What's with all the axles?

OK, so we call them 18 wheelers. I'm based in the SouthEast and have run all over and traveled all over all my life. Most places OTR trucks have 18 wheels, 5 axles. Other than the rare specialized or heavy haul truck that's all you see and of course day cabs with single screws and shorter trailers.

Every time I travel out West, especially the mountain states and NW I see tons and tons of axles on trucks. Lots of lift axles and I can sometimes figure out why but a lot of times they are just regular vans or reefers with 3 or 4 axles and seems like a majority of the tractors out there have 3 drive axles, usually one lifted. I even see shorter trailers that often have 3 or more axles, bull haulers with triple axle trailers, etc.

Why? Everywhere I go seems like the limits are the same, 80k trucks. What are all the extra axles for if you can balance most loads and survive the weather with a typical 5 axle, 18 wheel setup?

 

I have seen those trailers with 10 axles in Michigan. Specialized, dump haulers and the like usually aren't they?

It just seems weird to me to see regular vans and reefers with all the axles.

So, let's take a bull hauler trailer. Why 3 if most do it with two? I mean trailers full of cattle are gonna weigh pretty close to the same aren't they?