How your hoops are made
We go behind the scenes at Avon to learn a whole load about tyre design and build
Tyres are just black and round, right? Well, not exactly. To be specific, they would be brown if it wasn’t for an ingredient called carbon black being added to the mix, but more about that later. The point is that it’s all too easy to just dismiss tyres as dull and unimportant because they aren’t colourful or noisy, which is doing them and the people who design, test and build them a massive disservice.
It is true that, apart from a tread pattern, all tyres look the same, but it is also true that due to the complexity and variables of a tyre’s mechanical and chemical construction, they are anything but. Tyre tests that use rider feedback as well as lap times prove that they aren’t all the same, and that tuning a tyre for best grip, stability, wear and handling characteristics is every bit as hi-tech for the people whose job it is to make engines more powerful and more environmentally friendly, or the electronic systems smoother, more responsive and with more functions. It’s just that where people involved with motorcycle design tend to be engineers from a given background or discipline, tyre designers are a very different breed – chemists.
Tyres are big business, very big business, and because even the process that a tyre is manufactured affects how the tyre performs and its characteristics, getting past the reception area of a tyre manufacturer is basically impossible, such are the levels of secrecy surrounding every single stage of a tyre’s life – from concept to manufacture. When the chance came my way to have a poke around the Avon Tyres facility in Melksham and meet some of the design team, the significance wasn’t lost... so off to Wiltshire I went.
For some scale of just how big the motorcycle tyre industry is, Avon is a relative minnow because it only has 170 people on the shop floor, producing a mere 1200 tyres per day, every day. The total headcount for Avon at Melksham is more than 300 on the site that once also produced Avon’s car tyres; a sector in which Avon is much more prevalent. Car tyre production moved to Serbia in 2019, but before then the headcount was 1600 people, all on one site. At one point in the dark and distant past, Avon was actually allowed to reclaim some land where the River Avon flows, or rather flowed, right
past the factory. Imagine the response today if a tyre manufacturer wanted to move an entire river just to bring in even more chemicals and make more noise in the centre of a market town – just to make more tyres, gas masks, boats, even golf club grips... if it was made out of rubber, Avon probably made it at some point.
Today the only evidence of this happening are bricked-up arches at the base of some of the older buildings. Geography and history lesson over, it’s off to the lab for a lesson in rubber with motorcycle tyre development manager Ashley Vowles. As we walk and
talk, I’m keen to find out how Ashley ended up with such a cool job title.
“One of the reasons I got into studying polymer science is because I grew up in Wiltshire and there was an Avon rubber factory in every town in the county,” he said.
“It was a huge industry around here, and because of that the local college ran very good polymer science courses. It was so good that people travelled from all over the world to study polymer chemistry at that college.
“I was originally interested in polymer science and I was always keen on the automotive industry, so doing what I do today is pretty much my ideal job. After I left college at 18 years old, I was part of Avon Technical Products up the road and designed gas masks for nine years. When I was doing that, they put me back through college for more qualifications in polymer science.
“Today I work in the European tech centre and head up the motorcycle development team. My department is made up of a lot of young people, which is great, and they all have degrees in engineering of some sort. Some have studied motorsport, and some chemistry; we’ll bring them in from all areas, but the one thing they all have in common is that they’re motorcycle enthusiasts.
“We’re in a good place now. I have to present to the senior executives once a month, about 20 or 30 people, to update them on what’s going on. We cover sales and all sorts of stuff, and they’re all very happy with the direction we’re heading in, the products we’re developing, and the people in the team”.
As if to ram the point home that tyres aren’t just black and round, as soon as we arrive at the lab – where there are racks of kit with screens and flashing lights that wouldn’t look out of place in the villain’s lair of a Bond movie, not to mention men in white coats and safety goggles completing the look – Ashley explains the sort of things that go on.
