Also, you're going to eat more gas. That's all there is to it. You'll eat even more if you increase diameter much from about 30".

Plus, your speedo and odo will be off.

For example, a 285/60-18 is 31.5" in diameter, which makes roughly 98.91 inches per rotation.

A 245/60-18 (stock size) is 29.7" in diameter, making it 93.258 per rotation.

So, when the speedo reads 55mph, you'll actually be doing 58.3mph.
And, when the speedo reads 75mph, you'll actually doing 79.5mph.

I don't care, and I compensate for my 31x11.50-15 LTBs, but it's easy to forget and get pulled over.