Four-wheel-drive pickups and sport utility vehicles (SUVs) add a completely new dimension to the wheel alignment process when they’re equipped with wider or larger diameter tires than the original equipment (OE). More to the point, modern tires are manufactured in various aspect ratios (the percentage ratio between casing width and sidewall height), rim diameters, casing diameters, tread widths, tread designs, load ratings and maximum speed ratings. Of course, tires are an integral part of modern steering and suspension systems, not to mention they are often an equally integral part of modern safety features like anti-lock braking systems (ABS), electronic stability control (ESC), active braking and lane-change warning systems.
Whatever the case, alignment problems caused by larger tires aren’t always apparent on level, evenly paved surfaces encountered during city driving. But a camber angle suitable for an OE-spec tire can cause tire wear complaints when wider tires are installed and driven on crowned paved roads, common in rural areas. If a camber angle causes one edge of a wide tire to carry more weight, that tire edge will wear more rapidly. Similarly, if positive toe angle is excessive, the outer edge of the right front tire will work harder steering the vehicle toward the center of the crowned road. If negative toe angle is excessive, it will cause the left front tire to work harder steering the vehicle toward the center of the crowned road.
These concepts are basic, but they form the foundation for wheel alignment strategies that address tire wear and steering quality issues on four-wheel-drive pickups and all-wheel-drive SUVs. Unlike standard passenger cars, pickups and SUVs are driven not only on smoothly paved highways, but in rough trail and off-road driving conditions as well, which is the focus of this month’s Diagnostic Solutions.
TOYOTA WHEEL ALIGNMENT
Let’s begin by looking at a 2014 Toyota Tundra with about 40,000 miles on the odometer (see Photo 1). The customer has no complaint other than he feels that it needs a wheel alignment check and tire inspection after navigating some rough mountain roads. Following a thorough inspection of the steering and suspension systems, we’ll look at Toyota’s list of optional tire sizes, suspension ratings and body configurations, all of which might require different alignment specifications. With that said, let’s work through Toyota’s recommended alignment procedure and perhaps add a few steps of our own.
Toyota recommends inspecting the tire size and condition as the first step in the wheel alignment process. The left front tire shown in Photo 2 exhibits sidewall scuffing, which commonly occurs on rock-strewn mountain roads. More importantly, the slightly uneven wear, or “chopping,” on the outer tread lugs is normal for four-wheel-drive vehicles with high degrees of camber roll (refer to the Dec. 2016 Diagnostic Solutions article). All of the tires should be inspected for cuts, casing damage and proper inflation. The wheels should be inspected for loose lug nuts, cracking in the lug bolt area, bead chipping, damaged valve stems and mud inside the rim.
Pickup trucks can also have camber and toe angle-related problems caused by heavy weekend loads, which is why I prefer to take tread-wear measurements across each tread bar on all four tires. If all tread bars are wearing equally, I might assume that the right- and left-side camber angles are correct for the tire width, wheel offset and vehicle load. Finally, I rub my hand horizontally across the tread. If the tread feels rough in one direction and smooth in the other, the tire is scuffing over the road surface and creating a toe angle problem. In most cases, wear problems with wide tires can be addressed by adjusting camber and toe within minimum and maximum allowable OE specifications. See Photo 3.
Click here to read Part 2 of this story.