Steering shimmy at 80 – 90 km/h

[stephn]

Have a 2003 V8 S 61,000km. Recently had to have the power steering unit replaced as was causing wear on the fan belt in hard lock. Since then it has developed a Steering shimmy at 80 – 90 km/h (not evident at any other speed), still drivable just a slight tremor. The mechanic has advised that it is due to a flat spot on the front right tyre and has advised I replace all the tyres. I put the spare on the front right but still have the same problem.

Looking for some ideas before spending large on new rubber!

[JDNSW]

I would look at wheel balance and toe-in and inspect the discs, plus a check for loose wheel bearings. One would want to know why the flat spot got there in the first place!

John