Steering Wheel Shimmy

I put a new set of studded Hap 1's on my 01 Jetta about a week ago, drove it at speeds of less than 50 MPH for the first 100 miles to let the studs settle in--no problems.

First real snow (about 6-inches) this Monday and I had to drive a couple of hundred feet through unplowed snow in order to jump start my plow truck. First trip following, I brought the car up to highway speed on the interstate and immediately noticed a vibration/shimmy in the steering wheel. My first thought was that some of the deep snow had attached itself to a wheel and was throwing the balance off. Yesterday was above freezing (car also kept in garage overnights) so if there was snow stuck to the wheel, I'm reasonably certain that it would have melted by now.

I would now think that the wheels were not properly balanced when the snows were mounted, but this morning I noticed that the degree of shimmy is proportional to the amount of load on the engine. That is to say at a constant speed of say 65 0r 70 (cruise control on)the steering wheel will shimmy more when going up a hill and almost disappears on the downhill side. On level interstate, the shimmy is moderate. Shimmy also seemed to increase slightly when coasting (5th gear) to the exit ramp.

I've never experienced a wheel balance problem that changed according to the engine load. Any thoughts as to what may be going on here??

Sorry for the double post, Moderator please remove

Increasing load making the shimmy worse can be caused in part by a bad balance. Rotate the tires from front to rear and see if that helps. Or, just get the tires re-balanced. If a tire or wheel is out of round then a Hunter GSP 9700 (www.hunter.com to find a location if you don't know of one) can help. I had a very annoying shimmy that did exactly what you describe with all-season tires. Its much better since the tires were re-balanced.