2.2k words, about 15 min read
A companion piece to last month’s article, Bad Vibrations: Increased Pain from Molecular Compressions.
Vibrations are often highly unpleasant for those with CRPS, making riding in the car an uncomfortable or intolerable experience for many. People may limit time in the car or avoid going out to prevent being exposed to transit shaking.
A vibration absorbing seat cushion—such as memory foam or an air-filled wheelchair seat—can be highly practical for reverberations coming up through the seat into the body’s core. However, seat cushions do not help with the vibrations that come up through the floorboard into the feet and legs.
People often speak of their negative car experiences, so today I offer a practical, effective, and somewhat moderately priced DIY car mat to minimize transfer of rotational movements from the vehicle frame into the person. My personal assessment—which may not translate to your lived experience—is that this mat provides significant reduction for higher Hertz powertrain vibrations and moderate reduction for low sub-10 Hertz suspension system vibrations.
I have tested this mat for several weeks now in a car with fair-to-middling suspension quality. The bumps and jostlings from road debris and potholes can definitely still be felt, but the harshness of impact is notably blunted. The constant hum of the car itself is much more effectively mitigated and makes a massive cumulative difference in ride quality, especially over longer distances or if making multiple shorter trips in a day.
All together, this mat will be 2.4” to 3.25” thick, making it primarily oriented towards passengers. Users may need to move their seat backwards or upwards for comfort to prevent knees or hips from being at awkward angles, particularly for taller or lankier individuals. For safety reasons, drivers should not use more than the thin base layer to prevent pedal interference. Let’s begin.
Base layer
For the layer touching the vehicle floor, use heavy-duty butyl rubber matting. This is often advertised as “sound deadening,” “noise insulating,” or “vibration dampening” material. It uses low resilience to absorb lower-frequency structural vibrations and rumbles, turning energy into heat. These are often targeted towards those with large sound systems that tend to resonate through the vehicle’s frame, but they will serve the same function of muting vibrations from the road or engine.
The most practical and cost-effective choice will likely be a 10sqft, 80-mil [0.08 inches or 2mm] thick option. This can be purchased online for about $20. Cut the pieces to the size of the footwell and turn 2-3 layers into one thick, solidly connected layer through their adhesive backing to maximize their density and ability to mute vibrations.
The 10 square feet option I selected had nine 16”-wide pieces, which perfectly fit the width of my footwell. Three long covered my full footwell length, overlapping slightly, and then I stacked three high. This became a very solid, fairly heavy mat that filled the footwell quite snugly. Only the stack closest to my chair needed to have a small section cut out of the lower left corner to lay flat. I did the cutting before sticking all the pieces together, as each raised piece needed a slightly smaller section removed to keep a snug fit within the footwell.
These butyl squares are generally intended to stick directly onto the metal chassis, and their adhesive is very strong. If you do not want the base layer permanently attached to your vehicle, do not remove the backing of the bottom-most layer. Instead peel the backing away by an inch or two in order to overlap the layers together and then smooth the adhesive backing flat again after they are connected.
I recommend taping over the places where the adhesive backing is loose, so that any shifting during transit doesn’t peel it off and accidentally stick it to the flooring of your vehicle. Additionally, the edges should be secured with something like foil HVAC tape, roofing seam tape, poly film tape, automotive harness cloth tape, or gaffer tape to prevent the adhesive from seeping out the sides onto the floor during hot weather, especially if your car is carpeted.
If you feel the need to have additional stabilization, you can use some heavy-duty velcro to prevent sliding or shifting. If you have carpet, you can use just the velcro’s hook-side and it will attach directly to the fibers. If the butyl mat is both several layers thick and sized to fit snugly in the footwell, it is likely heavy enough that it will not shift or slide and may not need to be additionally secured.
Middle layer
To help feet float over heavy vibrations that don’t get absorbed by the base layer, choose rubbery, high-density, closed-cell foam; specifically, use thick and flexible NBR [Nitrile Butadiene Rubber] (preferred) or EVA [Ethylene-Vinyl Acetate] yoga mats, approximately a 1/2" thick. Cut to the size of the footwell and stack loosely in 3-4 layers to a height of 1.5-2". While these can be purchased new for about $20, a used NBR or EVA yoga mat will work just fine and be much more affordable.
Unlike the base layer, do not connect the yoga mat layers together with glue or other adhesives. Intentionally allow the middle layers to decouple with movement, which reduces the intensity of vibrations that make it to the top layer.
To prevent shifting or slipping, connect only the corners together using elastic bands, silicone grip dots, or small sections of non-slip carpet mesh or cupboard liners, allowing the individual layers to slide just a bit without moving too much when getting in or out of the car. As an additional option for those who feel the need, you can also place a tiny square of non-slip mesh or grip dots in the center of each layer for a bit of extra stability while still allowing the majority of the decoupling movement that dampens the vibrations.
When to replace?
The yoga mat will need to be replaced in 2-3 years as constant shaking and extreme temperatures will degrade it over time. Cabin heat during summer is the primary threat, but using a sun shield or tucking the vibration mat under the seat can significantly extend its lifespan. If you want your mat to fill the entire footwell, it will not tuck away well and you should pursue the sun shield instead.
Where is the most prominent slip point?
Personally, I have found that—without any form of added stabilization at the corners or center—the most sliding and shifting happens between the top two layers of the yoga mat closest to my feet as I get into and out of the vehicle. The butyl matting is too heavy to shift, the bottom layers of the yoga matting are held in place by the footwell, and the top-most layer grips the yoga mat quite well of its own accord. If you only have a little bit of additional grip to work with, I’d suggest prioritizing the gap between the highest yoga mat layers.
