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88 Eldorado Top Speed

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What is the top speed of an 88 Eldorado and where is that information written?

My Buddy has a 88 eldorado and we topped it out at 95 mph, but he also has 20 inch rims which are a little heavier. Im not sure where it is written or if it is even written anywhere

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The weight of a vehicle does not effect top speed per se, although it does effect how long it will take to reach top speed. Top speed is effected by aerodynamics (CD and frontal area) and horsepower.

The normal rule for wheel and tire changes is to make changes so that the overall diameter of the resulting wheel and tire remain the same. So to increase from 16" wheels to 17" wheels one might also go from /55 sidewall tires to /50 sidewall tires so that the overall diameter of the wheel+tire remain around 25" (in the case of the CTS). If the overall diameter of the wheel+tire are increased, it does change the effective gearing of the car.

To determine the diameter of the wheel/tire one would take the wheel diameter in inches (16, 17, 18, 19, 20, etc) plus twice the tire sidewall as a % of the tire bead width. Tires are given in mm, so a 225x55 tire is 225mm wide with a 55% sidewall, for 225*55= 123.75mm = 4.87 inch sidewall height. Remember in the diameter there are two sidewall (tire+wheel+tire), so the total theoretical diameter for my 225/55-16 tire+wheels is 16+4.87+4.87 = 25.74 inches. You will find your actual wheel+tire diameter can be slightly different and it is fairly easy to measure with a tape measure.

A larger wheel/tire actually give a higher potential top speed due to gearing, but make it harder to reach the top speed. For example, at 6500 rpm my CTS has a theoretical top speed in 4th gear with 25.74" diameter wheel+tire of 145.5 mph. It is electronically limited to 130 mph, but for argument sake let's say it was not. If the wheel+tire size were increased to 26.74" (by one inch), the top speed in 4th gear would also increase to 151.2 mph due to the change in effective gearing of the car. The acceleration would tend to decrease for the same reason.


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