Six ways to ruin your ride with terrible add-ons

It's been a tough few years for the car customizing market, as the slow economy drained much of the money younger owners had to spend on modifications, even tripping major aftermarket firms such as Trust (known for its subdivision Greddy). But Toyota and Subaru's release of the Scion FR-S/Subaru BRZ and the upcoming Ford Fusion have infused some life into the mix. And with the massive SEMA convention opening at the end of this month, we take a look at six aftermarket pitfalls to avoid.

1) Excessively wide wheels/tires. It goes without saying that "Donk" cars and their rubber-band tires are gaudily impractical, but there's also a trend to have wheels as "flush" with the fender as possible. To prevent the tires from scraping against the fender's inner lining, tuners often mount tires that are narrower than the wheel, which are then stretched to fit. While it may provide a Euro-aggressive stance, the tire's sidewalls aren't designed to handle such deformation, possibly leading to catastrophic tire failure. And although wheel weight can be offset with lighter forged wheels, the more plus-sized the wheel, the greater moment of inertia the car has to overcome.

2) Poorly designed aftermarket intakes. Intakes are a popular bolt-on modification because they provide power at low cost (typically around $200). But choose the wrong filter-on-a-stick and you can potentially wreck your engine. Cold-air intakes draw air near the bumper and away from the hot engine bay. The denser, cooler air may lead to more horsepower, but the filter is more susceptible to drawing in water, which can hydrolock the engine. Short-ram intakes draw air from within the engine bay, and make power by minimizing flow restriction; but in standing traffic the tubing warms up, leading to an initial drop in power known as heat soak.

3) Knock-off safety components. This week's federal warning about counterfeit air bags in thousands of cars highlights how the advent of eBay and flourishing, cheap overseas manufacturing have contributed to cheap replica parts. These companies can price parts at a fraction of cost because of the lower overhead; there's no need for engineers, stress testing, or marketing. No-name parts are harmless for cosmetic upgrades, but a safety liability when it comes to components such as suspension and brakes; they could be cutting corners by using inferior alloys, for example. And it may be a lesson you won't live to learn if a strut mount shears when rounding a mountain bend.