Tires: changing tire size, aftermarket rims, stock rims

Question
I'm sure the wheels are at least a 7 1/2  diameter and if they are will this work?
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The text above is a follow-up to ...

-----Question-----
I have a 2004 trailblazer with 245/65/17 tires on it . My father has four new tires 265/65/17 could I use these on my trailblazer.....
-----Answer-----
Michael,

If I have this right, your vehicle came with 7" wide rims.  A P265/65R17 requires a minimum of a 7 1/2" wide rim.

So, no, the tires will not fit.

Answer
Michael,

Everything I have looked up says the stock rims on a 2004 Trailblazer are 7" wide.  7 1/2" doesn't make sense, unless the rims are aftermarket rims.

However, there is likely enough room under the fenderwells for a tire 2 sizes larger, but that is not something I can guarantee, as the folks that know how large the fenderwells are think this information gives them a competitive edge and do not share it.

At this point I can't recommend you try this unless you verify that the rims are indeed 7 1/2" wide.  If they are too narrow, the tire tread will be "arched" and the vehicle may be a directionally unstable, especially in crosswinds.  In other words, the vehicle may seem to wander even though it is pointed straight ahead.  This "arching" will cause the tire to wear predominantly in the center, wearing out more rapidly than normal.