usually when wheels vibrate at a certain speed it is down to mainly the wheels not being balanced correctly or in some cases the tracking may be off

Three possibilitys come into my mind. Most likely is that the tires are out of balance, this would cause more of an over vibration not just steering wheel. Next most likely is a tire that has it's tread separating from the carcase of the tire, it would vibrate mostly the steering wheel. Last likely is that you have a bent wheel, it would also mostly vibrate the steering wheel but you have to hit something with one of the wheels (like a curb) in order to bend it. Any competent corner tire store should be able to fix this problem without any trouble.

Your tires are out a balance or you have what is Known as a seperated tire or a bulge spot in a tire can cause shaking. There was no need to do an alignment or brake pads and rotors unless it vibrates when braking? It sounds like someone sold you a bunch of stuff that wasn't needed. Also if you get a tire balance and it does't work it could be a rim that is bent or has a flat spot in it from hitting a curb or something.

Just like what the other answers said, it sounds like your wheels are out of balance. From http://www.familycar.com/CarCare/AlignmentBalance.htm "The symptoms of a wheel that is out of balance are: * Vibration in the steering wheel at certain highway speeds. * Vibration in the seat or floorboard at certain highway speeds. * Scalloped or cupped wear pattern on the tires Wheel Balance: Out-of-balance tires will cause a car to vibrate at certain speeds, usually between 50 and 70 mph. A tire is out of balance when one section of the tire is heavier than the others. One ounce of imbalance on a front tire is enough to cause a noticeable vibration in the steering wheel at about 60 mph. To balance a wheel, the technician will mount it on a balancing machine which spins the wheel to locate the heavier part. He will then compensate for the heavy part by attaching a lead weight on the opposite side. Many people are pleasantly surprised at how smooth their car drives after balancing all four wheels. Most high quality tires will hold their balance fairly well and go out of balance very gradually. If you notice a vibration that wasn't there the day before, it is possible that one of the lead balancing weights fell off. If you feel the vibration mostly in the steering wheel, the problem is most likely in a front wheel. If the vibration is mostly in the seat, the problem is probably in the rear. For those of you who are very sensitive about vibrations and your shop can't seem to get that last bit of vibration out, check to see if you have locking wheel lugs. Some locking lugs are as much as 1.5 ounces heavier than the other lug nuts which translates to about 1/2 ounce at the wheel rim. Try putting a 1/2 ounce weight opposite the locking lug and see if it helps."

The same thing happened to my car for a while. I didn't know why but I kept driving on it. Well, it turns out the metal frame in the wheel snapped and was shredding my tire apart. Luckily I found out early, and was able to get new tires. So, I guess I would check for that.

another possible thing could be your outer ti-rod,grab your tire and see if it wiggle in and out back and forth.at high speeds this causes a vibration.mines actually doing it now.

you need to get your wheels balanced other than that you have a defective tyre but i would lay money on the balancing

Do you have after-market wheels? You may need hubcentric rings. And no matter what anyone tells you, if Camber, Caster and Toe are all out of whack, it can, and WILL, cause a steering wheel shimmy/gyration. I have a BMW 323i with after-market wheels that had a bad steering wheel shimmy, although the car went perfectly straight. I had all of the suspension components checked-out, I had a road-force 4 wheel balancing performed, all new tires AND hubcentric rings; and it was not until I had a 4-wheel alignment that the shimmy VANISHED. Make sure your alignment shop is reputable; and, as always, you will get what you pay for.

Were your wheels balanced when they were rotated? Some shops will do this automatically, but others require a special request for wheel balancing and they'll charge a little extra for it.

Your tyre thread from the wheels may not be equally balanced.Your alloy rims could be dented.Your tie rods may be loose or bent. Your engine mountings could have suffered wear and tear. Your body mountings could have worn off.Your steering wheel bearings could have broken. Please check all of the above.

ever considered going on a diet ...it could be your fat ass weight that could be effecting the stability of your car imho