“This lab is used for developing compounds and testing competitors’ tyres. We also have another lab that we use as a control lab, where every rubber batch made for production can be checked for cure properties and hardness. In this lab, there are five people plus three chemists, so there are nearly 10 full-time staff just developing rubber compounds. They’ll pull apart competitors’ tyres, chop them up and break them down with nitrogen, then measure them at a molecular level to figure out what they’re up to, which is good to know but doesn’t guide our own development.
“My colleague who runs this lab is a materials development manager, so I’ll talk to him and the chemists about what we need from a compound or component, or I might give him a competitor’s tyre and ask him to make me a compound like it, and they do.
“They make a lab batch by mixing up the ingredients into slabs that go on a two-roll mill, which creates sheets that are still uncured. Rubber has no properties until it’s cured – or, to put it another way, cooked.
“It’s very much like a cake mixture. The chemical reaction hasn’t taken place yet; it’s the same for all rubber components. The only analysis worth doing on it in that state is with a rayometer, which helps us work out the best way to cure it. We need to know the
best temperature and the time needed for the best result, because the performance of the tyre depends on it.
“In fact, because we’re working at a molecular level, even the time and temperature the ingredients spend in the mixer has a massive effect on the finished tyre, so the chemists might change the temperature or time to change the properties of the tyre.
“It’s not just chucking it in and waiting for a bit. They might even mix a master batch and then put it back in and add the curatives and additives needed to get the chemical reaction; then they might put it back through again because some components like silica are hard to process and they can be hard on the machine, so some mixes need two stages, some need three.
“There are so many variables that can impact on the tyre’s performance. As well as compound development, we consider tread and sidewall development, compound material and ply materials, and even the cords can be made out of rayon, aramid, polyester, nylon, steel, or a combination of all of them.
“A tyre’s construction and tread work together, and every different part of the tyre has its own unique compound. For example, our new Supersport rear tyre, due out later this year, has 10 different compounds in it, and each compound has about 10 different chemicals and materials. It’s mind-boggling at times. The tread has a base compound that’s 0.5mm thick, which is there to bond everything together.
“Then there’s the main compound, which is in contact with the road – that itself is a dual compound. The sidewalls also have a unique compound. Then there’s the ply topping, filler compounds and the liner – all different.
“Then the cords need to be bonded in rubber, so that’s another compound. If you think about the variables, the number of combinations is well into the millions, and that doesn’t include the manufacturing process which affects the outcome. A change to literally any single part of the mix, ingredients or manufacturing process can alter the tyres characteristics.
“Usually we have a rough idea of what to do, but if it doesn’t work how we expect it, it gets re-done but with different tweaks. To get the compound I wanted to put into production for the Supersport tyre took four lab tests.
“We’ve got a lot of compound history, so there’s a lot of recipes we can go to straight away, but if we’re developing brand new compounds for a tyre, it can take two years. If we’re doing an upgrade to an existing tyre, it can take 12 to 18 months. If we’re adding a new size to a range, it’s about 12 months, so it’s a long process – there’s no shortcuts”.
It’s been 10 minutes since we got to the lab and my little brain is already hurting. It’s obvious who the brainiest person in the room is and it’s not me – it never is. Yet despite being hopelessly out of my depth, I am fascinated by the sheer amount of effort that goes into finding the magic combination of ingredients and processes out of literally millions of combinations to make the perfect tyre, and that’s just at a molecular level. There’s more stuff to keep Ashley and his team awake at night.
“Rotational grip is a lot to do with tread, but the way a tyre feels is determined more by the compound of the sidewalls and how we use different compounds in different ways. Do you want stiff sidewalls for best grip, or do you want longevity from the tread and soft sidewalls? Grip comes from compound and tread patterns; handling and stability is very much construction.
“Front tyres follow the same basic principles as rear tyres, but the forces and loads are different – you’ve got braking forces to consider instead of accelerating forces. Front tyres generally have softer sidewall because there’s less weight, plus you want more grip.
