High speed vibration, But not all the time Options

[porschecb]

New tires, new wheels, new shocks. 55 and up shake/vibration in the steering wheel. But here's the kicker. It come & goes. I can go for maybe a mile or even 2 or 3 and everythings fine then for some reason it starts back up again for maybe a mile or so then quits. Tried diff. speeds and seems like it makes a diff. but can't tell for sure. (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) and! it just stated. maybe a year after all the new stuff installed. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

[Tobra]

QUOTE (goose2 @ Sep 16 2005, 05:48 PM)

Sounds like a "harmonic" vibration. Something somewhere has a bit of looseness...it'll be smooth until just the right bump or rut or road surface gets a vibration going at just the right frequency...then it perpetuates itself or gets worse until you slow up, hit the brakes, or do something to break the cycle. This would explain the irregularity of it. Checked the inner tie rod ends and the steering rack bolts? Toe setting?

Super Beetles are notorious for symptoms just as you describe, and are a strut front suspension floor pan vehicle. Tie rod ends or ball joints get a little worn and at certain speeds, on certain roads, they shimmy and shake, on a SB you can also get this with worn struts. If the wheels are round, and nothing else pans out, it may just be some worn out stuff causing problems.