The pros and cons of modifying your car

Car customization can adversely affect your vehicle

Last updated: February 2014

Lifted suspensions can severely compromise vehicle stability

Car customization is a booming business. Consumers spend billions every year on aftermarket parts. Still, many modifications can adversely affect vehicle performance, raising warranty, legal, and safety concerns.

Will the warranty be voided?

While modifications don't necessarily void a warranty, an alternation that causes vehicle malfunction or damage can void warranties for related parts. For example, some oversized wheel and tire combinations can strike against sheet metal and steering components and cause damage. In this case, the manufacturer is not responsible for the cost of repairs. A safe way to modify your vehicle without this worry is to buy modifications approved by the automaker.

Are the modifications legal?

Some engine modifications can violate federal and state emissions laws. The vehicle will be denied a smog certificate and registration renewal if an illegal part is found during inspection, regardless of whether the vehicle passes testing. All engine modification must have a California Air Resources Board (CARB) Executive Order number marked on the part of under the hood. All states recognize CARB-approved parts.

Are the modifications safe?

Well-chosen modifications can improve a vehicle's braking and handling, but safety can be compromised with improper installation or poor quality parts. Chassis and suspensions are designed as an integrated system for reliability and safety, and random modification may disrupt that system.

Lifting the suspension to clear large tires is a popular modification for 4WD trucks, but will result in a higher center of gravity and compromised stability, even at low speeds.

Plus-sizing wheels and tires can severely alter a vehicle's handling and braking force to stop, which can adversely affect the suspension dynamics. Thin sidewall tires may not meet load ratings for some large trucks and SUVs.

Even adding seat covers can affect safety if they interfere with seat-mounted side-impact air bags.

Is it worth it?

Lowering the suspension can produce a harsh ride and make body panels more vulnerable to scrapes. Modified engines are often touchy and may require premium fuel. Performance brakes are often noisy, shed more dust, and require frequent pad replacement. Some body modifications require drilling or sheet-metal work that is expensive to reverse or repair. Finally, custom painting can be hard to touch-up and can "date" the vehicle.

E-mail Newsletters

FREE e-mail Newsletters!
Choose from cars, safety, health, and more!
Already signed-up?
Manage your newsletters here too.

More From Consumer Reports

The Best Matching Washers and Dryers These washer-dryer pairs cleaned up in Consumer Reports' tests.
Best 4K TVs to Buy Right Now The top picks from the hundreds of 4K TVs we've tested.
Best New Car Deals Save money on the cars that Consumer Reports recommends.
How to Pick the Right Size Generator for Your House Add up the items you need to power before making your choice.


Cars Build & Buy Car Buying Service
Save thousands off MSRP with upfront dealer pricing information and a transparent car buying experience.

See your savings


Mobile Get Ratings on the go and compare
while you shop

Learn more