BECAUSE NOT ALL AAA CERTIFIED MOTORCYCLE JEANS ARE THE SAME
We looked at four models of single layer jeans and arranged for them to be abrasion tested at an independent laboratory.
The results of which are shown in the chart below:
Since we first started to share our opinion on single layer riding jeans, a few years ago, our views have generated quite a lot of discussion and debate. Single layer jeans are being promoted as “tougher than leathers” and the number available on the market has grown, with some commanding extremely high manufacturers’ suggested retail prices; so, does the hype – and the price – actually stand up to scrutiny?
We looked at four models of single layer jeans and arranged for them to be abrasion tested at an independent laboratory. The test apparatus used was the EN 13595-2 “Cambridge” machine, because this delivers a numerical value that enables very clear and precise distinctions to be made between materials. By comparison, the EN 17092 “Darmstadt” machine generates only a pass/fail outcome and does not identify if a material was only just good enough to pass, or did so with a healthy margin of safety.
The results might be shocking to readers – they certainly were to us – because they demonstrated that far from being tougher than leathers – or a pair of Hood Jeans – their abrasion resistance is in some cases so disappointingly low it is no better than a pair of shop-bought denims, and certainly not the robustness and safety that should be synonymous with motorcycle riding jeans.
Our customers use and trust their Hood Jeans for all types of rides, on the open road and at motorway speeds, not just for urban rides around town. We honestly feel we cannot put that trust, our reputation, and most importantly our customer’s safety at risk by placing our name on a product that we don’t have complete confidence in.
For an in-depth article on the reasons why we do not manufacture ‘single layer’ motorcycle jeans, read below:
WHY HOOD JEANS DO NOT MANUFACTURE ‘SINGLE LAYER’ MOTORCYCLE JEANS
Reading this may just save your skin.
In recent years the single layer motorcycle jean has become a product seen in greater numbers, so why doesn’t Hood Jeans manufacture a single layer jean? The answer is straightforward: we simply do not believe a single layer jean gives the protection both ourselves and more importantly our customers would expect and demand from a Hood Motorcycle Jean.
Hood Jeans only produce jeans capable of being CE and UKCA certified to Class AAA EN 17092-2:2020; the highest level of protection specified by the standard.
Single layer denim has been around for many years. We first tested single layer denim back in 2010. That particular fabric did not meet the minimum levels of abrasion protection that we have always insisted on. We witnessed further drag tests of a single layer jean in 2015, once again the product performed poorly, failing very quickly. In 2019 with more single layer jeans coming onto the market we decided to look again at the product, this time producing a Hood Jeans single layer prototype. We ran abrasion tests on the product at SATRA Technology Ltd, the prototype receiving a 1.80 second result on the Cambridge machine. Compare that to the 7.2 second result achieved by the K-tech + stretch denim construction of the Hood SK11/AAA and K7/AAA (S) Jeans.
For urban rides a single layer garment would probably provide the protection needed. However, we know Hood Jeans wearers use and trust their jeans for all types of rides, on the open road and at motorway speeds, not just for those around town. We honestly feel we cannot put that trust, our reputation, and most importantly our customer’s safety at risk by placing our name on a product that we don’t have complete confidence in.
Over previous years the motorcycle jeans we had seen that had failed were those styles that had small panels of protective lining covering certain primary crash areas. These jeans failed to protect in the areas where the lining did not cover, causing injury to the skin below. More recently, the fashion for single layer motorcycle jeans seems to have taken over from the panelled style of lightweight motorcycle jean. However, we strongly feel that the single layer style of motorcycle jean also has major flaws, meaning riders could be putting themselves at risk of injury whilst believing they are fully protected.
So, what are our concerns?
- Failing of the single-layer denim from heat: Blended fibres used in monolayer jeans are based in part on the respective melting points of the commonly used materials. In ascending order these are 155 degrees for UHMWPE, 260 degrees for polyester, 295 degrees for polyamide, 300 degrees at which cotton decomposes, 330 degrees for Vectran and above 500 degrees for Kevlar and K-tech para-aramid – all values in Celsius. Testing conducted as part of the PIONEERS project has measured the temperature at the rider’s skin in a slide from 70kph/44mph at 143C. That’s close to the melting point of UHMWPE and may be exceeded at the point of contact with the road, but the key issue here is that in the case of UHMWPE in particular, a fibre woven in to supposedly increase strength of the fabric overall has a melting point of only just over half that of the material it is supposedly reinforcing.
