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Old 12-05-2010, 10:30 AM   #61
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what kind of roll out are most using with todays software(tekin)do most start with a certin tire size and adjust gearing
not sure what your asking for.. i'm too cheap to cut my tires apart the initial cut, so i adjust gearing from there.. actual target rollout depends on the class.. wgt i run in the high 70's low 80's
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Old 12-05-2010, 11:20 AM   #62
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i know with adding timing you gear down i just wanted to see what most where running early this year with v200,and know with 203-212.i don't cut my tires either in the beginning as i want to use as much of the tire as i can.you coming to minnreg next month
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Old 12-14-2010, 03:08 PM   #63
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I know that I am probably going to sound like an idiot here, but I don't understand this rollout stuff at all with regards to calculating gear ratio.

I am from the old school where you divided the pinion into the spur and came up with your gear ratio. As an example: My old school approach is to divide 30 into 100 and getting a gear ratio of 3.33 to 1

When I use this app and use a foam tire diameter of 2.3, the final rollout is 2.168 Is that my gear ratio? I just don't understand any of this!

I race 1/10 pan car with 17.5 brushless and 1 cell lipo on a carpet road course.

Please help
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Old 12-14-2010, 03:13 PM   #64
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Rollout is the distance that the car will move for one revolution of the motor shaft, so it takes into account gear ratio and tire diameter (pan cars), and also internal drive ratio (pulley ratio) for touring cars.

For Pan cars, the DTR is 1.0
For an Xray T2, the usual DTR is 1.7 (34/20) assuming 34 tooth and 20 tooth pulleys.

Tire Diameter x 3.14 (value of PI) = Tire Circumference
Tire Circumference / FDR = Rollout

Spur / Pinion = PDR

PDR x DTR = FDR

The “drive train ratio” (DTR) is the ratio of all the internal gears from the transmission, including differentials and pulleys. The drive train ratio is usually different for each model of car. Your owner’s manual should provide this information, but keep in mind that some manufacturers use the words “transmission reduction” to indicate the DTR. The DTR in most cases cannot be changed, unless you are able to change the number of teeth on the pulleys and/or gears.

The “primary drive ratio” (PDR) is the ratio between the pinion and spur gear. This number is commonly rounded up to the nearest thousandth after the decimal point.

The “final drive ratio” (FDR) is the ratio between the DTR and the PDR. This number is commonly rounded up to the nearest hundredth after the decimal point.

Rollout is the distance that the car moves forward for one revolution of the motor shaft (or pinion gear). Rollout is not affected by the motor, batteries, or electric components you are using; it simply defines how all of the gears, belts/shafts and tires work together to make the car accelerate and reach top speed.

Rollout is calculated using the circumference of a tire and therefore the diameter of both foam and rubber tires make a difference. The diameter is more important if using foam tires since they can be used with a diameter anywhere from 64 mm down to 54 mm. As foam tires wear and get smaller, your rollout value will change a lot more quickly. Rubber tires do not wear down nearly as quickly or as much so the change to rollout will be very small over time. Tire circumference is commonly rounded up to the nearest hundredth after
the decimal point. Rollout is commonly rounded up to the nearest thousandth after the decimal point for American standard (inches), and to the nearest tenth after the decimal point for Metric. Most rubber tires have a diameter of 63 mm (2.480 inches).
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Last edited by CarbonJoe; 12-14-2010 at 03:28 PM.
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Old 12-14-2010, 03:32 PM   #65
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Thank you for your help.

I race on a 65x36 carpet road course and the track owner suggested I true my tires to 58.4mm and use a 90T spur and a 43T pinion for a gear ratio of 2.09 to 1 Does that sound like I'm in the ballpark? Keep in mind that I'm racing a 1/10 pan car with Novak 17.5 brushless and 1 cell lipo.
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Old 12-14-2010, 04:57 PM   #66
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Those tires are way too big. Start off around 54.75mm (2.15 inches). 43/90 gives you a rollout of 3.23 inches (81.8mm), which is right around what a lot of 1/12 scale guys are running in 17.5. A lot will also depend on what ESC and ESC settings you are running.
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Old 12-14-2010, 06:05 PM   #67
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I'm using the Novak Havoc SS 17.5 motor and the Havoc esc that goes with it.

What gears would you use with the 58.4 tires?
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Old 12-14-2010, 06:34 PM   #68
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I'm using the Novak Havoc SS 17.5 motor and the Havoc esc that goes with it.

What gears would you use with the 58.4 tires?
For a rollout around 81.8mm, you'd use a 40 tooth pinion with the 90 spur. But, with tires that big, you may have problems with chunking or traction rolling. Foam tires usually chunk less the smaller they are, and the smaller side wall (stiffer) results in less chance of traction rolling.

Invest in a range of pinions in the 35 - 45 tooth range. As the tires wear, you'll need to change gearing to maintain a consistent rollout.
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Old 12-14-2010, 06:53 PM   #69
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Quote:
Originally Posted by 20 SMOKE View Post
i know with adding timing you gear down i just wanted to see what most where running early this year with v200,and know with 203-212.i don't cut my tires either in the beginning as i want to use as much of the tire as i can.you coming to minnreg next month
sorry, by initial cut i did mean that that i usually cut my tires once (generally in the 2.18-2.2 range) then i just let them wear and gear accordingly.. minnreg is in the plans, but nothing is for certain in my life between my kids, my job, and my wifes complicated schedule..

by the way, with 212 (which i like so far.. way better than 208) i tried to gear down (high 60's and low 70s) and hated it..
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Old 12-14-2010, 08:58 PM   #70
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OK, thanks again for the help. What if the tires were 55.8mm instead of 58.4mm? Would that be better?; and what pinion would I use with the 90T spur?
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Old 12-14-2010, 09:08 PM   #71
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OK, thanks again for the help. What if the tires were 55.8mm instead of 58.4mm? Would that be better?; and what pinion would I use with the 90T spur?
Yes, the smaller tire size is better. The pinion to use would be a 42.
Try the attached spreadsheet (zipped up). Tire size across the top, pinions down the left.
Attached Files
File Type: zip Improved 1-10 RollOut90ToothSpur.zip (17.4 KB, 28 views)
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Old 12-14-2010, 09:10 PM   #72
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OK, thanks again for the help. What if the tires were 55.8mm instead of 58.4mm? Would that be better?; and what pinion would I use with the 90T spur?
If you have an Android Phone, you can just download this app, you know the one that this Thread talks about, and it will help you calculate all these values.
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Old 11-30-2011, 11:26 AM   #73
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For anyone looking for a very convienient way to calculate rollout and/or final drive, RC Gears can help.
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Old 12-09-2011, 01:25 PM   #74
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Will this app work for an Ipod Shuffle?
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Old 12-09-2011, 01:35 PM   #75
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Will this app work for an Ipod Shuffle?
This app is for Android based devices only.
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