The Danger of Dubs
By Dan Kahn, Contributor | Published Jan 27, 2005
1 Rating
Dubs. Blades. Twenties. Rims. Unless you've been hiding under a rock for the past five years, you already know those weird words are nicknames for gigantic wheels. What started as an oddity at the occasional car show has evolved into a booming business, and everyone from tire retailers to car manufacturers have jumped on the bandwagon. Big wheels grab lots of attention, but are they safe? We asked a handful of industry experts, and their answers were eye-opening.
Bigger Isn't Always Better
Big-inch wheels started showing up on production cars in the late '90s, and by the end of the decade 18s were commonplace on most sports cars. Nobody expects a Porsche or Ferrari to ride like a marshmallow, so engineers design the platform to work with big wheels and low-profile tires. Unfortunately, the same principal does not apply to big trucks and SUVs.
"Suspension works as a system, and if you compare a Corvette to a truck, the Corvette is designed to work with big wheels and low-aspect-ratio tires," explains Frank Traverna, GM Engineering Group Manager for Vehicle Dynamics.
"The wheels that come on a new car or truck are specifically developed to work on that particular vehicle," Traverna says. "It's a full system approach. Balancing ride and handling is a trade-off, and you can't get a free lunch. When you switch to a low-profile tire, you increase the steering response but degrade ride and isolation. Isolation allows you to hit a pothole and keep rolling without bending a rim or getting bucked out of your seat. Eliminating that safety margin allows the force of a rough road to pass into the chassis. You could flatten a tire, bend a rim or in a worst-case scenario even damage the vehicle's suspension."
Traverna stresses that all new vehicles undergo extensive handling tests before they end up on the showroom floor. "As a matter of course we drive and engineer vehicles to have a margin of safety during those once-in-a-lifetime emergency situations," he says. "If you take a set of aftermarket wheels and tires and slap them on, it's unpredictable how the vehicle will handle in an evasive maneuver. It may feel like your vehicle actually handles better, but unpredictability can be very bad."
Trading Speed for Beauty
Looking good requires sacrifice, and most wheel shoppers are willing to give up a little ride quality for the look of flashy rollers. A rough ride is annoying, but big rims can also significantly degrade performance and safety.
"Anything that adds weight to the wheel and tire assembly affects acceleration and braking, and it hurts handling as well, since shocks aren't valved to control that much weight," says Ben O'Connor, an engineer for brake manufacturer Baer Inc. "It's not uncommon to gain 40 pounds when swapping a 16-inch wheel out for a 20-incher."
That extra mass hanging from the end of the suspension is called unsprung weight, which cannot be controlled by the springs of the car. Unsprung weight is difficult for the suspension to control, so engineers try to minimize it. It's the reason why racecars use lightweight magnesium wheels when the rules allow.
"If you dramatically increase unsprung weight, it will decrease wheel control," Traverna says. "Putting big heavy wheels and tires on a vehicle that wasn't designed for it can result in significant traction loss while you're traveling at speed. We build a lot of extra strength into our trucks and SUVs, so swapping 16s for 18s won't hurt anything, but bolting on a set of 22s can result in extra wear and tear on the suspension."
As you increase rotating mass, it's also harder for the brakes to stop the wheel from spinning. This can decrease brake life and increase braking distance. The same principal applies to acceleration, because a heavier wheel is harder to get rolling and acceleration is decreased. O'Connor claims that adding a set of big wheels can increase 60-0-mph stopping distance by as much as 20 feet. That can mean the difference between stopping short and being killed in an accident.
Several aftermarket brake manufacturers offer brake kits that help offset the added weight of big rollers. A typical rotor upgrade like the Eradispeed kit from Baer includes 15-inch brake rotors and a caliper relocation bracket, which lends the vehicle enough braking force to offset the added rotating mass. Rotor upgrade kits typically cost around $1,000, and they can be installed in a matter of minutes with simple hand tools.
Computers Can't Keep Up
Moving to a taller wheel and tire package can affect more than ride, handling and braking. Onboard electronics in new cars and trucks calculate vehicle speed based on the overall diameter of the wheel, the final drive ratio of the axle and how fast the wheel is turning. Changing the height wreaks havoc with these computations, and as a result the speedometer is no longer accurate.
