Boxing heavyweight world champion Mike Tyson once said, “Everyone has a plan until they get punched in the mouth.” I’ve been punched in the mouth and it turns out Iron Mike was absolutely correct. Besides a schoolyard scuffle during my youth, I have also been figuratively punched in the mouth while inside a racecar. Those impacts were unexpected and violent. And those impacts made me realize very quickly that my driving seat setup wasn’t as good as I had “planned.”

Containment racing seats, similar to the child seats we carefully strap our children into to go to school, are designed to protect us during a collision. Many of us forget that. We simply think of the seat as the piece that connects us to the racecar so we can see over the dashboard and instantly feel if the car is slipping underneath us. Yes, the seat does do those things, however, its main purpose, and what it was engineered and designed for, is to save you from injury during a collision.

When you are sliding sideways, running into stuff, and the dirt is flying, you start feeling right away if your racing seat is sufficient to protect you from injury.

Allow me to nerd out a bit on the physics involved with this thing called “occupant kinematics,” or your body’s movement within a vehicle during a collision. There are three parts to a collision. Part 1: Your car hits the wall (this is bad). Part 2: You hit parts inside the car (this is extremely bad). Part 3: Your internal organs collide with the inside of your body (this can be fatal). Automotive engineers and physicians realized, after a massive death toll on our public roadways for decades, that a metal dashboard and sturdy vehicle frames may help the vehicle survive a crash, but the occupants won’t be around to see those cars get repaired. The occupants will be six feet underground. From this realization is where we got the crash standards designed in the vehicles we have today. The idea is the car takes the brunt of the collision and we, the humans, “ride down” the collision. Cars, after all, are easily replaced.

Ride down is, simply, time. Most racecar drivers repeatedly slow from 100 miles per hour to zero during a race. However, we do that over 6 seconds under braking, which our frail human bodies can handle. If we slow from 100 miles per hour to zero when we hit a wall in just 30 milliseconds, we will not survive. Time can save your life. How you gain that time is by two parts. The first part is to have the vehicle crush during the collision – let the vehicle take the damage, not your body. The second part is to ensure you are securely attached to the vehicle so you, in the occupant seat, can enjoy the ride down of the vehicle’s crush — and not hit stuff inside the car. If you are not securely attached to the seat, you will then accelerate relative to the interior of the vehicle — the dashboard stops and you continue toward it — and that impact can injure you or be fatal. The better you are attached to the vehicle, the better your chances of walking away unscathed from a big hit. That is why your harnesses and the fitment of your containment seat are so crucial.

This Kirkey containment seat sourced from I/O Port Racing Supplies has a lot going for it: sturdy construction and halo containment for the driver’s head. However, not all humans are created equally. Even though you can order a Kirkey seat in different widths for your hips, the exact fit overall will depend on your body type and size. If you share the car in enduro races, unless your co-driver is your identical twin, somebody won’t fit as well as they should in the seat for their safety. The trick to solve this is individual foam inserts for the seat for each driver.
To bake this cake, you will need the following ingredients: TAP Plastics 2-part expanding foam, disposable rubber gloves, mixing bucket, mixing drill/mixing stick, painter’s plastic drop cloth, painter’s tape, heavy duty plastic bag, knife, course sand paper, and an old driving suit.

NASA Norcal racer Eli Cronbach, who runs Service Motorsports, was gearing up for an enduro and needed to create foam inserts for his Mustang. He wanted to help his different-size drivers fit better in the seat for safety and for his height-challenged drivers, to help them actually be able to reach the gas pedal. He had each driver on his four-driver team make their own seat mold. He used TAP Plastic’s X-30 polyurethane foam which will expand up to 30 times its original fluid volume. It comes in two parts which are mixed together one-to-one. This foam is often used by people creating molds or watercraft — it floats — and it works great for foam inserts for racing seats.

Two red Solo cups work perfectly to ensure the perfect one-to-one mix of the X-30 polyurethane foam for mixing.

Some painter’s tarps and garbage bags are the perfect items needed for containing the foam after it is mixed and begins to expand. Mix the X-30 and pour it into the garbage bag. Have the specific driver in an old racing suit sit in the seat with the garbage bag filled with the expanding foam under him or her. If you want a little riser in the base of the seat, or you need the seat to push you away from the back of the seat allow the foam to set for about five minutes before you sit in the seat. The working time for the polyurethane foam is about 10 minutes total.

First plastic is laid out on the seat to protect it and then a garbage bag filled with the one-to-one mix of polyurethane foam is dropped in. Painters tape can help to hold the garbage bag in the correct spot of the seat.

Some people do their seat molds in separate sections, the base, the lower back, and then the upper back. The three pieces will weld together when put into contact with a new mix of polyurethane foam. While the driver sits in the seat and the foam sets, they will feel some heat as the polyurethane foam works but it isn’t so hot that it will burn you through your suit. Pro tip: Don’t let this stuff get in your hair. My brother, Randy, had to endure a rough and painful haircut after some of the mix got in his hair.

Service Motorsports driver Randy Krider is working hard on his seat mold by just sitting on his butt. It took less than 10 minutes in the seat to form the mold.

This stuff sets up fast. There is no time to dilly dally. You have a total of 10 minutes to work with this material. Within 15 minutes the foam is hard enough you can begin cutting holes in it for things like a sub belt or to trim the edges near the shoulders. A sharp knife, like one you would carve a pumpkin with, works perfectly for this job.

The photo on the left shows the new mold inside the seat after the driver exited. The photo on the right is the mold out of the garbage bag with the seatbelt holes being cut into the mold.

A gritty sandpaper block (around 50 grit) will make quick work of smoothing out the foam seat mold. There will be minor bumps and holes from air bubbles or crinkles in the garbage bags during the setting time. This can be easily taken care of with some elbow grease.

Once the seat has the required holes cut in it for seatbelts, it’s time to use some gritty sandpaper and smooth out some edges.

This is a do-it-yourself project that will help you to be a better driver in your own car because it ensures you fit in the car better. Having a good fitment with a seat will ensure you don’t get fatigued as quickly in a racing car. With correct fitment, you are using your arms and legs for inputs with the wheel and pedals, as opposed to trying to keep you from sliding within a seat. This is an inexpensive way to be safer and faster. Win-win!

Here is the new seat mold in action during an enduro at Sonoma Raceway. Four drivers, each with their own custom seat mold, swapped in and out of the Mustang during the race.

The final project was a success. Each driver on Eli’s endurance racing team had their individual seat mold, which would help them fit inside the car better to enjoy better ergonomics and, more importantly, allow them to be one with the seat, which is one with the car to avoid injuries if a collision were to occur. Great work Service Motorsports!

Image courtesy of Rob Krider


  1. I prefer to sit on something NOT EXTREMELY FLAMMABALE as most people should in a race car…… Yet no mention in the article.
    “Rigid polyurethane and polyisocyanurate foams will, when ignited, burn rapidly and produce intense heat, dense smoke and gases which are irritating, flammable and/or toxic.”

  2. With respect (your not wrong) we focused on crash impact and should have mentioned that the final top covering is a flame retardant fabric. Many teams will also used Race/Gaff tape. My thought is that the seat mould sits in an aluminum seat tub, driver sits on top of the foam wrapped in fire cloth, in full fire suit. If the foam mould catches fire I/we are all ready in real trouble.

    • You could use the foam as a template to be later made of a dense rockwool, I don’t know how well it’ll last or how comfortable though, maybe the fabric could help that.

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