Can you go over 12k pounds on steer tires?

Depends on everything, tire rating, axle rating, etc.... probably have to permit it.

 

I'm over 12k every day, sometimes over 13k. Never been bothered yet. Doesnt mean tomorrow I won't though.

 

I used to do it all the time, never was bothered.

 

It depends on your equipment like @Powder Joints says.
In the past 12K was the limit, now is depends on your equipment with your load and your location when the cops/DOT look at you.

There is getting away with things and there is legal. They are not the same and one doesn't mean the other. Everyone is speeding some, all of those people not getting speeding tickets doesn't mean speeding is now legal.

 

My steer axle is rated for 13,200
My steer tires are rated for 14,320
The weakest link is the axle rating so maximum I can scale is 13,200.

One of the reasons I chose a long wheelbase tractor. I can have 34k on the drives and 300 gallons of fuel and still stay under 12k on the steer.
Main thing you need to do is find the perfect spot to set your 5th wheel at. I set mine 4+ years ago and haven’t moved it since.

For me running steer axle/tires at maximum weight is a dangerous habit. Especially with summer heat upon us. Nonetheless if you don’t have an option make sure you check tire pressure regularly and replace them when you start getting abnormal wear.

 

The 860 Volvo I had at my last company was in the mid-12k range on the steers pulling an empty flatbed. Loaded I was in the low-mid 13's. It was spec'd with a 13,500 front axle and the company had tires just for the Volvos that were a heavier load rating. There is no 12k lb regulation about steer axles, as long as the weight rating on the equipment isn't exceeded, you can exceed 12k.

 

This is

A weird one to me, how do long wheelbase trucks stay within the length law limits?

 

I don’t understand your question..

 

Don’t go on the roads that limit overall length.

When I pulled flatbed out west we had to be 12.5 to 13 on our steers when we maxed out our 7 axle inner bridge in order to gross 105k. Running around the Midwest at 80k gross I always had my fifth wheel to where I’d be 12300 on the steer when my drives were at 34k. That way I had a little wiggle room if I was maxed out at 80k.