A convertible has a number of advantages over your run-of-the-mill sedan. From the wind in your hair to the feeling of the sun on your skin, few cars project that carefree, cruising lifestyle quite as well as the convertible. Unfortunately, the same feature that makes convertibles so fun to drive can also be a major issue when it comes to safety. Just think about it: when a regular closed-top vehicle is involved in a serious crash that leads to a rollover, the roof takes the brunt of the damage. Designed by highly-skilled engineers––who ultimately answer to an automaker’s team of highly-paid lawyers––modern vehicle roofs are reinforced in a way that puts passenger safety at the forefront. Given the reliance on the roof as the first line of defense in the event of a rollover, this approach falls a little short when a vehicle lacks a roof.
Automakers have addressed this critical safety issue in a variety of ways, including roll bars and active rollover protection technology. While they differ in specifics, both systems rely on the same basic principle: making sure that, in the event of a rollover, something hits the ground before the top of the driver’s head. If your convertible lacks adequate rollover protection, or you’re in the mood for an upgrade, there are plenty of aftermarket options for drivers seeking a safer ride. Join us as we take a closer look at how rollover protection works and explore the process of upgrading your convertible.
Roll Bars and Cages
Roll bars are a popular aftermarket accessory for drivers looking to improve vehicle safety, but they also come standard on a number of convertible models. Generally composed of welded steel tubing, roll bars are exactly what they sound like––bars that protrude above the occupants’ heads, providing something for the ground to scrape against aside from your noggin. They come in all shapes and sizes, from simple hoops to complex designs that include four-way protection, reinforcing triangles, and more. Rolls bars don’t just make a convertible safer; they can also improve performance. The bracing provided by roll bars can stiffen the chassis, improve on-track stability, and give you that extra edge you need to log a new personal best.
The next step up is a roll cage. These aren’t unique to convertibles, and virtually all auto racing series worldwide require full-fledged roll cages, even in hardtop models. These skeletal frames not only protect the driver from above but also from the sides with an expansive cage that spans every corner of the compartment. This makes sense given the high speeds and tight cornering unique to such racing events, which is why you’ll never see a NASCAR vehicle logging laps around the track in anything but a full roll cage. A roll cage might be overkill for most convertible drivers––and would basically end up making the vehicle look more like a dune buggy––but they’re the ideal solution for certain high-octane applications.
In some cases, the decision on whether to go with a roll bar or cage comes down to a matter of regulations. Most auto racing series have strict guidelines covering the type of rollover protection that needs to be used. For example, the National Hot Rod Association (NHRA) requires a basic roll bar in convertibles that have a quarter-mile time of under 13.49 seconds. However, if a car is able to run the quarter mile in less than 10.99 seconds, NHRA rules dictate that a full roll cage be installed. It all comes down to protection, as a roll cage is able to offer a level of safety at higher speeds that a roll bar just can’t match.
Active Roll Bars
Active roll bars, on the other hand, are almost always a factory-installed feature and are largely limited to the higher end of the convertible sports car market. From Porsche and Lamborghini to Bentley and Buggati, active rollover protection provides a sleeker, more stylish alternative to the roll bars found in some more affordable convertible models. Instead of a rounded steel bar permanently protruding behind the headrests, these systems use deployable roll bars hidden inside a housing that fits just behind the front seats or, in some cases, beneath the headrest.
The active roll bars are invisible during regular operation but spring into action when the vehicle detects a dangerous combination of speed, tilt angle, and weightlessness. When those conditions are met, the roll bars virtually explode out of their housings, deploying in as little as one-quarter of a second. The system is activated by the same unit that deploys the airbags, giving drivers the protection they need when encountering the dreaded rollover. In many cases, these active roll bars can be easily reset post-crash but might require a little more repair work in the case of headrest-mounted versions and the like. That shouldn’t be too much of a deal breaker, however, as any vehicle that undergoes a rollover is certainly due for a trip to the repair shop (or scrap yard).
Some convertibles manage to get away without roll bars of any kind, but it’s a small list. Take the eighth-generation Corvette, for example. Chevy designed this modern sports car with extra-high-strength A-pillars that can support 2.25 times the weight of the vehicle. This brawny construction allows the Corvette to ditch the weighty and expensive active roll bar, increasing the vehicle’s power-to-weight ratio while keeping the MSRP relatively low. “You can turn the car upside down, and you can put another car on top of that, and still have room to spare,” said Corvette Chief Engineer Tadge Juechter.
Upgrading Rollover Protection
Whether your convertible came with factory rollover protection or not, you may be interested in upgrading to something more robust. Most drivers in the racing scene will be required to install roll bars and cages in their track vehicles, but even your weekend toy might benefit from an aftermarket roll bar. If you’ve got your heart set on throwing a roll bar or cage on your own convertible, you have a few choices to make.
Roll cages might offer the best protection, and active roll bars are a neat party trick, but a simple roll bar is the logical choice for most drivers. They are much more affordable and easier to install than full-on roll cages, which require a lot of prep work and even a little welding to fit in place, and often have to be custom-built for a specific car. Roll bars are also much easier to live with since most cages include awkwardly placed bars throughout the cabin, so we will focus on roll bars for the moment.
Roll Bar Examples: The Mazda Miata
Since aftermarket roll bars vary by make and model, it’s tough to give a good overview of the market as a whole. Instead, let’s take one of the more popular convertibles on the market and use it as a test case. The Mazda Miata is an ideal entry into the world of convertibles, still managing to deliver a fun ride despite its modest starting price. From 1990 until 2005, the Miata was sold without any built-in rollover protection, making it the ideal candidate for an upgrade. Later models do have roll hoops from the factory, but they are not particularly robust. The sports car’s low center of gravity means it tends to resist rollovers better than most models, but it never hurts to have a little extra protection.
Those looking for the best available protection for their Miata might want to start saving up for a Blackbird Fabworx GT3 Roll Bar ($1,195-1,495), which while an investment, is also one of the sturdiest on the market as well as being Sports Car Club of America (SCCA) legal. The same company also produces a line of more compact RZ Roll Bars for NC and ND Miatas that are fully compatible with the convertible top. Another good option is the Hard Dog Sport Roll Bar ($485-735). Affordable and perfect for both hard- soft-top Miatas, the Hard Dog Sport features double diagonal construction and a limited lifetime warranty.
While we tend to recommend professional installation when it comes to any potentially life-saving safety equipment, ambitious DIYers can take on most roll bar installation projects if they boast a certain amount of mechanical fluency. Most kits don’t require any welding, but you’ll still need a drill, a jack, jack stands, and assorted basics like sockets, wrenches, screwdrivers, and the like. Once installation is complete, there’s one last step to take before hitting the open road: the broomstick test. It’s about as simple as it sounds. Take a broomstick, and set one end on the top of the windshield and the other on the top of the roll bar. If your head (with a helmet on if you are taking the car to the track) is below the broomstick, the roll bar is good to go.
A Roll Bar Is Never a Bad Idea
Rollover protection should be one of the first projects for any convertible owner looking to get into the racing scene. While an aftermarket roll bar kit might set you back a few bucks, it’s a small price to pay for the critical protection it can offer in case of an accident. Aftermarket rollover protection or not, there is some good news out there for every convertible driver. According to a recent study by the Insurance Institute for Highway Safety (IIHS), convertibles are often just as safe as their hardtop counterparts. In fact, the IIHS found that crash rates and driver death rates were actually lower for convertibles than for hardtop versions. This might come down to a matter of driving style––maybe convertible owners don’t want to put the pedal to the metal and risk ruining a good hair day––but it does a good job of illustrating just how far factory rollover protection has come over the years.