Spyd

Lately my car has been suffering flatspots at high speed (around 80-90mph), the car judders every so often forcing me to back off the accelerator.

I'm just about to book it in for a service anyway, but was wondering if any of you guys knew what was causing this as i'll be doing alot of motorway driving this weekend and don't want the car beaking down or anything!

Hope it's nothing serious...