BMW E46 Racecar
A couple months ago we introduced you to professional skateboarder Rune Glifberg and his 2003 BMW M3, which he wanted to turn into a competition-ready club racer. We left off with Glifberg ripping out the interior-headliner, seats, carpet, door panels-and turning the car over to Evosport in Huntington Beach, Calif., for chassis prep in the form of a six-point chromoly rollcage.
Every bit of fabric, trim, and most other interior amenities were removed, laying bare the underlying metal surfaces, mechanical assemblies, and lengths of wiring strung along the floorpan like so much multicolored spaghetti. About the only bits to remain were the steering wheel-necessary to be able to still move the car-and a Sparco bucket seat bolted into the pan to give anyone driving it a comfortable place to sit while doing so. The sunroof-endowed roof section was also removed to make way for a carbon-fiber panel which will be installed later on.
Smooth, pretty weld seams are not only indicative of an experienced welder; they more often than not also indicate the basic quality of cage fabrication. Evosport fabricators put a lot of effort into making the cage structure both effective and aesthetically pleasing.
Smooth, pretty weld seams are not only indicative of an experienced welder; they more ofte
The factory sound deadening material was also left in place. According to Evosport's Brad Otoupalik, unless a customer is absolutely set on shaving every last ounce of unnecessary weight, most of the cars they prep retain sound deadening. In the case of the E46 M3, it represents only about 40 pounds and it's all applied to the floor sections, the most beneficial place to retain weight. Taking it all out would constitute a minimum two-day job, and depending on the complexity, it'd cost around $1,500 to $2,500-not worth the money in most cases.
With the inside stripped, it was on to cage fabrication. A rollcage is one of the most important safety components in any racecar and Evosport is adamant that this be the first upgrade in any sort of racing build. There are a couple ways you can go about it, depending on the type of track time you and your car will be seeing. Glifberg's is at the more serious end of the spectrum. "We consult with customers and see what they want to use the car for," Otoupalik says. "Rune is a professional athlete, a competitor-we knew he wanted to really go racing."
Mocking up the rear portion of the cage structure prior to welding.
Your basic four-point rollbar is really nothing more than a place to hang racing harnesses from. It doesn't do a whole lot to stiffen the chassis and offers no great degree of rollover protection since there's no reinforcement at the front of the cabin. And it doesn't offer any sort of shielding for your legs or from a side impact, which both become pretty important considerations if you're planning to go on-track with other like-minded competitors. For anyone truly serious about racing, Evosport recommends a six-point cage at the minimum, one that ties into all four suspension points and that includes lateral structures across the door thresholds to prevent cockpit intrusion. A basic six-point, TIG-welded race series-legal chromoly cage will run you $3,900.
Different viewing angles of the rear X structure.
Glifberg's has been taken a couple steps further to increase both chassis rigidity and overall safety. His cage is a six-point assembly, incorporating a second diagonal cross member at the rear that forms an X-shaped brace between the two shock towers. Glifberg's cage also incorporates a more robust structure across the driver-side door. Basic door bars would consist of two tubes that cross in the middle, forming another X and preventing outside objects-other cars, say-from entering the cockpit in case of a smash-up. Evosport offers an upgrade that does you one better, what they call a "pyramid bar." This incorporates both an X-shaped cross structure as well as what's known as NASCAR bars, essentially a setup that angles the bars outward, toward the door and away from the cockpit. This creates a larger cushion of dead space between the potential point of impact and the car's inhabitants. In this case, the NASCAR bars and the X-brace form a rigid pyramid structure, hence the name.
The finished and painted rollcage as seen through the missing rear window.
The extra diagonal brace in the rear, taking the cage from six to eight points, costs an extra $350; the pyramid door bars are available for $700 per door. Glifberg's cage has just one of those, on the driver side, taking his total cost to $4,950.
Now is a good time to point out why the cost is what it is. This cage has been fully fabricated from the ground up and grafted into the E46 unibody; it isn't some cheesy one-size-fits-all bolt-in number. Additionally, the mounting points where the cage actually attaches to the unibody are plinths which have been fully welded into the chassis. According to Otoupalik, there are two schools of thought when it comes to attaching a cage to the body. The old-school method simply attaches the circular cage tubing directly to the unibody metal, sans plinths. Evosport's method basically adds those plinth structures in between the cage tubing and the unibody, offering roughly four times more surface area than traditional methods where the cage connects to the chassis. This helps dissipate impact energy over a greater area, through entire cage and unibody and away from the driver-which is the whole point of installing a cage in the first place.
A look at how the pyramid door bar essentially covers the entire door threshold with its various members and cross-members; welding the rest back up; and the finished, painted structure.
A look at how the pyramid door bar essentially covers the entire door threshold with its v
Safety aside, there are also performance benefits gained from installing a solid, well-fabricated rollcage. Obviously it strengthens the unibody overall, but also stiffens and strengthens the suspension pick-up points. This allows you to run a more compliant suspension at the track, which in turn improves grip, handling, and power deployment. It's a common misconception that says the stiffer the suspension, the better.
"A compliant suspension is the goal of any track car, not to be stiff and low," Otoupalik says. "A more compliant suspension gives you more grip on turn-in, exit, and mid-corner-a nice stable platform. You swim through the turns, not skid through them. When a car is handling beautifully, it feels slow. It's not stepping out or losing traction, it just handles right. It may feel slower that way, but the clock says it's faster."
A closeup view of one of the more complex tube intersections. Seriously, you wouldn't want anyone but a master fabricator attempting to join all this together, would you?
A closeup view of one of the more complex tube intersections. Seriously, you wouldn't want
A few words about welding- another important consideration in any custom-fabricated rollcage is weld quality. Pretty welds-smooth, straight, looking like a flattened-out roll of coins-are not just aesthetically pleasing. They're indicative of a seasoned fabricator, one who knows his machinery and who has mastered all aspects of the weld: patience, temperature ranges, speed control. On the other hand, ugly, chunky welds may not only indicate an inexperienced or inattentive welder; they could also be indicative of improperly fitting bars and a poorly conceived structure. Good welds will usually speak volumes about the overall quality of fabrication.
With the cage assembled and grafted into the unibody, the final stage in the chassis-prep process is getting it painted. This, too, is a very important step. Without paint to protect the chromoly tubing, it will quickly begin to rust-and given your investment to this point, you definitely don't want that. Evosport usually uses light colors, like white, on its race cages to help with heat dissipation; it can get damn hot inside a hard-charging racecar. Glifberg chose Porsche GT3 RS orange, still a suitably light color but one that shows his own personal flair. Orange is a notoriously difficult color to apply and it took three attempts to get it all even, but the results speak for themselves.
With the cage done, it's time to start looking into mechanical performance upgrades. In the next installment we'll take a look at a few bolt-on bits for the suspension and engine bay.
A closeup of one of the plinths that join the cage to the tubing to the chassis pickup points. This offers about four times the surface area over simply welding the tubes directly into the unibody.
A closeup of one of the plinths that join the cage to the tubing to the chassis pickup poi
A bird's eye view of the finished cage and painted cockpit. From here you can really appreciate just how the rollcage ties into the various points on the unibody, and the protective shell structure along all edges of the cockpit, including the forward roof area and A-pillars.
A bird's eye view of the finished cage and painted cockpit. From here you can really appre