Tires: tire size, jeep grand cherokee laredo, jeep grand cherokee

Question
I have a buddy who owns an '04 Jeep Grand Cherokee Laredo.  It currently has P225 75R 16 tires that need replaced. He's found a set of used P225 75R 15 tires that he's considering buying and I'm trying to tell him not to do it.  This size of tire for an SUV doesn't seem to be safe or compatible with the rims (stock) he has.  I can't get him to listen to me, so want your thoughts so I can give him direction from an expert.  Thanks.  

Answer
Scott,

First, he has 16" wheels and 15" tires won't physically go on the rims - they will not mount.

But aside from that, he is looking at tires that have a lower load carrying capacity and overloaded tire failures sometimes have tragic results.  To prove it to him, have him look at the load index of both tires.