I have the feature on my Spektrum, but i never got around to knowing what it means. Can anyone explain it to me?

Expo is a setting that basically changes the curve of the servo movement. For example I run -10% on my steering to make it less sensitive around centre so the curve is a slight negative U shape. +10% for example would make it very sensitive around centre.

What do you mean by sensitivity? If i were to increase it, would the servo become faster at a certain point like center? Basically, it directs its power to one point of its turning ability. Something like that?

In a sense yes. Remember the opposite happens at full travel. If you slow it down around center it will be quicker towards full turn for example. And vice versa if set the other way.

It's easy enough to change/experiment with, suggest trying it on steering both ways with a considerable setting, should be fairly obvious with the car sitting and looking down at it while steering. In practice moderate settings are probably best for most uses, when it's even used.

Works the same on throttle or any other channel it's offered on.

When you say to slow it down around center, to what percent is that? My settings start at 0% and it sounds like center is around a certain percent.


If i were to increase/decrease the expo on my throttle/steering, how would that affect my engine and handling in a sense?

From what i've read, it sorta acts like a slipper clutch for nitro?

Well, it doesn't really "slow" the servo movement, but it brings it closer to a linear or exponential movement corresponding to how much you turn the wheel.

What the expo then does is change the servo travel to steering wheel travel exponentially. What this does is make it so if have negative expo your turn the wheel 100 percent, the servo will travel 100 percent as exponential doesn't change the endpoints, but then 50 percent turning the wheel may be just 35 percent actual wheels turning, and 25 percent steering input may result in just 10percent the wheels actually turn.

In simpleton terms, negative exponential makes the car smoother to drive and smooth outs initial steering input, but at the edges of steering input the car will feel twitchy.

Positive expo will create a very responsive car around center, one that is rather twitchy, but at close to max steering the inputs will smooth out.

Most people run between 10-20% negative expo as it makes the car easier to drive around neutral steering, where much of the steering needing fine input adjust is needed.

0% would probably be just linear.

If you program in a lot (say 50%+ in either neg or pos. )expo, and look at the wheels turning slowly, you should be able to see the wheels Turing compared to the steering inputs exponentially.

Ohh, I think I get what you mean by how much it will slow it...

You can make the servo stay almost neutral for a good portion of the steering input if you were to program in insane amounts of negative expo. It would go increasingly faster the more input was added though.

Yeah slow is a poor word choice, doesn't change servo speed. Just changes sensitivity, the amount of steering (or other channel) for a given amount of input.

Do you have one of the Spektrums with the large screen? If so it should display a graph that may help

An example graph I found might help.

Thanks guys. You explained it way better than I did

It frequently takes a few of us to row the boat. All good.

And with Spektrum, - expo and + expo are opposite to what you would actually think.

Thanks guys, i think im starting to understand. To clear things up for the steering (in simpleton terms), if i were to increase expo i would have to sacrifice smoothness for responsiveness right? And if i were to decrease expo i would have to sacrifice responsiveness for smoothness. Something like that?

From how panda described it, it sounds like negative expo "lowers" the input directed to the servo while positive "increases" it. In other words, i see it as neg slowing the servo and positive making it faster (in dummy terms)

So, what - expo usually is its actually +expo? and so forth.