I had two new front tyres fitted on Wednesday. During the drive home, I heard a sudden clatter as something (I presumed a stone) rattled up around one of the wheel arches. I thought nothing of it at the time and continued my drive home (along horribly congested roads, so didn't get any speed up).
Next day, when I joined the motorway and reached 70, there was a pronounced wobble on the steering wheel. Clearly that clatter was actually a balance weight coming off one of the wheels.
No mystery so far. But here's something I don't understand...
The wobble was barely detectable with my foot off the pedal, but it became MUCH stronger when I put my foot down. I don't mean at higher speeds - I mean that the wobble was only really there when the engine was under load at the same speed. I've experienced badly balanced wheels before, but this was different. Normally it always happens at a particular road speed, regardless of how hard you're pressing the go-pedal.
In fact, my immediate thought was that my DMF had gone, so I tried dropping down a gear at the same speed, and the symptoms were the same - but with a different engine speed. So it probably wasn't my DMF.
Today I got the fitter to come back and re-balance the wheels. I described the symptoms to the fitter, and he said "hmmm... it doesn't sound like a wheel balance problem". But he did it anyway, and sure enough everything is nice and smooth now, so it really was the wheel balance.
But why did it only wobble when my foot went down on the power? Does the engine torque somehow alter the suspension geometry so that the balance of the wheel becomes more crucial?
The problem's all sorted now, but I'm really interested to understand it better. Can't really see why it should happen. Any ideas?
Next day, when I joined the motorway and reached 70, there was a pronounced wobble on the steering wheel. Clearly that clatter was actually a balance weight coming off one of the wheels.
No mystery so far. But here's something I don't understand...
The wobble was barely detectable with my foot off the pedal, but it became MUCH stronger when I put my foot down. I don't mean at higher speeds - I mean that the wobble was only really there when the engine was under load at the same speed. I've experienced badly balanced wheels before, but this was different. Normally it always happens at a particular road speed, regardless of how hard you're pressing the go-pedal.
In fact, my immediate thought was that my DMF had gone, so I tried dropping down a gear at the same speed, and the symptoms were the same - but with a different engine speed. So it probably wasn't my DMF.
Today I got the fitter to come back and re-balance the wheels. I described the symptoms to the fitter, and he said "hmmm... it doesn't sound like a wheel balance problem". But he did it anyway, and sure enough everything is nice and smooth now, so it really was the wheel balance.
But why did it only wobble when my foot went down on the power? Does the engine torque somehow alter the suspension geometry so that the balance of the wheel becomes more crucial?
The problem's all sorted now, but I'm really interested to understand it better. Can't really see why it should happen. Any ideas?
I guess its like when you get wheel shimmy on a front wheel steered aircraft (if you fly an old Cessna for instance), you must use the elevator to make sure the front wheel has the correct weight applying on it.
