How to Size a Motorsport Helmet — NZ Fitting Guide
Aaron HarrisA motorsport helmet that doesn't fit correctly is less safe and less comfortable — and in a sport where your helmet is your most important piece of safety equipment, getting the fit right matters. This guide explains how to measure your head, interpret size charts, and what to look for when trying a helmet on.
Written by Aaron Harris — MSNZ Licence Examiner for helmets, racewear, FHR and HANS.
Step 1: Measure Your Head Circumference
The most important measurement for helmet sizing is your head circumference — the distance around your head at its widest point.
- Use a soft tape measure (or a piece of string you can then measure against a ruler)
- Position the tape measure just above your eyebrows at the front
- Run it around the widest part of your head — typically just above the ears and across the back of the skull
- Keep the tape level all the way around
- Record the measurement in centimetres
Measure twice to confirm. If you're between measurements, note both and refer to the size chart below.
Roux R1 SA2025 Size Chart
| Size | Head Circumference |
| S | 56 cm |
| M | 59 cm |
| L | 60 cm |
| XL | 61 cm |
| XXL | 63 cm |
If you're between sizes, contact Aaron Harris for advice before ordering. Getting the size wrong is an expensive mistake.
Step 2: Understand Head Shape
Head circumference is only part of the equation. Head shape also matters — heads can be broadly categorised as:
- Round oval — roughly equal front-to-back and side-to-side measurements
- Intermediate oval — slightly longer front-to-back than side-to-side (most common)
- Long oval — noticeably longer front-to-back than side-to-side
Different helmet brands and models suit different head shapes. The Roux R1 SA2025 suits intermediate oval head shapes well. If you have a long oval head, contact Aaron Harris before ordering to confirm fit.
Step 3: What a Correct Fit Feels Like
A correctly fitted motorsport helmet should:
- ✅ Feel snug all the way around — no pressure points, no gaps
- ✅ Not move when you shake your head side to side or front to back
- ✅ Feel slightly tight when new — the liner will compress and conform to your head shape over time
- ✅ Allow you to see clearly through the visor without the helmet sitting too low or too high
- ✅ Allow you to open and close your mouth comfortably
A helmet that is too loose will move around during an impact, reducing protection. A helmet that is too tight will cause headaches and discomfort during long sessions.
Step 4: Cheek Pad Adjustment
Most motorsport helmets — including the Roux R1 SA2025 — allow you to fine-tune the fit using cheek pads of different thicknesses. If the helmet fits well overall but feels slightly loose in the cheek area, thicker cheek pads can improve the fit without changing the shell size.
Harris Race Radios stocks Roux cheek pads in multiple thicknesses for the R1 SA2025.
MSNZ Helmet Compliance
A correctly fitted helmet is also a compliance requirement. MSNZ Licence Examiners check that your helmet fits correctly as part of the licence examination process. A helmet that is too large or too small may not pass examination, even if it carries the correct homologation.
Aaron Harris is an MSNZ Licence Examiner for helmets and racewear and can advise on fit and compliance before you purchase.
Get Expert Fitting Advice
If you're unsure about sizing, contact Aaron Harris before ordering. Getting the right fit the first time saves the cost and hassle of returning and exchanging.
📞 +64 27 449 9654
📧 aaron@harriscomms.co.nz