (static and dynamic)
 selecting the vehicle suspension hardpoints
 designing the structure of each component so that it is strong, stiff, light, and inexpensive
 designing the spring rates (frequency)
 designing shock absorber (damping)
 designing the rates of the bushings (compliance)
 analyzing the loads in the suspension
 analyzing the vehicle dynamics
Vehicle Suspension Static Targets:
 Vehicle Wheelbase
 Vehicle Track Width
 Tires & Wheels
 Vehicle Weight Distribution
 Unsprung Weight
 Sprung Weight
 Vehicle Center of Gravity
 Turning circle
 Ackermann
 Jounce travel
 Rebound travel
 Ride Heights at various states of load (Curb Wt vs. GVWR)
Vehicle Suspension Dynamic Targets:
 Wheel Frequency
 Lateral Load Transfer
 Roll moment (kg·m
2
)
 Roll Stiffness (degrees per g of lateral acceleration)
 Maximum Steady State lateral acceleration (in understeer mode) (g)
 Rollover threshold (lateral g load)

ROLLOVER THRESHOLD COMPARISON
Vehicle Type cg Height (inches) Track (inches) Rollover Threshold (lateral g-load)
Sports Car 18-20 50-60 1.2-1.7
Compact Car 20-23 50-60 1.1-1.5
Luxury Car 20-24 60-65 1.2-1.6
Pickup Truck 30-35 65-70 0.9-1.1
Passenger Van 30-40 65-70 0.8-1.1
Medium Truck 45-55 65-75 0.6-0.8
Heavy Truck 60-85 70-72 0.4-0.6
General Suspension (cont’d)

2. System architecture
Typically, a vehicle designer is operating within a set of constraints. The suspension architecture selected for each
end of the vehicle will have to obey those constraints. For both ends of the car this would include the type of spring,
location of the spring, and location of the shock absorbers.

For the front suspension the following need to be considered:
 the type of suspension (i.e. MacPherson strut vs. Double Wishbone)
 type of steering actuator (i.e. rack and pinion vs. Recirculating Ball)
 location of the steering actuator in front of, or behind, the wheel center (R&P-fwd, R.B.-rwd)
For the rear suspension there are many more possible suspension types, in practice.
Hardpoints
The hardpoints control the static settings and the kinematics.

Vehicle Suspension Hardpoints:
Front Suspension Rear Suspension
Scrub radius (distance)
Steering (Kingpin) Inclination Angle (SAI)
Caster angle
Mechanical (or caster) trail (distance)
Toe angle
Camber angle
Ball Joint Pivot Points (x, y, z)
Upper/Lower (Double wishbone, Multi-link,
Trailing Arm, etc.)
Lower (MacPherson strut)
Control Arm Chassis Attachment Points (x, y, z)
Upper/Lower (Double wishbone, Multi-link,
Trailing Arm, etc.)
Lower (MacPherson strut)
Strut Attachment/Pivot Point (MacPherson strut)
Hub Dimensions
Brake Rotor Dimensions
Brake Caliper Mounting Position
Brake Caliper to Wheel (min clearance)
Steering Rack Centerline
Tie Rod Pivot Points (inboard/outboard)
Spring Rate/Dimensions
Shock Absorber Dimensions
Bump Stop (length)
Shock Mounting Pivot Points (x, y, z)
Spring and Shock Installation Angle
Spring and Shock Absorber Motion Ratio
ARB (anti-roll bar) Dimensions
ARB (anti-roll bar) Spring Rate
ARB (anti-roll bar) Motion Ratio

Scrub radius (distance)
Caster angle (if applicable)
Mechanical (or caster) trail (distance) (if applicable)
Toe angle
Camber angle
Knuckle Attachment Points (x, y, z)
Dependent upon Rear Suspension
configuration.
Chassis Attachment Points (x, y, z)
Dependent upon Rear Suspension
configuration.
Hub Dimensions
Brake Rotor Dimensions (if disc brakes)
Brake Caliper Mounting Position (if disc brakes)
Brake Drum Dimensions (if drum brakes)
Brake Caliper/Drum to Wheel (min clearance)
Spring Rate/Dimensions
Shock Absorber Dimensions
Bump Stop (length)
Shock Mounting Pivot Points (x, y, z)
Spring and Shock Installation Angle
Spring and Shock Absorber Motion Ratio
ARB (anti-roll bar) Dimensions
ARB (anti-roll bar) Spring Rate
ARB (anti-roll bar) Motion Ratio







General Suspension (cont’d)
Design Results:

3. Front Suspension Rear Suspension
Roll Center Height
Anti-dive Instantaneous Center
Bushing Rates
Wheel Rates
Tire Envelope
Tool Clearance
Routing Clearance (i.e. hoses, brake lines, fuel
lines, electrical, etc.)
Roll Center Height
Anti-dive Instantaneous Center
Bushing Rates
Wheel Rates
Tire Envelope
Tool Clearance
Routing Clearance (i.e. hoses, brake lines, fuel lines,
electrical, etc.)

The kinematics describe how important characteristics change as the suspension moves, typically in roll or steer.

