Balancing performance and safety without ruining street manners

Photography Credit: Tradd's Photos

If you’ve been around this community for any length of time, you’ve certainly heard the sentiment: Cars these days are fast. Maybe faster than ever, and not just the swoopy track specials that manufacturers crank out at an alarming rate.

Even the ham-’n’-eggers like our BMW 435i–a car that sits no higher than third on the 4 Series performance depth chart, behind the M4 and 340i–crank out more than 300 horsepower and can easily top 130 mph heading into Turn 1 at VIR.

[Video: How to Drive Faster at Virginia International Raceway | Track Tutorial]

And while OEM safety systems are also better than ever, they’re designed to keep the occupants safe in a road environment, not necessarily on track. Add to all this the family and friends who want to see us using the available resources to enjoy our hobbies in the most responsible and safe way possible, and we decided that our 435i needed some safety hardware.

 

Step 1: Read the Rule Book(s)

We started with our class rules. Since our 435i would mostly be seeing time trial action in addition to street duties, we lined up the NASA and SCCA time trial rule books and looked at requirements and allowances in our chosen classes. 

On the NASA side, we had nearly unlimited options. NASA Time Trial classing is based more purely around weight, horsepower and contact patch, and organizers care very little about the prep it takes to get you to those numbers. That meant anything from a fully stock interior to one totally gutted with a full cage was on the table.

On the SCCA side, however, we had a few more limitations. We plan to run in the Sport division, which has its ethos firmly rooted in dual-use cars that are not just technically street legal but fully street usable. Still, allowances are made for safety systems–accent on “systems” here–which compromise some of the function of the cars.

In our case, we’re taking the intent of the Sport division seriously. Our 435i sees regular street use, not just as a fun cruiser but to do real-life stuff, like loading up that huge trunk at Sam’s Club or going out to dinner in German-appointed comfort. 

And this is one of those places where the conflicting realities of track prep and street use collide. On one side of the equation, we have a comfy street car that’s uncompetitive and not optimally safe on track, while on the other side we have a hacked-up monster with lots of trophies and a license plate it doesn’t really need.

So we know the struggle, but we still wanted to see if we could have our steak and eat it, too.

 

Step 2: Picking a Prep

Since one of our main focuses is going to be the SCCA’s Time Trials program, and since it has the most restrictive rule set, we decided to use those Sport division prep rules as our road map for safety upgrades.

This rule set allows safety to be upgraded as a complete system, meaning you can install a racing harness, but only if it’s paired with a proper racing seat, and those must be teamed up with proper rollover protection with at least four contact points to the chassis. Seats must be upholstered on their seating surfaces (no bare aluminum or carbon shells), and interior trim and rear seats may be removed to facilitate the installation of the roll bar or cage, but only at the minimum level required to get the job done.

All these guidelines sounded reasonable and attainable, but we still had second thoughts about them: We love a proper racing seat in a car–it’s as much a performance upgrade as a safety upgrade–but a seat requires a roll bar, and a roll bar requires drilling through our clean and well-preserved BMW’s chassis. Even a “bolt-in” bar requires irreversible modification to your shell to facilitate installation.

Or does it?

Our friends at BimmerWorld turned us on to the lineup of bolt-in bars from JP Marketing LLC. Jens Polte–who may be familiar to our readers after his top-10 UTCC finish in his M3 a few years ago–conceived and designed this bar to be a true bolt-in, using factory hard points, that does not require any permanent modification to the structure and as such is 100% reversible.

In our opinion, it’s kind of a game changer–and why we picked a coupe over a sedan since he doesn’t offer a bar for the four-door chassis. Like pro-level GT3 cars, the JP Marketing bar also leverages the OEM structure, picking up on the massively strong factory attachment points built right into the original unibody. There’s a lot of happy accidents here–BMW has placed reinforced attachment points for things like seats, seat belts and subframes right near ideal attachment points for a roll bar–and JP has capitalized on those fortunate coincidences and used them to augment its own supplemental safety system. 

Now that we had a plan for our safety gear, it was time to start putting it in motion. 

 

1. Roll bar installation starts with removal of front and rear seats. The front seats will go back in, but the rears will have to stay out to make room for the bar. Fortunately, our rules allow this. 

2. The JP Marketing bar leverages existing structural points for mounting, like this boxed-in section of the tub designed to secure the seat belts. These are heavily reinforced points used for the car’s own safety protocols, and they just happen to be in the ideal place to locate the main feet of the roll hoop. The front seat belts–now bolted through the foot plates–remain fully functional and accessible. The bar attaches via two backing plates with integral nuts. The job is easier if you rivet these plates in place, but you don’t have to. 

3. The rear seat mounts provide the other two attachment points: two heavy-gauge tabs joined in a double-shear connection. Installation requires the removal of the rear seat bottom and seatback, along with the two armrest trim panels in the rear seat area. 

4. The rear section is brought into the car first and bolted loosely into place–and note that the entire install takes place from inside the car, not beneath it. 

5. The rear and front halves of the bar connect via these clevis joints. This minimizes the amount of movement you need to connect the two sections once everything is in the car.

6. Then the main hoop is brought into place. This is a multi-person operation. Corners are sharp and the fit is snug, so you’ll want to protect surfaces and glass from scratches and breakage.

7. Now we could bolt the rear attachment points to the original rear seat mounts.

8. The clevis joints are bolted together, and all that’s left is torquing the mounting bolts.

9. We did make one permanent modification in the form of a slit in the carpet so it could better fit around the foot plates. Technically, you could leave the carpet bunched up and leave the car 100% unmolested, but we chose this integrated look. We located the slit in an unobtrusive spot that shouldn’t be entirely visible should we ever undo this install, but regardless, the result is a clean, integrated appearance.

Photography Credits: J.G. Pasterjak

10. BimmerWorld sells the JP Marketing bar starting at less than $2000, with final price depending on some color and finish options. It’s as close as you’ll come to a high-end, bespoke, integrated solution as you’ll ever see in an off-the-shelf piece, with endless bonus points for the non-destructive install. While this setup sacrifices our back seat–a dealbreaker for some–we’ll gladly take that trade for the increased rollover protection. The only thing our rear seat ever saw, anyway, was a backpack or gym bag, and those are still 100% realistic options in our current configuration. 

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