Tyre recipe: It's in the mix!
There are as many rubber compounds as there are grains of sand on a beach and it can be difficult to tell what is what. That's why I did some reasearch to find out.
There are as many rubber compounds for bicycle tyres as there are grains of sand on a beach and it can be difficult to tell what is what. For this reason, I spent time informing myself and along with the help of Roland Golderer from Michelin, I was able to shed some light on the mystery of tyre composition.
Different tyres have different responsibilities that make every rubber compound a compromise between various characteristics. Here, Roland was able to give me an overview of the base materials that make up a bicycle tyre: polymers*, sulphur, fillers and other additives. The majority of the base is made up of the polymers. To decrease wear and damage, fillers like carbon black and silica are added. The sulphur, under heat and pressure, links with the polymers to create more cohesion and elasticity. Other additives make the rubber more resistant to UV rays and keep it from becoming brittle.
The art of making a tyre comes down to finding the perfect mixture of materials that match the desired riding style. That is why there are often multiple rubber compounds built into the same tyre. For strength, the first layers are made of harder rubber that support the outer structure. The outer layer that makes contact with the ground is chosen depending on their intended use.
Tyre Construction
To better understand how a tyre is constructed, I took an old tyre from our workshop and sliced it open. This cut allows me to show you the four main parts of a tyre: the tread, tyre shoulder, carcass and bead.
The bead
The bead is the thicker area at the edge of the tyre, or in this case at the bottom of the cut. The core of folding tyres is made up of fabric strands that are woven tightly together to give the bead its stiff structure. As the name suggests, wired tyre beads are made of wire. When installing a tyre, the bead hooks into the inner side of the rim creating a seal when it is pumped up.
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The carcass
The carcass is the sidewall as well as the supporting structure of a tyre. It is made up of a rubber coated woven fabric. The denseness of the carcass is given in threads per inch, or tpi. The denser the weave, the higher the tpi value is. The thickness of each fibre is also important. When thick and thin fibres are mixed, they adapt better to ground conditions and has less rolling resistance. The thinner fibres, however, make the tyre more susceptible to impacts and cuts. On the other hand, thicker fibres dampen and make the carcass stiffer.
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Tyre Shoulder / Tread Lugs
The shoulder of road tyres and the lugs of MTB tyres keep the tyres on the road when cornering.
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Normally, softer rubbers are used in these areas because grip is more important than a reduced rolling resistance or increased durability.
However, lugs on MTB tyres cannot be too soft or they could fold and even break off while cornering.
Tread
The tread is where the tyre makes the most contact with the ground. Often harder rubber compounds are used to reduce rolling resistance and increase durability.
Various manufacturer's rubber compounds
Continental
BlackChili
BlackChili Compound is a rubber compound that is only produced in Germany. Compared to the previous best Activated Silica Compound, BlackChili tyres have 26 % less rolling resistance, a 30 % higher friction value (grip) and a 5 % increase in mileage.
PureGrip Compound
This new rubber mix, given the self-explanatory name “PureGrip”, is ranked just behind Continental’s BlackChili Compound and is being used in their performance products both in the road and mountain bike sectors.
Maxxis
Single
One compound throughout the tread optimized for longevity and performance
Dual
Two compounds used within the tread of select tires to offer lower rolling resistance and increased cornering grip.
Super Tacky
A special low rebound, high traction compound used in mountain tires.
3C Triple Compound Road
Triple Compound road technology utilizes three distinct silica compounds in different locations within the tread of the tire. The centre compound optimized for exceptional tread wear and low rolling resistance. The progressively softer shoulder compounds provide increased grip while cornering.
3C Triple Compound Mountain
Maxxis 3C Triple Compound mountain technology uses a harder, longer lasting base layer and two progressively softer top layers in order to optimize traction and stability. Maxxis offers three different configurations of their 3C Triple Compound mountain technology: Maxx Speed, Maxx Terra and Maxx Grip.
Road
Three compounds comprised of a harder, longer lasting centre and two progressively softer shoulder compounds for unparalleled rolling efficiency
Maxx Speed
Used primarily in Cross Country and Enduro tires, the two compounds in the outer layer are specially formulated to reduce rolling resistance and optimize tread wear and traction.
Maxx Terra
An intermediate compound configuration used in select mountain tires. 3C Maxx Terra is softer and offers more traction than 3C Maxx Speed, yet provides better tread wear and less rolling resistance than Maxx Grip.
Maxx Grip
A new name for the Downhill 3C compound configuration that you have come to know and trust. 3C Maxx Grip offers the ultimate in grip and slow rebound properties for unparalleled traction in downhill applications.
Michelin
GUM-X Series
Michelin GUM-X series is the latest generation of tyre compound developed by Michelin for their Michelin Wild Advanced Mountain Bike range. Their experience in the definition of these new rubber compounds enables mountain bikers to enjoy an excellent balance of performance between grip, efficiency and wear.
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MAGI-X Series
Michelin MAGI-X series is the latest Michelin Mountain Bike rubber compound for Enduro use. Developed and used in the “Enduro World series”, this rubber mixture offers very high efficiency with exceptional grip on the angle; but also excellent braking under the most demanding conditions. The MAGI-X series is mainly intended to be used on the front wheel.
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Bi-Compound
Bi-compound is the association of two mixtures of different rubber on one tread. The rubber compound in the centre of the tread assure optimal transmission of torque and traction when pedalling or when braking. The rubber compound at the edges of the tread, bring maximum performance and safety when leaning in a curve or a turn, with an exceptional level of grip on dry as well that on wet ground.
Onza
DCR - Dual Compound Road
Combination of two different compounds. 65a for low rolling resistance and long-life on the inside and 55a on the outside for perfect grip in all conditions.
RC3 - Triple Compound / Racing Compound 45a / 55a / 65a
This competition compound is made up of three different rubber compounds. The 65a compound forms the base of the tyre. 55a in the tread ensures a long life and reduced rolling resistance. The lugs are made of 45a for optimal cornering grip.
RC² or RC² 55a - Dual Compound / Racing Compound 55a/65a
Combination of two different compounds. 65afor low rolling resistance and long-life on the inside and 55a on the outside for perfect cornering grip.
RC² 45a - Dual Compound/ Racing Compound 45a/55a
Combination of two different compounds. 55a for low rolling resistance and long-life on the inside and 45a on the outside for perfect cornering grip. This compound offers best performance for competition riding.
RC65a - Rubber Compound 65a
65a rubber compound for good traction combined with good rolling characteristics and long-life.
Schwalbe
PaceStar
The PaceStar compound is the right choice for fast Cross Country use. The focus here being an extremely reduced rolling resistance.
TrailStar
This rubber compound is made for Enduro & Freeride riders. It is the perfect combination of reduced rolling resistance and grip.
VertStar
The VertStar compound is perfect for Downhillers. The tires are made for extreme grip and reduced rebound. Weight does not play a role here.
RaceStar
Tyres with the RaceStar compound are perfect for competition. They combine reduced rolling resistance with exceptional grip.
RoadStar
The RoadStar compound is made for sporty touring bikes. It rolls great and offers outstanding grip.
TravelStar
The TravelStar compound’s main focus is on its durability.
Rubber Compound / Application
I have created a table with the various rubber compounds organized by which type of riding they are good for. I hope this helps you find the correct compound that keeps you rolling on your rides.
* A polymer is a chemical bond made up of a long chain of molecule that organize themselves into structures.
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