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/vett...Gearshtm.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