“Inverted groves in front tyres are something we trailed in the 1980s. They look like they are pushing water into the footprint instead of away from it, but it’s such a small footprint that any amount of water is displaced quickly anyway.
“Now those inverted grooves are used by everyone. By having them the other way, we
were able to completely eliminate uneven wear during the tyre’s life and improve longevity due to the braking forces acting on the tread pattern.
“It’s not the same with a rear tyre because the forces are very different. If you put your rear tyre on the wrong way round, you could potentially have a problem because you would be running against its grooves, and with less forgiving forces.
“We also use sipes to limit the amount of tread flex and keep heat generation down; they’re the fine cuts you can sometimes see on the surface of the tyre.
“The land/sea ratio refers to the amount of tread pattern on the tyre tread (the bit that is in contact with the Tarmac). Tyres that are aimed at track use, like our 3D Ultra Extreme or Pirelli’s Supercorsa, are close the limit of what is allowed for a land/sea ratio on a road tyre.
“There’s a legal percentage of how much of the surface must have pattern; it’s quite generous, in so much that if you put a few cuts into a slick, that would probably be legal, except slick tyres aren’t road legal to start with, so it would still be illegal.
“While our Supersport tyre, which is due at the end of the year, isn’t a pure track tyre, it assumes that the bike will generally be used in dry conditions, so there isn’t as much emphasis on the tread pattern as a tyre that’s anticipated to be used more in wet conditions. Tread patterns don’t just help with moving water – they also help with tread wear, even when there isn’t much pattern.”
Our visit to the lab isn’t over yet. There’s more information to digest while appearing like I know what’s being said. It reminds me of school, except I quite like it here – and I really like anything to do with motorbikes.
The information overload continues with an introduction to some of the key ingredients that go into a tyre, while the secret ones are kept well out of sight – not that I’d know what they are, anyway.
“The main ingredients in terms of volume are carbon black, oils and polymers. The bulk
is natural rubber, which is the sap from rubber trees. It’s a natural product that’s got a smell to it, and it mostly from Malaysia.
“When I was on holiday in Sri Lanka with my wife, we were driving along this road and in the corner of my eye I saw this lady in the woods, so we stopped to see if she was okay.
“She was actually collecting the sap by hand from rubber trees in a little pot, and there were thousands of the trees. To collect the sap, they score the tree round its trunk and eventually the sap runs out and into a little pot they leave there to collect it.
“Often a tyre company will own the plantation, such is the demand for natural rubber. It was the first thing I studied at college, so it was quite cool to see it at its source. If you go to the Eden project in Cornwall, they’ve got rubber trees there.
“Then there’s synthetic rubber, which is man-made and very popular, and also styrene butadines, which will all be different grades and used in different ratios.
“The other main ingredient is oil. In basic terms, the more oil used in the mix, the softer the compound will be. As well as helping to process the ingredients in the mixer, it also changes properties like hardness. More oil makes a softer compound and vice-versa. Racing uses a lot of resin, which is hard when cold, but when it’s up to temperature, it’s soft, hence why race tyres and trackday tyres are rubbish when they’re cold and need tyre warmers. It’s also very important for processing, because you’re putting all those dry ingredients into a mixer and you need some moisture.
“There’s also carbon black, which makes the tyre black and acts as a reinforcement, sort of like a filler. So, if you want to design a tyre for a Harley-Davidson and get it to do loads of miles, you would put a lot of carbon black in it, while a sport touring tyre would have less but more silica and oils. The carbon black helps with durability, as well as being a filler and colour.
“Silica is a synthetic powdery product. It’s a really useful ingredient. It’s used for good wet weather grip and grip when it’s cold, because it produces heat quickly. Trackday tyres won’t have as much silica because they get pre-heated with warmers since they don’t work well when they’re cold. For example, our Cobra Chrome tyre for the US market – they have dry conditions, long straight roads and cover big miles – will have little or no silica and more carbon black compared to a sports touring tyre for the European market.
