Yesterday I had a flat tire on the front passenger side tire on my ML320 SUV. My wife didn't know about it and started driving, not realizing the tire was flat,
and a few minutes later came back and told me about it. I'm not sure how
far she drove on a flat tire (never a good thing to do). Anyway, I
temporarily put the spare donut tire on the car and took the wheel/tire to
Sears.

I told them to just fix the flat. They said they couldn't because the tire
was damaged from driving while the tire was flat. Ok, then I said replace
the tire with a new one. He said that's fine but they could/will not mount
it for me because the car is 4WD and the tread depth on the one new tire
would be so much more/taller than the remaining 3 that it could damage the
gear box. They are not authorized to put just one new tire on a 4WD
vehicle. I then said, ok give me two new tires then and put them both on
the same front axle. Again they said no as they could not - for the same reason
about the gear box stuff.

So I eventually caved in (perhaps I should not have) and purchased 4 new
tires for the car. So $600 later, instead of $125 later I have 4 new tires....

Today I went back to Sears and spent an hour there "speaking" with the
on-duty assistant manager as well as the auto center manager.
Originally the assistant said it was my fault, that I could have, at
the time, just declined everything and chose not to have anything done.
Well as I was there to get a flat fixed that was not my intention,
although I suppose I could have.

What I really liked was when he said that if I bring the car back with
the 4 new tires (wife has the car now) then he would gladly replace all
4 tires with my 4 old tires and refund my money. He still had my 4 old
tires as they had not been picked up for recycling yet. Actually he'd
put the donut back on where the flat was. He was actually serious when
he said that but I said that it was an unacceptable solution and was
quite surprised Sears would do such a thing.

They then said that it was Sears policy for all 4WD cars to not mount
new tires if you don't purchase all 4 of them new from Sears. When I
asked to see this in writing they flipped through there 'Ops and RMDS"
binder and could not find anything. I pointed out that there is
nothing prominently displayed in the area that a customer could see
that this was supposedly their policy. After a few minutes they said
they remember seeing something to the effect about the 'policy' on
their intranet. Again I said, I as a customer have no access to Sears
intranet and it wouldn't matter anyway - it should be displayed on a
wall somewhere so that a customer can see/read it and not just take it
at face value from a Sears technician. They were unable to produce
this mystery document from their intranet.
The Auto Center Manager did agree that it should be clearly available
for a customer to see and read (I'm surprised he even agreed about
this).

In any event, I called my local Mercedes repair center and asked them
about the 4WD issue and what they do/recommend when only 1 tire is bad.
He said that they recommend replacing tires in pairs on the same axle.
Which is what I offered to Sears yesterday and they declined to do
that.

The Auto Center Manager took me aside and said that if I show him the
owners manual or he can chat with the MB technician about replacing
tires in pairs (and not all 4) then he really owes me some money. At
this point it sounds like he would refund the two tires (and associated
balancing and disposal fees) and still let me keep the tires.

QUESTION: there is nothing about any of this in the manual, other than replacing
the front tires in pairs (what I had wanted to do).
Does anyone know Mercedes recommendation or restriction on replacing
just one tire? Do all 4 tires need replacement, just those on the same axle,
etc. Is this listed online somewhere where I can find it?

Thanks!
Walter