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Old 11-28-2008, 12:03 PM   #1
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Default Good starting point for gears in a BL stock truck?

Hey everyone. Just switching to BL and lipo this season, and I'm not sure where to start on my gearing. I have a GTB 17.5 setup with 5000mah lipo in a FT T4. I know it depends a lot on the track but just looking for a starting point here. I can adjust from there. We run off-road, semi-technical indoor dirt track. (SmacTrac in St. Charles, MO). When I ran brushed 27T, 18/87 worked very well for the torque needed for the jumps, and top end for the long straight across the front Any input would be greatly appreciated.

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Old 11-28-2008, 12:32 PM   #2
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if your running 17.5, your gonnna need to gear it really high to run right. I would say like 34/78 would be a good starting point for a truck, but you could go a lot higher than this. Im sure people with a little more knowlegde then i have will chime in on this.
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Old 11-28-2008, 12:39 PM   #3
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34/78 is about it with no mods , alot of people are running a modified t3 slipper or a turbo joes slipper elimanator , both of these allow you to run the spurs that bolt on so you can run alot smaller spur gear , like a 66 i think is pretty common , it also moves the motor forward , ray
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Old 11-28-2008, 12:49 PM   #4
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WOW...34/78 huh? that is like a 2.30:1 ratio seems pretty high. The novak manual says something about 2-3 teeth larger on the pinion than a 27t stock motor. That would put me at 21-23/87. I just want to make sure im not gonna overheat the motor and my new esc...
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Old 11-28-2008, 12:54 PM   #5
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ya, 33/34:78 is about right. start with a 31/32 and check motor temps. the temps shouldn't be higher than around 170F after 5 minutes. if too hot go down a tooth, if cold go up a tooth.
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Old 11-28-2008, 03:04 PM   #6
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there telling you right. I've run a slipper eliminator with 36-72 and it pulls strong and runs cool. Under 150 degrees.
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Old 11-28-2008, 04:06 PM   #7
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yep! I ran 32/78 on short tight tracks and 35/78 on long tracks.
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Old 11-28-2008, 10:16 PM   #8
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ok- next question... why is there such a big difference in the gearing ratios?

Looks like I'm off to the shop on the way to the track tomorrow!!
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Old 11-29-2008, 06:39 AM   #9
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very narrow power band on the low rpm side
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Old 11-29-2008, 09:04 AM   #10
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YEP! the 17.5 is a torque motor, there for you use ratio to make top end out of the low end torque it produces.Think like a deisel.There arent that much in the way of rpm, but theres a ton of power.
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Old 11-29-2008, 08:21 PM   #11
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Yea ran 33/78 in my B4 and i it could go way lower. i need one of those slipper eliminators.
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Old 11-29-2008, 09:25 PM   #12
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Seems Novak needs to update their brushless motor gearing chart

They have the 17.5 running a 7.5 fdr in a 2wd Truck while most people are running around a 6.0 fdr.

Anyone think AE or someone will come out with a bolt up setup that will allow for easier use of the needed smaller spur gears for 17.5 brushless setups?
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Old 11-30-2008, 12:32 PM   #13
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Quote:
Originally Posted by Dean Rawlinson View Post
Yea ran 33/78 in my B4 and i it could go way lower. i need one of those slipper eliminators.
Well it was a good night of racing last night at SmacTrac in St. Louis (st.charles). I could not find a 78 spur so I ran an 81 spur and a 31 pinon- which was all I could get under that 81! (motor was ALL the way back) I checked the temp on the motor after the first few runs and never got over 100 deg. Some of the guys talked about slipper eliminators to run smaller spurs (like a 66), but I am afraid of what kind of harm that would do to my diff. Over all, truck ran great, good power, good speed...maybe not enough top end though. That 78 spur is gonna make the difference. Thanks everyone for your advice...
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Old 11-30-2008, 02:14 PM   #14
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Quote:
Originally Posted by Xtant3150c View Post
Anyone think AE or someone will come out with a bolt up setup that will allow for easier use of the needed smaller spur gears for 17.5 brushless setups?
A couple of options:

Not sure if this works on a AE, I think it would, I just tried it on a Losi this weekend, seemed to worked great: Use a on road spur with Traxxas slipper pegs. Credit to JKRacing I think his name is.

Or Turbo Joe makes a slipper eliminator that also uses an on road spur. Speedtech I think it is carries them, or I think you can contact TJ. Thread:

http://www.rctech.net/forum/electric...very-soon.html

Last edited by Dave H; 11-30-2008 at 02:26 PM.
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Old 11-30-2008, 02:27 PM   #15
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Anyone think AE or someone will come out with a bolt up setup that will allow for easier use of the needed smaller spur gears for 17.5 brushless setups?[/QUOTE]
to get in the mid 60t spur range I think they'll have to redesign the slipper and go smaller on the pad size. Last night at Leisure I ran Turbo Joe's slipper eliminator in there 19t- 13.5 class. Geared @ 30-72 had no problem running down the 19t brushed trucks on there 90' front straight with my 2 year old 13.5 novak.
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