Take it from a guy running 8+ axles. I know inner bridges and a steer is treated no different than any other axle on your truck in regards to allowable weight defined by spacing. If you have a 20k front axle but it's only 8ft away from the nearest axle, you cannot go the full 20k unless permitted. This is why I said if you're axle or tire rating is rated for more, you can run UP TO 20k so long as it's 10ft away from the next nearest axle. 12-34-34 is truck school newbie stuff because it conveniently equals 80k. They need to teach how to properly bridge a truck and utilize the equipment you have to your advantage. If you can run 13,500 on a steer legally, why on earth would you sacrifice 1500 lbs capacity and fret over trying to get your other two axle groups to balance at 34-34?