MacKinnon Transport in Guelph, Ont., specializes in hauling heavy loads, primarily on flatbeds. And when you’re hauling between Ontario and Michigan, there’s no better setup than a nine-axle B-train.

Michigan’s regulations are unique within the United States, and they’re quite different than federal regulations governing Interstate highways.

In Canada, Ontario’s regulations are very different than those specified in the RTAC agreement. Michigan allows up to 11 axles that, if put together properly, can result in a truck at 164,000 pounds (74,389 kilograms) even on Interstate highways, where grandfather rights supersede federal regulations.

Ontario, while allowing trucks spec’d to interprovincial limits, also allows other configurations. On these, there is no limit on the number of axles although axle spacing and front-axle weight are critical in determining gross weight.

Axles are heavy in Ontario-10,000 kg on a single and up to 19,100 kg on a tandem. In Michigan, axles are lighter-only 5896 kg on a single and only one tandem at 14,515 kg on any configuration.

But Michigan allows a single axle at 8164 kg (18,000 pounds) if the spacing is at least nine feet away from any other axle.

MacKinnon’s nine-axle B-trains operate at weights up to 62,300 kilograms in Ontario and just over 62,000 kg (137,000 pounds) in Michigan. They’re held to 59,000 kilograms in Quebec because they are not the same as B-trains under the interprovincial agreement.

With a tare weight of 22,000 kilograms, maximum payload between Ontario and Michigan is just over 40,000 kg or 88,500 pounds. It’s less on hauls into or out of Quebec.

MacKinnon has two dozen of these B-trains. The lift axle on the lead trailer is nine feet in front of the three-axle group and just over nine feet from the tractor tandem so it qualifies for Michigan’s 18,000-pound weight limit.

The lift axle is raised in Canada as it isn’t needed. In fact, because of Ontario’s axle-spacing rules, allowable gross weight would fall if the axle were down.

The three-axle tridem is allowed 39,000 pounds in Michigan and the two fixed axles on the rear pup, also spaced nine feet, are allowed 36,000 pounds.

Some carriers operating between Ontario and Michigan use a slider axle on the pup so that they can reduce the spacing when in Ontario.

But sliders cost money and add to tare weight.

For the right axle-load distribution, the fifth wheel has to be set 10 inches ahead of the centre of the tractor’s tandems. Steering axles carry 5500 kilograms (just over 12,000 pounds).

Length limits are important to the spec’ing of these B-trains. In Ontario, because they are not spec’d to interprovincial limits, the vehicle’s overall length is held to 23 metres.

In Michigan, there’s no overall length limit (on most roads), but maximum trailer length is 28-1/2 feet.

MacKinnon’s lead trailer is 26 feet, 6 inches, and the rear pup is 28 feet, 2 inches. The effect of these various length limits is that the longest tractor MacKinnon can use has a wheelbase of 219 inches.