Have you ever noticed most tire manufacturers publish various specifications for each of their sizes? Those specs can include overall diameter, tire weight, tread depth and load specifications. One of the specs you normally see is “Approved Rim Width.” This informs you of the allowable wheel widths for a given size.Typically, tires that are mounted on the narrower end of the approved range provide more ride comfort, while the same size can offer increased cornering capability when mounted on the wider end of the scale. A tire mounted on a width in the middle of the range will offer a balance of ride comfort and handling.WHY ARE THERE APPROVED WIDTHS?
When tires are designed and developed, it is important that the sidewalls remain mostly perpendicular to the ground to achieve optimum performance. Tires are not designed to perform on wheels outside of the approved range. Mounting tires on too narrow or too wide wheels will put undue stress on the shoulder and/or bead area. Over time, the tire may develop cracks or fail in those areas. Tires installed on improper width wheels can develop an irregular wear pattern as well. Typically, the taller the sidewall, the wider the range of wheel widths are allowed.
“Mounting tires on too narrow or too wide wheels will put undue stress on the shoulder and/or bead area.”
A popular fad at the moment is called “stretching.” This involves mounting a tire on a much wider wheel than is approved. The result is a stretched look to the sidewalls. Mounting tires on wider-than-approved wheels can be dangerous for shop technicians. The extreme angles could cause the bead to rupture upon seating, resulting in injury or death.
Over time, the extreme angles of the sidewalls can cause fatigue in the shoulder and/or bead area, as mentioned earlier. This can result in catastrophic tire failure and could cause injury or death to the occupants of the vehicle. Additionally, stretching can result in belt separation as the tire will have a tendency to put more stress on the edges of the tread instead of a flat contact patch. In either case, tires that fail due to being mounted on wheels too wide are not eligible for warranty consideration. Is your shop prepared to handle the liability?
We recently saw 35×12.5R20s mounted on 20×14 wheels. The maximum approved width is 20×12. Don’t do this!”PINCHING”
Pinching most often occurs when tires are mounted on wheels that are too narrow for the size. This is often the result of the customer wanting to upgrade to a wider tire, but wanting to save money by keeping the factory wheels. Before mounting wider-than-stock tires on the factory wheels, you must confirm the original equipment wheels are wide enough for that size tire.
A common mistake is mounting 33×12.5R20 on factory wheels. Atturo, like most other manufacturers, requires an 8.5 inch wide wheel for this size. Mounting tires on wheels that are too narrow can cause a “wallowing” sensation for the driver as the sidewalls are no longer perpendicular to the ground. This condition is especially true of lower profile tires. Additionally, rapid center wear can occur due to the additional pressure in the center of the tread. And as mentioned before, bead and shoulder fatigue can occur over time.
While pinching and stretching may be fun to do to a baby’s cheeks it is downright dangerous for tires. Your technicians’ and customers’ lives depend on you fitting their tires to approved width wheels only. While customers may want to install the wrong size tire for their wheels for style or budgetary reasons, taking some time to educate consumers about the dangers can avoid potential problems down the road.Visit our Dealer Locator to find your local Atturo Tire Dealer who will help you fit the right Atturo tire properly.