Hi, I run an RC10GT truck and have been experiencing a bit of understeer during cornering. What can I do to combat this?

Thanks

Will

use dual-rate, move the ballstud on the servo horn outward, move ballstud on steering thing inward. One or more of those should help

Thanks Billiam I'll give that a try.

- Try using softer springs in front or stiffer springs in the rear.
- Rear diff too tight will cause understeer
- Toe in also causes understeer during corner entry
- Tires will also help but not sure about off road

Thanks dg2b, I think my diff may have something to do with it, it's set quite tight.

Hi, I new to RC world. May I know that what did you mean understeer?? Is this mean when we make a turn, it need big round to turn?? My also like this, pls advice how to reduce the big turn.

Understeer means you want to make a turn and the car want to go straight. Oversteer is vice versa.

Ok thanks dg2b, so may I know that how to make the steering turn more degree, mean when go to turn I no need to use big turn to turn a corner. Is this problem from my servo?? Thanks in advance.

khoo

Your issue may not be understeer. It may be that your servos are not extending.

If you prop (elevate) the front off the ground, turn your wheel through the remote, does the front wheel turn at least 45 deg. If not and your radio has a dual rate, you can adjust it there. If you have a digital radio with exponential feature, you can set it there too.

You can also check with what Billiam411 posted above.

Yes, I already adjust the daul rate all the way. My front tire set at this type \ / and at the rear tire are / \. So the front tire setting causing it need to use big turn to turn?? Sorry, I not understand what Billiam411 mention, can u help me on this?? Thanks.

khoo

Have to tried elevating the front tire and turning the tires with the remote to see if it turns at least 45 degrees?

Your front tire set to toe-out is okay, depending on how many degrees. Your rear tires set to toe-in is not helping you. Toe on the rear wheels is useful for tuning the handling of the car as it is exiting corners. You can try to lessen the toe-in for the rear to about 2 degrees and see what happens.

You can also try to use softer springs in the front.

Here are some effects on rear toe-in:
More straight-line stability
More traction out of the corner
Less steering
Less top speed


Here are some effects on front toe-out:
Quicker steering response
Less straight-line stability
Too much will cause greater wear at the inboard edges of the tires

What kind of car are we talking about? I may be able to give more setups if you have droop, caster/camber, adjustable shocks, etc.

Do you have sway bars?

I am running on Yokomo GT4. Pls help. Thanks.

khoo

I am not familiar with the GT4 but try these.

1. Make the tires (both front and back) in a straight line (i.e. | |). Run it and tell me the result.

2. Now toe-out the front. Test and give result

3. Softer springs in front. Test and give result.

4. Do you have front one-ways. Is your rear diff loose or are you using solid rear diff.

5. Does the car have droop, adjustable shocks?

6. Are you using an upgraded steering servo or just regular. Maybe it is not responding or pushing the tires under load.

7. What kind of tires are you using? Do you know the compound?

I might be able to suggest more if you respond to these.

dg2b, may I know that if I change the original steering servo to digital servo with stock AM Rx and Tx. Will this help?? Please advice.

This is also called a "pushing" condition, on full scale racers.
(Understeer = pushing = nose of car wants to hit the wall.
Oversteer = loose = rear end of car wants to hit the wall.)

If it's truly understeer, it won't matter which servo you use.
It simply means that the car wants to go straight ahead, even though the
wheels are turned plenty, and it should be turning. The problem with a lot of
RC cars is that they're at the very brink of lifting the front wheels off the ground
under hard acceleration, and this means you have less steering authority, as the
front tires just skitter along the ground, instead of biting and making the turn.

Positive traction rears, or very tight diffs, approaching posi-trac, make it even worse.

You'll have to transfer some weight to the fronts to alleviate, whether that be
through adding ballast, or adjusting springs and shocks or whatever.
It's all about having a full width patch of rubber firmly planted on the ground.
Sometimes camber adjustments will help out with this situation, too.
(If you have too small a contact patch while under hard acceleration)
You may make adjustments (or put lighter oil) in the diff, to loosen the car up some,
but I guess that depends on your setup a lot. If you have a locked-in rear, you're stuck.
If you feel that the servo isn't strong enough to turn the wheels while you're
really hauling, then yes, by all means try a better servo. It's just not that easy most times.


Also, just like in the full size cars... sometimes you simply have to slow down to
properly make it through the turn. Sometimes you have to go slower, to go faster


Hope that gives some ideas... and do know that I speak more from full-size than
from RC experience, but most of the stuff applies... I still have a slight problem with
my own RC10GT, but I blew the engine, so I've not had much of a chance to tweak.

C_Watkins, you mean I need to harder oil at the rear diff?? Front I using one-way. Will the tire cause this understeer??? If yes, I change slick to foam.

Harder? Not sure what that is or means, sorry.
Lighter, thinner, lower viscosity, etc... in the rear, is what I meant.
I guess improper tires for your surface could cause it too, yes.
Of course, dependant on the cause of the push, neither may help you out at all.


Only way to know, on a lot of the tweaks... is to tweak in the first place

Experiment!

Now I running Yokomo GT4 with stock electronic. So may I know that will you have the setup for parking lot track? thanks.

khoo

Very nice write up. Thank for the details.

The very same concept in a full size racer applies to rc cars. There are may factors of understeer (or oversteer) and one have to experiment.

tkhoo - did you by any chance tried the suggestions? What are the results.

get a sway bar and put it in the back. this would normally make for some oversteer but if you have understeer i wonder if it would make it normal.

Some if these have already been mentioned but this is what they do with full size cars:

Increase rear roll stiffness (stiffen or install sway bar, use stiffer springs)

Reduce front roll stiffness (soften or remove sway bar, use softer springs)

Reduce front toe in or create toe out

Reduce rear downforce (reduce spoiler angle of attack)

Increase front downforce (install spoiler or increase angle of attack)

Use wider front tires or a softer compound

Use a harder compound on rear tires

Consider adjusting CG fore of aft
^^ Experiment here ^^ on full size cars ones with rear engines tend to have more oversteer than those with front engines. Obviously you can't just move the engine but consider radio gear, batteries, etc.