Got Questions? We’ve Got Answers!

Why Overdrive the Front?

June 13, 2022 – video comment from EP RC

Q.Why does front axle overdrive work better than [just driving faster]? That must work better, as with overdrive on an axle you are constantly losing traction somewhere just to make any progress.

A. Overdrive (commonly referred to as ‘o/d’) is a rock crawling thing. Overdriving the front axle makes the front wheels turn faster than the rear wheels, typically by 5% to 15%, but there are implementations out there of up to 33%!

Overdrive can be achieved by driving the front axle faster or the rear axle slower. Ring and pinion gear ratios can be changed so the difference happens on the axle at each or either end. Alternatively some transfer cases have a provision to drive the front faster than the rear, such as the StealthX transmission from Element RC’s Enduro line.

Overdriving the front helps the vehicle maintain direction on difficult climbs where traction is low. It does this in two ways:

  • It lets the front pull the rear onto and through problems.
  • It also maintains a low loading effect on the suspension by way of that front/rear wheel speed difference. This is thought to aid traction on rock problems, though it would be undesirable on flat, high traction surfaces.

On steep ascents without overdrive, the rear has more of the vehicle’s weight on it and so often has more traction available than the front axles. With that extra traction, the rear will work to push the vehicle forward. This hinders it from turning in whatever direction you’re steering. It’s like a slow-motion, understeer effect that is undesirable on rock problems.

There are a few ways to address this understeer effect:

  • DIG (DIsengageable Gear) locks the rear drive, such as in the VS4-10 Phoenix and SCX10 III. You can then drag the nose of the rig around with the front while the rear stays in place. (You can also use DIG to ‘DIG up’ by loading the suspension and drive line before popping the rear drive back on, but that’s for another discussion!)
  • Remote locking and unlocking rear diffs (such as on the TRX4) also can help bring the vehicle’s nose to the direction you want by lowering the drive (or authority) over the vehicle’s direction from the rear.

Both of these options mean the front wheels do more of the work, pulling the vehicle round to whatever direction you want to face. Unlocking the rear diff isn’t as effective as DIG, but both have their place in crawling.

Overdrive is another way to address the understeer issue. By keeping the suspension slightly loaded and keeping more of the traction authority up-front with that higher wheel speed, your crawler will more consistently and reliably reach the line you’re trying to drive.

Element Ecto on Rocks

How to Set Steering End-Points?

June 11, 2022 – video comment from GabrielDuchi

Q. How do I program the steering limits with the RTR (Ready To Run) radio transmitter that comes with the RGT Rescuer EX86190?

A. What you’re after is the Steering EPA (End Point Adjustment). That’s the limiter that prevents the servo from trying to steer the wheels past their physical limits.

On the top of the radio there’s a lid. Under the lid are three sets of controls:

    1. the top switches are for channel reversing – you can ignore these unless you are making changes to the servo, motor or ESC at some later time.
    2. the top dials are for setting Trim (point of center).
    3. the bottom dials are for setting EPA (End Point Adjustment).

It’s the bottom dials we’re interested in. Steering is on the left and Throttle is on the right. Here’s how to adjust end point for your steering:

    1. Turn the radio and the car on.
    2. Dial the Steering EPA dial (the bottom-left one) back to zero.
    3. Turn the wheels to their maximum limit to the left.
    4. Increase the steering EPA dial (the bottom-left one) upward until the wheels reach their physical limit. Back it off just a shade.
    5. Turn the wheels all the way to the right. Observe closely to see if the servo is straining or if there’s more reach available by dialing the steering EPA dial back and forth a little.

One of Left or Right will be more limited than the other. Your aim is to find the furthest the servo can move the wheels without straining. Check you’re happy that the servo isn’t straining beyond its limit either way by turning that steering EPA dial back a shade if it’s needed. Then you’re all set!

I found this a little difficult to explain but in practice it is a fairly intuitive process once you know which dial to adjust. Happy driving! -Craig

Which Should I Buy – SCX10 II or III?

June 6, 2022 – video comment from Ivo Anjos

Q. I would like to see the SCX10 III Base Camp compared to a stock or mostly stock SCX10 II. There are some really good deals on SCX10 II and I would like to know if it is still a good budget option and how it compares with these more recent rigs.

A. I think you’ll find the SCX10 II will compare closely in performance to the Axial Base Camp. They’re similar enough in geometry and layout that there won’t be a lot in it.

You really could buy on price and get a similar experience – but there are a few things to keep in mind: over the 10.2, the Base Camp gives you adjustable chassis length and portal axles and, I think, better tires and definitely better shocks. Equipment quality is generally equal to or better in the SCX10 III Base Camp, then. But if you can get the 10.2 for, say, 60-70% of the 10.3 it may well be worthwhile for you. -Craig

Base Camp Descending Rock

Does the DC1 Body Fit the TRX4 Sport?

June 4, 2022 – video comment from Dayle Guy

Q. Do you think the DC1 Disco body will fit on the TRX4 Sport?

A. The wheelbase is an exact match. The DC1 body is slightly more narrow than the TRX4 Sport, so some consideration will be needed for the sliders and wheel dish depth. You’ll also want to change or at least bring in the bumpers, as they’re too long for the DC1 body in stock positions.

Here, we put the DC1 body on the TRX4 Sport. Body holes are in different locations, but with the DC1 body, you cut your own, so no problems there. It shouldn’t be too difficult to get this one to fit. Happy modding! -Craig.

About This Page

As we get more questions, we’ll add them here. Newest questions at the top. Thanks for reading!

Craig Veness

Craig Veness


Craig has been into radio control since the 90s and into RC crawling since about 2010, when a Losi MRC started the obsession! Now it’s all rocks this and crawl that and upgrade all the things! …You know how it is, right? Welcome home 🙂