Review of the Arai Quantum ST full face crash helmet


Note in the US this helmet is known as the known as Arai Signet-Q.

Arai describe it as ‘race-tested’ and it’s based on RX technology, but it really seems to be made for the all-rounder who takes long trips; ST = Sports Touring. Positive comments are that it works well when you wear it all day; it deals with speed once you get to the autobahns/motorways, but it also keeps you comfortable. It does this partly by making sure you can get the shape as well as the size just right for your own unique head before you start. It’s a slightly longer version of original Quantum – another 5mm from front to back – with inserts that allow you to adjust the fit for individual contours, using ‘peel off strips’ and replaceable inner linings to personalise the fitting. Arai have put plenty of thought into the lining because they assume you will wear it for extended periods. It isn’t cheap but, like any expensive purchase, if you get enough wear out of it, then you may well decide it is still good value. It’s been described as the kind of helmet you can forget you are wearing – especially true if your head is an Arai-shaped head (that means a long oval shape – i.e. it’s longer than it is wide).

  • Now replaced by the Arai QV-Pro
  • SHARP 4 star safety rated (out of 5)
  • Good fitting if your head is longer than wide (oval heads)
  • Plenty of ventilation
  • Good visibility
  • Quite noisy
  • 1.6Kg (about average)
  • Available in sizes XXS – XXXL
  • Price range: £350-£500 depending on model

Best places to buy an Arai Quantum ST?

It’s not widely available, but the Quantum ST is still available at Amazon UK the last time we checked. Please click the link below – and if you buy from them, we get a small sum from the sale at no extra cost to you – a massive THANKS! (it’s how we finance the site).


There’s a lot of impressive sounding technology to protect your thinking equipment – “super complex laminate … enhanced hyper ridge strengthening … triple density inner shell”. The super complex laminate is claimed to be 40% stronger than standard fibre glass and it all sounds very reassuring to the lay reader.

AraiArai Quantum ST in Diamond Black
Arai Quantum ST in Diamond Black

The original Quantum was awarded SHARP three stars, with good results for front and crown impact and the new ST is described by the manufacturer as “one of the few” that meets both ECE22-05 and SNELL M2010 standards”. It was SHARP tested in June 2015 and scored 4/5 stars, dropping points only on the left hand impact test (though bizarrely not the right) so, as far as we can tell, it should perform well in an accident.

If you consider comfort an element of safety, then being able to adjust fit size makes this a safer helmet than something that either moves too much or pinches when you’re riding it.

Hopefully you’ll not need it, but in an emergency, when the ambulance staff need to remove your helmet they’ll find the emergency release mechanism that allows the chin pads to be pulled off first so the helmet can slide away easily. As helmets become more sophisticated and have special safety features like this, let’s hope the emergency services get medical training that includes updated helmet awareness to take advantage of these systems.

Helmet Noise

There’s plenty of air rushing through when vents are open and that creates noise. But if you close vents and pull out the chin spoiler to maximum users reckon it makes a big difference. One advantage of the vent system is that the rear outlet not only lets the damp air escape but also acts as a kind of spoiler to improve airflow around the helmet and that smoother air flow does help noise reduction. In general, air tends to move smoothly along the shell rather than towards the body, with minimised turbulence (that also helps reduce buffeting).

Having said that, in comparison to other helmets, the Arai Quantum ST is generally reckoned to be on the noisier side.

In Content Black colours – nice.


Arai are proud of their wide range of helmet sizes. They’ll even make one to measure if you need it, but most people don’t as they use up to 6 outer shells then add a range of detachable inners shells in different shapes and sizes, matched to the normal head shapes for each continent. They say that for most of their helmets, there will be one unique shell size covering two fitment sizes (eg. one shell size for XXS & XS, another for S & M and so on).

The Quantum ST is advertised for XS/54 to XL/62 for general distribution but they do go as far as XXS to XXXL. However, there is so much adjustment to the standard shell, using those replaceable inserts, some users have had to reconsider their basic size on this particular model, as the new shape can make all the difference to where you start and finish within each helmet size.

Removable foam padding allows for small adjustments but owners report that the lining can take time to settle in, so you may have to allow for this when buying one new.


The Free Flow System (FFS) has vents front and back, top and bottom – it’s very effective at cooling in summer but can be pretty chilly in winter. Thankfully, most vents are easy to open and close with gloves on, although some people found the chin vent took a little practice. Except in the most disgusting weather, it’s pretty rain tight, and the most that has been reported so far is an occasional dribble from the top after several hours of heavy downpour.

For safety, all the vents and ducts are supposed to break on impact, so it remains to be seen how easy it is to damage them with careless handling (though no one reported any damage so far).


Arai Quantum ST crash helmet pro shade
Arai Quantum ST in diamond white with Pro Shade System fitted

The ST has very good overall vision, with an extra 10mm on the width of the visor, so you get a good sideways view as well (click here to see other helmets with wide visors). The visor is fairly flexible so you can change it quickly without any tools or fiddling about – a single lever gets it off and it clicks back easily.

Given the UK weather, we suggest you in the anti-fog insert (often included in the buy price but worth checking when you buy). An easy-to-use Pinlock enabled visor is increasingly common on more expensive lids and the Quantum ST is no exception. Briefly, it means your anti-fog insert is located using two locking ‘pins’ on the visor that ensures the insert stays in place and forms a good seal between an anti-fog insert and the main visor. The Arai Quantum ST insert fits into what they call their “cavity shield” so it covers practically the entire visor area, with no misty margins, and you still get good vision even on potentially steamy days.

