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

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