Assuming the Karrier are rated for 2271 # load capacity they should work fine .
Load Range D tires are only rated for 2271 # in the Kumho 857 size 205R14 if they are inflated to 65 psi . Same with Karrier .
If you only inflate them to 50 psi they are only rated for a load range C which might be a rating of 1820 # or so .
RV steel wheels have zero reports of failure on this forum due to overinflation .
CapriRacer ( tire engineer ) has repeatedly posted that an overloading of weight capacity of a steel wheel is of far more concern than failure of a wheel due to overinflation .
The wheel engineers have to build in so much weight capacity that inflation to 80 psi would not be a concern .
You can inflate to 65 psi with your steel wheels without concern .
The fact is relatively few RV wheels have a psi rating and those most often are aluminum .
When a wheel fails ( assuming no wreck ) it tends to develop a hairline crack often at a shoulder of the rim . The tire deflates and the wheel does not blow up assuming one is checking his psi often . You have a flat and the wheel will no longer hold pressure .
Some posters have gotten confused as to psi ratings for wheels when in fact those charts are to show the weight rating and the Necessary psi to achieve that weight rating .
The best thing one can do is to improve the load rating in pounds as shown on the sidewall of the tire .
Brand is less important than the load rating .
Either a Kumho or Karrier is a better choice with a 2271 # weight rating than the maxxis at 1820 # or 1870# .
As a bonus the Kumho are rated to LT criteria and a speed rating of 106 mph IIRC .
To answer the question about 215/75R14 tires mounted on a wheel that came mounted with a 205/75R14 , it will work fine .
I had a trailer that I did Exactly that .
No problems as long as your fenders will clear the slightly larger tire .
