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Old 12-03-2007, 09:58 PM   #1
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Default help w/RDX gearing please

hi all ok i have a RDX that i'm looking to race, it has a 78 spur gear, NOW what pinion should i use, i'm used to setting up a car to a XXX-S and i don't think a 32 tooth pinion will work it drops the gearing to 4.35 about , anyway i'm running carpet stock motor i just need a starting point,

PS everytime i try to do a search my computer says errror,, so sorry if its a repost ,, thanks jon
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Old 12-03-2007, 10:03 PM   #2
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I would start with a 24 tooth pinion if you are running Rubber tires. If you are running foam tires I would go up one or two teeth. You will be in the ball park with those pinions. Of course the size of the track may change it more. If you are running on shorter than 90 ft straight I would gear down to maybe a 22 tooth for Rubber tire. Especially on tight and technical tracks.

Remember that the internal drive ratio changes from car to car usually. The RDX uses a 2 to 1 ratio. So it would be Spur / Pinion x 2.

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Old 12-03-2007, 11:13 PM   #3
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Quote:
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I would start with a 24 tooth pinion if you are running Rubber tires. If you are running foam tires I would go up one or two teeth. You will be in the ball park with those pinions. Of course the size of the track may change it more. If you are running on shorter than 90 ft straight I would gear down to maybe a 22 tooth for Rubber tire. Especially on tight and technical tracks.

Remember that the internal drive ratio changes from car to car usually. The RDX uses a 2 to 1 ratio. So it would be Spur / Pinion x 2.

Jeff
ok this is the part i don't get :-(
Remember that the internal drive ratio changes from car to car usually. The RDX uses a 2 to 1 ratio. So it would be Spur / Pinion x 2.

thanks jon
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Old 12-04-2007, 08:34 AM   #4
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Most guys will describe the gearing in final drive ratio as its easier for anyone to calculate on their own chassis what gearing to use, because the gear ratio of the chassis will vary depending on what chassis you use. Mine for example is 2.25.

So you can use any combination of spur gear and pinion gear to get the same final drive ratio.

hth
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Old 12-09-2007, 08:29 AM   #5
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Default I'm in the same boat

If I read Jeff's reply right, I should be starting with a 22 Pinion and a 48 spur gear. I will be running rubber tires on cement on a 50x55 foot track. Is this a correct assumtion?
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Old 12-09-2007, 10:12 AM   #6
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Are you running a RDX chinewbie? With rubber tires running stock or 19t, I either have a 23, 24, or 25 tooth pinion with a 78 tooth spur gear(stock spur). the RDX has a 2.0 internal ratio. so you take 78 tooth spur and multiply that by the internal ratio which is 2.0. You get 156. then take 156 and divide the pinion, lets say 24 tooth pinion, and you come up with 6.5 final drive, which is a good starting point for a co27 or a komodo dragon. You will need to go up or down depending on your track size. Gear so your car maxes out slightly before the end of the longest straightaway. Now if your running brushless...then I have no idea how to gear those things. All you need to remember is spur x internal divided by pinion.
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Old 12-09-2007, 04:30 PM   #7
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Red face I will be running brushless.

Jimbo,
Thanks for the reply. I haven't gotten my kit yet, but I want to have everything "in-house" when I get it. I ordered a Novak 5.5 brushless motor to in the Phi. I will keep looking for the correct pinion gear.
Thanx.
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Old 12-09-2007, 05:57 PM   #8
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Default ok ok ok

ok something is not right ,, i raced today, and i was running a co27 with a 25 pinion and a 78 spur , well i go that motor up too 255 degrees. then i put another co27 in it and and changed the pinion to a 22 tooth, well i was getting run over in the straightaways , so then i put a 24 tooth pinion on that same motor and i got about 4 mins out of it and it started smoking then i hit it with a temp gun and it was at 360 degrees, so i just changed the motor to a monster stock and put a 22 pinion and finished the main (last) but finished it, so what do i do from here ? thanks JON :-)
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Old 12-09-2007, 07:55 PM   #9
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Make sure you don't have a blown bearing binding your drivetrain. How big is your track? Do you have the stock pulleys or optional small pulleys?
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Old 12-09-2007, 08:26 PM   #10
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Make sure you don't have a blown bearing binding your drivetrain. How big is your track? Do you have the stock pulleys or optional small pulleys?
that was the first thing i did the bearings are fine and there ceramic, the track is kinda big i race in stocktonrcracing.com i changed the spurr toa 64 pitch tonight 106t and i added a 31 tooth pinion, and i'll see what it can do at the next race :-) thanks for your help, JON
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Old 12-09-2007, 08:45 PM   #11
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That will put you at a 6.8 final. I would go to a 33 pinion for rubber tire. that puts you at 6.4 final. You are racing rubber tire correct?
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Old 12-09-2007, 09:30 PM   #12
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hey there yes i am RP30 , i will switch to a 33 tooth pinion ,, are you a sponcered driver ? i need parts, i cant get them anywere around here, and the last parts i ordered over a week ago i still have not gotten them ,, ok well thanks for the help JON
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Old 12-09-2007, 10:11 PM   #13
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superiorhobbies.com will have all the parts you need.
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