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For transmission cars you need to know it's ratio for direct drive you use only tire diameter divided by gear ratio (spur/pinion).
The difference you stated for example if tire and spur size were unchanged then the 2.50 is a larger pinion, while the 2.35 uses a smaller pinion.
Transmissions vehicles
transmission ratio multiplies by tire diameter (distance across x Pi 3.14) divided by gear ratio (spur/pinion) = rollout
Direct drive pan cars
tire diameter (distance across x pi or 3.14) divided by gear ratio

2,685 Posts
parma24 said:
hey what is roll out

how do u find out roll out

what is the gearing of 2.50 roll out and that is the gearing of 2.35 roll out


You don't need charts or graphs?? You need math! :cool:

** Note: this formula is for pan car 1/12 or 1/10 scale cars with no trans..


Rollout = tire size (inches) X 3.142 X Pinion size / Spur size

To find pinion size at a certain rollout the Formula is this:

Pinion = Rollout X Spur size / Tire size (inches) X 3.142

Just rotate the formula to what you need...and keep it smiple! :thumbsup:

No, I just stayed at a Holiday Inn Express last night!
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