A breath deflector also helps and there’s a pull down chin spoiler with three positions which is a useful touch.

But what about sunny days? The helmet comes with a clear visor as standard but a ‘Pro-Shade’ option is also available. This is a sun visor which fits over the clear visor. You can raise or lower it easily and it locks in position, so you just need to decide whether it is worth up to £99 extra and, if so, do you fit it before you leave the house? Some users preferred to avoid the choice by making their own sun strip on the original clear visor while others, with a stronger or more reliable sun, were more grateful.

Again, some retailers are offering a Pro Shade free of charge with the helmet, so worth shopping around (at the time of writing clicking the link at the bottom to our partner retailer will get you a Pro Shade included in the price).


The ST version is elongated – 5mm longer than the original – so it’s better for those many heads that are not standard ovals. Side cheek pads can be put in or taken out to get a perfect fit for all face shapes, with and without bulges and beards. The Facial Contour System (FCS) also allows headband room to be adapted for the individual; with the goal of making the final result good fit all over without feeling too tight.

Many owners say it’s the perfect fit for their head shape. You tend to hear lots of people say their head is an Arai shape – and that generally means they’re folks with longer oval heads as that is who Arai generally target with their lids. So if that’s you, then you may well find that the Quantum ST is the ideal helmet for you.

With a bit more chin space from the previous Quantum, and adjustable foam lining, you can swear at white vans and chew the remains of your scotch egg whilst remaining perfectly cradled inside the shell. It also makes it easier to get off at the end of the day.

If you wear it for long enough, as you might, you can take out the whole of the interior, wash it and put it back, but the Dry-Cool© lining keeps you fresh enough in the short term.

Arai Quantum ST in fluorescent yellow
Arai Quantum ST in scary fluorescent yellow

Looks & Graphics

There are up to 13 design options on line – possibly fewer in your local shop – but one of them is scary fluorescent yellow. Car drivers have no excuse for not seeing that one coming! It’s fair to say that Arai tend to opt for more subdued and plainer colour schemes, but none of our owners claimed they bought it because of how it looks, more for how it feels and how well it seems to be made.

Other stuff – fasteners and glasses

The fastening is a double-D system. You either like them or you don’t but in our experience they’re easy to use and fairly reliable. Once you master doing them up with either cold or gloved hands, they are certainly secure and they’re quite easy to undo. It’s also a pre-requisite fastener for an ACU Gold sticker to take the helmet on a track day.

Glasses are less of a problem because you have more adjustment to play with. Owners don’t report any problems using the Quantum ST with glasses. If you only use sunglasses, a Pro-Shade might mean you won’t have to any more.

Best places to buy an Arai Quantum ST helmet?

It’s not widely available, but the Quantum ST is still available at Amazon UK the last time we checked. Please click the link below – and if you buy from them, we get a small sum from the sale at no extra cost to you – a massive THANKS! (it’s how we finance the site).

Quantum ST video

A quick video of the Quantum ST from J&S.


The Arai Quantum ST is well liked by owners. It has good ventilation, but can be a bit noisy. It scored a creditable four out of five stars for safety when tested by SHARP which should mean its safety performance is up there with some of the best. The build quality is good and owners like the comfort; you can personalise the fitment of the Arai Quantum ST to a surprising degree and, if you’re a long-oval head shape, ought to be able to get the ideal fit. At this price point there are some great alternatives (see below) but the Arai Quantum is a quality performer and well worth a look.


There are lots of alternatives – click on our top 10 best helmets to see which lids we’d recommend you buy. Here’s a couple worth checking out. The HJC IS-17 is a fantastic helmet – it’s 5 star rated (the maximum) by SHARP for safety, is all day comfortable and great value. If you’re wanting something a bit more exclusive (read pricey!) then the Shark Race R carbon fibre lid might be what you’re after. It’s another 5 star rated full faced helmet that’s got great build quality, light weight and with a wide visor for improved visibility. Both these lids are better options than the Quantum ST – unless you have a long-oval head in which case, the Arai might work better for you.

If you’ve found this Arai Quantum ST review helpful – or if you’ve owned an Arai Quantum ST, we’d love to hear what you thought about it – please let us know in the Comments area below. For other motorcycle crash helmet reviews, including other Arais, visit our All Crash Helmet Reviews section or our Only SHARP 4 or 5 Star Helmet Reviews section.

Best places to buy an Arai Quantum ST?

It’s not widely available, but the Quantum ST is still available at Amazon UK the last time we checked. Please click the link below – and if you buy from them, we get a small sum from the sale at no extra cost to you – a massive THANKS! (it’s how we finance the site).

Definitely want an Arai?

Here you'll find all our Arai crash helmet reviews and previews including full face, flip-up and open face helmets.


  1. about the Quantum ST Pro
    Personally I love this helmet,I commute a daily 80 miles and have had this helmet for 2 years and would rate it the best I’ve had had the bright yellow one which I believe does increase us motorcyclists of being seen and as far as I am concerned Im staying with bright colours
    The other aspect is comfort this helmet is super comfortable and the lining is of very high quality I think the best among other helmets this is what you pay more money for and in my view well worth it
    Also the visor system is excellent I have the pro shade and pinlock insert all very easy to change and gives great wide vision
    So overall I give it 10/10


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