In some western states you can go over 80000 on a spread axle trailer.We run to the northwest doing ltl freight every other week and usually weigh around 85000 on a 53ft. reefer with a 12 ft. spread.Sure have to know what your doing when loading a spread so you don't get over on the drivers.

 

There is also another setup, a spread axle with a front or rear axle slide, so you can slide it closed like regular tandem and run 34 000 or spread it out and run 40 000, some place like manitoba canada don't allow 10 foot spread axle tandem trailers at all, its either a closed tandem or tridem with 3 axles.

All we have a is fixed spread axles so we can't run into manitoba at all.

I think the only way it would be legal is too dump the air from one axle and chain it up off the ground and then run 20 000 on the other axle


I have also heard manitoba has a special permit that allows 26 000 on a spread axle but i don't know.

 

Spreads react differently to how they are loaded, sometimes they will pivot on the front axle and sometimes on the rear, depending on the weight on each axle which makes a differenc both backing and going forward, so companies are kinda wary about putting newbie drivers on them. And let's face it, a lot of the drivers out there are newbies so that's why you see more tandems than spreads.
Spread is the only way to go, cuts out saying (if you are going to load something 15 feet long and bringing you close to gross) "should I sit it there or move it back four inches".