[LUKEDAVIE]

I installed new wheels and tires on my 2011 x3 28i xDrive. They are 19inch TSW Nurenburgring wheels, the back one is slightly larger in width than the front. The wheels came off a 2003 m3 from Facebook marketplace. While putting new tires on to see what looks best fitment-wise, we ended up putting the front tire slightly smaller than the back. The car drove great but noticed traction control engaging while accelerating at speeds over 60mph. It didn't always do this but if I turned the traction control off I would not have a problem so I disregarded of this happening. A few months down the road I noticed the car shifting weirdly. It kinda jults when stopping or accelerating like when it needs to shift gears. This turned into vibrations while driving as well. If I drive with traction control off and shift manually it helps it not do this as much but I can definitely still feel it. Machanic said he thinks it might be the wheels being different sizes and need to further look into that. Has anyone got advice for me? Is it the wheels or is my transmission just messed up or maybe a combination of both?