Rear Bump Steer

Aug 9, 2010 update on ansonivan's 1988 Volkswagen Scirocco

The rear suspension in the car is from an A2 golf/jetta. I swapped in the complete subframe/control arms/spindles/struts and welded a solid bar in place of the steering rack in order to lock the tie rods in place.

The car has always suffered from weird rear suspension behavior, mostly severe rear squirm in corners. I finally took the time to investigate, I measured the rear toe with the suspension at full bump and full droop. When measured at the tire the rear is toeing out by almost a full inch as the suspension compresses. Not good.

My friend Jake noticed that the rear struts have a little bit of positive caster, with his help I moved the strut top back into a slightly negative caster position and measured the dynamic toe again. Happily it stayed almost perfectly neutral through the complete range.

In order to correct the rear caster issue I’m going to move the sub frame forward and the strut tops back. This time I’ll actually measure the caster :)


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