Hey all, I've had this problem in the front end ever since I've owned the car and it's got far more aggressive in the last few weeks. If I go around a u-turn at highish speed the car makes this god awful vibrating/ratcheting noise that almost sounds like the steering rack is going to fall out the car or something. I took a video it's a really bizarre sound http://www.youtube.com/watch?v=rQF3uJdN1pU

The front end has been entirely restored I've even taken it to Pedders and they can't figure it out. The only things left that haven't been replaced are the steering rack itself and the inner tie rod ends (but I've checked them), and a few of the big bushes that are fine.. even the tyres are near new and aligned. It makes no sense if anyone has any ideas I'd love to hear them! cheers

Try swap your front rims with the rears? Then go for the u turn see what happens could be a warped rim/tyre

Check tightness of the rack mounting bolts.
If the wheel alignment isn't spot on, or tyre pressure isn't right, it will make that noise.....mine does it when the alignment isn't right.
I have 235/60R15 tyres on genuine 15 x 7 mags.