Vehicle Suspension Dynamics Analysis:
Bundorf Analysis
Slip angles (degrees per lateral force) (front/rear)
Tire Cornering Coefficient (lateral force as a percent of rated vertical load per degree slip angle)
Tire Cornering Forces (lateral cornering force as a function of slip angle)
Linear Range Understeer (g)

Once the overall vehicle targets have been identified they can be used to set targets for the two
suspensions. For instance, the overall understeer target can be broken down into contributions
from each end using a Bundorf analysis. A Bundorf analysis is a way of describing the
characteristics of a vehicle that govern its understeer balance.
The understeer is measured in units of degrees of additional yaw per g of lateral acceleration.
The difference between the circle the wheels are currently tracing and the direction in which
they are pointed is the slip angle. If the slip angles of the front and rear wheels are equal, the
car is in a neutral steering state. If the slip angle of the front wheels exceeds that of the rear, the
vehicle is said to be understeering. If the slip angle of the rear wheels exceeds that of the front,
the vehicle is said to be oversteering.

Steering Analysis
Bump Steer
Roll Steer
Tractive Force Steer
Brake Force Steer
Ackerman change with steering angle

Roll Analysis
Camber gain in roll (front & rear)
Caster gain in roll (front & rear – if applicable)
Roll Axis
Roll Center Height
Instantaneous Center
Track

Load Transfer Analysis
Unsprung weight transfer
Sprung weight transfer
Jacking Forces

Roll Couple Percentage Analysis
Total Lateral Load Transfer Distribution (TLLTD)
General Suspension (cont’d)

The analysis for these parameters can be done graphically, or by CAD, or by the use of kinematics software.

4. Compliance analysis
The compliance of the bushings, the body, and other parts modify the behavior of the suspension. In general, it is
difficult improve the kinematics of a suspension using the bushings, but one example where it does work is the toe
control bush used in Twist-beam rear suspension
Loads
Once the basic geometry is established the loads in each suspension part can be estimated. This can be as simple
as deciding what a likely maximum load case is at the contact patch, and then drawing a Free body diagram
Detailed design of arms
The loads and geometry are then used to design the arms and spindle. Inevitably some problems will be found in
the course of this that force compromises to be made with the basic geometry of the suspension.

Section Width on Measuring Rim Width https://bndtechsource.wixsite.com/home/tire-data-information
The distance between a tire's sidewalls measured at the widest part of the tire. Each size of tire is measured on a
specific rim width. Note: Section width varies approximately 0.2” (5mm) for every 0.5” change in rim width.

5. General Suspension (cont’d)
 Wheels (C5) http://wheels.corinthian.se/
o Front = 17in x 8.5in
 Offset = 56mm (2.205in)
 Bolt Dia. = 4.75in (120.65mm)
o Rear = 18in x 9.5in
 Offset = 63mm (2.48in)
 Bolt Dia. = 4.75in (120.65mm)
o Tires (C5) https://bndtechsource.wixsite.com/home/tire-data-calculator
o Front = P245/45ZR17
 Inflation Pressure = 2.5bar (36psi)
 Static Rolling Radius @ Curb Wt = 311.7mm (12.27in)
o Rear = P275/40ZR18
 Inflation Pressure = 2.5bar (36psi)
 Static Rolling Radius @ Curb Wt = 325.9mm (12.83in)

 Track = 1490mm (58.66 in) Front & Rear (modified C3)
 Wheelbase = 2489.2mm (98.0 in) (stock C3)
http://www.carfolio.com/specifications/models/car/?car=22495

Note: Wheels/Tires & Track fit within the C3 stock track (58.7in/59.5in – frt/rr) with P255/60R15 tires on
stock 15in x 8in rims.
Susp Analysis
Axis
Susp Analysis
Axis
X
Y
X
Z Z
X
Y
X

6. Ackermann Steering

To avoid tire scrub when a vehicle is turning draw perpendicular lines from all four tires. If the perpendiculars
from the front tires intersect along the lines drawn from the unsteered rear tires then you have classic Ackermann
for one particular steering angle. Example: Turning radius curb-to-curb = 17.6ft (5.36m)
% Ackerman = [Angle Inside Wheel (di) - Angle Outside Wheel (do)]/ 100% Ackerman Angle (dd)
Where the 100% Ackerman Angle (dd) is:
tan
-1
(WB/ ((WB/tan (Angle outside wheel)) - Front Track)) - Angle of outside wheel =
(dd) = tan
-1
(L/((L/tan(do)) - tf)) - (do)


(dd) = tan
-1
(2489.2/((2489.2/tan (28.4)) - 1490)) - (28.4) = 10.24deg
% Ackerman = (di CAD SIM/di @100%)*100 = 83.2%

8. General Suspension (cont’d)
 Vehicle Weight = 1606kg (3542lb)
 Front Left Vehicle Weight = 404kg (891lb)
 Front Right Vehicle Weight = 404kg (891lb)
 Rear Left Vehicle Weight = 399kg (880lb)
 Rear Right Vehicle Weight = 399kg (880lb)
 Weight Distribution (Frt/Rr) = 50.3% / 49.7%
 Weight Distribution (Left/Right) = 50% / 50%
 Front Left Unsprung (susp. components) Weight = 47.6kg (105lb)
 Front Right Unsprung (susp. components) Weight = 47.6kg (105lb)
 Rear Left Unsprung (susp. components) Weight = 53.8kg (118.5lb)
 Rear Right Unsprung (susp. components) Weight = 53.8kg (118.5lb)
 Sprung Weight = 1403.9kg (3095lb)
 Center of Gravity Front = 1252.2mm (49.3 in)
 Center of Gravity Rear = 12367mm (48.7 in)
 Center of Gravity Height (from ground) = 431.8mm (17 in)
http://www.longacreracing.com/articles/art.asp?ARTID=22


