NismoSkyline17

I'm used to running on asphault with rubber tires so rollout is not a factor. Now I'm racing on carpet and need to calculate rollout. I checked all the other rollout threads and they just give the websites to get charts. I don't need charts. Any person can punch numbers into a program to come up with a chart. I want to know the mathmatical formula to come up with those numbers. I am also looking for an average rollout for a tuned stock motor on a small technical track. BTW I use mm in measuring the tire diameter.

Thanks in advance.

Smalls

Tire size times PIE (3.14) divided by spur times pinion.
Ie. 1.74*3.14=5.4636 / 98 = .05576 (rounded) * 38 = roll out of 2.11

There are other ways, but that is how I do it.

NismoSkyline17

Thanks Smalls.

That seems to sound right.

F. Alonso

iTrader: (10)

is your figure for sire size in inches, centermeters, millimeters???

Also, does the diametric pitch of the gears affect it at all??

MManson

iTrader: (2)

What kind of PIE do you use in your rollout?

pecan? apple, cherry? or pumpkin?

newracer

If you are running a TC you also need the internal ratio in the formula. I use tire diameter*PI*pinion/spur/internal ratio

I like pumpkin pie!!

E.J. Evans

Here is a great site done by a buddy!

http://www.gearchart.com/

NismoSkyline17

Thanks newracer. I was wondering why the formula that was previously mentioned was also on a 1/12th forum and the numbers I was coming up with didn't seem right.

E.J.- I was looking for the accual formula to calculate rollout so I would have the knowledge to make changes to compensate for a change. Not to have a bunch of charts that mean squat.

Smalls

I gave you the 12th scale roll out. You never said it was for TC ( although I assumed it when I saw rubber tires ), but you never said what it was for and what your drive ratio was...

pops

iTrader: (1)

You only need one chart, (for each type of car) as your foams wear down, it will tell you what pinion to use.