In a semi-trailing arm setup, the pivot axis of the suspension arm sits at an angle between parallel and perpendicular to the vehicle's centerline. This geometry causes the wheel to gain negative camber and toe-in as the suspension compresses, improving cornering grip compared to a pure trailing arm.
Heard on the job
The bushings on the semi-trailing arms are shot, which explains the massive rear tire wear.
Insider tip
This was the standard rear suspension for rear-wheel-drive German cars for decades before multilink setups took over.