I notice my steering shakes / vibrates pretty rapidly at 100+mph, what could this be caused by? A bent front rim?

I had my alignment done about a year ago.

Most likely an unbalanced front wheel? Your local tire shop should re-balance them for you.. also do check tire pressure..

realignment will help. But 100+ shouldnt really be going that fast in the US. But I do anyways.

Yeah most likely just unbalanced, also whats the tire wear like on your tires?

When I've had issues like that in the past with other cars, wheel bearings and bent wheels were the culprits. I sincerely doubt that alignment would have any effect on this.

It's prolly your tires.

There's two kinds of wheel balancing. The standard type is static balancing. Most shops do those. It's balanced for typical road speeds. If you want wheels to be balanced for high speed, you need to go to a shop that does road force balancing. They not only balance the weight offset for the wheel but also factor in the weight offset of the tire. They basically are neutralizing the weight offset of both together. Used primarily for performance applications. But you could end up paying $20-$30 per wheel for that. I would try that first. If that doesn't get rid of the vibe you need to be looking at rotors or suspension bushings.

Is it also called a 'dynamic' balance? I was told there were 2 types of balances available, static where they only add one row of weights if needed and dynamic, where they add 2 rows on either ends of the rim if needed.

I guess. They don't always put on a second row of weights. If the rubber offset is in line with the wheel offset, they could go as far as deflating the tire completely and repositioning it on the wheel to make each weight offset go opposite of the other so they can add as little weight as possible. It's difficult for me to describe. But there's much more involved when doing a road force balance than a simple static balance.

I'm thinking it's your tires.

There are several possibilities but I'd begin with having your tires balanced, that's gererally the culprit....Gary

Try a rebalance and go from there.

100 mph? Why?

Just keep it under a 100.. no need to be in such a hurry.. lol

Thanks for the tips guys...
I probably will check for a bent rim and start with the balancing to see first.

If it is bent, I may purchase 2 more OE Rays rears to have square 19x8.5 and see how that handles

On another note, I am an auditor and have been working 14 hours a day lately, so driving at 100 mph home at 11PM in an empty freeway should be forgivable

This makes it that much worse of an idea... Stay safe bro, would hate to see a story on the news about you losing control or falling asleep late at night.