BA Xr6 Vibration

[spookster123]

I need help with a front end vibration even mechanics cant diagnose.
In the suburbs all is perfect everyday. On the freeway tho at approx 105kph and very randomly, the car will begin to get a front end vibration. This very quickly escalates to a severe shudder. Enough to have to back right off which sometimes fixes or eases off. However if I just slightly touch the brake pedal it breaks into a wild shudder. Wild enuff to have to back right off and possibly pull over. It then may not even happen again for hours of driving OR it may happen several times again over the next several KM's.
As I said this is very random. I travell often Melb to Warragul, 100's km's return trips and most trips the ride is normal and smooth as a bubs bum. But other trips it may happen 2 3 0r 4 times.
Ive had brakes machined, Booster checked over and front end components checked over. No one seems to know the cause

[gkhn]

Put the front wheels to rear. Rear to front.
See what happens..

[foxtrot3]

Hi. Adjust the booster to master cyl clearance to stop the brakes from dragging when hot. If it still happens after that change the lower control arm inner bushes. Cheers MD

[spookster123]

Originally Posted by foxtrot3

Hi. Adjust the booster to master cyl clearance to stop the brakes from dragging when hot. If it still happens after that change the lower control arm inner bushes. Cheers MD

Mate, I reckon (hoping) you may be bang on the money. I was speaking to a bloke earlier who said he had the exact same problem. Couldnt diagnose it for months then changed control arm bushes even though they seemed ok, and problem solved. The thing is I had my mechanic go over all that stuff and he also said they all seemed ok. And I do trust my mechanic, been seeing him for years. Never the less, that is definately next on the list.

Thanx m8

[spookster123]

I forgot to mention I have tried 4 different wheels