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C3 Corvette Chassis Upgrade 2013
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C3 Corvette Chassis Upgrade 2013

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C3 Corvette Chassis Upgrade 2013

C3 Corvette Chassis Upgrade 2013


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  • 1. C3 Corvette Chassis Upgrade General Suspension http://en.wikipedia.org/wiki/Automotive_suspension_design http://www.carbibles.com/suspension_bible.html http://auto.howstuffworks.com/car-suspension.htm 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
  • 2. • Ride Heights at various states of load (Curb Wt vs. GVWR) Vehicle Suspension Dynamic Targets: • Wheel Frequency • Lateral Load Transfer • Roll moment (kg·m2 ) • 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) 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
  • 3. 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) Dependant upon Rear Suspension configuration. Chassis Attachment Points (x, y, z) Dependant 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: 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.)
  • 4. 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 oversteer ing. 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. Compliance analysis
  • 5. 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 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 ever 0.5” change in rim width.
  • 6. 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) http://bndtechsource.ucoz.com/index/tire_data_calculator/0-20 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 AxisSusp Analysis Axis X Y X Z ZX Y X
  • 7. 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 = [32.1 – 28.4]/10.24 = .36 = 36%
  • 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
  • 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 = 10mm (.394in) 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) • Alignment – Service Manual o Front Individual Toe +0.04 O +/- 0.10 O (Design set to 0.0 O ) o Front Individual Caster +0.4 O +/- 0.50 O (Design set to 0.0 O from 6.5 O ) o Front Individual Camber -0.20 O +/-0.50 O (Design set to 0.0 O ) • 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
  • 10. • 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
  • 11. 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 = 0.759 unit/unit (C5 modified) MAR2013 • Coil-Over Shock Installation Angle = 65.1 O MAR2013 • Frt Roll Center Height = 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
  • 12. 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
  • 13. 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 (351.536mm) 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)
  • 14. • Front Shock Length at Ride Height = 298.93mm (11.769in) • Front Spring Length at Ride Height = 201.4mm (7.929in) • Front Spring Load @ 52.6mm (2.071 in) Deflection (Ride Ht) = 1035.7lb
  • 15. Front Suspension (cont’d) Source: Jounce_vs_Shock_Length_vs_Shock Angle.xls Source: Susp_Project_Tasks_Calculator_10MAR13.xls
  • 16. 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 = 2.73in (69.342mm)
  • 17. • 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).
  • 18. Front Suspension (cont’d) • Bushing Material = Polyurethane • Bushing Rate = Dependant 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)
  • 19. o Wall Thickness = 4.5mm (.177in) o Spring Rate = 546.45 lb/in (95.7 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 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 SolidOutput 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.
  • 20. 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
  • 21. 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 Anle) 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
  • 22. Front Suspension (cont’d) • Steering Ratio = 12.7:1 • Steering wheel turns lock-to-lock = 2.27 • Steering Rack Movement o Left = 54mm (2.362in) o Right = 54mm (2.362in) • Turn Angle o Inboard = 32.1 O o Outboard = 28.4 O • Turning Radius o Curb to Curb = 5.361m (17.5ft) @ 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
  • 23. 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) • Alignment – Service Manual o Rear Individual Toe -0.01 O +/- 0.10 O (Design set to 0.0 O ) o Rear Individual Camber -0.18 O +/-0.50 O (Design set to 0.0 O )
  • 24. • 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
  • 25. Rear Suspension (cont’d) • 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 • 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 = 0.724unit/unit • Shock Installation Angle = 77 O
  • 26. • 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
  • 27. 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) 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 = 0.724 o Wheel Rate (lb/in) = (Motion Ratio) 2 x (Spring Rate)
  • 28. “Lets 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) = (0.724) 2 x (700 lb/in) = 366.9 lb/in o Spring Rate = (Wheel Rate) / (Motion Ratio) o Spring Rate (lb/in) = 700 lb/in
  • 29. Rear Suspension (cont’d) • Anti-Roll Bar (tubular) 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