Tires: Using different tires than whats on my van, lumina apv, size rims

Question
QUESTION: I have a 2003 Montanna van.  My tires now are P225/60R16.  My question is can i use tires lower P numbers or lower or higher R numbers.  I know nothing about tires and the men in my life are not alot of help to me.

ANSWER: Sherry,

DO NOT change tire size.  There are load carrying capacity issues and clearance issues that are just too complicated to explain in a short Q&A format such as this.  

- BUT -

P225/60R16's are incredibly popular, so you should be able to find what you need without much difficulty.

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QUESTION: Ok sorry for sounding stupid but if i find tires that are used for a season not on rims how do i know what size rims i need or will any 5 bolt rims work?

Answer
Sherry,

Rims are also an area that is too complicated for a simple Q&A.  But here are some guidelines:

If the rims do not go on a GM, they will not fit.  Also, the seller should indicate they fit a GM minivan like yours - A Transport or a Lumina APV, etc.  If the seller doesn't know, pass them by.