Gearing down Revo 3.3 for larger tires.

[corneileous]

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.

 

[tntpoof]

there are many gear ratio calculators online.

 

[corneileous]

there are many gear ratio calculators online.

Hmm. I know there’s gear calculators for big trucks but I didn’t know there was some for rc cars. Mind pointing some out? I was just curious to read what others hav tried.

 

[BobP]

Just drop down two teeth On the pinion And it should Do what you want . You can order Set of pinions and then change them out And figure out what works best for you As it does not work for everybody in the same ratios

 

[corneileous]

Just drop down two teeth On the pinion And it should Do what you want . You can order Set of pinions and then change them out And figure out what works best for you As it does not work for everybody in the same ratios

So when you say down on the pinion, you mean up on tooth count?

But yeah, I realize what everyone does probably won’t work for the next guy but I’m not looking to copy, I’m just looking for what other people have done to gear down their revo for larger tires.

 

[BobP]

So when you say down on the pinion, you mean up on tooth count?

But yeah, I realize what everyone does probably won’t work for the next guy but I’m not looking to copy, I’m just looking for what other people have done to gear down their revo for larger tires.

yes up on pinion or down on spur

 

[tntpoof]

RC Gear Calculator (radiocontrolinfo.com)
wasn't aware they made pinion sets you could buy and swap out for nitro.. Id do the reverse of what above has said Id go down in pinion gear size . ie 14 to a12.not up as tires size

 

[corneileous]

RC Gear Calculator (radiocontrolinfo.com)
wasn't aware they made pinion sets you could buy and swap out for nitro.. Id do the reverse of what above has said Id go down in pinion gear size . ie 14 to a12.not up as tires size

Well now I’m confused. One person is saying to go up in tooth count and you’re saying to go down. Which is it? And that gear calculator looks pretty neat but I have no idea how many teeth are on the pinion gears and ring gears in my car’s differentials. I’ll have to research that.

 

[corneileous]

I found a video on YouTube last night from Traxxas that talks about how to lower your gear ratio for more acceleration and to raise your ratio for more top speed and they said that less teeth on the pinion gear/clutch bell, more teeth on the spur gear will decrease top end and increase bottom end and after doing a little bit more research, I found out some interesting stuff…

Since my Revo is the older 5309; and there is a newer 5309, I found out that the newer 5309’s came with a 14 tooth clutch bell and those 6.3 inch tall Traxxas Talon tires. They also came with a 38 tooth spur gear.

I’ll have to wait until I get home to see exactly what spur gear my older 5309 has but after looking at the parts list that originally came with my truck this morning, my truck actually came with a 15 tooth clutch bell. It also came with the smaller 5.75 inch tires so I’m thinking, if Traxxas went down a tooth on the pinion gear on the newer 5309’s to accommodate for the larger diameter tires, I’m definitely thinking I need to upgrade my clutch bell from a 15 tooth to a 14 tooth. I’m not sure at this point if I need to change my spur gear or not because like I said, I didn’t look at my original parts list to see what spur gear my truck came with.

 

[olds97_lss]

What gearing did you have before?

There are two things with the Talon EXT's, they are larger OD and considerably heavier than the normal Talon's.

Talons are 9.1oz, EXT's are 13.9oz. That's around a 50% increase of rotating mass.

I'd drop at least 2 teeth on the bell with what you were using with normal talon's as a starting point.

 

[corneileous]

What gearing did you have before?

There are two things with the Talon EXT's, they are larger OD and considerably heavier than the normal Talon's.

Talons are 9.1oz, EXT's are 13.9oz. That's around a 50% increase of rotating mass.

I'd drop at least 2 teeth on the bell with what you were using with normal talon's as a starting point.

Original gearing on my Revo hasn’t been changed so what I have is the stock 15T clutch bell and a 38T spur gear.

But yeah, since those Talon EXT tires are pretty heavy and that they’re slightly taller than even the 6.3 inch tall Talons that came on the newer #5309 Revos, instead of going down two teeth on the clutch bell- which I don’t know where I’ll find one because all Traxxas has for replacement clutch bells is a 14, 15, 16 and 17 tooth.

They don’t make anything less than 14 tooth bell but with that said, since going up a tooth on my spur gear will lower my ratio even more, in order to do like what you’re saying, can’t I’ve pretty much just accomplish the same thing by going down to a 14 tooth bell and up from a 38T to a 40T spur gear?

