Newly Tired Dually

Putting new tread on a dually pickup truck
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Ever notice how different makes of footwear vary slightly in fit, even if they're both exactly the same size? That's even truer when it comes time to replacing your tires. Recently we had to put some fresh rubber on a '96 Dodge dually pickup, but found that we couldn't just use the same code on the sidewall of the existing tires (LT235/85R16). Those, from a different manufacturer, were larger than the factory-recommend size (LT215/85R16).

Same But Different

That's because the spacing between the pairs of rear tires was not the same for the two different companies (especially around the sidewall bulges at the bottom, where clearance is critical, particularly when you add a heavy load). On the older Michelin tires, the spacing was about a half-inch, but new Bridgestones with the identical size code would have overlapped about an inch. (And there's no shoe stretcher available to make these booties fit better, either.)

Getting down to the nitty-gritty numbers, if we had used the old tire's sizing, the Bridestone's Dueler A/T Revo would be 4.9 percent larger in overall diameter than the recommended OE tire size, and the company engineers indicated that we needed to stay within +/- 3 percent. We also considered going to a LT245/75R16 size, but that would have required two-inch spacers.

Sure, we could have added spacers to make sure there's sufficient daylight shining between the sidewalls, but we decided to start with a simple stock setup on this go 'round, partly because this work truck is used for hauling heavy loads (boat docks), and we were more interested in durability and reliability than appearance.

Downsizing?

Were we disappointed by going to a slightly smaller tire than what was already on the vehicle? Not at all. We noticed an immediate improvement in handling. A wider and taller tire can create more rolling and turning resistance so, while the truck used to track like a freight train with the old tires, it was anything but agile when changing lanes. By comparison, the Bridgestones provided a much crisper turn-in.

Nimble handling and a diesel dually are not normally paired together, but we should point out that the new Bridgestone Dueler A/T Revo is specifically designed to provide a powerful grip and smooth ride for premium performance, both on and off-road, even as the tread wears.

How so? The dual-layer tread compound has an inner tread layer that is exposed as the tread wears, enabling the tire to better grip the road. For enhanced off-road durability, the tire incorporates a two-polyester body ply design. The Dueler A/T Revo comes in 15-, 16- and 17-inch sizes for a total of 13 P-metric and 14 light truck applications, and thus fits a wide variety of domestic and imported pickups, SUVs and light trucks. The tire is available in load ranges C, D and E in the light truck sizes. Bridgestone's Dueler A/T Revo carries a UTQG rating of 500 A for traction and B for temperature and comes with a 50,000-mile limited warranty.

Tire Life

Speaking of miles, what's the best way to prolong the life of any tire? Rotating them preserves balanced handling and traction, and evens out the wear. Keep in mind that the fronts get scrubbed more from steering action, and need to be relocated to the rear every 3,000 to 5,000 miles, even if they don't show obvious signs of wear. With a dually, however, the rotation pattern might be slightly different, depending on the wear.

For a dually with normal wear, the inner tire on the rear should be moved to the front, with the outer rear one on each side taking its place. The fronts are then relocated to the outer rear position. However, if the rear tires are showing irregular wear (more than the front) then the inner rear tire should trade places with the outer one. On the other hand, if the fronts show irregular wear, swap them with the outer rear tires.

Does it matter if the tires cross over from side to side? Years ago, tire manufacturers were concerned about tread splices opening up and tires were marked with a direction of rotation. With today's tires, this is not a big concern. They usually can be rotated to any appropriate wheel position and, in fact, it's a good idea to move a tire to a position that allows it to roll in the opposite direction (which is what would eventually happen with the normal rotation pattern described above).

Why Dually?

Why even consider having dual tires on a pickup in the first place? They are used on the non-steering axles of heavy-duty trucks to increase their load capacity and help maintain vehicle drivability in the event of a flat rear tire. Placing two tires on both ends of a single axle nearly doubles the weight that the axle can carry and allows three properly inflated tires to temporarily carry the weight originally allocated to the four tires if a rear tire loses pressure or goes flat.

By using the same size tires and wheels singly on the steering axle and dualed on the drive axle, the load capacity of the vehicle is increased, all tires can be rotated periodically and the vehicle can be outfitted with a single spare tire and wheel. However in order to accommodate dual rear tires, these vehicles are equipped with distinctive wheels, as well as unique front and rear axles. All of their wheels feature extreme offsets to allow them to be installed center-to-center on the rear axle. In effect, the inner wheel uses extreme positive offset to allow the tire and wheel to be placed traditionally on the axle (with its backside over the axle), while the outer wheel uses extreme negative offset and is installed on the axle with its center against the inner wheel's center and its "backside" facing outward.

Obviously, all four tires on the rear drive axle must be equivalent. Ideally this means tires should be the same model and have identical remaining tread depths. Any discrepancies between the four tires will result in the taller tire(s) being forced to carry more than their fair share of the load. It's also better to have the fronts the same size as well, so you can interchange the tires between any location on the vehicle.

Resource

Bridgestone/Firestone North American Tire, LLC, www.bridgestonetire.com

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