Wheel shimmy+vague steering at 60+mph

My 78SC developes a slight vibration at 60+mph and the steering feels vague, at speeds less than 60 the car steers precise and has no vibration,I've tried experimenting with tire pressures and it gets much worse with more than 29+lbs in front , tires seem it good shape they are P7s .Where should I start ? Would tie rods cause this or what would typically wear out 1st ,the car has 109,000 miles and is otherwise in mint condition. Thanks for any input

Spend $20 and get your front wheels balanced, and I bet the problem will go away. Wheel weights often fall off, and that will throw things off. Vibration at a certain speed is a certain indicator, as is increasing the tire pressure causing increased vibration. Try that, and let me know, I bet that's the problem! I hope this helps.

Another symptom of wheel shimmy besides wheel balancing is front wheel bearings, loose "A" arms,(check the mounts for cracks) loose tie rods, and even steering racks.

After the wheel balance and if the problem persists, check the above areas.

Good Luck.

I had the same problem on my 87 when I bought it.. here's what I found... balanced tires (fixed about 20-30%), next I found loose wheel bearings (from the last brake job, I suspect) (tightening solved another 20%), Replaced ball joints and struts(solved problem completely). then an alingment and all was well.

Ball joints were easy to replace as long as lower nut wasn't frozen (1 was)...

Thanks for the replys ,i agree it probably is a combination of things , the wheel does seem to have a little play at 60+ also, would this be my tie-rods?

[This message has been edited by jryerson (edited 09-03-1999).]