gear ratios / speed in gears

[Ecosseven]

evening all,

I am trying to work out the maximum speed in each gear based on the following information.

Gear ratio.
Final drive ratio.
Wheel and tyre size.
red line of 7200rpm.

Any idea how I calculate the max speed in each gear?

Thanks in advance.

[stevesingo]

Google...

http://www.boosttown.com/gearbox_differential/spee...

[stevieturbo]

Exactly there are dozens of similar calculators online

[Ecosseven]

Thanks guys.

[Pumaracing]

stevieturbo said:

Exactly there are dozens of similar calculators online

Most if not all of them I suspect getting the tyre rolling radius wrong. It's actually only about 96% of what you would calculate from the width, aspect ratio and wheel radius.

Example - 185/60/14 tyre.

Sidewall height is 0.6 x 185mm = 111mm

Wheel diameter is 14 x 25.4 = 355.6mm

Tyre diameter is 355.6 + 111 + 111 = 577.6mm

Actual rolling diameter of a part worn tyre is 96% of that = 554.5mm

97% for a new tyre and 95% for a shagged one.

Edited by Pumaracing on Tuesday 27th November 15:00

[PaulKemp]

Some tyre manufacturers will quote rolling radius, if they do I manually put it in or adjust the profile/width to get as close as possible
97% or so is close enough for road use IMHO

[Stan Weiss]

If you are looking at your lower gears then most any of these will do. If what you want is top speed in high gear you better find one that wants torque / Hp at different RPM as well as your vehicles CD and frontal area or else you could be in for a big surprise.

Stan