BurbMan wrote:
I would just put it up for sale and not discuss the tires...let the buyer ask how old the tires are, and if it becomes a sticking point in the sale, strike a deal with him then.
Don't forget everything else in the coach is 15 years old too....the buyer may be worried about something else entirely, he may not care about the tires but want a concession on the refrigerator (for example), who knows? The point is don't try to anticipate what the buyer may or may not want, just put it up for sale and go from there.
If you get a buyer on the fence, you could use the "I'll split the cost of new tires with you" as an extra incentive to close the deal.
What BurbMan said! Excellent advice.