LAVAL, Que. – A presentation on the results of a University of Laval engineering study concludes wide base tires cause less surface damage than duals.

But tire manufacturers and carriers will have to wait for the full report, further deep thinking by Transports Quebec and an industry/government get-together before learning whether the new generation of wide base tires will be granted the same load limits, year-round, as duals.

Manufactures, including Michelin, Bridgestone/Firestone and Continental Tire North America tout the tires as superior alternatives to duals, citing increased comfort and stability, weight savings of about 454 kilograms per truck for a four-axle switch and fuel savings as high as 10 per cent.

The tires are already legal everywhere in the United States at load limits competitive with duals, according to Ralph Beaveridge, director of marketing – truck tires for Michelin North America (Canada) Inc. Existing Canadian regulations, which reflect the additional damage-potential of the old 65 series of large tires, limit the per-axle load when running wide base tires to 9,000 kilograms in Ontario, 8,000 kilograms in Quebec and just 6,000 kilograms per axle in the rest of the country. For inter-provincial carriers then, the load penalty makes running wide base tires uneconomical. The load limits are competitive for U.S.-bound loads, except when spring thaw restrictions are in effect.

Earlier research done at the Virginia Polytechnic Institute and State University showed that the new generation of wide base tire was not more damaging to the road base than duals. The study, says Beaveridge, “essentially shows that there is no significant road damage caused by wide base tires compared to duals. I like to refer to the wide base tire as damage neutral.” Canadian Transport Ministry pavement engineers, however, zeroed in on the absence of data on the tires’ effects on the road surface, this prompting Transports Quebec to commission the University of Laval study.

Results of the University of Laval study, which compared 11R22.5 and 12R22.5 duals against the 385/65R22.5 large and the 455/55R22.5 extra large are months overdue, but a 19-page paper prepared by the researchers states that the 455 tire, a member of the Michelin X-One family, causes less vertical deflection (for discussion purposes this could be thought of as less stress or damage-potential) of the top 25 millimetres than either of the dual tires.

The study would seem to contradict the Virginia Polytechnic study results when it says that the duals cause less roadway base deformation than the extra wide tire.

“Virginia Tech concluded that for pavement damage to become an issue, it has to happen at the level of the substructure, because the road surface is a wearable surface. In warm weather the surface will start rutting at any loads. The rutting doesn’t become a permanent problem until the substructure is damaged,” says Beaveridge.

The full University of Laval report might be issued in May or June, says Gervais Corbin, who is responsible for the weights and dimensions dossier with Transports Quebec.

“We are still waiting for the complete reports. Our experts will study it.”

As soon as the report is issued tire manufacturers, trucking companies, Transports Quebec and the University of Laval researchers will get together and try to reach a consensus on the meaning of the study results, according to Corbin. Other Canadian MoTs will be watching closely for Quebec’s decision.

Meanwhile, as many as 10 Quebec trucking companies, including Transport Gregoire, Cascades, Transport Robert and Trans West, and companies elsewhere in Canada, are using the wide base tires. Some were not the least bit amused that they had to take them off during this year’s spring thaw, says Beaveridge.

One user, Dan Freight in Joliette, has been collecting wear data and driver comments on stability, handling, traction and unusual performance conditions for Michelin and Bridgestone/Firestone.

“So far, we have had a good response from the drivers, who like the handling and performance,” says Brian Rennie, Bridgestone/Firestone’s director of engineering.

Beaveridge, who has been pursuing this issue for more than 18 months, is excited about the University of Laval paper, which he understands as having concluded that, in sum, the tires are no more damaging than duals, regardless of load or tire pressure.

He is also rather frustrated at the reluctance of Canada’s MoTs to accept the tires.

“The government should be jumping for happiness that they can allow these results,” he says.