A great deal of the shifting can also be reduced by adjusting how you get in and out of the vehicle, particularly if you are someone who tends to pivot on the heel of your foot, which causes the layers to pivot with you. Redistributing some body weight to a third point of contact—such as the ceiling grab handle or a portable mobility tool designed to be temporarily inserted in the door's strike plate to aid those with stability issues (name brand version Stander's HandyBar)—can be massively assistive in reducing the shifting.
Is there a practical difference between using three or four layers of yoga mat?
I was able to tell the difference. It is noticeable enough to me that I put the fourth layer back in the stack, even though it raises the top layer above the door sill and significantly increases the shifting risk unless additional measures are implemented. For someone who has long legs or who really struggles with bending their joints or who isn’t able to raise where their rear end actually sits in comparison to the mat via a cushion or seat controls or who has significant stability challenges getting in and out, removing that extra half-inch to increase leg room or drop the entirety of the mat below the door sill may provide significantly more comfort and peace of mind than the little extra vibration reduction the fourth layer brings to the table.
Top layer
To absorb ultra-fine, higher-frequency hums, use a 3/4"-1" memory foam mat with a gel-enhanced or high-density polyurethane core and a vinyl or weather-proof outer layer instead of fabric. Too thin—such as a 1/2”—doesn’t offer enough density to absorb the hums, but too thick—such as over 1”—allows for too much jiggling. I found a thickness of 4/5” [0.8”] to be ideal for me. Those with very sensitive feet should avoid deep or heavy texture stamps on the vinyl.
Cold temperatures will make the top layer extremely hard, so warm the cabin before driving or bring the memory foam into the house during wintery weather when not in use to keep the top layer soft and absorbent.
To prevent slipping or sliding, get a mat that comes with anti-slip silicone dots or other treaded backing options and tuck the edges under the door sill or the footwell if there’s enough space to do so.
When to replace?
If the rubbery layers of the yoga mats in the middle layers can be felt against the heels or if the memory cells remain collapsed or pop back up instantly instead of slowly melting back to flat, the memory cells have degraded and need to be replaced. Uncut mats will last for 12-18 months and cut mats will degrade faster.
For those who prefer to buy a larger mat and cut it in half, use a sharp utility knife to size it to the dimensions of your footwell and seal edges with heavy-duty gorilla tape, HVAC tape, roofing seam tape, poly film tape, or silicone caulk to protect the foam against moisture damage. Keep the spare half as replacement for when the memory core begins to degrade due to "foam fatigue" in 3-12 months, depending on use and driving habits. New vinyl memory foam mats can be purchased online for between $15-20.
Yoga Mat Testing
Not sure if the yoga mat you’re looking at is NBR or EVA? Firmly press your thumb into the mat for 5 seconds, then let go.
NBR is heavy for its size and feels gummy, doughy, and soft with a dull or matte finish, has porous or foamy edges on the cross-cut, and horizontal ridges or ribs on the surface. A thumb sinks deeply, and the dent stays visible for a few seconds before melting flat. It rolls tightly and easily, and will droop, flop, or hang like heavy rubber.
EVA is lightweight and feels firm, springy, plastic-like, and air-filled with a waxy or sheeny appearance under light, has solid and smooth edges, and often has smooth surfaces or is stamped with geometrics. It resists thumb-pressing, will pop back up instantly, and stiffly resists folding or rolling.
Avoid yoga mats made of PVC, TPE, or natural rubber.
PVC makes for very thin yoga mats that completely compress with a sticky or plasticky feel that smell like a shower curtain.
TPE makes lightweight yoga mats that bounce back quickly like EVA, but they lack shock-absorption and have a velvety or powdery feel.
Natural Rubber makes for incredibly heavy yoga mats that are usually very thin with a fabric-like weave on the back and an intense tire smell.
Additional Considerations for Drivers
Since most of the mat layers won’t work for those who need to operate foot pedals, here are three alternatives to consider in addition to the thin butyl mats. Drivers should aim to keep their vibration reduction methods to under ¼” [6mm] and secured to the floor to prevent safety hazards.
⅛” to ¼” commercial-grade high-density SBR [styrene-butadiene rubber] or closed-cell neoprene sheets. These do not compress and absorb low-to-mid frequency vibrations.
3mm to 6mm industrial-grade anti-vibration equipment matting made of compressed recycled rubber compounds. These are tough, high-grip, do not compress, and are designed to mute mechanical hums from machines or treadmills.
Vibration-dampening shoe insoles made of Sorbothane or Poron XRD, which absorb up to 94% of impacts and high-frequency mechanical shocks. This is considered the safest option for drivers as it is in direct contact with one’s feet and will never interfere with the pedal clearance.
Quick DIY Reference
- 2-3 layers of solidly connected, heavy-duty butyl rubber matting, about 80-mil / 0.08 in / 2mm thick, seal edges, can use velcro to connect to vehicle flooring for extra stability
- 3-4 loose layers of NBR or EVA yoga matting, total height of 1.5-2”, connected only at the corners with optional non-slip mesh at the very center for extra stability
- ¾”-1” memory foam matting with weather-proof exterior, high-density core, and anti-slip backing, if possible tuck edges into sill or footwell to prevent shifting
Closing
This DIY vibration-absorbing mat is customizable to the size of your specific footwell dimensions, easy to replace in sections as parts degrade over time, and can be made as thick or thin as you need it to be for optimal vibration reduction. May you find this as useful as I did and may it greatly expand your quality of life and transit comfort.
Thanks for sticking with me, I hope you learned something, and I hope to see you next time.