Talmier

I have used the gearing ratio calculator and read the gearing thread and would just like a little more info to complete the puzzle.

So far usuing a 24t pinion on a Traxxas Bandit with a (what I believe to be) 7.5 T brushless motor if anyone can help me verify that.

The pinion that comes with the car is 26T which brings up a rollout ratio of 1.3XX where as the 24t pinion comes out as 1.2XX does this indicate a 24T pinion is the better option?

It also comes with a 31 Pinion for increased speeds however it looks as if that should only be used for on road (not sure why).

Though it also lists that a 33T pinion can be used.

So my question is If I am going off road how close can I go to 31T pinion?

I thought anything more then +10 % in each direction was bad, then I saw the equipment the maker sends out exceeds that from the start

Am I right to believe that if i decrease the number on the pinion that I will get a car closer to the ratio which is better and also faster but with less acceleration?

Or is it I increase the number for that eg: from 24T to 31 for example (for a stronger top speed)

guver

My Feedback: (325)

Try this calculator , it is exact. http://www.scriptasylum.com/rc_speed/_top_speed.html

I would thik you will want a pinion that is much smaller than 24 or 31 or 33. (unless you are going for top speed runs)

Talmier

Does a bigger number provide more speed or does a smaller number?

guver

My Feedback: (325)

for a pinion gear bigger numbers will produce higher top speeds. (provided the motor has enough power to pull it)

Talmier

Is there a way I can tell what are the max and min pinion sizes eg: using the manufactors guide lines eg: 33 for the max pinion size. Or does it also depend on the motor. Its a Speed passion drift master twin turbo which I beleive has 8000KV

Access

Just ignore the old notions of 'rollout' and such. With brushless you gear for the top speed you want and based on temperature. Temperature is the only reliable way to set the max gearing of a given setup. As long as it's not overheating, you can continue to gear up.

Be sure to check the temperature of all three critical parts, the battery, ESC, and motor though. If the ESC is overheating and the motor is running cool, in some cases this can be due to extreme undergearing.

guver

My Feedback: (325)

If you're asking what will physically fit then I have a chart that is very close. If so what spur is on?

I am guessing that if you are running an 8kv motor , stock height tires , and even 5-6 cells that it is grossly overgeared already and needs to have a much smaller pinion.

Talmier

Thanks guys I am starting to understand a little better.

The spur is 76T

I can't understand how some of the guys are getting outrages speeds on their motors like 70 -100 mph with out over heating the motor.

I am using a 2 cell lipo.

Is there anyway I can verify the KV of the motor I got it in a combo pack with my ESC

If I might add I've never been on such a helpful forum.

Guver what size pinion would you reccomened and wouldn't that slow the car down dramaticly?

guver

My Feedback: (325)

My chart shows a 20-21 tooth and higher will fit. Probably even a 35 tooth plus would fit.

It is maybe from about 2:1 to 4:1 and 2:1 would be twice the theoretical top speed as 4:1 would be.

guver

My Feedback: (325)

I'm showing a quick calculation of 8000 x 7.4 volts with stock tires and 20x76 gears to be well over 50 mph.

I'd recommend close to a 6:1 ratio or maybe around 15x87 to slow the car down. If you're going to top speed runs then by all means gear it 2:1 and see if the motor/battery has the power to pull it.

Talmier

I get where you are coming from so if I were to drive it on say the road for top speed try a ratio of 2-1.

Does a smaller Gear ratio give more advantages off road then?

I can now see why people mix there pinions around for different situations then

guver

My Feedback: (325)

2:1 is quite fast (too fast) and I doubt the motor/battery has enough power to pull much over 60 mph. Try a 4:1 for street , but yea a lower ratio is more controllable , quicker accelerating for smaller dirt areas. Depending upon the specific area or track it may never be possible to attain 30 mph anyways. You can also figure that on the fastest part of the track is where you want it to top out at max speed. Anything geared higher than that is a waste.

rustlerdog

That calculator is awesome.. thank you for posting that.

I have a quick question.

Motor/ESC: a Mamba Max with the 4600 motor in the combo

Using 90T 48P stock rustler spur
18T pinion
I come up with a final ratio of 5:1 (not quite sure how to get a 6:1 ratio mentioned?)
Reduction is 13.6:1

according to you guys you can somewhat ignore the over or under 10% rule so long as the ESC and or motor are not overheating (at or less then the 150-160 mark)?

Basically I am just looking to take it as easy as possible on the motor/transmission/drive train. I do not do speed runs or plan too... Primarily run on grass/sand/dirt for bashing.