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1989 Mustang GT and Wheel Diameter Changes


     So you are thinking about getting rid of your stock 15" or 16" wheels and buying some 17" wheels, ever wonder how that will effect the performance of the car.
 
     Here is the general rule, A taller tire is faster, A shorter tire is quicker. By making the outer diameter of the tire taller, you are essentially reducing the torque your car has. Also note that horsepower is based on your torque. (Horsepower = (Torque X RPM)/5252 )
 
     Another key point here, is that if you switch to a taller wheel, but use a low profile tire, you probably have not changed the out diameter of the wheel enough to care. A 225/55/16 tire is actually almost an inch taller than a 225/45/17.
 


The test below is using a stock 1989 Mustang GT, 5-speed.
 
Test 16" 17" 18"
0-30 MPH 2.2 2.2 2.3
0-40 MPH 3.8 3.2 3.2
0-50 MPH 5.1 5.1 5.2
0-60 MPH 6.5 6.6 6.7
0-70 MPH 9.1 9.2 9.2
0-80 MPH 11.3 11.3 11.5
0-90 MPH 14.8 14.0 14.1
0-100 MPH 18.1 18.3 18.5
1/4 Mile 15.2 15.2 15.2
Trap Speed 91.4 MPH 91.4 MPH 93.4
Top Speed 141 139 137



The test below is using a modified 1989 Mustang GT, 5-speed. Modifications included, TrickFlow heads, Cobra intake, E303 Cam, and exhuast work.
 
Test 16" 17" 18"
0-30 MPH 2.0 2.0 2.0
0-40 MPH 2.5 2.6 2.7
0-50 MPH 4.0 4.0 4.0
0-60 MPH 5.0 5.0 5.1
0-70 MPH 6.0 6.1 6.2
0-80 MPH 8.0 7.3 7.4
0-90 MPH 9.6 9.6 9.7
0-100 MPH 11.4 11.5 11.6
1/4 Mile 13.3 13.3 13.4
Trap Speed 109.6 MPH 109.2 MPH 108.5
Top Speed 158 160 166

 


 
© 1998 Michael Lee
© 2004 Michael Lee