Shaking at certain speeds, then slowly subsides
 

At around 40 - 60 mph, my car will have a pretty significant vibration. Heavy enough to cause my voice to undulate. And the steering wheel visibly shakes.

It usually only occurs when the car has been off for several hours, and the vibrations usually subside after about 10-15 minutes. Some days it is worse than others. The inconsistency is very confusing.

This has been a pretty persistent problem for me. Since I first noticed it, I've gone through a balance & alignment, and even got a new set of tires.

From browsing around the site, I've seen similar problems with engine mounts. Could this be it? Any other thoughts?


2006 Mazda 3 - 85,000 mi

Tires get flattened spots on them when sitting, if your pressure is low that makes it worse. Certain tires make more vibration with this flat spot than others.
It's possible that you have a strut seizing up and transfers the vibration more... or one that's completely gone allowing the tire to vibrate uncontrollably.

It may be possible that you have an engine mount issue (2006 was in a recall for the upper mount). If that mount is weak, it could start vibrating when the wheel starts it going - though I haven't seen that sort of thing on my own yet.

Well, I have a couple question about this.

When you experience this vibration, does it diminish or stop when you reach your cruising speed?

Have you had the vehicle inspected to make sure all the suspension, motor mounts, and drive line parts are in good working order?

The vibration does not cease when I reach cruising speed. It does, however, diminish after about 10-15 minutes of driving.

I have not had those things inspected. I never really knew what to tell them to inspect. Would you recommend doing that?

Well I agree with DJS at this point that it's most likely something suspension/drive train related given that it goes away after driving the car around. So it sounds like you have something that's seizing up while the car sits and get worked out after driving for a while.

If it were a motor mount it should be constant, similarly with flat spots on the tires, wheel balance, and alignment. There is a chance that you have a "harmonic-out-of-balance" issue which is where one or more of your wheels are slightly out of balance and the effect is most pronounced when the wheels are in phase and least when they're out of phase. However since this starts fairly reliably after the car's been sitting I really doubt that a harmonic issue is the case.

I discount the flat spot idea since you've said that you got new tires and I personally haven't experienced flat spots in tires from a vehicle sitting overnight or event for a few weeks. This is just my experience, so take that for what it's worth.

I asked if the vibration subsided or stopped at cruising speed because that would be indicative of an early symptom of CV joint failure/wear which is difficult to diagnose without taking the front end apart and inspecting the CV axles for wear which is about 4 hours of labor.

If visual inspection of those parts above turn up zilch (about an 1-1.5 hours at a shop) then I don't know what to tell you other than the outside chance that it is one of the axles.

thanks for the response guys, i appreciate it.