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Old 05-22-2012, 06:24 PM   #1
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Default Comparing Different Gears, Same Rollout. HELP!!!!

I wondering if someone could explain the difference in gear sizes compared to calculated rollout. Im referring to 1/12 scale, 1:1 drivetrain of course. I currently run an 84/36 = 2.33 in my 13.5 boosted 12th scale. I was wondering if i changed my spur to a 73 and ran a 31t pinion what would happen. 73/31 = 2.36, basically identical rollout, but with a larger pinion and smaller spur, what would I achieve, more punch, top end, over heat, or being the same rollout, absolutely nothing change? Any help would be appreciated. Thank you
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Old 05-22-2012, 06:30 PM   #2
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I currently run an 84/36 = 2.33 in my 13.5 boosted 12th scale. I was wondering if i changed my spur to a 73 and ran a 31t pinion what would happen. 73/31 = 2.36, basically identical rollout, but with a larger pinion and smaller spur,
Um no, that's smaller pinion AND smaller spur.

Only difference, car will handle slightly worse. You want the motor as far forward as you can get it.

Also, there is a whole thread about this in here somewhere. Dig it up if you really want to know more but be aware, about 88% of it is wrong.
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Old 05-22-2012, 06:39 PM   #3
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I meant smaller spur and pinion. Are you saying no real change, besides motor being further back? No change in temp or speed? Thank You
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Old 05-22-2012, 06:53 PM   #4
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I meant smaller spur and pinion. Are you saying no real change, besides motor being further back? No change in temp or speed? Thank You
Nope. Some will argue it but it's basic physics and really not all that complicated. That's not to say you might not see some significant differences in lap time but as I said before, that has more to do with motor position which is a pretty big factor with pan cars.
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Old 05-23-2012, 03:04 PM   #5
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In theory at least the smaller gears would have less rotating mass and would accelerate quicker but the reality is the difference in all but the most special of situations is minimal. With that said Iv'e known people who totally believe it's a distinct advantage. I don't think so. Go for proper weight distribution, not much argument there.
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Old 05-23-2012, 03:18 PM   #6
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I just want to be able to run blinky 17.5 and 13.5 boosted without changing my spur. So I would need to run such a small spur for blinky with a large pinion, and by keeping that small spur, I could run 13.5 boosted. But if I keep the large spur, I won't be able to achieve the rollout needed for blinky 17.5. Does that make sense?
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Old 05-23-2012, 03:29 PM   #7
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Consider using 2 different Axles w/ 2 different spur gears to make your life easier.

You are already changing the motor out, might as well change the complete axle too.
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Old 05-23-2012, 03:36 PM   #8
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Great point! I didn't consider that. Thank you
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