Key Takeaways
- Underlayers add a fire-resistant layer — and an insulating air gap — between the driver and the suit.
- Never wear everyday cotton-blend or synthetic clothing under a race suit: synthetics can melt onto the skin.
- Our underlayers are knitted from meta-aramid (Nomex®): tops, trousers, boxers, socks and balaclavas.
- Order your true size — underlayers are cut close to the skin and should not be sized up.
Why wear fire-resistant underlayers?
A race suit's protection depends on layers. Every extra layer, and the thin cushion of air between layers, slows the transfer of heat to the skin. A fire-resistant base layer under the suit adds one more barrier — often the difference between a minor injury and a serious one.
Underlayers also make the suit more comfortable: they absorb sweat, stop the suit from sticking to your skin and keep the suit cleaner for longer.
What not to wear under a race suit
Everyday clothing has no place under a fire suit. Synthetic fabrics such as polyester and nylon can melt in high heat and stick to the skin, which makes burns much worse. Even ordinary cotton offers no flame resistance. Many series rulebooks require fire-resistant underwear for exactly this reason — check yours.
The complete underlayer set
Our Nomex® knit underlayer range covers every area under the suit:
- Base layer tops and trousers — long-sleeved and full-length to cover the arms and legs.
- Boxers — fire-resistant underwear for complete coverage.
- Socks — protecting the feet and ankles inside the racing shoe.
- Balaclavas and head socks — protecting the head and neck under the helmet, where the suit collar and helmet meet.
Shop the auto racing base layer and auto racing balaclava.
How underlayers should fit
Underlayers are cut for a close, next-to-skin fit. Loose fabric bunches under the suit and is uncomfortable in the seat, so order your true size and do not size up. Our size guide has the full chart for tops, bottoms, balaclavas and socks.
A balaclava should sit smoothly under the helmet with no folds at the forehead or neck, and the opening should leave clear vision. Sleeves and legs should reach the wrists and ankles so they overlap gloves and socks.
Karting underlayers
Kart drivers wear base layers and balaclavas too — for comfort, sweat control and helmet hygiene rather than fire protection. See our kart racing base layer and kart racing balaclava.
Caring for underlayers
Wash underlayers after every event: mild detergent, no bleach, no fabric softener, and a cool wash so the knit keeps its shape. Our race suit care guide explains why.
Teams and retailers can order underlayers in bulk, in colours and with branding, or as private label. Request a quote.
Frequently Asked Questions
Do I need fire-resistant underwear under an SFI suit?+
Many series require it, and it adds protection under any suit. Check your series rulebook — and never wear synthetic clothing under a race suit, because it can melt.
Should I size up my Nomex base layer?+
No. Underlayers are designed to fit close to the skin. Order your true size using our size guide.
What is a balaclava for in racing?+
A fire-resistant balaclava protects the head and neck under the helmet, covering the gap between the suit collar and the helmet.
Have a project in mind?
Talk to our manufacturing team about your racewear — stock, private label or fully custom.