One visor instead of two. The LS2 IRID Dynamic in its clear version is a photochromic screen that darkens in sunlight and clears again when the light drops, and this is the FF805 Thunder GP Aero in matt carbon supplied with it. Before the specification: at its lightest the Dynamic sits at 60 per cent light transmission, which makes it a daylight visor rather than a night one. The reasoning is a few paragraphs down, and it is the thing to understand before you order.

What a photochromic visor is actually doing

The tint is not a filter that gets switched. It is a layer of molecules that change shape when ultraviolet light hits them, absorb more visible light in that state, and relax back when the UV goes away. No electronics, no battery, nothing to charge — LS2 describes it as a fully mechanical system, and in the sense that matters, it is.

LS2 quotes the swing as 60 per cent down to 20 per cent visible light transmission, and the transition as 0.09 seconds. We pass that on as the manufacturer's figure and note that it is remarkably fast for the chemistry: most photochromic eyewear takes seconds to darken and considerably longer to clear. Treat it as a claim about the darkening step rather than a stopwatch you will be able to reproduce in a tunnel.

Where photochromics disappoint people

Three things, none of them faults, all of them worth knowing.

They need ultraviolet, not brightness. Behind a tall screen — and screens are polycarbonate or acrylic, both of which absorb UV — a photochromic visor darkens less than it does in open air. If you ride behind a big touring screen, expect a lighter tint than the number suggests.

They are temperature dependent. In the cold the darkened state goes darker and takes longer to clear; in high summer the tint is a little weaker. That is inherent to the chemistry rather than a defect in this visor.

And a photochromic never reaches the darkness of a dedicated dark visor. Twenty per cent is a proper tint, but it is not the near-black of a track screen — the dark version of this visor exists precisely because of that gap.

One more, about time rather than weather: photochromic layers fatigue. The molecules survive a large but finite number of cycles, and after several years of daily sun a photochromic screen darkens less deeply and clears a little more slowly than it did new. Nobody publishes a cycle count, ours included, so treat the visor as a wearing part on a long timescale rather than a permanent fitting.

Sixty per cent, and what that means for riding at night

A visor has to pass 80 per cent light transmission to be approved for use at any hour. Between 50 and 80 per cent it is still approved, but marked for daytime use. LS2 gives the Dynamic's lightest state as 60 per cent, and 60 sits in the second band.

So the way to use this helmet is the way it is packed: the Dynamic goes on for the day, and the helmet's own screen goes back on when you know you are riding home after dark. LS2 homologates the clear Dynamic for road use and does not publish the marking on the visor itself, so treat this paragraph as our reading of their own numbers rather than a quotation from the label — and check the marking on the visor you receive if you often ride at night.

Matt carbon

The shell is left in a matt clear coat, so the 6K weave is visible but does not throw highlights. It photographs flat and it hides fingerprints, which is most of the reason people choose it.

The trade is permanent. A matt clear coat cannot be polished: a swirl mark or a scuff that would come out of gloss with a mild compound stays in matt for the life of the helmet. Wash it wet, never dry, and keep abrasive cloths away from it.

The helmet under the visor

100 per cent carbon fibre in a 6K weave, one outer shell size across XS to XXL, 1,280 g declared with a 50 g tolerance, ECE 22.06, double D-ring. The GP PRO above it uses a 9K cloth, three shells and carries FIM homologation; this one does not.

One shell for the whole range is the specification worth checking in person. The outside volume is the same at every size and the difference is made up in padding, which works best in the middle of the range.

Air, and the anti-fog you get twice

Intakes at the chin, the brow and the crown, channels through the EPS, an exhaust under the rear spoiler, a breath deflector behind the chin bar.

Fog is handled two ways here, which is unusual. The Dynamic visor carries its own anti-fog coating that LS2 says holds for 120 seconds in their test, and the box also contains a Pinlock 120XLT MaxVision lens for the standard screen. If you commute in winter, the Pinlock on the clear screen is still the stronger of the two.

The release tabs

Red tabs at the base of the cheek pads pull the padding out of the shell so a helmet can be taken off a rider without rotating the neck. It is the equipment you hope never matters, and it is standard across the GP Aero range rather than an option.

ECE 22.06 for the helmet

Eighteen impact points against the old standard's five, several impact speeds, an oblique impact on an abrasive anvil that measures rotational acceleration, and a Brain Injury Criterion assessment. Accessories are tested fitted. Required across the EU since January 2024.

What this helmet does not have

• No FIM homologation. The FF805 Thunder GP PRO carries it; the GP Aero does not.
• No drop-down sun visor — the photochromic screen is the answer to that problem here.
• A clear state of 60 per cent, which is not a night-riding transmission. See above.
• One outer shell size across six helmet sizes.
• No SHARP, ADAC or Snell result for any FF805 Thunder.
• No noise measurement published, and none invented here.

In the box

• LS2 FF805 Thunder GP Aero helmet — Matt Carbon
• LS2 IRID Dynamic Clear photochromic visor
• Carrying backpack
• Tinted visor
• Pinlock Max Vision 120XLT anti-fog lens
• Tear-off films
• Reflective stickers

LS2 publishes one packing list for the whole GP Aero model and does not issue a separate one for the versions supplied with a Dynamic visor. The list above is that packing list plus the visor the article number is built around.

Size guide

Size	Head circumference
XS	53–54 cm
S	55–56 cm
M	57–58 cm
L	59–60 cm
XL	61–62 cm
XXL	63–64 cm

Specification

• Model — LS2 FF805 Thunder GP Aero
• Part number — 168058813
• Finish — Matt Carbon
• Supplied visor — LS2 IRID Dynamic Clear, photochromic, road homologated
• Photochromic range — 60 to 20 per cent visible light transmission
• Homologation — ECE 22.06
• Shell — Carbon 6K, single outer shell size
• Weight — 1,280 g ± 50 g (helmet, LS2 figure); visor 20 g
• Retention — double D-ring with Emergency Release System
• Sizes — XS to XXL, 53–64 cm
• Anti-fog — Pinlock 120XLT MaxVision supplied; the Dynamic visor has its own coating, tested to 120 seconds
• Transition time — 0.09 seconds, fully mechanical, no batteries
• Ventilation — chin, brow and crown intakes, spoiler exhaust, breath deflector
• Interior — removable, washable, laser-cut hypoallergenic foam

• 1x LS2 FF805 Thunder GP Aero helmet — Matt Carbon + IRID Dynamic Clear
• 1x LS2 IRID Dynamic Clear photochromic visor
• 1x carrying backpack
• 1x tinted visor
• 1x pinlock Max Vision 120XLT
• 1x tear-off films

Size guide — all measurements