I have a 2006 Cadillac SRX V6 - original tires P235/65 - R/17 103H front and rear tires are P255/60 - R/17 105H. Why the difference in size and do I need to replace them with the same? The rotation process seems weird and what will it do to the handling and ride if I purchase all 4 tires the same??

ck here

https://www.fixya.com/cars/t18863328-knock_sensor_location_cadillac_srx

Hi Amber,
I presume that you want to change the oil on the Cadillac. The link below will tell you how to change the oil, where the drain plug is and where the filler is a. It will tell you where the dipstick is.
Oil Filter Change Cadillac SRX 2004 2009 2006 Cadillac SRX 3 6L V6
This is a good, clear video.

if its the 3.6 v6 staring from the front of engine passenger side head is 123 driver side head is 456 if its the 4.6 v8 it is front head 2468 and back head is 1357 starting from the left to right

I had the same question and I finally did replace my tires with the same size and I am very happy with the results. The reason they are different sizes was to increase the performance of the SRX. I have 18" wheels and put on ( 245-60R-18 Michelin Lattitude) tires. The reason I selected this size was to minimize the speedo error to 1 mile per hour. I did that by going on line to a tire calculator and compare the original size to the replacement I selected. Now, depending on your rim size you might find that you may have to select a different tire then I. The rule is to keep the spreedo error under 3 MPH. The ride quality was greatly improved with my selection.

If the vehicle came with a spare tire then yes you can use it. As to whether or not it is a full size spare tire I wouldn't be able to answer that, as on some models a full sized spare is an option and I have no way of knowing if that option was purchased or not.

Hello, If you will check on the drivers door fram there should be a placard telling you the size and pressure and if I'm correct they should be directional tires. Yes I would take it back to the dealer. Cadillac recommends the proper tires for thi car

The firing order is 1-2-3-4-5-6. Cylinders are located on the driver's side front to rear of engine 1-3-5 passenger side front to rear 2-4-6.

I would certainly replace the axle with play. But this may not be all. Could be wheel bearing as well.

you have a computer for your control on your car. It is set up so only the factory front and rear tires sizes will work, any change, it picks it up. this should solve the problem.