Driving my Holden Monaro CV8Z 2005 on the weekend when I noticed a new sensation - that being a constant vibration that increased with speed and occurred when I reached speeds over 65 - 70 km/hr. It WASN'T a harmonic vibration or sensation (meaning the vibration wasn't like a pulsing sensation - it was continuous) and progressively got much worse as I increased speed.
After doing a bit of investigation - checking the little balance weights on ALL wheels (all good none had come off), then checking if any weights have been thrown off the tailshaft and additionally check my tailshaft center bear (again ALL good).
I stepped back and sat on my back step having a drink and noticed that my rear left tyre was CONVEX in shape (meaning it dipped in the centre of the tyre) and was obviously puzzled. Now I know a concave shape would indicate an over inflated tyre, but for the life of me I didn't know what could case the opposite shape. Until that is I took off the back tyre and had a look. Now you could not only see the indent but you could definitely feel it as you rubbed your hand perpendicular to the tyre (from outside to inside). The tyre structure had basically failed and created a lump on the inside edge (not the outer edge) of the tyre causing it to be oddly shaped and hence the vibration.
Changed TWO rear tyres - went for a spin on the motorway 110km/hr +++++ and no issues.
Hope this helps anyone that may have a similar issue. I would suggest if you get this described vibration to check all the things I mentioned above
