How to Mount a Splitter (Safely)

Build it to fail. No, seriously.

Posted by Roger on December 11, 2020

Splitters are amazing functional aero pieces on a track or race car. Unfortunately, they can also be unwieldly, and can cause a lot of collateral damage to your car if you ever hit anything while it's attached to your car.

We at StudioVRM can't afford to buy new bumpers and subframes on a regular basis, so we use a mounting mechanism that not only makes it easier to live with a full-length splitter, but has some built-in safety mechanisms in the case the worst case scenario becomes reality.

Here's how we do it:

Quick Releases Everywhere

In order for a front splitter to make a significant difference on track, it must be large, it must protrude forward of the bumper at least a few inches, and it must be within 4" of the ground. This also means that you will need some very low ramps or have a quick way to remove and reattach the splitter in order to do anything under the car (or for that matter, load it onto a trailer). Due to the high cost of low-profile race ramps, we recommend the latter.

Instead of bolting the splitter blade directly to the chassis, we used PCI-Style quick release splitter brackets for a Civic and modified them so they would fit into the factory tie-down mounting holes. These quick release brackets have an ingenious design. When locked in place, the brackets are solid. The weight of the splitter (as well as any downforce it generates) is supported by the two burly bolts in between the top and bottom halves of the bracket, and there's very little play in any direction. But if you pull the detent pin in the middle of the bracket, the two halves slide apart, allowing you to unhook the splitter and remove it from the car in a matter of minutes.

Because the Super Touring Under class' Advanced Aero regulations allow for a splitter that extends 3" past the bumper, we need splitter support rods to prevent the splitter blade from bending excessively. Our support rods of choice are the DIFTech quick release splitter rods. Similar to the splitter mounting brackets, these support rods use detent pins that you can pull to quickly unhook them from the car.

These rods are designed so you can replace the fasteners that attach them to the splitter and bumper, which for reasons we'll get into later, are very important. They also have two built-in weak points designed into the threaded parts of the rods, which are a very handy safety feature in the event of the worst-case scenario.

Built-in Breakaways

In addition to being an almost essential convenience, these quick releases serve an important secondary function: They act as built-in weak points that allows the splitter to break away from the car in the event of a big hit.

Why do you need a breakaway? Well, splitters stick out a fair bit from the front of the bumper and are therefore the first thing to contact a wall, a ditch, or another car. If a splitter is solidly mounted to the chassis of your car, the forces of any impact will transmit right through the mounts and bend or break whatever it's attached to. Sure, the splitter will absorb some of those forces, but not all of them. And even if it does, you don't want a big chunk of splitter piercing your radiator or wreaking havoc in your engine bay. Especially if it happens to be made of aluminum, carbon fiber, or Tegris.

Fortunately, the pins and fasteners in these quick release mounts and supports are thin enough that they can act like this type of fail-safe. Just by using this type of mount over a solid bracket, you get an added level of assurance that, in a crash, the splitter will separate from the car safely without tearing up the body.

 

Use the Right Fasteners

Many splitter mounting brackets and support rods come with round head recessed hex bolts to secure the hardware to the splitter blade. While they have a nice low profile and do look good, they are a terrible in this application. Throw them out or save them for something else.

The reason is that splitters spend most of their working lives scraping across the ground as you brake, corner, and straddle the red and white striped kerbs at your local racetrack. By the end of the day, the shallow hexagonal hole in the head would have been worn down that you won't be able to get an Allen key in it, making it impossible to remove and replace the bracket.

If possible, replace these round head bolts with elevator bolts. Elevator bolts have flat bottoms that sit flush against the bottom of your splitter blade once tightened and won't be subject to the same wear as regular bolts.

If you can't get elevator bolts, use regular hex-head flange bolts. Not only do these bolts have the advantage of being cheap and readily available, but they can also be easily removed even when the heads have experienced a bit of wear.

Some companies sell bolt-on wear plates that you can bolt to the bottom of your splitter. While these do look very good, they aren't necessary. Instead, take a page from the handbook of pro racing coach Todd Reid and bolt a few stubby large-diameter bolts on the edges of the splitter. These bolts will serve the same function as those expensive wear plates and will be much cheaper to replace.

Live Demonstration

So this is all well and good. But how do we know whether all these measures work in real life?

Well, due to a clumsy off-track excursion by our team's official test and race driver (me), we have real data that shows how these breakaway mounts work in real life.

Here's an in-car video that shows exactly what happens when you run into something hard with your chassis-mounted splitter.

That divot in the outfield is quite a bit deeper than it looks on video. When we drove over that bit, the splitter dug into the dirt and the car launched into the air by a few inches before thumping back to the ground.

Fortunately for us, the breakaway mechanisms worked exactly as planned. The entire splitter blade broke away from the car in one piece, leaving the delicate underside of the StudioVRM Prelude untouched as it bounded through the bumpy grass-covered runoff.

 

Aside from a pair of slightly dented splitter brackets, the only other damage to the car were these holes on the sides of the bumper cover. This was our fault. We had bolted an additional set of support rods to the sides of the front bumper cover to help support our extra-wide splitter through fast sweepers. While this did help keep the edges of the splitter held high enough so they wouldn't drag on banked turns, it also meant that the plastic holding the support rods were weaker than the breakaway points built into the support rods.

Fortunately, this wasn't a big problem. Plastic repair kits are so cheap and are easy to use that even the ham-fisted of home mechanics will be able to patch up a broken front bumper. All we did was a bit of ABS plastic filler, shaped it with this $12 hot iron, and sanded it flat. All we need is a bit of touch-up paint, and , our damaged bumper cover will be ready to go back on the car.

 

Conclusion and Recommendations

While it's natural to assume that everything on your car should be as strong and durable as possible, it's not the case with things like front splitters. Take the time to design weak points into the car to ensure that a small mistake or a minor bump with a competitor won't result in expensive, race-ending damage to your car.

Remember, splitters are cheap and disposable. Don't be afraid to sacrifice it to save your car... or, for that matter, to save your race.