Originally Posted by Army

I agree with getting someone who knows their onions to look at the front suspension - it might be worth your while looking on the wheel rims to see if there is a missing balance weight.

Check both sides of your wheels - sometimes when tyres are fitted weights are added on both sides of the wheel. (Well for a good balancing job that's often the case)

Otherwise your experience reminds me of a really old film "My Cousin Vinney" when they get this special sort of mud in their tyres... (excuse me if you haven't seen it - and don't worry your life is still complete having not seen it)