Sliding Tandems vs Spread

2016 WESTERN TRAILERS 48 ft For Sale in Boise, Idaho

That looks like a sliding front axle. Usually when the boxes are mounted in the center and they have that low flap bracket on the front axle it’s a slider.

 

I have always preferred to have my drives as heavy or heavier than the trailer axles when possible. I just don't like that tail waggin the dog feeling when close to 40k on the spread, so I tried to load accordingly. If you were say 35k on the spread you could slide the front back to wherever you needed to be to get it to 34. It didn't always work that way, but sometimes. Also, in Idaho anyway and I think most NW states, you could go 38k on 8+' spread, and 39 on a 9+ spread. That was handy sometimes as well, and those are some of the reasons why I would go with the back axle as stationary. Of course you can get them so both axles slide independently as well.