# How To Get Your Roll Out



## GEORGE LARRABEE (Jan 18, 2006)

Ive been told a million times how to get the roll out but can some one tell me again how to get the roll out. I would really appreshiate it if some one can help me. Thanks George Larrabee


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## IndyRC_Racer (Oct 11, 2004)

Better yet, has anyone programmed their scientific calculator to figure our roll-out?


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## OvalTrucker (Dec 14, 2003)

Here's the formula on a regular calculator: Tire Diameter X 3.14 X pinion / Spur.


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## DIRTsportsman (Oct 1, 2006)

Truckers equation is for 1:1 transmission like a pan car i belive you will have to factor in you cars internal drive ratio as well although i dont no where.LOL


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## pancartom (Feb 26, 2002)

i'm an idiot


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## SuperXRAY (Jul 10, 2002)

Holy cow....what's the deal guys?

*Direct-Drive cars:*
Roll-out = 
Tire Diameter x PI (3.14159 I use) = CIRCUMFERENCE OF TIRE
Spur / Pinion (120/43 is 2.7907 for example) = GEAR RATIO
_________________
_TIRE CIRCUMFERENCE / GEAR RATIO = ROLLOUT_

Let's say your Tire Diameter is 2.25, that gives you a TIRE CIRCUMFERENCE of 7.0686. Your Gear Ratio is 2.7907 (as above), so your _rollout is 2.533_.

*Transmission Cars:*
Tire Diameter x PI (3.14159 I use) = CIRCUMFERENCE OF TIRE
(Spur / Pinion = GEAR RATIO) x DRIVE RATIO (or Transmission Ratio if you prefer) = FINAL DRIVE RATIO
_________________
_TIRE CIRCUMFERENCE / FINAL DRIVE RATIO = ROLLOUT_

Let's say your Tire Diameter is 2.25, that gives you a TIRE CIRCUMFERENCE of 7.0686. Your Gear Ratio is 2.7907 (as above), and your transmission ratio is 1.77, so your Final Drive Ratio is 4.9395, giving you a _rollout of 1.431_.

(break)

I can't believe there are two posts that are incorrect. You DO NOT multiple the circumference times spur...it is TIRE CIRCUMFERENCE DIVIDED BY GEAR RATIO, that's it! To the original poster, you should have searched for 'Calculating Rollout' on here or on Google, and you would have found it immediately. (not trying to be mean, but those that posted incorrect answers need to quit).


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## SuperXRAY (Jul 10, 2002)

If you used pancartom's equation, you would have a rollout of 19.726...good luck finding that one on the rollout wheel. If you used the first response with an equation, you would have a rollout of 36,473.976, HA!

Rollout isn't used only in R/C racing, it's used in every racing aspect, even non-racing venues have to use it, so it's not a debatable concept.


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## really fred (Sep 3, 2006)

pinion x tire circumference / spur = r.o.


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## SuperXRAY (Jul 10, 2002)

That only works for direct-drive cars, really fred.


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## really fred (Sep 3, 2006)

really

fred


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## ML23 (Aug 22, 2006)

what number do u want to shoot for for a touring car for your roll out


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## OvalTrucker (Dec 14, 2003)

Well EXXXCUUUSE MEEEE!:tongue: 
I made a typo in my post. It was supposed to be divided by the spur. I have corrected it.


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## SuperXRAY (Jul 10, 2002)

Scott...no, I meant quit posting incorrect answers... 


ML23, your question is ambiguous, it cannot be answered unless you know what track you are running, it also completely depends on what motor you run, not just what brand, etc....it's best to talk to your local guys about that one, as they will be the only ones that know about a specific track.


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## OvalmanPA (Mar 21, 2000)

Hey guys............have been reading these threads and finally remembered this little program I downloaded quite some time ago. It's pretty simple but VERY effective. You can even open up the source file and input your own gearbox ratios but I think right now I have most of the ones in it you'd need.



Edit...........file to large to upload here.......Click here to download the file. :thumbsup:


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## LittleR/CGuy (Apr 8, 2006)

Gahhhhhh!!!is This Math Class Or Wat!?!


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## Manning (Mar 2, 2004)

Rollout is the distance traveled for one revolution of the motor. Simple. 

Bigger tracks need a bigger rollout, smaller tracks need smaller rollout.


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## jenzorace (Dec 23, 2005)

OvalmanPA said:


> Hey guys............have been reading these threads and finally remembered this little program I downloaded quite some time ago. It's pretty simple but VERY effective. You can even open up the source file and input your own gearbox ratios but I think right now I have most of the ones in it you'd need.
> 
> 
> 
> Edit...........file to large to upload here.......Click here to download the file. :thumbsup:


This is cool you can figure the rollout for when a offroad buggy tire balloons.. Try it youll laugh. I race alot of buggy tires outside. Thats why i thought of checkin this out.


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## garyrcdoc (Oct 15, 2005)

If you have the palm OS in a PDA, you can download RC RACER from palm gear for free, it has a lot of gearing calculations as well as other handy applications for RC. If you can't find it, let me know and I can sent you a copy for free

Gary

[email protected] (put RC RACER in your description...)


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## snopro31 (Dec 11, 2004)

Would it not be easier to go to gearchart.com and print out a roll out chart for your car and take ti with you to the track is someone says theya re usign X roll out you just look at your chart and find either the tire size you need or the pinion spur combo you need.


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