front rear
f / r=51.4% 48.6%
left =26.0% 24.5%
right =25.4% 24.1%
l = 98in
trf =58.66in
trr =58.66in
a = 47.6in
b = 50.4in
y' =29.83in
y'' = 0.00in
h = 17.12in
as = 47.0in
bs = 51.0in
ys' =29.90in
ys'' =-0.07in
hs = 17.78in
front=52.1%
rear=47.9%
Wt = 3542lb
LF = 920.5lb
RF = 900.5lb
LR = 866.5lb
RR = 854.5lb
Ws = 3095lb
Wuf = 210lb
Wur = 237lb
Wu1 = 105lb
Wu2 = 105lb
Wu3 = 118.5lb
Wu4 = 118.5lb
Vehicle
Corner Weight
(curb w/driver)
Wheelbase
Sprung/Unsprung Weight
Sprung Weight
Weight Distribution
(curb w/driver)
Unsprung Weight
Vehicle CG (W)
Sprung Wt CG (Ws)
Track
Vehicle Weight
Sprung Wt Distribution
Sprung
Wt CG
Vehicle
CG

9. Front Suspension
 SLA (Short/Long Arm) Double Wishbone (C5) http://www.eugeneleafty.com/Corvette.asp
o SIA (Steering Inclination Angle) = 8.8
O

o Caster Angle = 6.5
O

o Mechanical Trail = 35.5mm (1.398in)
o Scrub Radius = 8.5mm (.335in)
o Brake Rotor Dimensions - Front
32mm (1.26in) --- rotor thickness
70mm (2.756in) --- center hole diameter
38mm (1.496in) --- inner face of hub to inner rotor surface
190mm (7.48in) --- inner hub diameter
217mm (8.543in) --- outer hub diameter
325mm (12.795in) --- rotor diameter
o Brake Caliper to Wheel (min clearance) = 6.5mm (.256in)

 LCA Pivot Points (from Susp Analysis Axis) MAR2013
o Front = X= 161.41mm, Y= 330.47mm, Z= 171.453mm
o Rear = X= -223.59mm, Y= 330.47mm, Z= 171.794mm
o Lwr Ball Jnt = X= 16.114mm, Y= 709.937mm, Z= 171.582mm

 UCA Pivot Points (from Susp Analysis Axis) MAR2013
o Front = X= 125.231mm, Y= 408.968mm, Z= 490.138mm
o Rear = X= -158.378mm, Y= 394.428mm, Z= 431.364mm
o Upr Ball Jnt = X= -17.505mm, Y= 663.901mm, Z= 468.989mm

 Anti-dive Instant Center (from Susp Analysis Axis) MAR2013
o X= -1405.866mm, Z= 172.839mm

10. Front Suspension (cont’d)

 Shock Mounting Pivots (from Susp Analysis Axis) MAR2013
o Lower = X= 12.425mm, Y= 646.203mm, Z= 204.222mm
o Upper = X= -16.978mm, Y= 495.073mm, Z= 464.33mm

 Steering Rack Centerline (from Susp Analysis Axis) MAR2013
o Centerline Cross-car @ X= 124.11mm, Z= 273.775mm

 Steering Rack Pivots (from Susp Analysis Axis) MAR2013
o Inboard = X= 124.154mm, Y= 370.041mm, Z= 273.656mm
o Outboard = X= 120.099mm, Y= 724.654mm, Z= 284.518mm

 Coil-Over Shock Motion Ratio (@ Ride Ht.) = 0.759 unit/unit (C5 modified) MAR2013

 Coil-Over Shock Installation Angle (@ Ride Ht.) = 65.1
O
MAR2013

 Frt Roll Center Height (@ Ride Ht.) = 13.474mm (.53in) (above ground level) MAR2013
Roll Center Height Discussed:
[“In the old days it was common to use roll-center height as an adjustment to tune the chassis.
The theory is, by raising the roll-center height at one end of the car, you get more weight transfer
at that end. There are two problems with this method and it is no longer used.
First, raising the roll center does increase the weight transfer due to roll-center height, but
it decreases the weight transfer due to body roll. This introduces complications into the chassis
tuning process that are hard to figure out. Whenever you make two changes at once with a
chassis adjustment you are in for trouble, and if the changes act in opposite directions, then you
make a bad situation even worse!
The second and by far the worst problem is the almost impossible task of changing roll-
center height without changing the suspension geometry radically. People used to move the
upper A-arm of the double A-arm suspension, thinking it would only alter the roll-center height, but
they were changing the camber characteristics and bump-steer of the suspension at the same
time. These multiple changes make adjusting roll center a very risky and confusing guessing
game with independent suspension. To me it seems so much easier to use adjustable anti-roll
bars. They are not only easier to adjust, but the anti-roll bars give you an infinitely fine
adjustment.”] “How to make your car handle” by Fred Puhn

11. Front Suspension (cont’d)

 Shocks = Strange - Double Adjustable - S5004
http://www.strangeengineering.net/catalog/index.html
http://www.strangeengineering.net/catalog/pages/116.jpg
http://www.strangeengineering.net/catalog/pages/122.jpg
http://performanceshock.com/2-1-2-id-springs/2-5-x-10/1810b0500
o Extended Length = 13.84in (352mm)
o Compressed Length = 10in (254mm)
o Rec. Ride Height = 11in - 11.375in (298.5mm - 308mm)
o Rec. Spring Length = 10in (254mm)
o Stroke = 3.86in (98mm) [without bump stop]
o Bump Stop = .563in (14.3mm)
o Front Coil Spring = 500 lb/in
(10” free length, .52” wire dia., 3.54” OD, 7.63 AC, 2 IC, SAE 9254 Chrome Silicon)
http://forums.corvetteforum.com/autocrossing-and-roadracing/1957758-c5-spring-rates-and-antisway-
bar-sizes-97-04-a.html (post#5 - REF: C5 Z06: 526lb/in Front, 714lb/in Rear)
















