By Ed Garsten
Gannett News Service

MILFORD, Mich. - It's the bling that can result in a bone-jarring bang - plus-size wheels and tires that aren't perfect matches for the vehicles they adorn.

Often clad in chrome, some containing spinning centers, and made popular by the hip-hop community, accessory wheels and tires have become a $3.23 billion business - double what it was a decade ago, according to the Specialty Equipment Market Association, a trade group that represents custom auto parts makers.

Plus-size wheels began gaining fans on the West Coast about five years ago. The fad has been fueled by such TV programs as Monster Garage and Pimp My Ride that showcase customized vehicles.

Plus-size wheels and tires are at least one size larger in diameter than those that were installed as original equipment on a vehicle. Twenty-inch wheels have taken on the moniker "dubs." Plus sizes also have plus-size prices and can cost up to $20,000 for a set of four tires and wheels.

When buying plus-size wheels and tires, consumers must make sure the products have been designed to fit their vehicle, experts say.

Many plus-size products are made by aftermarket suppliers - companies that market parts and accessories that can be installed after a vehicle leaves the factory - and sold by dozens of tire and wheel retailers. Automakers also are increasingly offering their own custom parts brands, including a new line of plus-size wheels and tires from General Motors Corp.

"If you put aftermarket tires and wheels on - it's kind of a crap shoot," said Frank Taverna, GM engineering group manager for vehicle dynamics. "It might work great or it might not. You might have some balance or vibration problems, or speedometer calibration might be thrown off. There's a gamble."

The Specialty Equipment Manufacturers Association denies suggestions that some aftermarket products may present quality or safety risks.

"In no way, shape or form would I allow wheels from our manufacturers to be put in a nonsafe category," said Carl Sheffer, vice president of original equipment manufacturer relations at SEMA.

David Champion, senior director of Consumer Reports auto test facility in East Haddam, Conn., said GM is right to caution customers that aftermarket tires and wheels could pose a risk.

"The trouble with the aftermarket is there's not an awful lot of testing and regulation that goes into developing the tires and wheel packages for these vehicles," Champion said. "The consumer can go with the aftermarket and maybe void their warranty, or go to GM, buy the tire and wheel package, and keep their warranty intact."

Jim Gutting, director of GM tires and wheel systems, said the performance of electronic devices such as antilock braking and stability control systems can be compromised when plus-size tires and wheels are installed. The exaggerated dimensions of aftermarket tires and wheels can throw off the calibrations of safety devices.

"The (antilock brake system) is calibrated to a certain tire's characteristic," Gutting said. "It's sitting there looking at tire pressure and knows what the properties of the tire are."

Sheffer said consumers can purchase aftermarket plus-size tires and wheels for any American brand, as well as Toyota Motor Co.'s Scion brand, that are built to the automaker's specifications, because of new collaborative efforts.