This is an interesting topic, one I am sure has been beaten to death by anyone remotely contemplating the jump to 40's and does not regularly wheel with guys/gals who are running 40's. I have run both and have a 2008 now that runs 40 inch MTR-K's. The equipment changes needed to safely run 40's without being freaked out at every ledge is substantial for sure. 1 ton full float axles, wider WMS-WMS, gearing, driveline upgrades, the inevitable drain on power, (because we all want sports car pep) with our now bloated 6300 plus pound, 40 inch tired trail eating monsters, breaks, a well engineered suspension, and steering upgrades... Is it worth it? Depends... I ran 37's for years, and if I was going to drive a jeep on the road a lot I would just stay with 37's. My last jeep with 37's drove great, and wheeled just fine. My new jeep has 40's, was built from the ground up for that very purpose, is a blast to drive , handles very well, and has an unhealthy desire to stop at every gas station and say hello, how you doin....
Some people have a ton of knowledge, drive really well, typically wheel with other jeeps on 40's and can afford to sink the price of a house in North Carolina into a jeep... Building a jeep to run 40's doesn't make me or anyone else a better driver, nor does it make me or anyone else someone to be looked up to, heck, I know plenty of guys who can't drive for crap, but rely on 40's and HP to look good. The perfect line, thats impressive to me, if you can pick and run the perfect line, who cares what size tires your running. I personally will look you in the face and say "that was a great line" and I will gladly follow you, no matter what size tires your running.
Performance is subjective, but it starts with equipment that is matched, balanced, stable. In the end equipment will be measured on the sliding rule of the drivers ability to actually control all those parts and make them function well in the environment He/She has chosen to utilize them on. My .02 Can you afford to build a sound jeep capable of handling 40's???? If so, go for it, if not, half hearted attempts to look good running 40's will cost you in the end when you would have been better off running the perfect line on your 37's... FLAME ON