 Front Shock Length at Ride Height = 302.25mm (11.9in)

 Front Spring Length at Ride Height = 196.2mm (7.724in)

 Front Spring Load @ 49.28mm (1.94 in) Deflection (Ride Ht) = 970lb

12. Front Suspension (cont’d)
Source: Jounce_vs_Shock_Length_vs_Shock Angle.xls

13. Source: Susp_Project_Tasks_Calculator_FEB2018.xls https://bndtechsource.wixsite.com/home/fundamental-
vehicle-dynamics






Car:
Vehicle's Curb Weight with Driver (lb)
Driver's weight (lb)
Front Rear
Front/Rear Distribution (%) 51.4% 48.6%
Left Distribution (%) 26.0% 24.5% Spring Rate (kg/mm) 8.93 12.50 [Kφ] Roll Stiffness incl. Bush Flex (ft-lb/rad)98124.61169784.525
Right Distribution (%) 25.4% 24.1% Spring Rate (lb/in) 500 700 [Kφ] Roll Stiffness incl. Bush Flex (ft-lb/deg)1712.5981217.970
Front Rear Static Tire Rate (lb/in) 1436.8961627.058 [Kφ
t] Total Roll Stiffness front & rear (ft-lb/deg)
Axle Weight (lb) 1821.0 1721.0 Spring Motion Ratio (in/in) 0.759 0.728 [Rφ] Roll Rate (rad/g)
Left Corner Weight (lb) [measured w/driver] 920.5 866.5 Wheel Rate (lb/in) 287.83 370.99 [Rφ] Roll Rate (deg/g)
Right Corner Weight (lb) [measured w/driver] 900.5 854.5 Ride Rate (lb/in) 239.80 302.11
Unsprung Corner Weight (lb) [measured] 105 118.5 Roll Stiffness (ft-lb/deg) to Ride Rate (lb/in) 4.549 3.377
Left Sprung Corner Weight (lb) [w/driver] 815.5 748
Right Sprung Corner Weight (lb) [w/driver] 795.5 736 [Mφ] Roll Couple or Roll Torque (ft-lb) 2569.84 1827.63
Sprung to unsprung ratio 7.671 6.262 Natural Frequency (CPM) cycles per minute 102.47 121.77
Unsprung to sprung ratio 0.130 0.160 Natural Frequency (Hz) 1.71 2.03 Load Transfer due to Body Roll (lb/g) 525.71 373.88
Load Transfer due to Roll Center Height (lb/g) 14.56 23.27
[W] Total Vehicle weight with driver (lb) Load Transfer due to Unsprung Weight (lb/g) 42.37 50.47
[W
S] Total sprung weight (lb) Lateral Load Transfer w/ ARB (lb/g) 582.63 447.62
[W
U] Total unsprung weight (lb) Compression (%) 67.0% 56.6% Total Lateral Load Transfer w/ ARB (lb/g)
Rebound (%) 60.3% 51.0% Roll Couple or Roll Torque Distribution 58.4% 41.6%
TLLTD (Total Lateral Load Transfer Dist.) 56.6% 43.4%
[L] Wheelbase (in) Lateral load transfer (lb/g) to Ride Rate (lb/in) 1.548 1.241
[t] Track (in) 58.66 58.66 [Kφ] Roll Stiffness (ft-lb/rad) 34380.72243314.275 LLT/roll ride rate to Spring Motion Ratio 1.174 0.904
[h] CG Height (in) [Kφ] Roll Stiffness (ft-lb/deg) 600.057 755.977 LLT/roll ride rate to ARB Motion Ratio 0.990 0.930
Chassis to Ground Ride Height @ Curb Wt (in) [Kφ
t] Total Roll Stiffness front & rear (ft-lb/deg)
[h
r] Roll Center Height (in) 0.53 0.92 (using Ride Rate in calculations) Elastic load transfer w/ ARB (lb/g)
Roll Axis Height at CG (in) [Rφ] Roll Rate (rad/g) (Load Transfer Due to Roll Angle)
[h
l] Roll Moment Arm Length (in) [Rφ] Roll Rate {springs only} (deg/g)
Unsprung CG Longitudinal Location (in) 50.16 47.84 (using roll rates which used ride rate)
Roll Stiffness (ft-lb/deg) to Ride Rate (lb/in)2.502 2.502 ARB Roll Stiffness incl. Bush Flex (ft-lb/rad)57501.55025247.573
ARB Roll Stiffness incl. Bush Flex (ft-lb/deg) 1003.591 440.653
Wheel Deflection (in) 2.799 2.000 [Mφ] Roll Couple or Roll Torque (ft-lb) 1945.92 2451.55 [Kφ] Roll Stiffness incl. Bush Flex (ft-lb/rad)91882.27168561.847
Spring Deflection (in) 2.123 1.456 [Kφ] Roll Stiffness incl. Bush Flex (ft-lb/deg)1603.6481196.630
Force In Spring (lb) 1061.6521019.231 Load Transfer due to Body Roll (lb/g) 398.07 501.51 [Kφ
t] Total Roll Stiffness front & rear (ft-lb/deg)
Overall Shock Length (in) 13.84 12.84 Load Transfer due to Roll Center Height (lb/g)14.56 23.27 [Rφ] Roll Rate w/ ARB & Bush Flex (rad/g)
Shock length calc w/single motion ratio (in)* 11.717 11.384 Load Transfer due to Unsprung Weight (lb/g) 42.37 50.47 [Rφ] Roll Rate w/ ARB & Bush Flex (deg/g)
Shock length measuerd in CAD simulation (in) 11.900 11.440 Lateral Load Transfer w/o ARB (lb/g) 455.00 575.25
