Spinning yarns
Knitted uppers are now common on cycling shoes, but what are their benefits? And should you go for knitted, woven or something else entirely?
It has been a long time since knitted garments were the sole preserve of your nan. Knitted fabrics have been used to make shoe uppers for almost a decade in sports such as football and athletics, and have been gaining in popularity in top-end cycling shoes since 2018.
Compared to cycling shoes made with conventional uppers of synthetic leather, those with knitted uppers tend to come with a set of bold performance claims – better breathability, improved comfort and reduced weight among them. So how are they able to boast such advantages?
‘The uppers are created with electronic knitting machines which link loops of yarn on needles,’ says Fizik product manager Giovanni Fogel.
‘The machines are able to seamlessly change the yarn direction to create different stitching patterns within the fabric. This means we’re able to design and create functional zones with engineered performance in key areas, such as vents and mesh openings for enhanced breathability.’
The uppers can often be made from a single thread and can be engineered to conform to the foot for a much closer fit than traditional uppers, creating a seamless, single-layer structure that
allows shoemakers to substantiate those big performance claims.
Rapha’s accessories and hard goods design manager, Jon Freeman, is quick to point out that not all of these new-fangled uppers are stitched equally, however. Where knitted uppers use a single yarn, woven uppers are made from two yarns crossing each other to form the fabric. Rapha uses a proprietary ‘Powerweave’ woven fabric in its Pro Team and Exploro Powerweave shoes.
‘Knitted uppers offer sock-like comfort, which is ideal for running and other sports where the foot is very active. But in cycling the foot needs to be held in place much more so that it remains stable and connected throughout the pedal stroke. They need to maintain these properties when wet too, which is really hard to achieve with a knitted fabric because they have higher levels of multi-directional stretch and typically hold on to water. In contrast, woven fabrics offer more controllable levels of stretch and are stronger. They also maintain that high level of comfort so in our opinion they offer a better balance of comfort and performance for cycling shoes.’
Fizik’s Fogel counters that, when engineered correctly, knitted designs such as its Vento Infinito Knit Carbon 2 shoes can offset any downsides that may otherwise come naturally to the fabric construction.
‘Our knit construction has targeted areas of heat-fused polyurethane fibres, integrated to create support where the foot needs it,’ he says. ‘So our shoes provide all the support the rider requires. However we’re talking about an open mesh. The trade- off for letting a huge amount of air in is that water comes in too when it rains. You could argue these shoes work best in the summer, when rain is less likely. Nevertheless, the yarns are treated for water repellency, which means that while the upper may let the water in, the fabric doesn’t absorb it. Plus with the enhanced ventilation the shoes will dry out quicker anyway.’
Mixed materials, mixed feelings
Giro was ostensibly the pioneer of the knit upper construction in cycling shoes (Giro’s Empire E70 Knit shoes and Fizik’s Infinito R1 Knit shoes were released within days of each other), but the fabric plays a conspicuously small role in the brand’s current portfolio. Synchwire is the more dominant material, which is an ultralight mesh that has been thermally bonded to a layer of polyurethane film.
‘Our knit shoes were polarising, and although knit cycling footwear is a valid technology and has advantages in certain applications it just did not fit with our plan,’ says Peter Curran, Giro’s footwear product manager. ‘Synchwire allows us more freedom to stiffen areas, add ventilation and create visual interest. This is due to the simplicity of die-cutting film and mesh and bonding the layers together. Knit has the advantage of being produced in one operation, but there’s more commitment to one design due to the high production minimums.’
Giro moving on from knitted construction suggests the technology might not be all it’s cracked up to be, but Rapha’s Freeman says because the upper is so tunable there are still exciting prospects ahead and the technique can only get better.
‘With Powerweave there is always scope to improve and we’re working on the next generation already,’ he says. ‘Our Explore shoes took the woven fabric further, adding TPU yarns that are bigger, tougher and sit proud of the polyester yarns to take the brunt of abrasive impacts, improving durability without affecting comfort. Equally, though, we’re looking at new yarns and yarn placement beyond that. The process offers the potential to seamlessly change the properties of the upper in different areas.’
Compared to conventional shoes, those with knitted uppers come with bold performance claims – better breathability, improved comfort and reduced weight among them