Since safety systems like antilock brakes and stability control rely on speed data to keep the vehicle from getting out of control, their ability to function properly is drastically decreased. Throw in added variables like altered wheel mass and tire grip, and the systems many people pay extra for are no longer effective.
Shop Smart
Adding a set of fancy new wheels doesn't have to be a complicated or dangerous proposition. By shopping smart and selecting a wheel/tire package that was engineered to work with a specific vehicle, you can upgrade the looks and handling of your vehicle without taking any chances. Finding a trustworthy wheel and tire shop is the first step in making a smart purchase.
"The key to going with a plus-size wheel is working with a dealer who understands proper fitment and can get you a product that is appropriate to your vehicle," says Matt Edmonds, VP of Marketing for The Tire Rack. "They need to understand unsprung weight and how it can affect handling and braking."
"We always recommend to our customers that they maintain the stock overall diameter," Edmonds says. "A reputable dealer will also consider load capacity, which is how much weight the wheel can hold. Some aluminum wheels are designed to be lightweight and very strong, so they can support heavy loads without increasing unsprung weight. When looking at load capacity, especially if you own a large SUV, consider the fact that once you add gas, people and possibly a boat or trailer, the vehicle can nearly double in gross weight."
Several major retailers like The Tire Rack have comprehensive Web sites that showcase wheels that have already been proven to work on your vehicle, and you can even check out how your ride will look with the wheels bolted on.
Car companies are also getting into the wheel game, and factory-designed and -tested big-inch rims are available right off the showroom floor at your local GM and Ford dealership. The advantage of a factory-approved wheel is that it was designed and engineered by the same people that built your car. Most major dealerships can even recalibrate your speedometer and safety systems if necessary.
Rollin' Down the Road
Remember, riding on big-inch rims may look cool, but those big-brained engineers who designed your chariot spent a lot of time making it safe and pleasant to drive. If you're willing to sacrifice a ride quality in the name of style, fine, but don't compromise when it comes to safety. Find a shop capable of upgrading your brakes and drive ratio as well as the wheels and tires. Now if you'll excuse us, we have to figure out where to get 20s to fit our '74 Gremlin.
Bigger Isn't Always Better
Big-inch wheels started showing up on production cars in the late '90s, and by the end of the decade 18s were commonplace on most sports cars. Nobody expects a Porsche or Ferrari to ride like a marshmallow, so engineers design the platform to work with big wheels and low-profile tires. Unfortunately, the same principal does not apply to big trucks and SUVs.
"Suspension works as a system, and if you compare a Corvette to a truck, the Corvette is designed to work with big wheels and low-aspect-ratio tires," explains Frank Traverna, GM Engineering Group Manager for Vehicle Dynamics.
"The wheels that come on a new car or truck are specifically developed to work on that particular vehicle," Traverna says. "It's a full system approach. Balancing ride and handling is a trade-off, and you can't get a free lunch. When you switch to a low-profile tire, you increase the steering response but degrade ride and isolation. Isolation allows you to hit a pothole and keep rolling without bending a rim or getting bucked out of your seat. Eliminating that safety margin allows the force of a rough road to pass into the chassis. You could flatten a tire, bend a rim or in a worst-case scenario even damage the vehicle's suspension."
Traverna stresses that all new vehicles undergo extensive handling tests before they end up on the showroom floor. "As a matter of course we drive and engineer vehicles to have a margin of safety during those once-in-a-lifetime emergency situations," he says. "If you take a set of aftermarket wheels and tires and slap them on, it's unpredictable how the vehicle will handle in an evasive maneuver. It may feel like your vehicle actually handles better, but unpredictability can be very bad."
Trading Speed for Beauty
Looking good requires sacrifice, and most wheel shoppers are willing to give up a little ride quality for the look of flashy rollers. A rough ride is annoying, but big rims can also significantly degrade performance and safety.