Unsprung deflection (in) 0.634 0.529 Total Lateral Load Transfer w/o ARB (lb/g) Roll Stiffness (ft-lb/deg) to Ride Rate (lb/in) 4.26 3.32
Overall chassis deflection (in) 3.432 2.529 Roll Couple or Roll Torque Distribution 44.3% 55.7%
TLLTD (Total Lateral Load Transfer Dist.) 44.2% 55.8% [Mφ] Roll Couple or Roll Torque (ft-lb) 2518.32 1879.15
Load Transfer due to Body Roll (lb/g) 515.17 384.42
Avg. Wheel Load (lb) 1482.59 1318.66 Load Transfer due to Roll Center Height (lb/g) 14.56 23.27
Δ Sprung weight from static (lb) 562.09 452.16 ARB Motion Ratio (in/in) 0.639 0.749 Load Transfer due to Unsprung Weight (lb/g) 42.37 50.47
Δ Wheel deflection from static (in) 1.10 0.98 Virtual torque arm (in) 8.9 8.51 Lateral load transfer w/ ARB & Bush Flex (lb/g) 572.09 458.16
Total Wheel deflection (in) 3.90 2.98 Total Lateral Load Transfer w/ ARB & Bush Flex (lb/g)
Δ Spring deflection from static (in) 0.84 0.71 Roll Couple or Roll Torque Distribution 57.3% 42.7%
Total Spring deflection (in) 2.96 2.17 TLLTD (Total Lateral Load Transfer Dist.) 55.5% 44.5%
Total Force in spring (lb) 1479.66 1516.58 ARB Spring Rate (lb/in) [Check ARB targets]543.612 164.494
Δ Unsprung deflection (in) 0.39 0.28 ARB suspension rate, (lb/in) 444.596 184.623 Lateral load transfer (lb/g) to Ride Rate (lb/in) 1.520 1.270
Total Overall chassis deflection (in) 4.29 3.25 Wheel rate from ARB (lb/in) one wheel bump222.298 92.311 LLT/roll ride rate to Spring Motion Ratio 1.153 0.925
Chassis to Ground @ Test weight (in) 4.38 4.52 Additional roll stiffness (ft-lb/rad) 63743.88926470.251 LLT/roll ride rate to ARB Motion Ratio 0.972 0.952
Additional roll stiffness (ft-lb/deg) 1112.541 461.993
Wheel deflection at 1g per Roll Gradient (in) 0.826 0.826
Wheel Rate including ARB (lb/in) 510.129 463.300 Shock deflection at 1g per Roll Gradient (in) 0.627 0.602
[Mφ
t] Total Roll Couple or Total Roll Torque (ft-lb) Ride Rate including ARB (lb/in) 376.473 360.616 ARB deflection at 1g per Roll Gradient (in) 0.528 0.619
[Fys] Sprung Wt (lb) 1611 1484
[Fyu] Unsprung Wt (lb) 210 237 Elastic load transfer w/ ARB & Bush Flex (lb/g)
(Load Transfer Due to Roll Angle)
Percentage of roll rate from springs 35.0% 62.1%
Percentage of roll rate from ARB 65.0% 37.9% Geometric load transfer (lb/g) 15.62 28.43
Percentage of roll rate from ARB incl. Bush flex62.6% 36.8%
Front Rear
601.64 427.87
589.57 439.93Roll Percentage: Front Rear
Wheel rate from ARB: Front Rear
2800.28
0.0282
1030.25
1030.25
ARB Rates: Front Rear
Vehicle Dimensions:
Front Rear
Wheel Frequencies:
Spring Damping
Percent Critically Damped (at 50mm/sec):
3542
3095.0
447.0
RearFront
Vehicle Weights:
Roll Rates (ARBs included): Front Rear
2930.57
Roll Rates (w/o ARBs):
0.0600
1356.033
0.0269
1.54
1030.25
Static Deflection @ ride height: Front Rear
Deflection at 1g (outside wheels): Front Rear
4397.47
Roll Data at 1g: Front Rear
17.12
5.24
Front Rear
Front Rear
3.44
Roll Rates (w/ARBs & ARB Bush flex):
0.730
17.05
Master Suspension Calculation Data
Project XXX
Spring Rates:
Front Rear
3542
200
1.61
98
* The values shown are based on singular inputs into empirical equations. During the travel of a suspension system, these singularinputs can change due to
various factors (i.e. angular deviations within the motion ratios, force deviationsdue to bushing deflections, changes in damping, etc.). While this data is useful
for initial design, development, and comparison purposes, it is highly recommended to use a 3D Suspension Analysis software to accurately determine the
suspension design results throughout its entire range of travel.
A
B
C

14. Front Suspension (cont’d)

 Motion Ratio = [(distance from LCA pivot to spring mount/ distance from LCA pivot
to lower ball joint) x sin(spring angle)]

 Front Wheel Rate = (Motion Ratio)
2
x (Spring Rate)

