It's not the weight for COG purposes or wind drag, it's just one HEAVY sucker to be tossing up or lifting up and tossing down, particularly in cold/freezing weather. OEM rims and tire aren't so bad. The Scorpion (below) is running beadlock rims and 34's, each of which weighs nearly 150 lbs.
That's one heavy spare to be lifting up and down, and it maxes that capacity of the rack all by itself without the other gear I keep up-top.
I keep a Tuffy Box on top loaded with recovery gear including an X-Jack, jumpers, tow strap, extra shackles, etc. I also mount a power tank to the OEM rack and keep 30 liters of fuel on top, and a Hi-Lift jack and shovel. What would I do with all that if I had a tire up there?
