WHY WE DO NOT TRUST OR MANUFACTURE ‘SINGLE LAYER’ MOTORCYCLE JEANS
Reading this may just save your skin.
For a number of years, we have voiced concerns about ‘Single Layer’ motorcycle jeans and just how low the level of protection that they provide can be. During this time, we have tested many ‘single layer ‘denim constructions. None have achieved a level of performance where we would be happy to put our name on the product.
It has been suggested that the cost of introducing a ‘single layer’ jean has moulded our opinions. This is not the case. We could have easily introduced a ‘single layer’ Hood motorcycle Jean in 2019, and put it on the market at the same price as our lined motorcycle jeans. The fact is, currently we just don’t trust this type of product. The reasons below are genuine beliefs and findings based on our twenty-three years’ experience of producing quality motorcycle jeans, expert opinions from our partners within testing, certification and CE and UKCA standards, added to results from U.K test facilities.
In 2019 we carried out research, testing some of the latest ‘single layer’ denim fabrics available. We also produced a full-specification prototype Hood ‘single layer’ jean to help with our investigations. Laboratory testing of the Hood prototype ‘single layer’ jean suggested it would reach an AA classification; however, alarms started to ring after we performed a simple rub test – a rudimentary assessment, but one which we considered would provide an indication of how the material would stand up to routine wear and tear, not only its safety performance. After a very short distance in contact with a commonly-found coarse surface, the ‘single layer’ denim sample failed, and a hole appeared. When repeating the same rub test on a double layer construction no holes appeared. The samples were then sent for more in-depth laboratory abrasion tests. On the Cambridge Abrasion Machine, the ‘single layer’ denim achieved a 1.8 second result. Compare that to the 7.2 second result achieved by the K-tech + stretch denim construction of the SK11/AAA and K7/AAA (S) Jeans. The protection levels of the ‘single layer’ denims just don’t reach our expectations, so we wouldn’t feel happy to supply our customers with such a product.
We understand people are looking for comfort and wearability, but any motorcycle jean worth consideration should also give the protection needed when called upon. With regard to comfort, the weight of the Hood ‘single layer’ prototype was a major surprise. We expected it to be much lighter compared to the more extensively lined K7 Infinity Jean; however, the ‘single layer’ version only weighed in slightly lighter – by just 136grams to be exact. We feel this small saving wouldn’t make much difference with regard to comfort, especially when taking the compromise with the loss of protection into account.
In the past the motorcycle jeans that we saw that had failed were those styles that had small panels of protective lining covering certain so-called crash areas. These jeans failed to protect exactly where the lining didn’t 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 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.
We acknowledge that, when new, the ‘single layer’ type of denim (a cotton / man-made fibre mix) is relatively strong. During this time, it can pass some of the new CE classifications. However, what happens to the ‘single layer’ denim after a year or two, after the jean has been worn and washed several 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 protection as when they were first tested? Our experience suggests not. I therefore wonder whether the brands involved should consider including a ‘use by date’ on their products? Again, I think probably not.
I have witnessed one ‘single layer’ jean that was a little too long for its owner; this caused the wearer to step on the back of the hem, and after only a few times being worn the denim had worn through. This really doesn’t fill you with confidence! If you put your trust in a ‘single layer’ and that one layer fails, there is no second chance; no second layer to save your skin. The deterioration seen with cotton does not happen with the K-tech fabric, so even if the outer denim fails there will always be the 100% para-aramid layer to save your skin.
‘Single layer’ denim just does not afford the same level of protection as a double layer construction. The main factor for this is that any benefits provided by the hi-tech protective fibre are simply diluted by the lower-performing cotton it is combined with to construct the denim. Some aramid / cotton denims feature a 24% aramid / 76% cotton construction. This means the single layer material contains over three times more cotton than aramid within the mix. This simply does not give the same protection level as a 100% aramid layer.
Further concerns I have about 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 – all values in Celcius. 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.
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.
In the ‘real world’, just how strong is a brand-new pair of ‘single layer’ Jeans? In RiDE Magazine’s July 2019 issue, they performed a ‘destruction test’ on twelve motorcycle jeans currently on the market.
Four of these were ‘single layer’ jeans: they scored 2/10, 4/10, 5/10 and 6/10 for protection. The double layer Hood K7 Infinity Jean scored an impressive 10/10 for protection; the K-tech lining remaining totally intact throughout all four tests and resulting in the K7 Infinity Jean being awarded a RiDE ‘Best Buy’ triangle.
