Troy Lee D4 Carbon

Troy Lee D4 Carbon Helmet – The King of Helmets?

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George has a long and happy history with Troy Lee helmets – will the D4 Carbon keep a smile on his face?

Being 6’ 6” limits your ability to test stuff. Test bikes are generally supplied in a medium or large, clothes the same; I am however becoming a bit of a specialist in helmets (which must be why my wife keeps referring to me as one?).

Troy Lee D4 Carbon
George’s happy face

Last year we reviewed these full face trail lids and there is some detail in that review about my helmet history. In short, I crash a lot and subsequently I’ve sampled and destroyed a lot of full face helmets. Two in 2018, two in 2019 and double that in peaks. None in 2020 though, which makes me feel both happy and sad at the same time, which you may note as a theme. 

I’ve had this Troy Lee D4 Carbon since March but whenever Wales hasn’t been locked down tighter than Mickey Rourke’s face I’ve been assigned Tier (who knows what number but you’re not going anywhere) status and restricted to essential journeys only. Thus, I’ve become an infrequent Innerleithen visitor but have probably only worn the D4 for 7 or 8 full days over the summer plus a few afternoons recently whilst trail riding to re-familiarise myself with it.  

Troy Lee D4 Carbon

A bit of background… This helmet’s predecessor the D3 Carbon was my favourite full face. Like my favourite pair of jeans there’s just something reassuring about the fit, it just feels right for my head; unlike the Bell Full-9 Carbon for example where the chin guard feels a bit too close to my mouth, or the Fox Rampage Pro Carbon which feels a bit tight across the temples; so, we’re starting in a good place.  

Troy Lee D4 Carbon
LOUD D3 for comparison

I’ve had a good few Troy Lee D3 helmets and there’s this thing that happens when I put the boxfresh lid on for the first time. Initially, I think it’s going to be too small and I get a moment of slight worry, butterflies in the tummy (oh please don’t make me have to go through the hassle of boxing it up and sending it back) before realising moments later that it’s just snug and will loosen up very quickly. I had the exact same feeling from the Troy Lee D4. 

Dad joke time: Have you heard the one about the man who challenges his wife to tell him something that will make him feel both happy and sad at the same time (yes, we’re back to the theme, I did warn you)? If you have, you’ll know the punchline, if not Google it. Happy and sad was how I felt when adorning the Troy Lee D4 Carbon for the first time; I couldn’t really feel much difference between the D3 and the D4, which was both reassuring and disappointing.  

There are many claimed improvements though. Let’s start with safety: The lid is constructed from TeXtreme carbon fibre which is a technology based on thin ply and spread tow principles – me neither, but the clue is in the capital X and the crisscross design on the helmet; it’s constructed with crisscrossed strips of carbon rather than full sheets. Internally there’s EPS foam, a MIPS C2 liner, removable cheek pads and externally a breakaway peak. Fastening is via a (titanium) double-D ring which is the most secure way of fastening a full face as it’s the least likely to come loose. Troy Lee claims that this is the safest helmet they’ve ever made and it complies with CPSC 1203, CE EN1078, ASTM F1952-DH, and ASTM 2032-BMX safety certifications so, who am I to argue? 

Troy Lee D4 Carbon

Next, there’s ventilation: In total there are 24 (count ‘em) vents to keep your head cool. Most noticeably there are vents on top and to the rear which are new or larger than on the D3. I didn’t make it to the alps this summer (or for the record the summer before that, and yes, I will continue to mention it until the situation is rectified, thank you) so I couldn’t tell you for sure how effective it is but at no time during my time riding in the Scottish Borders did I feel like my head was too hot. 

Finally, there’s weight. My XL Troy Lee D4 Carbon tipped the kitchen scales at 1,070g, the XL D3 Carbon at 1,290g so they’ve shaved a solid 17% off. 

Other bits of interest: I’ve only used it with Oakley goggles but their frames fit perfectly, and the liner is washable. My test helmet was supplied in stealthy black but typically there are a range of wild designs available. As you would expect for a helmet costing £500 it comes complete with a helmet bag (very handy if you ever take it on a plane and don’t want to put it in your luggage) and a spare peak (although mine didn’t have one).  


In summary, the Troy Lee D4 Carbon makes me very happy. I haven’t managed to use it as much as I’d like but it’s been faultless when I have. I’ve thought about how you could improve it and I can’t really think of anything; the only thing that makes me sad is the price. It’s not a cheap piece of kit (although there is a more reasonably priced composite version) but it’s the new standard in DH helmets. The king is dead, long live the king!

Troy Lee D4 Carbon
George’s happy face

Review Info

Brand: Troy Lee
Product: D4 Carbon Helmet
Price: £500
Tested: by George Thompson for

After taking a 17 year break from exercise, George rediscovered mountain bikes in 2008. Six years later, at 40 years of age he started racing Downhill and the following season somehow ended up on the Revolution Bike Park Race Team. As the other members of the team fought for podiums and National Series victories, George searched for mid-pack mediocrity. In a bit to add some value #makingupthenumbers was born; a blog about their race weekends and in particular life towards the back of the field.

More posts from George

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