 Front Wheel Rate @ Ride Height = (0.759)
2
x (500lb) = 288.04 lb/in
…why wheel rate = spring rate * (motion ratio)
2
, and not just spring rate * motion
ratio?
 Because it's a force, and the lever arm is multiplied twice.
 The motion ratio is factored once to account for the distance-traveled differential of the
two points (A and B in the example below).
 Then the motion ratio is factored again to account for the lever-arm force differential.
Example: K
|
A----B------------P
o P is the pivot point, B is the spring mount, and A is the wheel. Here the motion ration
(MR) is 0.75... imagine a spring K that is rated at 100 lb/in placed at B perpendicular
to the line AP. If you want to move A 1 in vertically upward, B would only move
(1in)(MR) = 0.75 in. Since K is 100 lb/in, and B has only moved 0.75 in, there's a
force at B of 75 lb. If you balance the moments about P, you get 75(B)=X(A), and we
know B = 0.75A, so you get 75(0.75A) = X(A). A's cancel and you get
X=75(0.75)=56.25. Which is [100(MR)](MR) or 100(MR)
2
.
http://forums.nasioc.com/forums/showthread.php?t=1703154 (post#6)

Note: Above only shows the Wheel Rate for the coil-over shock assembly. For the Total
Wheel Rate (in one-wheel bump or roll condition) add the Wheel Rate from the ARB (anti-
roll bar).

 Static Deflection = 2.799in (71.095mm)

 Ride Frequency [NF=188/sqrt(SD inches)] = 118.7CPM (1.98Hz)
NF = Natural Frequency in Cycles Per Minute (divided by 60=Hz)
SD = Static Deflection in Inches
A typical average family sedan = natural frequency 60 to 90 CPM (1 to 1.5Hz).
A high-performance sports car = natural frequency of about 120 to 150 CPM (2 to 2.5 Hz).

15. Front Suspension (cont’d)
 Bushing Material = Polyurethane
 Bushing Rate = Dependent upon Deflection (see below)





 Anti-Roll Bar (tubular)
http://forums.corvetteforum.com/autocrossing-and-roadracing/1957758-c5-spring-rates-and-antisway-bar-
sizes-97-04-a.html (post#5 - REF: C5 Z06: 30.0 mm-front / 23.6 mm-rear / 4.5mm/3.5mm thickness)
o O.D. = 30mm (1.181in)
o Wall Thickness = 4.5mm (.177in)
o Spring Rate = 543.6 lb/in (95.4 N/mm)

Front Suspension (cont’d)

 Anti-Roll Bar (tubular) cont’d

“This formula does not take into account the flex of the bushings used to mount the sway bar, which can
be significant. It also doesn't account for when the lever arms are physically longer than the actual lever Back to Master Data
Front: Bushing Flex during Roll:
Bushing
Rate
(lb/in)
Load Loss
due to
Bush Flex
(lb)
Bushing
Deflection
(in)
Wheel
Travel
(in)
ARB travel
w/o Bush
Flex
(in)
ARB travel
subtracting
Bush Flex
(in)
Load due
to Wheel
Travel
(lb)
Total Load
including
Bush Flex
(lb)
22000.00 2.873 0.006 0.500 0.320 0.313 142.15 139.28
5.746 0.013 1.000 0.639 0.627 284.31 278.56
8.618 0.019 1.500 0.959 0.940 426.46 417.84
11.491 0.026 2.000 1.279 1.253 568.62 557.12
14.364 0.032 2.500 1.599 1.566 710.77 696.41
1003.6(ft-lb/deg)
25.3 1112.6(ft-lb/deg)
difference = 109.0(ft-lb/deg)
Rear: Bushing Flex during Roll:
Bushing
Rate
(lb/in)
Load Loss
due to
Bush Flex
(lb)
Bushing
Deflection
(in)
Wheel
Travel
(in)
ARB travel
w/o Bush
Flex
(in)
ARB travel
subtracting
Bush Flex
(in)
Load due
to Wheel
Travel
(lb)
Total Load
including
Bush Flex
(lb)
22000.00 0.580 0.003 0.500 0.375 0.371 69.152 68.572
1.161 0.006 1.000 0.749 0.743 138.305 137.144
1.741 0.009 1.500 1.124 1.114 207.457 205.716
2.321 0.013 2.000 1.498 1.486 276.610 274.288
2.902 0.016 2.500 1.873 1.857 345.762 342.860
440.7(ft-lb/deg)
24.4 462.0(ft-lb/deg)
difference = 21.4(ft-lb/deg)
Effects of Bushing Deflection
Bushing
Spacing
(in)
ARB Roll Stiffness including Bush Flex =
Bushing
Spacing
(in)
ARB Roll Stiffness including Bush Flex =
ARB Roll Stiffness w/o Bush Flex=
ARB Roll Stiffness w/o Bush Flex=
ARB Rate including Bush Flex (body roll):
ARB Rate including Bush Flex (body roll):
0
2
4
6
8
10
12
14
16
0.5 1.0 1.5 2.0 2.5
Load Loss (lb)
Wheel Travel (in)
Load Loss due to Bushing Flex
Front Load Loss
Rear Load Loss Back to Master Data Back to ARB Rate Target
Front: Front: Target
Motion Ratio: 0.639(in/in)ABR rate: 543.612lb/in 543.79
Virtual torque arm (A): 8.9in ABR effect Wheel Rate (one wheel bump):222.298lb/in
Length of center (B): 32in ABR effect Wheel Rate (body roll): 444.596lb/in 444.74
Physical torque arm (C):10.79in
OD in millimeters: (D) 30mm
ID in millimeters: (if hollow) 21mm
Rear: Rear: Target
Motion Ratio: 0.749(in/in)ABR rate: 164.494lb/in 164.68
Virtual torque arm (A): 8.51in ABR effect Wheel Rate (one wheel bump):92.311lb/in
Length of center (B): 32.28in ABR effect Wheel Rate (body roll): 184.623lb/in 184.83
Physical torque arm (C): 9.2in Back to Wheel Rate Target
OD in millimeters: (D) 20mm
ID in millimeters: (if hollow) 0mm
ARB (anti-roll bar) Rate Calculator
The diameter inputs are in millimeters since that is how ABRs are usually sold. This calculation does not take into account flex allowed from ABR bushings, which
can be very significant when using soft rubber bushings.
See Effects of Bushing Deflection below.
A - Length of end perpendicular to B (torque arm - inches)
B - Length of center section (inches)
C - Length of end (inches)
D - Diameter bar (millimeters)

