So what is it? Why is it important? and how do I work it out?

Once I have done this how do I use it to work out the poss speed of the car?

I am asking this as I am trying to make a program to calculate it all for me.

I have already worked out ratio calcs.

Many thanks and ello! :thumbsup:

If you are running oval this may help:

Rollout is defined as the number of inches a vehicle moves forward per revolution of the motor.

Rollout is calcuated:

(Tire diameter x 3.14) / (Spur x Pinion)

For example say you are running a 2.22 tire, 116 spur and 40 T pinion
Rollout would be a 2.41

Various factors can come into play when properly trying to gear a car. Overall Track runline, Width of corners (tight vs sweeping), straight away length, surface of the track, RPM/Torque of the motor, etc

That makes much better sense cheers!

Right now to had that to my program!

I think it should be:

(Tire diameter X 3.14) / (Spur / Pinion)

or

(Tire diameter X 3.14) / Spur X Pinion

or just

Tire diameter X 3.14 / Spur X Pinion


Parentheses make a difference in evaluation of terms.

calculating is not a problem but how do you come out with a number first. Lets say run line 140-what would be a good start in roll out number. I normaly run short to medium tracks. and depending on motor I would adjust from there. What is the exact formula for run line to roll out? Usulay its what you hear to run and base it off there, but everyones motors have different rpm and torque. I sold my dyno so no longer have the program.

calculating is not a problem but how do you come out with a number first. Lets say run line 140-what would be a good start in roll out number. I normaly run short to medium tracks. and depending on motor I would adjust from there. What is the exact formula for run line to roll out? Usulay its what you hear to run and base it off there, but everyones motors have different rpm and torque. I sold my dyno so no longer have the program.


190' - 2.25
180' - 2.15
170' - 2.10
160' - 2.05
150' - 2.00
140' - 1.95
130' - 1.90
120' - 1.85
Go up about .25-.30 points for an Epic 19T
about .40 point or more for a Ti 19T
Those are some good starting points for a stock motor!

Brandon Snyder