Option is to buy 225/40/17 slightly used for very good price or pay full price for 225/45/17 or 215/45/17

 

find yourself a tire size calculator for comparison of overall diameter etc and see what the difference is.

 

what wheels? oem?
i've ran 255/40/17s on 17x9 +22 in the fronts

 

AP2 wheels. Calculator says -2.2% difference in diameter. 255/40/17 show +1.7 difference by the way.

 

damn just missed local sale for 225/45/17 tires i needed.....2 for 50 bucks with 1k miles on them ! 225/40/17s still available though...

 

I would not do it personally. The sidewall will be shorter by 6.75" which would mean over half an inch smaller overall diameter. Plus, what would you run in rear? Different model tires? Tires are not anything to cheap out on.

 

same model for rear. set is 225/40/17 and 245/40/17

i am picky about tires and usually dont go cheap, but its a really good deal....

 

Your numbers make zero sense!
Sidewalls for 225/40-17 will be shorter than 225/45-17 by .05*225mm, or 11.25mm, just under 1/2". Difference in diameter will(obviously!) be twice this amount, or just under an inch.
Agree with the point regarding running compatible front/rear tires.

Q for op: what make and specific model tire are youfinding in225/40-17, and what make/specific model and size rears would you be running them with?

 

Ah, I see. This size pairing is not a problem, other than 225/40s probably wanting a 7.5" wide rim...
Other concern being: what make/model tire? And how does this tire match up with your wants/needs/usage?

 

^Sorry if that was confusing. I was comparing to the stock 215/40/17.