I find that a constant shaking in the wheel is always a wheel and/or tire problem. Not to say that a bad joint can eventually cause the tire problem to develop shaking. Think of it this way. If your car has perfect wheels and tires, but a worn out steering gear, then it will not shake unless you hit a particular bump that sets up a resonance. But, on a smooth road, you should be able to drive any speed without shaking. When I say "resonance", I have had several cars with completely worn out suspensions, and they drove perfectly (albeit sloppy) at all speeds. But occasionally I'd catch a bump just right so it would start a resonance and the wheels would slam back and forth violently against the sloppy joints until I slowed down enough to bring it out of resonance. But once the shaking stopped, I could speed right back up with no shaking at all...at least until I hit the perfect "bump" to start it again.
So...from above I gather that if your wheels and tires are good, but suspension bad, you do not get a constant, predictable shaking at any particular speed.
Now let's take a car with perfect wheels and tires and a brand new suspension. It won't shake and drives great. What if I introduce toe in? It will not shake, it will just pleasantly scrub the tire treads down to the cords. Same with toe out, accept the car handles wildy with toe-out. Same with castor and camber. If your wheels and tires are good, then you do not get a shaking from a bad alignment. From the first analogy with the worn out suspension, you also do not get shaking from good wheels and tires and a worn out suspension either. Just one caveat...if you run a set of tires with a worn out suspension, the tires can eventually wear cups into the tread, which can then cause shaking. But, by then it is a tire problem causing the shaking, not the worn parts.
This has been long winded, but if you are still with me, these are my conclusions from dealing with shaking over the years:
A constant shaking in the wheel is ALWAYS a wheel or tire problem.
To finish this out...another example. I took our 19 year old Range Rover to Discount this summer for new tires. The car then had a shimmy at highway speeds. I took it back to Discount, and they re-balanced the new tires. No help, still a shimmy at highway speeds. I then carefully checked the suspension, and found the front ball joints worn...so I replaced them. Took it back to Discount for a second rebalance on the tires. Bummer...still a shimmy at 65mph. Then I detected a very slight wear in one tie rod end...so I replaced all the tie rods. STILL a shimmy!!
The way this ordeal wound up, I took it back to Discount and told them that I had replaced everything that was loose, and the tires started the shimmy to begin with, so by deduction, the problem HAS to be their new tires. I wanted them replaced with a different brand if they could not fix it. Here it got interesting. They ran a test on the car and determined that the tires were actually slipping on the wheels! I had never heard of such a thing. But they did something (chemically) to prevent the tires from spinning in relation to the wheel...rebalanced for a 4th time...and the car was finally great to drive at any speed without shimmy.
The moral, shimmy is ALWAYS a wheel or tire issue. New tires are not immune.