I did verify with Traxxas this morning when I was on the chat line with them that going down to a 14T bell and up to a 40T spur gear would lower my gearing even more than just only going down to a 14 tooth bell and leaving the 38 tooth spur gear that’s on there alone.

 

[olds97_lss]

I forgot, I use 1/8th sized clutch on mine, so I can still find 12T and 13T bells that work.

I run 14/40 on my BB revo, but I have slayer final gears in the transmission which are a lot taller than revo gears. So my "gearing" is crap for suggestions on that thing... I run 16/38 on my 21TM revo, but I'm running arrma kraton tires/wheels on that, combined with more power than the 3.3, also not a great comparison for you.

Go to 14/40 and see how that works for you. You will have to change your 2-speed shift point as well, since it will be spinning the transmission slower. You will need to back the screw out a bit so it will shift.

 

[corneileous]

I forgot, I use 1/8th sized clutch on mine, so I can still find 12T and 13T bells that work.

I run 14/40 on my BB revo, but I have slayer final gears in the transmission which are a lot taller than revo gears. So my "gearing" is crap for suggestions on that thing... I run 16/38 on my 21TM revo, but I'm running arrma kraton tires/wheels on that, combined with more power than the 3.3, also not a great comparison for you.

Go to 14/40 and see how that works for you. You will have to change your 2-speed shift point as well, since it will be spinning the transmission slower. You will need to back the screw out a bit so it will shift.

How big are those Arma Kraton tires compared to the talon EXT’s? Mind you, they are heavier than the stock 5.75” talons like you were saying, and taller at, what did I say, 6.5 inches? Oh, and I do have the same motor I guess, the OS21TM. Everything else like the transmission gears and differential gears is all original.

Oh, and thanks for that advice about adjusting the trans shift screw as well. Right now it hits second gear just the same as it always has but yeah, I would imagine that if I dropped in a 14/40 gear combo or even just a 14/38 combo that it might not shift right.

 

[olds97_lss]

I put the weights of them in this:
https://www.rctalk.com/forum/threads/a-list-of-tires-mostly-mt-that-i-have-been-maintaining.129667/

Just went through my photo's... I don't have a single photo of those tires next to any relatively common tire. I'll pull the truck off the rack tonight and line oen up next to an EXT, talon and 3.8 trencher, the post that up for you.

 

[corneileous]

I put the weights of them in this:
https://www.rctalk.com/forum/threads/a-list-of-tires-mostly-mt-that-i-have-been-maintaining.129667/

Just went through my photo's... I don't have a single photo of those tires next to any relatively common tire. I'll pull the truck off the rack tonight and line oen up next to an EXT, talon and 3.8 trencher, the post that up for you.

I was just curious about those Kratons compared to the ext talons when you told me what spur gear/pinion gear combo you use. But anywho, I just ordered me of a 40T spur gear for my Revo so I can see what that does.

I do still plan to get that 14 tooth clutch bell some day but since my girlfriend asked me what I wanted for Valentine’s Day, I couldn’t think of nothing so I gave her a small list of rc parts and unfortunately, that clutch bell and the bearings that go with it were included in that list....lol.

 

[olds97_lss]

Here's a comparison:

Narrower than the EXT's, similar OD and as mentioned, lighter.

 

[corneileous]

Since were talking about gearing, how do I figure out the final drive ratio for this car if I was to go outside of the spur gears and clutch bell gears the Traxxas has? What about factoring in for custom tire sizes?

Now that I figured out how to use the chart below, I can figure out what my first gear and second gear final drive ratios are if I just go down to a 14-tooth bell, just up to a 40-tooth spur.

 

[StayZEN]

Hi there I'm new to nitro, how can i make this revo 3.3 push more torque? thank you.
i found out that its totally different from electric

 

[Greywolf74]

if you want more torque you need to either decrease the tooth count on your clutchbell or increase the tooth count on your spur gear.

 

[STONER RC]

Hi there I'm new to nitro, how can i make this revo 3.3 push more torque? thank you.
i found out that its totally different from electric

"R/C Gearing 101 — Roger's Hobby Center" https://rogershobbycenter.com/rc-gearing-101