BFGoodrich Tires | Ask the Experts

Plus Sizing Made Easy
June 25, 2003

BFGoodrich tire expert Jon Henderson answers your questions about putting larger diameter wheels on your sport truck.

First, the good news: BFGoodrich® Tires offers a range of g-Force T/A®^KDW plus-size tire packages specifically designed to enable you to bolt on larger diameter wheels to most late model pickups and SUVs without fender well clearance problems (see accompanying chart) or throwing off your speedometer by more than a few percent. In some cases, 4-6 inches taller. Which means you can make a major transformation in the appearance of your vehicle without doing major surgery. But you will probably suffer some loss in ride comfort with bigger tires and wheels.

That's because your wheels get heavier as they get bigger, Henderson says. "That means adding unsprung weight to the vehicle, which adds load that the suspension wasn't designed for." Also, the plus-size tires typically have shorter sidewalls.

Henderson went from the stock 16-inch package on his 1999 Chevy Silverado to 18s, adding 88 pounds of unsprung weight to the vehicle. "That's 22 extra pounds of unsprung weight per wheel," says Henderson. "Added weight makes it that much harder for the suspension to react to the input of a bump or a directional change."

But Henderson says the difference is not as great as you might think, even with the maximum size available.

"I tried 24s on my truck (up from 16s OEM) and expected the ride to be like iron. Instead, I was surprised at how comfortable they were, even though the sidewall is only three or four inches high."

Even with BFGoodrich g-Force T/A®^KDW tires specifically designed for plus-sizing,
it is essential to have a tire expert trial fit your plus-size wheels and tires to make sure there are no clearance problems or other issues that could affect the safety of your vehicle. For example, even a small difference in wheel offset (how deep the bolting surface is set within the wheel) can sometimes create clearance and safety issues.

"BFGoodrich plus-size tires are designed to be within three to four percent of the dimensions of the original equipment tire," Henderson says. "That makes clearance problems a non-issue with most late model pickups and SUVs, provided that you stay with the stock vehicle height."

Henderson says speedometer accuracy is not a problem with bigger sizes, for the same reason. But he recommends suspension upgrades to cope with significantly increased tire-wheel package weight.

"If you're going to go up several sizes in tire-wheel size," Henderson says, "you should consider upgrading your shocks and maybe even the springs to help the suspension cope with more weight than it was designed for."

Also, Henderson says, upgrading the brakes is a good idea if you're going to bigger wheel sizes and plan to use the vehicle for towing, such as towing a boat.

Henderson cautions that you must take into consideration a host of factors before lowering your vehicle's ride height for a more aggressive look — a popular move for sport truck owners and builders. "If you change the ride height, all bets are off," Henderson says, in terms of clearance, comfort and handling. Always consult an expert to see which tire size and wheel offset will work best for the ride height you're aiming for.

Chart of BFGoodrich® g-Force T/A® KDW plus-size fitment options for some popular pickups

NOTE: Customization of Tires, Wheels or Suspension on SUVs and Light Trucks:

Due to their size, weight and higher center of gravity, vehicles such as SUVs and light trucks do not have the same handling characteristics as automobiles. Because of these differing characteristics, failure to operate your SUV/truck in a proper and safe manner can increase the likelihood of vehicle rollover.

Modifications to your SUV/truck tire size, tire type, wheels or suspension can change its handling characteristics and further increase the likelihood of vehicle rollover. Whether your SUV/truck has the original equipment configuration for tires, wheels and suspension or whether any of these items have been modified, always drive safely, avoid sudden, sharp turns or lane changes and obey all traffic laws. Failure to do so may result in loss of vehicle control leading to an accident of serious injury or death.

See Archives 2007 2006 2005 2004 2003 2002