Missed matched tires, Hi Pro next to a Low Pro on trailer?

The 295/75 means that the side wall is 75% tall as the width which is 295.
The same with the 275/80, the side wall is 80% tall as the width of 275.

The difference between the two tires when new is about on tenth of an inch more in over all height, they may be run side by side legally and with no problems.

The problem comes with pairing a old and new tire together as they can have severe height differences due to wear, sometimes you are better off seeking a used tire so that the height of the tires are more closely matched.

If you can't get a good used tire or replace both in that spot then have the new tire mounted on the outside with the older tire on the inside, this will allow the crown of the road to help keep a tire from getting chewed.

 

Tech is correct. They are the same overall size just different aspect ratios.
They're both LP 22.5

Your biggest difference is putting new next to worn ... You should have replaced them as a new pair to do it correctly.

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Looks like driver error as much as the guy that put it on. Safe to say you paid the bill and drove without looking at it. Absolutely no way you could not have seen this if you would have looked.

 

I've had some trailers with mismatched tires, the one I have right now has 3 different sizes out of 4 possible tires on the drivers side, and they are all wearing WHACKED, and it shakes the whole truck over 65 mph. Can't wait to get rid of it.

 

So... Your concern puzzles me. The 275 was put on last week? And since that point Petro put on the 11r22.5? Clearly you have mismatched tires but I'm not seeing how your timeline and descriptions make sense.

Also as stated above, you really should have looked before you left. The argument that you can't read the size on the inside tire is INVALID. It's not that hard to crouch under and look at the back side.

The tire shop definitely appears to have failed you. But they aren't the only ones