Gearing down revo 3.3 for larger tires.
01-30-2021, 07:43 PM
#1
Thread Starter
Gearing down revo 3.3 for larger tires.
Looking for advice on what the best spur gear/pinion gear combo would be for my Revo 3.3. Factory tires are those Traxxas Talons size 5.75x3.8-3.8. My new tires are the Traxxas Talon EXT’s that are actually a little narrower at 3.5 inches but they are 6.4 inches on the same size 3.8 inch wheels.
The optional spur gears available are a 36T and a 40T with a 38T as standard and for pinion options, there’s a 15, a 16 and a 17T with the 14T as standard. I’ve never changed the gears so what would work best? Sure, top speed is nice but if it’s too speed is a little less that 45, that’s fine, I just want pretty much my stock gear ratio back now that I have these taller tires. Oh and I don’t have the 3.3 motor anymore, I have the OS21TM motor.
Thanks.
The optional spur gears available are a 36T and a 40T with a 38T as standard and for pinion options, there’s a 15, a 16 and a 17T with the 14T as standard. I’ve never changed the gears so what would work best? Sure, top speed is nice but if it’s too speed is a little less that 45, that’s fine, I just want pretty much my stock gear ratio back now that I have these taller tires. Oh and I don’t have the 3.3 motor anymore, I have the OS21TM motor.
Thanks.
02-18-2021, 06:01 AM
#3
Gearing for tire size is a give/take affair.
How to get the correct gear choise depends on what you want to achieve in the end. That OS engine is a really nice upgrade for the 3.3 BTW and will give you a little more flexibility on your gearing....to a point anyway.
Basic rule of thumb is smaller pinion bell will help turn the larger tires better and give you faster acceleration, but you lose a bit of your top end speed. Larger pinion bell gives you more top end speed, but takes a little longer to get there. Go to large and you can bog the engine down and make clutch work really hard.
And it depends on whether you want to bash or do speed runs. I personally don't do speed runs so going for top end speed isn't needed. For larger diameter tires, dropping a single tooth on the pinion can help. But only if needed. If your OS is tuned and running correctly, you should be fine with stock gearing and slightly larger diameter tires. On the Traxxas OEM 3.3 engine, I would certainly drop a tooth for larger tires, as power output of the 3.3 is more far more limited then the OS engine is. If you can easily spin the tires out of the hole with the OS engine, then you may want to go with a slightly larger pinion. If its at all sluggish, then consider going with a smaller clutch bell. But that said, I would only go up/down 1 tooth at a time until you find the sweet spot for you use.
Good Luck
How to get the correct gear choise depends on what you want to achieve in the end. That OS engine is a really nice upgrade for the 3.3 BTW and will give you a little more flexibility on your gearing....to a point anyway.
Basic rule of thumb is smaller pinion bell will help turn the larger tires better and give you faster acceleration, but you lose a bit of your top end speed. Larger pinion bell gives you more top end speed, but takes a little longer to get there. Go to large and you can bog the engine down and make clutch work really hard.
And it depends on whether you want to bash or do speed runs. I personally don't do speed runs so going for top end speed isn't needed. For larger diameter tires, dropping a single tooth on the pinion can help. But only if needed. If your OS is tuned and running correctly, you should be fine with stock gearing and slightly larger diameter tires. On the Traxxas OEM 3.3 engine, I would certainly drop a tooth for larger tires, as power output of the 3.3 is more far more limited then the OS engine is. If you can easily spin the tires out of the hole with the OS engine, then you may want to go with a slightly larger pinion. If its at all sluggish, then consider going with a smaller clutch bell. But that said, I would only go up/down 1 tooth at a time until you find the sweet spot for you use.
Good Luck
02-18-2021, 06:49 AM
#4
Thread Starter
Thank you for your reply. The setup I'm looking more for is I guess bashing wit a little bit of top speed, I dunno...lol. Actually, just what's good for my motor, centrifugal clutch and drivetrain but I guess I should state that as soon as it warms up, I have a 14-tooth clutch bell on and a 40-tooth spur gear on to see how they do with these taller EXT Talons. I'm hoping this will be a good combination being that since the newer Revos already come with a 14-tooth clutch bell and taller 6.3" tires, my even taller and heavier tires should accommodate well to that gear combo.