- Weakening of the single-layer denim from heat: As mentioned in concern one, the melting temperature of UHMWPE is low, quoted from 130-160°C depending on the source. Due to the nature of the structure of the long chain PE molecule it will reduce its tensile strength as the temperature increases. One academic paper indicates; (a) the variability in melting point of UHMWPE, depending upon source, with some fibres reaching their melting point at a temperature lower than that recorded in the PIONEERS tests; (b) that the fibre starts to lose its tensile strength well below the melting point, and (c) that the point can be reached where the sudden onset of catastrophic failure occurs. As you can see, this suggests that even if UHMWPE fibres do not reach their melting point, they can still be significantly weakened by heat. The fibre’s strength falls off a cliff with the increase in temperature.
Tensile strength versus tensile testing temperature of a UHMWPE fibre (λ = 100, 5.0wt.% Hifax A) showing the ductile to brittle transaction upon decrease of temperature (from). At 152°C orthorhombic crystalline material transforms into the hexagonal phase. Crosshead speed 10mm/min, sample length 50mm
(Source: Tensile deformation of high strength and high modulus polyethylene fibers. H. van der Werff and A. J. Pennings. Department of Polymer Chemistry, University of Groningen, Groningen, The Netherlands)
- Deterioration of the cotton element of the single-layer denim over time: what happens to the ‘single layer’ denim after a few years, once the jean has been worn and washed many times? At what point does the cotton element of the fabric start to deteriorate and lose its strength, as happens with all cotton / denim fabrics? At this point will the jeans provide the same level of protection as when they were first tested? Our experience suggests not. It has been said K-tech para-aramid loses its strength with washing, but this statement is highly misleading. It is true that K-tech is affected by water, but the effect is so small the amount cannot be quantified, meaning it is virtually unaffected. And when the K-tech dries it returns to its original strength. I guess very few fabrics gets stronger with wear; however, we all know what happens to denim and the knees of our favourite jeans over time. Of course, the deterioration of the outer denim still happens with our jeans; however, with a Hood lined motorcycle jean you always have the second layer of 100% K-tech para-aramid to save your skin.
- Dilution of protective fibres within single-layer jeans: The reasoning here is that any benefits provided by the hi-tech protective fibre whether it be Kevlar or UHMWPE are simply diluted by the lower-performing cotton it is combined with to construct the denim. Some single layer denims feature a 40% protective fibre / 60% cotton construction. Some single layer denim has an even lower percentage of the protective fibre. This means all single layer denim jeans contain a far greater percentage of normal cotton, and a lesser percentage of the protective fibre. How can this provide the same protection level as a 100% K-tech para- aramid protective layer? There are, of course, denim-look jeans which are manufactured entirely from man-made fibres, with no cotton content whatsoever. These will not display the same degradation highlighted above, but the choice of which fibres to use could prove extremely important in terms of their respective melting points.
- Shear-force injury: The term ‘single layer’ is a little misleading as ALL ‘single layer’ motorcycle jeans really should incorporate a second lining, to reduce shear-force injuries. These are the skin abrasions which can occur due to the movements between the outer fabric, when it is in contact with the road surface, and the wearer’s skin, which cause the back surface of the outer material to transfer these forces direct to the wearer’s skin. This is entirely different to the injuries which can occur when the fabric of the jeans is breached, a hole or tear appears, and the road surface can make contact with the wearer’s skin. Shear force injuries, commonly referred to as “lining burns”, were responsible for the urban myth that man-made linings melt during a slide. The actual mechanism of injury was first discussed by respected motorcycle clothing expert Paul Varnsverry in the late 1980s, given the name “shear force” by Dr Roderick Woods in the early 1990s, and is a term which continues to be used today by both Paul Varnsverry and Dr. Chris Hurren, of MotoCAP. Linings in garments are essential to providing “shear-force interception” and they do this by remaining static on the wearer’s skin, whilst the movements of the outer layer take place against the reverse face of the lining. Multi-layer constructions amplify this benefit.
Multi-layer constructions work in the same way as do laminates, which outperform the individual properties of each separate layer from which they are constructed (the whole is greater than the sum of the parts). In addition, the separate layers can move relative to each other, improving flexibility
Not all AAA rated jeans are the same: We have always supported the EN 17092 standard. In 2018 we were the first company in the UK to be certified Class AA: prEN 17092-3 and again in 2021 Hood Jeans were the first company to be awarded UKCA certificates by Satra. However, we do have a couple of criticisms of the standard.
- We feel the abrasion level is set too low, and the highest classification being too easy to achieve. Meaning some products with relatively low abrasion resistance can achieve the same highest classification as a garment with much higher protective qualities. I have seen some companies compare their single layer jeans to full race leathers and fully lined motorcycle jeans, just because all were classified AAA. I wonder do these companies really believe these garments are all of comparable levels of abrasion protection. I really feel there needs to be a higher level of classification to indicate to riders the real difference in protection.