16. arm they form (a bent bar, like the front sway), but that affect is pretty minor.”
http://forums.nasioc.com/forums/showthread.php?t=1279944


Tubular vs. Solid ARB - Front
Input
Tubular Solid Output
Conversion
OD ID
Wall
Thickness
Result
mm in mm in mm in mm in
30 1.181 21.00 0.827 4.5 0.177 28.01 1.103

“On first inspection, this may be hard to compare to the traditional solid bar offerings from other
manufacturers. UUC's tubular design requires that in order to make a comparison to the outside diameter
(OD) of a solid bar, some calculations are required. The inside and outside diameter of the bar must be
analyzed to determine how big a solid bar would have to be to provide the same stiffness. This requires
taking the OD to the 4th power, subtracting the inner diameter (ID) to the 4th power, and taking the fourth
root of the whole thing.”
http://www.uucmotorwerks.com/html_product/sway_barbarian/html_sway_bar/description2.htm

Even though the tubular bar isn't actually stronger, the advantage of the hollow cross section is a significant
weight reduction without significant loss of resistance to torsion. In some (most) cases, this trade-off is
worthwhile.
When comparing a solid sway bar with a tubular bar of identical material and arm geometry, you need to
subtract the inside diameter (i.e. wall thickness times 2) to the fourth power from the outside diameter to
the 4th power, and then take the fourth root of the whole thing.
In "Excel-speak", think (SQRT(SQRT((OD^4)-(ID^4))).
http://forums.bimmerforums.com/forum/archive/index.php/t-334213.html

17. Front Suspension (cont’d)

 Anti-Roll Bar (tubular) cont’d
o Motion Ratio = [Distance between the lower coil-over mount and the lower control arm inner
pivot point / Length of the lower control arm]



Motion Ratio = (B/A)*sin(ARB Link Angle)







o Motion Ratio = (9.61in / 14.94in)*sin(90
O
) = 0.643

o Wheel Rate (lb/in) = (Motion Ratio)
2
x (Spring Rate)
“Now, what matters isn't the spring rate of the bar, but the spring rate at the wheels. To get the
wheel rate of the sway bar, we multiply by the spring rate (K from above) by the square of the
motion ratio.”
http://forums.nasioc.com/forums/showthread.php?t=1279944
o Wheel Rate – ARB Bump (lb/in) = (.643)
2
x (546.45 lb/in) = 225.93 lb/in
o Wheel Rate – ARB Roll (lb/in) = 2 x (225.93lb/in) = 451.86 lb/in

B
A
ARB Link
Angle

18. Front Suspension (cont’d)

 Steering Ratio = 12.7:1

 Steering wheel turns lock-to-lock = 2.27

 Steering Rack Movement
o Left = 55mm (2.165 in)
o Right = 55mm (2.165 in)

 Turn Angle
o Inboard = 32.1
O

o Outboard = 28.4
O


 Turning Radius
o Curb to Curb = 5.36m (17.59ft) @ 100% Ackermann
o Curb to Curb = 6.3m (20.66ft) Actual

 Full Jounce/Rebound from Ride Height per CATIA Kinematics:
o Full Jounce = 62.1mm
o Full Rebound = 66.7mm
o (CATIA not set to correct vehicle SLR)

 Full Jounce/Rebound from Ride Height Calculation:
o Full Jounce = 69.3mm
o Full Rebound = 59.2mm

 Alignment – Service Manual (at Ride Height) www.corvetteforum.com/forums/c5-tech/2331172-
adjusting-camber-and-caster.html
o Front Individual Toe -0.04
O
+/- 0.10
O
(CAD Design set to 0.0
O
)
o Front Sum Toe -0.08
O
+/- 0.20
O
(CAD Design set to 0.0
O
)
o Front Individual Caster +6.5
O
+/-0.5
O
(per Customer)
o Front Cross Caster Within +/-0.5
O
--
o Front Individual Camber -0.20
O
+/-0.50
O
(CAD Design set to 0.0
O
)
o Front Cross Camber Within +/-0.5
O
--

19. o Rear Suspension
 5-Link (C4) [“Upper and lower lateral links, twin trailing links, toe link. As used on the Chevrolet
Corvette C4 rear with the drive shaft acting as the upper lateral link”]
http://www.susprog.com/susptype.htm
 Rear Suspension Geometry http://www.eugeneleafty.com/Corvette.asp
o Rear Caster Angle = 1.2
O

o Rear Mechanical Trail = 6.83mm (.269in)
o Rear Spindle Length = 123.0mm (4.843in)
o Rear Kingpin Angle (Inclination) = -7.1
O

o Rear Scrub Radius = 162.3mm (6.39in)
o Rear Side-view Swing Arm Angle = 6.48
O

 Brake Rotor Dimensions - Rear
26mm (1.024in) --- rotor thickness
70mm (2.756in) --- center hole diameter
42mm (1.654in) --- inside face of hub to inner rotor surface
182mm (7.165in) --- inner hub diameter
202mm (7.953in) --- outer hub diameter
305mm (12.008in) --- rotor diameter
o Brake Caliper to Wheel (min clearance) = 41.166mm (1.62in)

