Shaking at highway speed

Just having the wrong tire size is not going to cause a vibration.

The way to fix this is use a vibration analyzer. The dealer should have one and I would call the manager and tell them they need to use the tool if they have one.

If they do not have one, then they need to pay for another dealer to use theirs.

https://www.2carpros.com/articles/steering-wheel-shakes-when-accelerating-or-braking

If none of this works, then we need to find out if the axles are bent.

Start with finding out if you feel the vibration in the seat or in the steering wheel?

If it is in the seat, start with measuring the rear hub runout and this will tell us if we have a bent hub/axle.

If it is in the steering wheel, then the front is the issue.

Lastly, they will have to check for vertical runout on the axle hub to see if we have a housing issue as well allowing up and down movement.

However, all of this will be clear if we have a vibration analyzer. That will tell us what type of component is causing the vibration because this could be a driver shaft as well.

Let's start with this and go from there. Thanks

This is a great place to start, thank you so much. I'll get this vibration analysis and report back. Thanks again!

Sounds great. Thanks.

If they are not sure how to read it, have them right down the following info and I can help figure out the cause.

All this info is when the vibration is there-
Hertz reading
RPM
Speed
Tire size
axle ratio

With that info, I am sure we can narrow this down.

Thanks