What Car? Q&A: July 2009 - Bad vibrations
A) The chances are the problem lies under a wheel arch rather than the bonnet, and it's probably caused by an imbalanced wheel.
This means that one section of a tyre or wheel is heavier than another section. When you reach relatively high speeds, the car's weight is no longer enough to suppress the wobble, and that's why you notice a vibration through the steering wheel.
The remedy is simple: pop into your local tyre fitter and they will re-balance the wheels for around £10 each. The process involves fitting a small weight to part of the wheel, which counters the imbalance and should stop any vibrations.
They should also check for loose wheel nuts, as that could also be a reason for wheel wobble – and one that needs to be remedied right away.
Although the problem is relatively minor, we'd advise getting it sorted as soon as possible. Imbalanced wheels don't just make for uncomfortable driving, they cause increased wear to suspension, steering components and tyres.
In the unlikely event that this doesn't cure the problem, head to your local dealer for further diagnosis.