R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Thread Tools Search this Thread
Old 01-21-2005, 04:46 AM   #1
Tech Regular
Join Date: Dec 2003
Location: Orlando, Fl
Posts: 458

What are the equations for roll-out, final-drive, and any other important ones related to touring car racing, thanks.
TC3er is offline   Reply With Quote
Old 01-21-2005, 05:18 AM   #2
Tech Elite
kufman's Avatar
Join Date: Feb 2004
Location: Elburn, IL
Posts: 3,406
Trader Rating: 5 (100%+)

Final drive:

(Spur/pinion)*internal ratio

Internal ratio: Diff Teeth/pinion pully teeth


(Pi*D)/ Final Drive Ratio

D=diameter of tires
Brushes? We don't need no stinking brushes!!!
kufman is offline   Reply With Quote
Old 01-21-2005, 05:31 AM   #3
Tech Regular
ddesros2's Avatar
Join Date: Nov 2003
Location: Windsor, Canada-eh!!
Posts: 401
Trader Rating: 8 (100%+)

On a direct drive car (like a 12th scale) use the following:

MMPR (MilliMeters Per Revolution, It's how far the car will travel in mm when the motor makes one revolution)

W= Wheel diameter in mm

S= Spur gear teeth (ex: 96T spur)

P= Pinion teeth (ex: 25T pinion)

MMPR= (P/S)*(3.1416*W)

Example: My 12th scale has a monster Pro and 39 MMPR is a good rollout for that motor. What Pinion do I use??
I measure, W=46mm, My spur is 96.

Round it off to P=26T

So slap in a 26T pinion and it's go time!!

For cars with internal drive ratios (Like a TC3, it has an internal drive ration of 2.5:1) Check your user manual for the drive ratio and add it to the above equation like so:

DR=Drive ratio (Ex: DR=2.5 for a TC3)

MMPR= (1/DR)*(P/S)*(3.1416*W)

Example: I'm running a 19T spec motor in my TC3, what pinion do I use. Guys at the track say that 25 MMPR is a good start.
I measue, W=65mm (full size TC tire), My spur is 100T

Round it off to 30T or 31T

Select the 30T or the 31T and try it out.

This equation can be applied to any car, a AE B4 has a 2.6:1 drive ratio so just apply it as above.

Hope this helps.
Custom Clod crawler; T3 2011; XII Link; Hyperdrive Pro 3; 777e
ddesros2 is offline   Reply With Quote
Old 01-21-2005, 01:55 PM   #4
Tech Regular
Join Date: Dec 2003
Location: Orlando, Fl
Posts: 458

Thanks guys, are there any other important ones relating to touring?
TC3er is offline   Reply With Quote
Old 01-21-2005, 06:04 PM   #5
Tech Master
Join Date: Jul 2003
Posts: 1,000
Trader Rating: 4 (100%+)

I've put a makeshift Excel based Calculator on my website.


The rollout Calc is linked at the bottom.

There is an area to put in:
Tranny Ratio
Tire Diameter

Just leave the one you are trying to calculate Blank... enter the others and it will give you what you need.

ie.. if you want a certain rollout but need to know what pinion to use you just enter all of the info but the pinion and it will tell you which pinion to use.

Some guys with Mozilla have said they had trouble with the calc... it is based on Microshaft software so who knows... though i would imagine there is a plug-in for such. Anyway... I'm working on a couple others that aren't dependent on Microsofts Internet Exploiter! lol May never come to fruition though... I barely know jack about this web stuff! lol
JKA is offline   Reply With Quote
Old 01-21-2005, 06:13 PM   #6
Tech Regular
Join Date: Dec 2003
Location: Orlando, Fl
Posts: 458

That is whay I am doing for myself, I created a VB program and just making sure I have everything I need.
TC3er is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off

All times are GMT -7. It is currently 09:05 PM.

Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net

SEO by vBSEO 3.5.0