For some reason the front of my truck has begun to shake terribly at around 70MPH. I've had the tires balanced twice and saw for myself that it showed perfect balance on the rotating spin machine that most tire companies use. Still the vibration continues. My truck has 29,000 and the tire look almost new. Any ideas of what could be causing the shakes and vibration? It came on suddenly. Thanks for any help

I would rotate the tires front to back see what happens.

What Mackin said. Not sure about disc brakes but maybe a warped rotor. A slight bulge in a tire could cause a vibration also (maybe what Mackin is thinking)

If you rotate the tires you could spin the rotors to check for any drag. I had this happen to me on an old (86) Buick but if its the rotor you should really notice the 'shakes' when you apply the brakes.

Well, went back to Discount and had them rotate front to back and still had the same shake. They took the tires off and placed them on a load stress machine. Bingo, three of the 4 tires were out of stress limits for sidewall flex. They said that would cause sever shaking at highway speeds. Discount replaced all four tires no charge. I have used Michelin LTX M/S for years and never had problems with them. I guess I got a bad batch that didn't show up until about 25,000 miles.