- EN 17092 uses the Darmstadt abrasion machine. Unlike the Cambridge machine used for EN 13595 the Darmstadt machine does not give a time of when a material has failed. It simply provides a pass or fail result. This means a product can just scrape through the abrasion test for EN 17092, but be given exactly the same ‘pass’ result and classification as a product that has much greater abrasion protective qualities and has passed the EN 17092 abrasion test by a much greater margin.
Hood Jeans – Cambridge Machine Data
The construction of SK11-AAA Jean and K7-AAA (S) Jean – stretch denim and K-tech para-aramid have been tested in accordance with the tougher EN 13595-2:2002 impact abrasion test on the Cambridge Machine, recording a 7.2 second result, a result that meets the highest EN 13595 ‘Level 2’ performance requirement specified by the standard.
Hood Jeans – Darmstadt Machine Data
- Initial speed: 707 rpm
- Time to stop: 6.5 seconds
- Distance to stop: 93.7 metres
This passes the AAA classification to European Standard EN 17092-2:2020. The highest class for protection.
Be wary of so called “slide times” – a term which does not appear in either EN 17092 or EN 13595. Time does not form the criteria by which a pass/fail result in the EN 17092 impact abrasion test is defined – that is set by whether a hole has appeared at the end of the test which is larger than 5mm in any direction. Motorcycle clothing expert, Paul Varnsverry, commenting in a discussion on social media, had this to say about the use of the term ‘slide time’: ‘“Distance to stop” and “time to stop” – of the test samples in the Darmstadt abrasion machine – are required to be entered into test reports to establish the coefficient of friction that exists between the materials that comprise the test specimen and the concrete surface of the device. I have results for a construction that passed for Class “AA” that differs in so-called “slide time” by only 0.4 of one second compared with a construction that achieved an “AAA” result. This is insignificant if read in the context of respective levels of protection, but as I have already stated, this is not the purpose of the data.’
‘Real world’ testing: In RiDE Magazine’s July 2019 issue, they performed a ‘destruction test’ on twelve motorcycle jeans then on the market. Four of these were ‘single layer’ jeans: they scored 2/10, 4/10, 5/10 and 6/10 for protection. The lined Hood K7 Jean scored an impressive 10/10 for protection; the K-tech lining remaining totally intact throughout all four tests and resulting in the K7 Jean being awarded a RiDE ‘Best Buy’ triangle. The only other jean on the test to also be awarded 10/10 for protection was another lined motorcycle jean, this one by an Australian company.
HOOD SK11-AAA JEAN and K7-AAA (S) JEAN: CE and UKCA certified to EN 17092-2:2020 for Class AAA garments; the highest level of protection specified by the standard.
The SK11-B and K7-B (S) Jeans Hood B rated jeans are constructed in exactly the same way and to the same standards as the Hood AAA versions. Meaning the abrasion protection is also exactly the same in all Hood Jeans. The only difference is the B rated Hood Jeans do not come with hip and knee armour. This can be useful for people that own multiple pairs of Hood Jeans and want to swap their armour between jeans, saving themselves the cost of the armour. However, most people purchase the AAA versions that come with the hip and knee armour.
We have set out our stall over the years and our business philosophy is quite clear: The highest levels of protection, for not the highest price.
It has been suggested the technology used in single layer garments is so sophisticated it puts the product out of our capability, and that deep pockets are required to afford the minimum order quantities for single layer fabrics, again making the product only accessible to the larger brands. The people saying this obviously do not know the scale of our sales, or the technological excellence of the companies that we have now worked alongside as partners for many, many years. The truth is in 2019, had we wished we could have easily released a Hood single layer jean, and sold it at the same price as our lined jeans. The minimum quantity of single layer denim would only add up to around 25% of our current denim requirements, so would have been easily achieved. The fact Hood Jeans didn’t release a single layer jean had nothing to do with technology or cost, and everything to do with protection.
When comparing the Hood abrasion resistance results from the Cambridge test machine to those of two flagship single layer jeans, both costing £349.00; the Hood lined jean was over 12% stronger to the first single layer jean, and an incredible 128% more abrasion resistant compared to the second, both single layer jeans made by the same brand.
The opinions we hold are moulded by our twenty-four years’ experience manufacturing motorcycle jeans. However, there are industry experts, scientists’ journalists and many riders that are backing our views.
ALL motorcycle clothing should by now be CE and UKCA certified. However, we still feel a little homework is required before purchasing motorcycle wear. If you are reading this, then you have already committed the time to do your research. You therefore deserve to find a jean that works to protect. We feel that product should be a lined motorcycle jean, whether that is a Hood Motorcycle Jean or a lined jean from another brand. We wish you well in your search.
Thank you for taking the time to read my words.