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Old 12-11-2003, 06:25 AM   #1
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Default Gear ratio conversion

Hi, I wonder if there's a rule to convert gear ratio? For example, I am running XRAY with drive ratio 1.77 and my FGR is 6.09 (124/36*1.77)
What if I go for a car with a drive ratio 2.4375, how should I estimate the spur and pinion gear to go for? Thanks!
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Old 12-11-2003, 07:31 AM   #2
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Hi Discuss18,

You can't, because you have two variables - spur and pinion.
You must choose the teeth of one of them and then calculate the other.
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Old 12-11-2003, 07:37 AM   #3
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Quote:
Originally posted by gearless
Hi Discuss18,

You can't, because you have two variables - spur and pinion.
You must choose the teeth of one of them and then calculate the other.
So, what if I choose to use 93 pinion, then I should go for 37 spur? (93/37*2.4375) = 6.1

or I keep 124 pinion, then I go for 49 spur (124/49*2.4375) = 6.1 too
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Old 12-11-2003, 08:26 AM   #4
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The easiest way to figure out ratios and be able to compare them from car to car is to use rollout instead of just final drive. Rollout takes into consideration all of the variables. Rollout uses pinion, spur, ring, pinion, tire diameter. It its the gear that hits the track so it will crossover any setup to the track size and layout. Plus I believe rollout is esential when using the ever changing diameter foam tires. Here is a good place to get gear and rollout charts.gear and rollout chart hope this helps.
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Old 12-11-2003, 10:35 AM   #5
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Actually, I have a better one at my site (haven't worked on the rcracing.com site in over a year). Go here: http://www.arroyoc.com go to:

Utilities --> R/C Car Gear Ratio Calculator, it has a more updated car list and I also added a target rollout chart.
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