The term ‘single layer’ is a little misleading; ALL ‘single layer’ motorcycle jeans should really incorporate a second ‘Airflow’ mesh lining. This layer reduces shear-force injuries; the skin abrasions which occur due to the movements between the outer fabric, when it is in contact with the road surface, which causes the back surface of the 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 used to be called “lining burns” and 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.
Slide times are another question we have been asked about over the past two years. We guess this is because of the new EN 17092 motorcycle clothing standards. Many brands are quoting the so called ‘slide times’ for their jeans, but the real purpose of the figures is for the laboratory to check how the EN 17092 abrasion testing machine is functioning and it is not included in the criteria for assessing whether a material passes or fails. On the EN 17092 Darmstadt abrasion test, the pass / fail criteria are established by the size of hole (if any) when the machine comes to a halt, and not the point of failure of the sample.
Slide times, along with distance to stop, are calibration measurements for the EN 17092 test apparatus, to determine whether or not the coefficient of friction between the test sample and the abrasive surface is within specific parameters. One test sample may ‘slide’ further compared to another, however just because it slides further doesn’t make it better; it simply means it has less drag on the road compared to a sample that has more drag. There is a school of opinion that a garment with a higher coefficient of friction might be better, because the rider will slow to a halt in a shorter distance and might avoid collisions with roadside obstacles which a garment with a lower coefficient of friction might cause them to hit. The crucial thing is, has the material passed the test and at what performance level specified in the standard?
Please be aware of two misleading tricks we have seen from some companies:
- The deliberate attempt to fool people by quoting test times from the Cambridge machine against ‘slide times’ from the Darmstadt machine. We have seen one company that claimed its product’s 10:00 second (higher than level 2 – EN13595 standard) test result from a Cambridge machine was bettered by an 11:00 second slide time tested on the Darmstadt machine. This is not the case and test results and so-called slide times from both machines should not be compared against one another in any way. They are different test methods, with different pass criteria, and conflating the two either demonstrates a lack of comprehension or is simply disingenuous.
- I have seen some (but not all) abrasion resistance times which have been generated on Cambridge-type impact abrasion machines set up to test motorcycle gloves. The motorcycle glove standard EN 13594:2015 specifies a 120-grit abrasive belt, which generates entirely different results to the OP60 belt specified in the motorcycle clothing standard: EN 13595-2:2002. The abrasion resistance times on the glove belt can be up to three times longer than those on the clothing belt, so the ‘real’ clothing result might be as little as one third of the reported value. Check the CE certification of the garment thoroughly and look for the CE User booklet and ‘Declaration of Conformity’; if these are not available then the products are probably not fully CE certified.
The combination of our stretch denim with the K-tech and mesh lining in the SK11/AAA and K7/AAA (S) Jeans have been tested to the following on the Darmstadt machine:
- 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.
During our history we have collated a large amount of data and information from real crashes, our own drag tests and independent test houses. Until 2017, all testing was performed on the Cambridge machine; however, with the introduction of the new PPE standards (EN 17092), the Darmstadt machine is now used. The Darmstadt machine does not give the actual time to failure for the material; instead, it replicates a slide and tests whether perforation of the construction is smaller than half a centimetre. This means a material could far exceed the level needed, but by how much is not known. It also means a product may just reach the required level, but by the smallest of margins, yet would achieve the same certification classification as a product that far exceeds the requirement. To compound this problem, the abrasion test levels for the new PPE standards have not been set that high, this is the reason for our concerns that some poor products may sneak through and achieve certification.
For this reason, we have decided to continue to test on both the Cambridge and Darmstadt machines, so we can back-check data from current testing with data from that of the past twenty years.
There have always been two types of motorcycle jeans on the market, the jean that offers a token effort towards protection and the jean that puts protection at the top of its list of priorities. Hood Jeans have always sat firmly in the second category. We have been producing motorcycle jeans for over twenty-three years, and during that time a Hood Jean has never failed to protect its owner when called upon, a fact we are very proud of. We understand comfort is an important factor. This is why we have spent so much time over the years focussing on development of softer, more breathable fabrics. We do, however, feel the double-layer construction is an important design feature that works by increasing performance and helps bring the protection level of a man-made material closer to that of decent leather.
ALL motorcycle clothing should by now be CE certified, however I totally feel a little homework is still required before purchasing. If you are reading this, then you have already committed to giving the time to do this research. You therefore deserve to get a product that works to protect and is also comfortable. I feel the product should be a lined motorcycle jean, whether that is one from Hood Motorcycle Jeans or from another brand. I wish you well in your search.
Thank you for taking the time to read my thoughts.