i've had "shimmy" on 86 560SEL at around 65-70 for few years, even after replacing all worn front end parts, and numerous rebalancing.
been on a 2000 mile trip and it just drove me nuts... so pretty much identified the problem as the right front tire. replaced it with the spare and shimmy is gone.
next step is to replace all the tires... they're more than 5 years old, a "good" tire guy told me after he rebalanced them that he "really" believes the tires are too old and just need replaced. said they weren't really out of balance. 1/2 an ounce at most. he drove the car and was sure it was the tires.
guess he was right.
