old school vrs new school

[Jeff65]

Originally posted by fordkid68
Jeff65 will the 4.10 still seem to much with bigger then normal tires on the back.


69fastback I like the sound of that. thanks.


thanks
fordkid

Wheel wells on classic Mustangs aren't big enough to handle tires of the width and diameter that it truly affects gear ratio. Here's an example:

Assume you use 3:89 gears and up the tire diameter from 25.4" to 27.5" (I doubt you can get a tire bigger than this in the wheel well and also have proportional width).

Calculate:

25.4x3.14=79.4
27.5x3.14=86.4
86.4/79.4=1.08

Hence you get 8% less gear.

For 3:89

3.89x(1-.08)=3.89x0.92=3.58

The tire effect is such as to reduce the gear ratio by one step.

For 4:11

4.11x0.92=3.78

3:78's are okay with five speed having overdrive of 0.68 or so but you will still shift three times quickly before the car starts to gain speed.