My son’s wife has a PT Cruiser, she told me last night that it has a shimmy at 70 mph. What are the causes of this ? I told her to take it to a shop as soon as she can (but she rarely takes my advice.)
Couple of thoughts.
How worn are the tires? One of my cars developed a shimmy a few thousand mile before I would have normally replaced them, the shimmy stopped with new tires. I would also check the tire pressure and the lug nuts for tightness. Any recent curb hits?
Shimmy can also be known as “the death wobble.” Make sure you tell your daughter-in-law this and tell her she needs to get that looked at by a competent front end shop. The death comes into play when components from the vehicle leave suddenly at 70mph or the driver simply loses control at that speed. Either way…it’s not a pretty sight. Also…+1 for edb1961.
Hard to say. It could be something as simple as a wheel balance weight has fallen off. Or as complex as a transmission/driveline problem. What a mechanic would do probably – after a visual check to something obvious – is drive the car, a feel what happens as 70 mph is approached. They’d do it twice, one time a slow acceleration towards 70 mph, and the second time, a harder acceleration towards 70 mph. Then they’d increase the speed to above 70 mph and take their foot off the gas and feel what happens as the speed goes down through the 70 mph range. Those results would provide clues to isolate the cause.
I had a car a while back that picked up a load of mud inside one of the front wheels. It was several ounces. Man did it ever SHIMMY.
1000 possible causes, but most of them turn out to be either balance, wear-induced balance, alignment, or normal wear on the struts and/or bushings… um, how old is the car?
A good shop needs to take a look-see. Tire wear can provide good clues, but even then they’re only clues… not final diagnosis.
A few summers ago I drive away from a dollar store and suddenly developed a terrible wobble. The crack sealer used in the parking lot had just been applied, not sand was spread over it, and my tire ended up with a strip of it that had pulled up out of the crack. Took me a few hours with the wheel off and bug & tar remover to get that stuff out of my tire tread.
Simple test: Swap the tires front to rear.
If the shimmy stops, it’s the tires and/or wheels - usually balance. But if it doesn’t stop, it’s something else.
Tires can separate internally and cause shimmy. Rotating and balancing will either move the problem or fix it.
knfenimore said: "Tires can separate internally and cause shimmy. Rotating and balancing will either move the problem or fix it. "
Sorry, but No!
Separated tires can only be fixed by replacing them. Balancing tires only fixes an out-of-balance problem.
Rotating tires helps determine if a problem is in the tires (and/or wheels) or not. There are many things that can cause a shimmy, and this helps sort the the problem a bit. Plus, there are other tire and wheel related issues that can cause a shimmy.
I meant that if they are separated, rotating would move the problem. You might as well balance them at the same time. That way if it’s a balance issue it will be taken care of.
I think that you should stress to your daughter that this shimmy could be a warning sign of a catastrophic failure in the steering components of the car.
It should be looked at ASAP by a competent mechanic.
Tell her to imagine herself doing 60+mph down the highway and loosing complete control of the car. Herself and/or the other drivers on the road are at great risk.