“Silica is very hard to process because it’s abrasive on the mixers. Many tyre companies limit themselves to small amounts for this reason. I can honestly say that we use a lot compared to some – as much as we can.
“Then there’s sulphur, which every single compound will have because it enables the curing reaction and the cross-linking between the components to give the rubber its properties and change it from the stringy chewing gum state it comes out of the mixer in, and then assembled into a tyre, to a finished rubber.
“Cross-linking is the chemical reaction in the compound that can affect its final properties, such as wet grip, dry grip etc.,
and mileage. Loads more ingredients go in, like antioxidants, which get changed by small fractions that will also change the properties of the tyres. Obviously, there’s some secret ingredients too, which will stay that way.
“The way the tyre is produced means every ingredient ultimately contributes to the overall performance and characteristics of the tyre, irrespective of what the chemicals do to it before the manufacturing process. If we control the manufacturing process, we also control the chemical reactions and therefore control the end product.”
After up to two years of developing several compounds for a new tyre in a lab, the next stage is to make some prototypes, which is a surprisingly manual and hands-on process, even once the tyre is fully in production. The tread is extruded from a massive version of the same mixer and roller in the lab, except this one mixes batches of rubber 250kg at a time.
The carcass is assembled on a rotating drum by layering the plys that contains cords, and a liner that keeps the air in the tyre when it’s on the rim. A laser guides the operator where to line up each ply, then the machine turns for a given rotation/length, and the process is repeated depending on how many plys the tyre might have. The layers build and the cord is at different angles on each ply. Then the finished carcass gets the tread applied, and finally is given its rough shape by being stretched around a ring that’s filled with compressed air before going off to be cooked in a press.
I’m given the opportunity to briefly join the Avon workforce and assemble a tyre to see how difficult it is, and in doing so momentarily become part of the only workforce in the UK to be making a motorcycle tyre here (Avon is the only British motorcycle tyre manufacturer to still make its tyres on UK soil). Very soon – like, seconds later, I’m politely removed from the machine and told “it was a good try” by my host.
The next stage is the cooking process in one of the presses, where the raw tyre is put into a mould that contains the tread patterns and cooked for an undisclosed amount of time at an undisclosed temperature and pressure from the inside via a bladder filled with boiling water.
When the tyre comes out of the press, it’s red-hot and therefore really soft, so can deform easily; it’s still cooking and very fragile, so it gets inflated with cool air to manage the cooling process and hold it in the exact same shape it would be on a bike until it stabilises. Once cooled, that’s it. The tyre is ready for testing, and Ashley takes up the story.
“If it’s a brand new product, such as our forthcoming Supersport tyre, once we’re happy with its cross section, an initial build of the tyre will be supervised by the factory technical team. Then we’ll deliver it to the rig test team to make sure that it passes the required legislation, but also that we are happy with those pass marks, because we want a degree of safety.
If we are happy with the numbers, then we’ll go to the bike test phase. Finally, if we are happy at the end of that process, we’ll go into a small production build of about 40 tyres that haven’t been supervised by technical to test of repetition and the production process.”
I spent most of the day at Avon with my jaw on the floor at the sheer scale of the place, and the complexity of not just the design of a tyre, but also the manufacturing process... how each single part of the process – from the selection of chemicals to how the tyre is cooled once it comes out of the press – is critical to what you and I feel on the bike.
It is sad that a lot of the manufacturing that once took place at the site has been moved to Serbia, but the need to free up more space for motorcycle tyre production is as strong today as it was when they moved the river Avon once upon a time to create.
Walking around the factory and through the corridors, I can only imagine what it must have been like in its heyday.
That said, my interest is in motorbikes and motorbike tyres, not cars or economics. To have picked the brains of someone like Ashley makes me wish I paid better attention to my teachers at school. It was a real treat.
One last question, though. “You mention that the next part of the process is bike testing… can I come back please?”