Here’s one. Don’t know if it’s easy or not…I was proud to figure it out, though.
As I left the house, I turned up my collar to the cold and winced at the brightness. Yesterday’s snow had changed into a real “parka-and-sunglasses” kinda day.
The night before, the car was driving flawlessly, getting me home from the ski resort. The next day, however, there was a pronounced shimmy that got very noticeable (worryingly so) at highway speeds.
Immediately, I questioned the tightness of the lug nuts, and prepared to exit. As I did so, I realized another likely answer. I stopped, verified the lug nuts were OK…and touched a part of the car.
In so doing, I determined the cause of my troubles, that it was benign, and would shortly fix itself…as it did.
What was wrong with the car? What did I touch?
Snow melted and refrozen into part of the wheel or tire tread?
I’ll echo off @oblivion’s answer and say snow/ice was built up in the wheels. We used to call this “the Loring Shimmy” up in northern Maine years ago.
Gee, that obvious, huh?
…sigh…
Yeah, I parked the car with (balanced) snow packed rims. The rotors were hot enough to melt the snow, which puddled, then re-froze once the rotors cooled. The ice threw off the balance.
I thought I was thinking pretty sharp to diagnose that!
I never had that experience, but when I lived in Colorado sometimes in the AM on the coldest days I’d drive the truck and at first it felt like the wheels were square instead of round. Bouncing up and down feeling. The tires were in fact out of round. Overnight they had sort of frozen into the shape they were when parked, elongated, with big flat spots. In a quarter mile or so they returned to their prior round shape. But it was like riding a bucking bronco for a few minutes.
I had a similar problem with an utterly different cause a couple of years ago. We had a summer heat wave with temps reaching 104+ every day for a week. I had to stop fairly hard at an intersection, which packed the treads of my tires with molten tar–there was practically a lake of it at the precise point where I stopped. The tires of my car being apparently cooler than the road, the tar solidified, leaving me with a suddenly hopping, shimmying, bouncing car when 30 seconds earlier it was fine. My first reaction was of course a big %#$?! It took some careful scraping of all 4 tires with a pocketknife to get enough of the tar out for the car to return to normalcy.