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Old 03-24-2005, 11:04 PM   #1
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Default 19Turn 1/12th scale rollout...

Hey all.

I'd like to pick the brains of all the 12th scalers here who run 19T on carpet. What is a good target rollout I should be aiming for?

I seem to range between 39.00 and 45.00. (Tires measured in mm)

I go 39.00 for longer runs and practice, then I gear for 45.00 for racing.

What rollout do you guys usually roll?


Pinion x Tire Diameter (mm) x pi
----------------------------------------
Spur
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Old 03-25-2005, 08:29 AM   #2
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Tire Size X 3.14 (Pi) = X

And then

Spur / Pinion = Y

X/Y= Rollout. Thats what i use and it seems to work pretty well.

In stock i usually run a lower rollout then usual because of the small tire size, i was running around 38.5. But i usually like to go in between 38-43 rollout.

In 19t i tend to just keep the same pinion gear as stock and runs very nicely also. Its all trial and error and the key is tire size in my mind.

Jon
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Old 03-25-2005, 10:35 AM   #3
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What motor? The C2 and QM need to be geared very differently.....
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Old 03-25-2005, 12:07 PM   #4
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Quote:
Originally posted by JDXray
Tire Size X 3.14 (Pi) = X

And then

Spur / Pinion = Y

X/Y= Rollout. Thats what i use and it seems to work pretty well.

In stock i usually run a lower rollout then usual because of the small tire size, i was running around 38.5. But i usually like to go in between 38-43 rollout.

In 19t i tend to just keep the same pinion gear as stock and runs very nicely also. Its all trial and error and the key is tire size in my mind.

Jon
Your rollout equation is wrong.

If you do it like you state, the end result isn't even a whole number:

Tire diameter (44mm) x Pi (3.14) = 138.16
-------------------------------------------

Pinion (25) x Spur (88) = 2200



Therefore:

138.16
-------------
2200


= 0.0628


Wrong equation.
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Old 03-26-2005, 09:11 PM   #5
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Quote:
Originally posted by vtl1180ny
What motor? The C2 and QM need to be geared very differently.....
Running Chameleon 2 with Putnam brushes, Purple/red springs.
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Old 03-26-2005, 10:50 PM   #6
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We run 19T 1/12th all season. I know nothing about rollout and don't care about it, the track is my rollout calculator......

Anyway, I run a Br00d C2, 767 with vertical slot, red/green springs, 96 spur, 28-29 pinions, 1.77 tires. Medium size track.

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Old 03-26-2005, 10:56 PM   #7
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I run C2's with 767's and green/green at about 44mm rollout. You're running some heavy springs for a light car.
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Old 03-27-2005, 07:46 AM   #8
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Quote:
Originally posted by Soviet
Running Chameleon 2 with Putnam brushes, Purple/red springs.
Purple/Red on 1/12th?? Ouch.... Lighten it up, you don't need the torque, you want the RPM's... Go green/Red or Green/Green....
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Old 03-27-2005, 08:07 AM   #9
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Quote:
Originally posted by Soviet
Your rollout equation is wrong.
Actually his equation is correct.

When you used his equation you did it incorrectly by multiplying the spur and pinion. You are supposed to divide the spur by the pinion.

Rollout= (Tire diameter * 3.14) / (Final Drive)

To get the final drive on a 12th you divide the Spur by Pinion.
So...

Rollout= (44mm * 3.14) / (88/25)
Rollout= (138.16) / (3.52)
Rollout = 39.25 mm


Hope this helps. I've never ran 19T in my 12th but would love to do it next year. I'd like to see what some people are running for a 19T rollout.

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Old 03-27-2005, 02:21 PM   #10
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Not sure if you read the rollout equation wrong or if i typed it wrong, sorry.

Tire Size X 3.14 (43mm x 3.14=135.02)

Then,

SPur / Pinion (96 / 28=3.42)

135.02/3.42=about 39
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Old 03-27-2005, 02:23 PM   #11
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Default equation

Should you always use this method./
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Old 03-27-2005, 04:32 PM   #12
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Quote:
Originally posted by JDXray
Not sure if you read the rollout equation wrong or if i typed it wrong, sorry.

Tire Size X 3.14 (43mm x 3.14=135.02)

Then,

SPur / Pinion (96 / 28=3.42)

135.02/3.42=about 39

Ahh...same math...different equation layout. Gotcha.

Yeah...I was running purple/red to get some spank out of the corners. However brush-life is severely decreased. I'll try greens.
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