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Cars unstable
with greater side-force
and better tyres
at front wheels

Several people killed in skidding accidents
after mounting new tyres at front wheels only
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a non-profit research society

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December 21, 1996

Avoid accidents (tomorrow)
by understanding (today)
the relevant laws of nature

Tyre side forces (S), their sum or 'resultant' (F) and its application point (P)

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Small sideslip oscillations are always occuring, due to road unevenness, aerodynamic forces, etc.
However, the current sideslip tends to be amplified by the resulting external forces, if their sum, F, applies to the vehicle (at P) in front of the centre of gravity, T (about which the vehicle is rotating).
Therefore, the vehicle may become unstable (like the upper car), when the side forces increase more with the sideslip angle at the front tyres than at the rear.

Hydroplaning at the rear wheels only may be simulated and perceived in this skid training car

Yaw Stability may be lost ...

... and your car may spin around by itself (like the nearmost yellow Combi Coupé in the picture) because:
Spin-out and plow-out cars before collision

Spin-out may also be triggered ...

Official Statistics of Sweden indicate that instability and rear wheel skids are much greater problems than poor steerability for the average driver when roads become slippery. Accidents with oncoming vehicles "Head-on" and Single vehicle accidents (poor directional stability) contribute to a significantly greater percentage of the accidents when the road has ice or snow on its surface. Compare the left and right columns in the diagram, showing annual averages from the years 1988 to 1995.

Accidents and Killed 1988-95
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To be completed later with descriptions of relevant accident cases
Under Construction

Webpage opened in February. To VETA website in April 1996.


Best Wishes from Sweden and Lennart Strandberg
Charter Chairman of the non-profit VETA society
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