[AmarilloMike]

Hi:
Did I do this speed calc right?
Engine speed = 6250rpm
Wheel Diameter = 26"
Rear end ration = 3.73
Fifth gear = .68

(6250/(3.73x.68))x((26/12)/2)x3.1416=95.3 mile per hour

That seems awfully slow for a top speed (6,250rpm is the rev limit on my motor)!

Mike

 

[AmarilloMike]

Oops! left out two numbers

(6250/(3.73x.68))x((26/12)/2)x3.1416/5280x60=95.3 mile per hour

Mike

 

[SVT]

189.5

 

[johnh]

Mike,

Circumference of a circle is pi*d or 2*pi*r. You're using pi*d/2. Get rid of the 2 in the denominator.

 

[DrDave]

Mike,
At first glance, I'd say the trouble is here:

(6250/(3.73x.68))x((26/12)/2)x3.1416

To get circumference, it's diameter*Pi, or 2*Pi*radius. Not diameter*Pi/2, which is what you have.

(6250/(3.73*0.68))*(26/12)*3.1416/5280*60 = 190.6

Of course I could be wrong...
-Dave

 

[Brendan]

Mike,

Remember thats a theoretical calculation too. That assumes that the car has enough engine power to overcome wind drag and other rolling resistance to get the car up to ~190 in 5th.

It also assumes you could find someone nuts enough to try!

-Brendan

 

[AmarilloMike]

Thanks - I was using PIxD/2. I dont't want to go 190, but I want to be able to go faster than 95 (I think).
I was messing with rear end ratios when I started fiddling with this.
Mike

 

[andy dunn]

2 Gear Comparisson
Speed vs. RPM For Tire and Gear Ratio

http://www.smokemup.com/auto_math/mph_range2.php