[lornecherry]

I replicated your exact problems while testing different surfaces. Here's what to do:

1) Never run the d'NaNo unless on a track. The sticky tires, very low ride height and a flaw that seems to let stuff get wrapped around the inside of the front axle, make these cars a touch finicky to maintain. With two dogs and two cats and a dusty basement, I'm cleaning my car's wheels and bearings a lot more than I'd like. The issue is serious enough for me to try to find solutions with either raising the ride height ever-so-slightly and/or different wheel and tire combinations, in addition to keeping the track squeaky clean. (I think there is a static electricity issue in my house or generated by the cars also)

2) Spin the front tires with your fingers while the car is upside down down to see if both wheels turn very freely. If one, or both are gummed up, you'll need to disassemble the front knuckles and clean out the inside axle. If even a small hair or impurity is wrapped on the axle, it will cause the car to pull to one side. The natural torque steer of the engine will also be exaggerated.

Remember, one hair to the d'NaNo' scale is like a rope being tossed into the axle of my Durango. This is why you need to run only on clean surface. I'm sure your problem will go away once you clean out the front end.

3) Some chassis and body styles do turn slightly better to one side I find, but it is minor and can somewhat be corrected by choosing the correct grip of tire and a good surface. If you are traction rolling on rubber, then I suspect the problem is mostly a gummed up front end or a differential that's improperly setup (see 4 below)

4) The differential needs to be lubricated -- the out-of-the-box stock unit is tighter than a recessionary budget. It will loosen up over time, but all my cars performed much better with the upgraded Kyosho ball diff. and that upgrade alone will definitely help your problem. Yes, the stock unit is actually quicker, but the upgraded bearing unit is much smoother.