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Wobble at speed


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Long shaft swingspring GT6 

I get terrible rotational vibration at anything over 70mph (closed road of course😉

I've had it since I built the car 12 years ago. Everything was replaced at the time of build and has been replaced at least once more since in that time. 

I have checked the hub runout on the face of my rear discs today and got 0.25mm n/s and 0.10mm o/s. (0.25mm is just under 10 thou) 

Would this be enough to cause the vibrations? 

My Alloy wheels balance up fine but they always use the hub centre. The small chassis is obviously stud centric. Would this make a difference? 

I've swapped all wheels around several times during the 12 years of ownership. 

Ive bought a set of used alloys today to try out as I can only put it down to my alloys. 

The one thing I've yet to check using the dti is that the driveshafts are running true, I'll do that tomorrow 


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Propshaft? The small chassis cars are badly afflicted by propshaft vibration, I think due to the relatively light and flexibly mounted diff which provides little damping. 

In my experience, even propshafts that have been balanced and rebalanced off the car can still cause problems and I’ve resorted to on-car balancing with jubilee clips more than once.

Conversely I’ve had bent wheels, driveshafts and hub flanges that have been bent enough to bring comments from following traffic that did not produce vibration.

GT6 with its relatively short prop has less weight to throw about but is perhaps more prone to unfavourable operating angles.


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