Question 1

How do I measure my head for a bike helmet?

Accepted Answer

Wrap a soft tape measure around your head about one finger-width above your eyebrows and ears — the widest point. Keep the tape level and snug but not tight. Record the circumference in centimetres, then match it to the size chart on the helmet you are considering. Always sanity-check against the specific brand chart: a 57 cm head is a medium in most Giro and Bell models, but can sit at the top of small in some Kask or POC lines.

Question 2

What does MIPS do, and is it worth paying extra for?

Accepted Answer

MIPS (Multi-directional Impact Protection System) is a thin low-friction liner that lets the shell rotate slightly relative to your head during an angled impact, reducing rotational forces that are associated with concussion. Independent testing (including Virginia Tech and Folksam) consistently shows MIPS and MIPS-equivalent helmets score better than non-MIPS models in the same price range. For road, MTB, and commuter riders the $20–50 premium is one of the highest-value upgrades you can buy in cycling.

Question 3

Do I need a CPSC, CE, or ASTM certified helmet?

Accepted Answer

In the United States any helmet sold for bicycle use is required by the CPSC to meet the CPSC 1203 standard — look for the sticker inside the shell. Europe uses EN 1078 (CE marked). MTB / enduro / downhill riders should look for ASTM F1952 (downhill), which adds chinbar and higher-impact testing. Skate-style bucket helmets sometimes carry both CPSC bike and ASTM F1492 skate ratings, which is why they are popular with BMX and dirt-jump riders.

Question 4

How often should I replace my bike helmet?

Accepted Answer

Manufacturers broadly recommend replacement every 3–5 years even without a crash, because EPS foam slowly degrades from UV, sweat, and sunscreen. Replace immediately after any significant impact — even if the outer shell looks fine, the foam may have crushed internally and won't protect you a second time. Kids helmets often need replacing sooner simply because kids grow out of them; recheck fit every season.

Question 5

What size helmet does my child need?

Accepted Answer

Kids helmets generally start around 47 cm circumference (toddler) and go up to 56 cm (youth). Giro Scamp, Bell Sidetrack, and Lazer Pnut all cover the toddler-to-early-school range; Smith Wilder Jr. and Bell Span cover older kids. Measure just as you would for an adult; tighten the dial fit so the helmet does not rock forward or backward when the child shakes their head, and leave two fingers of space above the eyebrows.

Question 6

Are road, MTB, and commuter helmets interchangeable?

Accepted Answer

They overlap more than they used to, but each style makes trade-offs. Road helmets prioritise weight and ventilation (often 20+ vents, 200–250 g) and offer little rear coverage. MTB helmets add visors, extended rear coverage, and sometimes chin bars, at the cost of more weight and fewer vents. Commuter / urban helmets lean on safety features like integrated lights, reflectivity, and sometimes MIPS, in a rounded shape that fits comfortably under a hood. Any CPSC-certified helmet is legal to ride with, so pick the one that matches how you actually ride.

Question 7

How tight should a bike helmet feel?

Accepted Answer

Snug but not painful. With the dial loosened, the helmet should sit level on your head — front edge two fingers above your eyebrows, side straps forming a V just below your ears. Tighten the dial until the helmet does not shift when you shake your head side to side, but you can still slide a finger between the pad and your forehead. Chin strap should let one or at most two fingers fit between the strap and your chin.

Bike Helmet Sizing & Buying Guide

Sizing & fit guidance

What to look for when buying

Top helmets picks

Giro Register MIPS

Bell Nomad MIPS

Smith Persist MIPS

POC Omne Air SPIN

Lazer Z1 MIPS

Kask Protone Icon

Troy Lee Designs A1 MIPS

Abus Urban-I 3.0

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