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TUTORIAL
FOR MIATA SUSPENSION DESIGN SPREADSHEET
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Copyright © 2008 Shaikh
J. Ahmad / Fat Cat Motorsports
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Send any comments or questions
to:
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shaikh@fatcatmotorsports.com
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SOLID FRONT BAR
SET-UPS
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For explanations, move the mouse over the red lettering below!
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Front
sway diameter
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Rear sway diameter
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Front spring
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Rear Spring
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Bounce frequency (Hz)
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Roll Stiffness
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Front Roll
Couple (FRC)
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COMMENTS
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mm
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mm
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lb/in
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lb/in
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Front
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Rear
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lb-ft/deg
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%
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Move
the mouse over the red carrot for the tutorial!
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Stock 1990 with manual transmission
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Step 1
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1990 with 7/8" front sway bar. 19% greater roll stiffness, higher
FRC
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Step 2
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1990 with 7/8" front and 5/8" rear bar. +48% roll stiff., much lower FRC
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Step 3
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1990 with 7/8" front bar and FM springs. Bounce freq. and roll
stiff go up
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Step 4
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1990 with 7/8" front, 5/8" rear bar and FM springs. FRC very
low!
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Step 5
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1990 with 7/8" front and NO rear bar. FRC 63%, just higher than stock.
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Step 6
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1990 with 7/8" front bar and 375/250 Eibach race springs Bounce
freq. higher
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Step 7
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Your
turn! Look at the 'Springs_Sways' tab for combinations to try!
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Step 8
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1990 with Tein Basic, Tein SS, or Tein Flex. Note very low FRC!
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Step 9
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1990 with Tein Basic and no rear bar.
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Step 10
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1990 with Tein Basic, 7/8" front bar, no rear bar. Almost back to
stock FRC.
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Step 11
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1990 with Tein, 7/8" front bar, substituted 6kg/mm for 5kg/mm rear
springs.
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Step 12
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1990 with stock springs and 7/8" front bar. Typical autocross
setup.
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Step 13
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1990 with stock springs and 15/16" front bar. Typical autocross
setup.
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Step 14
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1990 with Spec Miata setup - good starting FRC for track/high-speed
setups.
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Step 15
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1990 with 1" solid front bar, no rear bar, 550/325 spring rates
(STS2/CSP)
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Step 16
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TUBULAR BAR SET-UPS
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Front sway
diameter
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Front sway wall thk
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Rear sway diamter
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Front spring
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Rear Spring
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Bounce frequency (Hz)
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Roll Stiffness
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Front Roll Couple
(FRC)
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COMMENTS
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mm
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mm
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mm
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lb/in
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lb/in
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Front
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Rear
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lb-ft/deg
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%
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1990 with Racing Beat tubular front bar (1 1/8" OD).
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Step 17
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1990, typical STS2 or CSP autocross setup.
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Step 18
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Experiment with different spring and sway bar combinations!
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Step 19
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Vehicle weight (lb)
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Sprung
weight
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Driver weight (lb)
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Front
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Tire weight
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Total vehicle weight
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Rear
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Weight dist (%)
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Wheel weight
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Front
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Unsprung
weight
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Rear
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Front
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Vehicle Track
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Rear
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Front
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Rear
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Front sway bar specs
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Swaybar motion ratios
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Arm length (mm)
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Bar length (mm)
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Bar length
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1.6 OE arm length
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1.8 OE arm length
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1.6 FM arm length (inner)
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1.6 FM arm length (outer)
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NB arm length
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Front
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Rear
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Spring
motion ratios
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Rear sway bar specs
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Front
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Bar length
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NA / NB OE arm length
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1.6 FM arm length (inner)
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1.6 FM arm length (middle)
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1.6 FM arm length (middle)
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Rear
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DATA FOR SPRINGS
AND SWAY BARS
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Swaybar rate (lb/in)
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Unit converter
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K
= G X (Dia)^4 X
PI X (2.2*25.4/9.81)
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Deg F
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Deg C
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lb
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kg
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in
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mm
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(Arm length)^2
X Bar length X 16
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Note: Dimensions meas'd only for OE 19mm bar
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Arm length (mm)
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Bar length (mm)
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Deg C
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Deg F
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kg
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lb
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mm
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in
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(hollow
bar ID = OD - 2 * Wall thk)
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Front OD
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Wall thk
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OD (mm)
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ID (mm)
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Raw rate (lb/in)
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Wheel rate
(lb/in)
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kg-(force)
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N
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lb
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kPa
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psi
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bar
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19mm
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0.000
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20mm
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0.000
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N
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kg-(force)
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lb
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psi
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kPa
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bar
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13/16"
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0.000
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21mm
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0.000
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lb
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kg-(force)
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N
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bar
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psi
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kPa
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22mm
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0.000
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7/8"
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0.000
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kg/mm
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N/mm
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lb/in
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toe (in)
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wheel dia
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toe (deg)
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.93 in
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0.000
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0.000
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24mm
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0.000
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0.000
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N/mm
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kg-f/mm
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lb/in
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toe (deg)
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wheel dia
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toe (in)
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1"
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0.000
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0.000
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1 1/8" (90-97)
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lb/in
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kg-f/mm
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N/mm
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1 1/8" (99-01)
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1 1/4" (01-05)
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Rear bar NOTE: A,B,C meas'd for 12mm bar
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Rear OD
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Wall thk
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OD (mm)
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ID
(mm)
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Raw
rate (lb/in)
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Wheel
rate (lb/in)
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11mm
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0.000
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0.000
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12mm=
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0.000
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0.000
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1/2"
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0.000
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0.000
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14mm
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0.000
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0.000
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9/16"
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0.000
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0.000
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15mm
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0.000
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0.000
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5/8" (FM)
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0.000
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0.000
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