Speedo Gear info

[-=Jeff=-]

formulas for calculating the correct gearing

We will do 2 scenarios.. one going from a 3.45 to 4.10

one going from a 315/35R17 to a 335/30R19 wheel

Assuming the car is a 3.45 ZR-1 the Drive gear is 15t and Driven is 42t

http://www.*************.net/c4/vettenuts/SpeedometerGearshtm.shtml
**CF** nice speedo gear chart

First the wheels:

25.7"dia (17) and 27"dia (19)

figure out the difference.. 27/25.7 = 105%

now (Drive New/Drive Old) * (Driven Old/Driven New)

or (15/15) * (42/X) = 105%
(1) * (42/1.05) = X
(1) * (42/1.05) = 40

check
(1) *(42/40) = 105%

so for the tires change to a 42t Driven gear

for the 3.45 to 4.10

3.45/4.10 = 84.14%

(13/15) * (42/43) =

.8666 * .976 = 84.6%


to get the right gearing it will take a little work

but it is not too bad

[rhipsher]

The best way would be to put that in an Excel spread sheet with all of the formulas in the background so when you change gear ratio or tire size it recalculates the outcome. Maybe when I have some more time I'll create it. Then it could be made a sticky or put in the tech section for everybody to use. :thumbsup:

[GrayZ]

OH thank goodness, i was afraid to click on this post,
I was terribly afraid it was a picture of Jeff in a speedo.... :jawdrop:
I want to take this time to thank the powers that be
it was not... :thumbsup:

[-=Jeff=-]

OH thank goodness, i was afraid to click on this post,
I was terribly afraid it was a picture of Jeff in a speedo.... :jawdrop:
I want to take this time to thank the powers that be
it was not... :thumbsup:

:sign10:

You would just be jealous anyway :mrgreen:

[GOLDCYLON]

OH thank goodness, i was afraid to click on this post,
I was terribly afraid it was a picture of Jeff in a speedo.... :jawdrop:
I want to take this time to thank the powers that be
it was not... :thumbsup:


My eyes.... My Eyes :eek:

[XfireZ51]

OH thank goodness, i was afraid to click on this post,
I was terribly afraid it was a picture of Jeff in a speedo.... :jawdrop:
I want to take this time to thank the powers that be
it was not... :thumbsup:


Keith,

It would mean the end of civilization as we know it.