Car heads for the bush....

[gearhead]

We have been going to the bmx track lately, lotsa fun.
I have a problem with my off road gas buggy:
when i accelerate hard it takes a hard turn left or right both? i cant remember.
I had the diff set up loose then i tightened it and no difference, checked for a frozen bearing, nope.
It just wont accelerate in a straight line anymore like when it was new.
camber, toe in all set. 3 deg rear camber.
maybe my rear shocks are too stiff, not letting it get even traction?

[Grinder]

I know with our 1/12th scale cars if you have your diff too tight it pulls to the right.  Make sure nothing else is binding, etc.... it doesn't need to be siezed to make it pull one way....

[Tom]

Our 1/12 scale cars pull to one side on acceleration due to the asymmetrical design of the rear axle assembly.  This is particular to pan cars.

When it comes to off-road cars, the problem can be caused by several things.

I'm not sure what kind of car you've got, but if the motor is mounted in-line (like in a 1:1 rear wheel drive car), the torque reaction of the motor will cause it to turn one way better than the other.  This is the major handling flaw of the Associated TC3 on-road touring car.  If the motor is mounted transversely (like in a 1:1 front-wheel drive car), you have better handling.

The two other most significant things are the tweak and binding in the suspension.  The tweak refers to the weight the left and right wheels have.  You adjust this on off-road cars by ballancing the ride-height adjusters (spring collars) on the shocks, and by ensuring the left and right shocks are the same length.

Binding is obvious; it can be easy to bend a shock shaft on an off-road car in a crash or other incident, and a slightly bent shaft can bind the suspension, causing handling like you describe.

These are the three most likely things that pop to my mind, but I haven't raced off-road in ten years, so my dirt tuning skills are a tad rusty.

[jarrodH]

try it on the ashalt to eleiminate the chance of it just being that it is the dirt thats not consistant, loose, packet, or that the car isnt siting flat. if it still does it on the cement, then its something with the car

[Tom]

Well, what matters is trying it on a level surface, and very little pavement in this part of the world is level.

Since you care about how it handles on dirt, I'd suggest trying it on dirt, but running in both directions on the same surface.  If your car is set up incorrectly, it'll always turn in the same direction.  If your car is set up correctly, it'll always turn in the same compass direction, the same amount when running towards you and away from you.

If it always turns to the left, you are getting more traction with the right rear, or more drag (which you already investigated) on the left rear.  Conversely for the right.