1. The whole process starts just after dawn in remote areas of Thailand. Local farmers tap their rubber trees, slowly extracting the raw latex. It ’s a small labour-intensive operation and not what you’d expect when it comes to supplying comparative commercial giants such as Kenda. The latex has chemicals added and is dried before being shipped in block form to the Kenda factories in Taiwan and elsewhere in Asia.

2. Once at the factory, the latex is mixed with synthetic rubber and additives such as sulphur, carbon black, antioxidants, accelerators and zinc oxide. The actual makeup varies depending on the characteristics required from the end product. It’s all mixed together at high temperature in a huge Banbury machine like this one and forms a gum-like blend of molten rubber.

3. With the components thoroughly mixed, the rubber is drawn out into sheets called ‘skins’ and this is stockpiled awaiting the next steps. This batch has that familiar black and rubbery look thanks to the carbon additive. The carbon serves to enhance durability and this rubber is likely to wind up as tyre tread.

4. Here the rubber is being rolled out and cut to the required width in preparation for the extrusion machine. The batch being processed here doesn’t have the carbon black additive as it’s destined to become a sidewall or a coloured strip on the tyre shoulder.

5. Next the long band of rubber is pulled along a series of rollers towards the extruder. This extruder has two entrances that can feed simultaneously. It allows them to combine different compounds into a single cross section of tread. This process allows them to create their DCT (dual compound tread) models which feature softer and grippier rubber on the sides and a longer lasting strip in the middle.

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We visit the Kenda factory where Steve Thomas takes a behind the scenes look at how our tyres are made.

From Trees to Treads

Tyres are something that we tend to take for granted. They’re not as shiny and exciting as a fancy anodised component or carbon trinket but they play a critical role in determining the ride quality of your bike. Rudimentary as they may appear, there’s an elaborate and labour intensive build process behind every tyre; we dropped into the Kenda factory in Taiwan to see first-hand what is involved.

Kenda mightn’t be the best known when it comes to MTB tyres but they are huge and produce for a number of ‘big name’ tyre brands. The facility that we visited is dedicated to making tyres for bicycles and motorbikes as well as all types of inner tubes (there are even bigger factories that handle the automotive and truck tyres).

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Factory Tour Photography by Steve Thomas

HANDS ONIt’s a hot and very odorous place, such is the nature of rubber, but what really hits home is the absolute hands-on element to the process—from start to finish. Sure, there is a whole lot of machinery involved but each one of these machines is hand operated, checked and observed.

On an average day, some 70,000 inner tubes and 20,000 bike tyres will come out of this factory. Kenda has a number of other factories scattered throughout Taiwan, China and Vietnam. As a group their manufacturing capacity stretches to 395,000 inner tubes and 258,000 bike tyres—that’s a whole lot of rubber!

Amazingly, every single tyre and tube is hand checked. Every inner tube is inflated, checked and then left pumped up for 24 hours. This heavy hands-on element is apparently commonplace within the tyre business; it gives a whole new appreciation for each and every rubber doughnut that we trash on the trail.

Here’s a breakdown on the basic steps that go into making the tyres that we ride… MBA 1

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While there's plenty of machinery involved, the manufacturing steps are hands-on and labour intensive.

6. The extruder uses a combination of high pressure and heat to form the tread section, so it’s cooled in water as it exits and continues along these rollers. While this rubber now has the correct makeup, it doesn’t have any tread—that comes later.

7. Next the rubber strip is wrapped around this tyre building drum. Here the tread laid up along with the rubberised fabric plies that form the tyre casing. With everything in place – plies, puncture protective layers, tread and even the tyre logos – strands of aramid fibre are wrapped around the drum to form the tyre beads. The drum expands to compress the components together, and once bundled up, you have what’s called a ‘green tyre’. This machine requires a skilled operator and plenty of training.

8. In the case of non-folding tyres, the wire beads are rolled and formed on this machine before being added to the tyre casing on the building drum. As with aramid beads, obtaining the correct diameter is critical; a fraction too big and the tyre can blow off the rim, too tight and it’ll be difficult to fit.

9. Pressure and heat now complete the manufacturing process as the tyre is cured. The green tyre is placed in a mould with a special tube inside. It’s then heated to 175 degrees celsius and left to cook. The tread rubber liquefies and is forced into the mould to form the tread pattern. This vulcanising machine can produce a range of different tyres; from road

to MTB and even motorbike tyres. Different moulds are placed inside to produce the desired tread pattern and tyre shape.

10. Fresh out of the mould and still with the pressurised tube inside. Once it has cooled you’re left with a tyre that’s ready to roll but it still needs to go through the quality control stage.

