The juddering is caused by the blades not being at the correct angle to the glass. The rubber must flip at the end of each stroke so that it is being stroked back on the glass, just like a window squeegee. If the blad does not flip it judders.

The solution.

Turn off the ignition whilst the wipers are in motion to stop the blades in mid stroke.
Remove the wiper blades.
Observe the angle of the flat of the end of the wiper arm in relation to the screen.
Using two pairs of pliers, and protecting the arm with some pieces of leather, twist the end of the arm so that the flat at the end, even though angled away from the glass, is as near as possible parallel to the glass.
Refit the blades and check that in mid stroke, when lifted slightly away from the glass, they are at 90° to the glass.
Test with some water on the screen and adjust again if necessary.

Good replacement blades can be contructed from Bosch or other quality wiper blades. There are a couple of threads on this topic.

Peter

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