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Troy Lee Designs D4 Carbon helmet review

First Look: The D4 is the latest in Troy Lee Designs' best-selling helmet line. Here are our first impressions of the latest carbon version

What is a hands on review?
Troy Lee Designs D4 Carbon Helmet
(Image: © Sean Fishpool)

Early Verdict

If money is no object, you’re not going to be disappointed by the D4 Carbon. It's noticeably lightweight, premium looks and feel, and sophisticated construction makes this a classy all-day option for downhillers


  • Very light
  • All-day comfort
  • Sophisticated safety features
  • Awesome looks


  • Not cheap

If you watch pro downhill mountain biking, freeride or BMX racing, you’ll be familiar with the Daytona series full-face helmet, which has been winning races since the late 1990s. The D4 is the latest in the best-selling family line and one of Troy Lee Designs' best full-face mountain bike helmets and is available as its lightest-ever carbon-shell model at below 1,000g or as a cheaper composite option. We take a look at Troy Lee Designs top of the range D4 Carbon full-face helmet.

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Troy Lee Designs D4 Carbon Helmet

The aesthetic of the D4 Carbon is unmistakably Troy Lee Designs (Image credit: Sean Fishpool)
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Troy Lee Designs D4 Carbon Helmet

The EPS construction is kevlar reinforced and lined with MIPS (Image credit: Sean Fishpool)

Design and aesthetics

The D4 is more angular and aggressive than the D3. Its silhouette is classic Troy Lee, and if you want their signature stunning paint options, you have a number to choose from, as well as plainer colorways.

Increased airflow was a design priority, and there are more external vents than before, now with open steel mesh covers. Inside, the washable liner has been redesigned, with more channels for airflow and rear vents with no mesh to allow heat to escape easily.

The pads and chin strap are soft and comfortable with a really premium smoothness, and the titanium D-rings are secure and easy to use

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Troy Lee Designs D4 Carbon Helmet

The D4 features aggressive angles and more vents (Image credit: Sean Fishpool)
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Troy Lee Designs D4 Carbon Helmet

Removable cheek pads can be quickly released to help removal of the helmet in the event of an emergency (Image credit: Sean Fishpool)
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Troy Lee Designs D4 Carbon Helmet

Rear vents don't have any mesh to help heat escape the helmet (Image credit: Sean Fishpool)


The D4 Carbon isn’t just designed to be lightweight, but it packs a number of sophisticated safety features. 

The ultra-thin ‘spread tow’ carbon layup in the outer shell ticks both boxes - higher strength and lower weight (and great looks). 

The EPS inner is protected across the whole helmet, including the edges, to protect against abrasion. There’s also kevlar reinforcement. The inner is also protected within the vents, for added durability and a sleek look.

The only place the inner foam is not covered on the outside is in a slender wedge shape above the bottom edge near the side of the jaw. This is a deliberate ‘suspension system’, designed to crumple more easily if the helmet smashes against the collarbone in a crash, potentially reducing the risk of a collarbone break.  Also, this part of the inner, along with the chin bar, is made of expanded polypropylene (EPP) which is softer than the rest of the inner layer.

Between the inner foam and the pads is a familiar MIPS system, designed to reduce rotational forces to the brain in a crash. And significantly, there are quick-release cheekbone pads, which allow first-aiders to remove the helmet more gently.

On the outside, the height-adjustable visor is designed to break off in a crash, rather than risk twisting the head, and the shear screws are easily replaceable. 

Troy Lee Designs D4 Carbon Helmet

The D4 is comfortable enough to wear all day (Image credit: Sean Fishpool)

Early verdict

The light weight of the D4 Carbon is noticeable, and the improved airflow over the D3 should make it a comfortable all-day lid in most UK conditions, even if there are better-vented options on the market.

If the $550 / £500 RRP is outside your budget, consider the $395 / £375 Composite version, which lacks the technical sophistication of the carbon shell, and comes with a less classy bag, but otherwise is identical and weighs in at only 50g more.

Tech Specs: Troy Lee Designs D4 Carbon Helmet

  • Price: $550 / £500
  • Weight: 997g (size M)
  • Sizes:  XS-XXL, via three shell sizes and different thickness pads
  • Vents: 24
  • Rotational protection: MIPS C2 liner
  • Colors: 5

What is a hands on review?

'Hands on reviews' are a journalist's first impressions of a piece of kit based on spending some time with it. It may be just a few moments, or a few hours. The important thing is we have been able to play with it ourselves and can give you some sense of what it's like to use, even if it's only an embryonic view.