"SINGLE AXLE TRACTOR" How different does it handle? ??

Accidental Trucker You are wrong about Oregon weights. Triple trailers can have a gross weight of 105,500# on 7 axles at 100 foot wheelbase. That would be a single drive axle tractor. I drove thrm for 10 years over Government camp and I-5.

 

I'm guessing that 1mpg gain was based on both loaded and unloaded driving?

 

Traction has two huge factors foot print( how many square inches of surface area touching the road) and ground pressure ( how much weight you have per square inch) . More tires have more surface area , but half the ground pressure. So if the load was the same , and legal to be pulled by a single axle . The single axle would have twice the ground pressure. On dry flat ground it would be a wash. That said I have had a tandem axle get "hung up" because of the second axle . Not letting the axles flex to remain in contact with the ground. Several manufacturers are pushing 6x2 set ups ( a single drive truck with a tag axle) . These really need to be on lift axles, to improve ground pressure .

 

Spreading out the weight over more axles has its advantages too. In the early 2000's a lot of loggers in Western Canada went to tri-drive trucks (3 live drive axles, 1 steer. 4 axles total on tractor). My dad said he could barefoot into a lot of places that he had to chain up his tandem drive trucks. I think a lot of that has to do with spreading the weight out over another axle plus having the tractive advantage of 4 more drive tires.

 

He was floating because the was nothing to grip. Reason you will see farm tractors running up to triple tires per wheel end . Trying to float across freshly turned ground .But both are off road apps.

 

There's a guy in Western Alberta who had a custom Peterbilt with 4 live drive axles and single steer axle. There's a few pics of it on Hank's Truck Forum. I'd post a pic of it but he'd prefer that the images not be distributed off his website. Just thought it was pretty gnarly. I think he was allowed to operate it on the highway with an OD permit but I can't confirm that 100%

 

I run 105,500 gross every night in North Dakota with a single axle and triples. All depends on the state.

 

Here is what I drove the first day we got it and the first time I ever driven a single axle... Goose neck with no brakes and a lot of snow

Edit: turns on a dime rides stiffer because of the single axle absorbing every pebble

 

Correct, it was an average based on our IFTA miles, running unloaded was probably better than 1mpg, running loaded probably a bit worse? But that is what it worked out to. Also keep in mind "singling out" a tandem truck you keep the original rear drive axle, when you order as S/A truck, you get the RS230 that #### rear is about half again the size and weight of a regular half a tandem set.

I always wondered how much more parasitic loss that axle has over a standard rear.

 

http://www.odot.state.or.us/forms/motcarr/od/2805.pdf

From the Oregon extended weight permit:

"Power units must be equipped with a tandem drive axle except: Power units of doubles placed into service prior toApril 1, 1983, may have a single drive axle and operate over 80,000 pounds."

A little awkwardly worded, but abundantly clear that single drive axle trucks are no longer legal, unless grandfathered in.