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Old Mar 09, 2013, 10:52 AM
Registered User
United States, NY, Dexter
Joined Sep 2009
23 Posts
Question
sf501 nitro to brushless gear ratio ?

Going to convert a sf501 nitro to brushless.
Have a thunder power 13.5 sensored motor and a lrp sphere tc esc.
Probably go with 48 pitch gears.
What would be a starting gear ratio / size 48p pinion and spur?

Thanks
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Last edited by pfindeis; Mar 09, 2013 at 04:46 PM.
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Old Mar 09, 2013, 01:58 PM
Kungsangen, Stockholm, Sweden
z_dad's Avatar
Sweden, Upplands-Bro Municipality
Joined Dec 2011
254 Posts
The original primary gearing (motor gear to first) for the SB5 is 21/87, it makes 4,1429 motor revolutions per layshaft revolution.
As long as you have secondary gearing (front chain pulley to rear) fixed to 2,5 (20/50, original sb5) you will end up whith a final ratio at 10,537. This seems to a be very good start for motors 4500-6000kv.
In clear terms: 87/21x50/20 = 4,1429 x 2,5= 10,357
Put in the relevant nubers for your bike to reach the final gearing.
I wouldn't go under 9 total, unless you know your electrics well. Higher than 10,5 makes for less top speed unless you have a very high kv rating.
Hope this helps for starters.
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Old Mar 09, 2013, 02:23 PM
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United States, NY, Dexter
Joined Sep 2009
23 Posts
Quote:
Originally Posted by z_dad View Post
The original primary gearing (motor gear to first) for the SB5 is 21/87, it makes 4,1429 motor revolutions per layshaft revolution.
As long as you have secondary gearing (front chain pulley to rear) fixed to 2,5 (20/50, original sb5) you will end up whith a final ratio at 10,537. This seems to a be very good start for motors 4500-6000kv.
In clear terms: 87/21x50/20 = 4,1429 x 2,5= 10,357
Put in the relevant nubers for your bike to reach the final gearing.
I wouldn't go under 9 total, unless you know your electrics well. Higher than 10,5 makes for less top speed unless you have a very high kv rating.
Hope this helps for starters.
Yeah i don't understand that math. Sure is a lot easier with online car gearing charts.
Maybe i should reword my post to what size 48p pinion and spur
Thanks though
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Old Mar 09, 2013, 05:44 PM
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dragbikebam's Avatar
Memphis, TN USA
Joined Apr 2009
936 Posts
you can run the HPI or X-ray 48p spur from 84 to 96. I prefer 90 to 93 with a 22 to 26 pinion. With a 13.5 I would go with a 90/26 to start then go to a 28 pinion if you want more top end..
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Old Mar 09, 2013, 05:53 PM
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United States, NY, Dexter
Joined Sep 2009
23 Posts
Hey thanks alot
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