I have been getting a judder under braking, very badly at high speed. Is it possibly warped brake discs or is it the suspension. I had a mechanic look at it a couple of days ago and he said the suspension was fine, spent an hour and a half looking at it. It has been making a knocking noise over bumps which is why i had it in the garage. Couldn't find the cause of that either. Could that be down to warped discs aswell. Any help will be greatly appreciated. It's a 20v turbo by the way.