"Anything that adds weight to the wheel and tire assembly affects acceleration and braking, and it hurts handling as well, since shocks aren't valved to control that much weight," says Ben O'Connor, an engineer for brake manufacturer Baer Inc. "It's not uncommon to gain 40 pounds when swapping a 16-inch wheel out for a 20-incher."
That extra mass hanging from the end of the suspension is called unsprung weight, which cannot be controlled by the springs of the car. Unsprung weight is difficult for the suspension to control, so engineers try to minimize it. It's the reason why racecars use lightweight magnesium wheels when the rules allow.
"If you dramatically increase unsprung weight, it will decrease wheel control," Traverna says. "Putting big heavy wheels and tires on a vehicle that wasn't designed for it can result in significant traction loss while you're traveling at speed. We build a lot of extra strength into our trucks and SUVs, so swapping 16s for 18s won't hurt anything, but bolting on a set of 22s can result in extra wear and tear on the suspension."
As you increase rotating mass, it's also harder for the brakes to stop the wheel from spinning. This can decrease brake life and increase braking distance. The same principal applies to acceleration, because a heavier wheel is harder to get rolling and acceleration is decreased. O'Connor claims that adding a set of big wheels can increase 60-0-mph stopping distance by as much as 20 feet. That can mean the difference between stopping short and being killed in an accident.
Several aftermarket brake manufacturers offer brake kits that help offset the added weight of big rollers. A typical rotor upgrade like the Eradispeed kit from Baer includes 15-inch brake rotors and a caliper relocation bracket, which lends the vehicle enough braking force to offset the added rotating mass. Rotor upgrade kits typically cost around $1,000, and they can be installed in a matter of minutes with simple hand tools.
Computers Can't Keep Up
Moving to a taller wheel and tire package can affect more than ride, handling and braking. Onboard electronics in new cars and trucks calculate vehicle speed based on the overall diameter of the wheel, the final drive ratio of the axle and how fast the wheel is turning. Changing the height wreaks havoc with these computations, and as a result the speedometer is no longer accurate.
Since safety systems like antilock brakes and stability control rely on speed data to keep the vehicle from getting out of control, their ability to function properly is drastically decreased. Throw in added variables like altered wheel mass and tire grip, and the systems many people pay extra for are no longer effective.
Shop Smart
Adding a set of fancy new wheels doesn't have to be a complicated or dangerous proposition. By shopping smart and selecting a wheel/tire package that was engineered to work with a specific vehicle, you can upgrade the looks and handling of your vehicle without taking any chances. Finding a trustworthy wheel and tire shop is the first step in making a smart purchase.
"The key to going with a plus-size wheel is working with a dealer who understands proper fitment and can get you a product that is appropriate to your vehicle," says Matt Edmonds, VP of Marketing for The Tire Rack. "They need to understand unsprung weight and how it can affect handling and braking."
"We always recommend to our customers that they maintain the stock overall diameter," Edmonds says. "A reputable dealer will also consider load capacity, which is how much weight the wheel can hold. Some aluminum wheels are designed to be lightweight and very strong, so they can support heavy loads without increasing unsprung weight. When looking at load capacity, especially if you own a large SUV, consider the fact that once you add gas, people and possibly a boat or trailer, the vehicle can nearly double in gross weight."
Several major retailers like The Tire Rack have comprehensive Web sites that showcase wheels that have already been proven to work on your vehicle, and you can even check out how your ride will look with the wheels bolted on.
Car companies are also getting into the wheel game, and factory-designed and -tested big-inch rims are available right off the showroom floor at your local GM and Ford dealership. The advantage of a factory-approved wheel is that it was designed and engineered by the same people that built your car. Most major dealerships can even recalibrate your speedometer and safety systems if necessary.
Rollin' Down the Road
Remember, riding on big-inch rims may look cool, but those big-brained engineers who designed your chariot spent a lot of time making it safe and pleasant to drive. If you're willing to sacrifice a ride quality in the name of style, fine, but don't compromise when it comes to safety. Find a shop capable of upgrading your brakes and drive ratio as well as the wheels and tires. Now if you'll excuse us, we have to figure out where to get 20s to fit our '74 Gremlin.