 Anti-squat Instant Center (from Susp Analysis Axis) MAR2013
o X= -1654.561mm, Z= 416.253mm

 Camber Strut Pivot Points (from Susp Analysis Axis) MAR2013
o Inboard = X= -2486.124mm, Y= 153.895mm, Z= 201.626mm
o Outboard = X= -2486.136mm, Y= 603.673mm, Z= 187.505mm

 U-Joint Pivot Points (from Susp Analysis Axis) MAR2013
o Inboard = X= -2488.901mm, Y= 197.893mm, Z= 339.184mm
o Outboard = X= -2488.913mm, Y= 620.911mm, Z= 325.9mm

 Tie Rod Pivot Points (from Susp Analysis Axis) MAR2013
o Inboard = X= -2687.532mm, Y= 30mm, Z= 304.36mm
o Outboard = X= -2687.619mm, Y= 526.349mm, Z= 288.724mm

20. Rear Suspension (cont’d)

 Upper Trailing Arm Pivots (from Susp Analysis Axis) MAR2013
o Forward = X= -2158.46mm, Y= 528.781mm, Z= 410.388mm
o Rearward = X= -2437.841mm, Y= 528.781mm, Z= 407.136mm

 Lower Trailing Arm Pivots (from Susp Analysis Axis) MAR2013
o Forward = X= -2122.795mm, Y= 528.781mm, Z= 312.566mm
o Rearward = X= -2438.986mm, Y= 528.781mm, Z= 242.548mm

 Shock Mounting Pivots (from Susp Analysis Axis) MAR2013
o Lower = X= -2421.968mm, Y= 470.593mm, Z= 153.7mm
o Upper = X= -2330.675mm, Y= 363.445mm, Z= 408.433mm

 Rear Roll Center Height = 35.275mm (1.389 in) (above ground level)

 Coil-Over Shock Motion Arm Ratio (@ Ride Ht.) = 0.724unit/unit

 Shock Installation Angle (@ Ride Ht.) = 77
O


 Full Jounce/Rebound from Ride Height per CATIA Kinematics:
o Full Jounce = 62.1mm
o Full Rebound = 66.7mm
o (CATIA not set to correct vehicle SLR)

 Full Jounce/Rebound from Ride Height Calculation:
o Full Jounce = 69.3mm
o Full Rebound = 59.2mm

 Alignment – Service Manual (at Ride Height) www.corvetteforum.com/forums/c5-tech/2331172-
adjusting-camber-and-caster.html
o Rear Individual Toe -0.01
O
+/- 0.10
O
(CAD Design set to 0.0
O
)
o Rear Sum Toe -0.02
O
+/- 0.20
O
(CAD Design set to 0.0
O
)
o Rear Thrust Angle -0.0
O
+/- 0.10
O

o Rear Individual Camber -0.18
O
+/-0.50
O
(CAD Design set to 0.0
O
)
o Rear Cross Camber Within +/-0.5
O
--

21. Rear Suspension (cont’d)

 Shocks = Strange - Double Adjustable - S5003
http://www.strangeengineering.net/catalog/index.html
http://www.strangeengineering.net/catalog/pages/116.jpg
http://www.strangeengineering.net/catalog/pages/122.jpg
http://performanceshock.com/2-1-2-id-springs/2-5-x-8/188b0650

o Extended Length = 12.84in (362.1mm)
o Compressed Length = 9.5in (241.3mm)
o Rec. Ride Height = 11in - 11.375in (279.4mm-288.9mm)
o Rec. Spring Height = 7in-8in (177.8mm-203.2mm)
o Stroke = 3.36in (85.3mm)
o Bump Stop = .563in (14.3mm)

 Rear Shock Length at Ride Height = 290.7mm (11.44in)
 Rear Spring Length at Ride Height = 161.8mm (6.37in)
 Rear Spring Deflection at Ride Height = 35.6mm (1.4in)
 Rear Spring Load @ 35.6mm (1.4 in) Deflection (Ride Ht) = 980lb

o Motion Ratio = [Distance between the lower coil-over mount and the lower control arm inner
pivot point / Length of the lower control arm]
http://www.proshocks.com/calcs/imotion.htm
o Motion Ratio = (13in / 17.5)*sin77deg = 0.728

o Wheel Rate (lb/in) = (Motion Ratio)
2
x (Spring Rate)
“Let’s assume the spring moved 0.75 inches, the lever arm ratio would be 0.75 to 1. The wheel
rate is calculated by taking the square of the ratio (0.5625) times the spring rate. Squaring the
ratio is because the ratio has two effects on the wheel rate. The ratio applies to both the force and
distance traveled.”
http://en.wikipedia.org/wiki/Suspension_%28vehicle%29#Wheel_rate
o Wheel Rate (lb/in) = (0.728)
2
x (600 lb/in) = 318.0 lb/in
o Spring Rate = (Wheel Rate) / (Motion Ratio)
o Spring Rate (lb/in) = 700 lb/in

22. Rear Suspension (cont’d)

 Anti-Roll Bar
http://forums.corvetteforum.com/autocrossing-and-roadracing/1957758-c5-spring-rates-and-antisway-bar-
sizes-97-04-a.html
o O.D. = 21mm (.827in)
o Wall Thickness = 0mm (solid)
o Spring Rate = 226lb/in