So, when I first got my Lexus...It had gotten a flat on the road, and the guy had put a stock wheel he had for the car, though it was only a 16, and the car is dropped on 19s. The tire size of the 19s are 245/35 r19, and the spare was 215/60 r16....and when I was driving it home from about 20 mph to about 50-55 the car would like shake/seem wobbly. but at 60 it drove smooth. But I did have about and hour and a half drive home. I replaced the tire that needed replacing, and have been driving the car around for a week now, and the shaking/wobbliness had stopped, and now it is starting to mildly shake from 35-50 mph, while you speed up, but more when you press on your brakes... I have no clue what to check, should i get all the tires remounted and balanced? Or could it possibly be rotors/calipers/ brakes over all? I get super paranoid and even think as far as to go get my engine an overall inspection to make sure the mounts are still good...Please do give me some suggestions as to what this could be.