11. Kenda employs a team of full-time QC staff; they have to inspect every single tyre once it has passed through the curing process. Monthly performance tests are conducted to ensure they’re working effectively. Defects are randomly planted in the production line. If someone fails to detect a fault, they’ll need to undergo training if they want to regain their qualifications and return to the QC inspection team.

12. Kenda also produces 70,000 inner tubes per day at this factory, and like the tyres, every single one is QC checked before it ’s packaged and shipped. They are inflated to 140% of their intended size and lef t for at least 12 hours. The tubes are deflated and packed the following day—this process is said to weed out most defects.

13. Once through the quality control phase, the products are packaged, stockpiled and shipped out across the globe. Although, with a good chunk of the world’s bikes still built in Taiwan, much of their stock is distributed locally for new bikes. With the sort of numbers produced by Kenda, it’s clearly a big operation.

Tyre GlossaryAramid – An extra-strong synthetic fibre that’s often employed in the bead of a tyre. It’s commonly referred to as kevlar, which is a brand of aramid fibre.

Bead – The anti-stretch bands that wrap around the innermost part of the tyre. They’re commonly made from aramid on mid-to-upper end tyres and wire on the cheaper ones. Wire is really strong but adds weight compared to aramid. Aramid has the added benefit of being foldable. Strength is especially important if you’re running a tubeless setup as this typically places greater stress on the beads.

Butyl – A rubber that has low air permeability. It’s ideal for inner tubes as well as the inner surface of tubeless compatible tyres.

Casing – The rubber infused fabric that lies underneath your tread. It extends down the sidewalls and wraps around the beads to hold the tyre in shape.

Dual Ply – Commonly found in gravity tyres, these have a double layer of nylon plies. This gives the casing a more solid structure, providing better impact resistance and allowing for lower tyre pressures without excessive tyre squirm.

Durometer – A measurement of rubber flexibility. Low durometer rubber (50 for example) should offer better grip on rocks and roots but will wear faster and the knobs will be more prone to folding over rather than digging in. Hard rubber – a durometer of 70 – should last and roll well but will lose out when it comes to grip. Kenda (and most other tyre brands) can produce multi-density treads that combine different durometers within the one tyre.

Folding – Kevlar, aramid or carbon beads don’t stretch but they are flexible. As a result, these tyres easier to ship and store. Kevlar and carbon beads are also lighter than the wire that’s typically found in more affordable tyres.

Latex – The natural rubber that’s harvested from rubber trees. It is mixed with additives and synthetic compounds to form the rubber that you’ll find in a Kenda tyre.

Sidewall – The part that lies between the tread and the bead. Sidewalls used to be beige in colour but black is now more common on mountain bikes. This portion of the tyre is relatively thin and

can be prone to cuts when ridden through rocky terrain. As a result, many brands use special materials to reinforce the sidewalls.

Single Ply – These have a single layer of nylon plies wrapped over the casing they conform well to the terrain and tend to be lighter.

TPI – This stands ‘Threads Per Inch’ and refers to the number of individual threads found within one inch of the casing material. Low TPI casing (60tpi for example) means you’ll have more rubber moulded into the larger voids that lie between each thread. With high TPI casing (say 120tpi), there’s more fabric and less rubber. In general terms, low TPI casing tends to be thicker, more robust and cut resistant but slower rolling and rougher to ride. High TPI tends to be thinner, lighter and smoother rolling but the added flexibility offers less sidewall support at lower air pressures.

Tread – The rubbery bit that connects you with the trail—it provides the traction. Big knobs don’t necessarily equate to better grip; you need to factor in the rubber durometer, tread pattern, casing flexibility and suitability for your particular riding conditions; lots of big tread lugs won’t help you in thick mud—it’ll just clog up and you’ll be left with a 3kg semi-slick tyre!

Tubeless Ready – With an appropriately designed rim, virtually any MTB tyre can be mounted without inner tubes using liquid tyre sealant. However in recent years, tyre manufacturers have recognised the popularity of sealant based tubeless setups and now design most of their MTB tyres stronger with more airtight beads, and sidewalls that are less porous.

UST – Designed by Mavic in France, this is a fully airtight tubeless tyre system. When paired with a matching UST rim, no sealant is required to ride tube-free. As a result it’s a mess-free system but many people choose to add sealant anyway to self-heal small leaks and punctures. UST tyres are heavier than the equivalent tubeless ready version. They’re also more expensive with a limited choice of models available.

Vulcanise – The application of heat to the rubber and additives to cure it into the finished product.

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Factory Tour

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