I have a 2008 LR3 with 255/60R18 tires. Can I replace with P245/60^18 tires?

You can. They will be just a little shorter in height but will work just fine. IMO

Approximtely how much shorter?

Not much at all. You probably won't be able to even see the difference. Let me see if I can find the exact difference for you.

http://www.discounttire.com/dtcs/infoTireMath.dos -- check this out. It will show you the exact differences. The difference in height is just less than half an inch.

Second opinion: dandyoun is spot on. You will never notice a thing. The treadwear from use is more than the difference you have in the tires. I am new here but it has occurred to me dandyoun knows what he is talking about, every time. I have never seen a post of his I disagree with...not that I am any sort of genius but consistent in his advice.

timiwine I think you should click dandyoun a "best answer"...it is the highest compliment you can give him for his effort. Thank You

Thanks for the vote of confidence fordnut.

Well dude credit where credit is due....