Car tires are a big source of microplastics pollution, but what about mountain bikes?

One of the biggest contributors to the microplastics pollution scourge is the wear and tear from motor vehicle tires on roadways. But what about bikes?

And more specifically, what about mountain bikes that are often ridden directly through forests and along trails?

A team of scientists at the University of Bayreuth decided to look into this question. They carried out the first real-world study that measures how much tire material mountain bikes leave behind as they roll through nature.

Their goal? To understand how even environmentally friendly forms of transportation might be adding to the microplastic problem.

Understanding tire microplastics – the basics

Every time a car hits the road, its tires wear down bit by bit – and that wear releases microplastics into the environment.

Tires are made from a mix of synthetic rubber, plastic polymers, and chemical additives, and as they roll, tiny particles get scraped off and tossed into the air, soil, and water.

These microplastics from tire particles can settle along roadsides, wash into storm drains, or get carried by the wind, eventually finding their way into rivers, oceans, and even the air we breathe.

The problem is bigger than most people realize. In fact, microplastic pollution from tires is one of the largest sources of microplastics in the environment – even more than what comes from plastic bags or bottles.

These particles don’t break down easily, and once they’re out there, they can harm aquatic life, contaminate food chains, and possibly impact human health.

Mountain bike tires also shed microplastics

The research team designed a straightforward but revealing experiment. Nine mountain bikers received brand-new tires and were asked to ride as they normally would.

Their routes were recorded using GPS, and the tires were weighed in the lab at regular intervals to measure how much rubber had been worn away.

The results showed that mountain bike tires shed about 3.5 grams of material per 100 kilometers. That adds up to as much as 88 grams per bike per year.

While that may sound like a lot, it’s only a small piece of the bigger picture. Tire wear from cars and trucks releases around 11 grams of microplastic per 100 kilometers.

In Germany, this accounts for more than half of all road-related microplastic emissions and over a third of total microplastic pollution in the country. Compared to that, mountain biking contributes less than 1%.

The first 500 kilometers matter more

The researchers also discovered that the first few hundred kilometers on new tires caused more abrasion than subsequent journeys.

This is likely because the outer edges of the tires wear down quickly at first, and small manufacturing residues – like the tiny rubber “hairs” found on new tires – get rubbed off quickly.

“Our study provides the first reliable data on the amount of tire abrasion from mountain bikes under real-world conditions,” said doctoral researcher Fabian Sommer.

“The results show that while mountain bike tires release microplastics directly into nature, the amount is significantly lower compared to motorized vehicles. This highlights another advantage of cycling as a sustainable mode of transport.”

Other bikes may also add microplastics

The research team isn’t stopping with mountain bikes. They’ve already launched a follow-up study to compare tire abrasion rates across different types of bicycles, including road bikes, gravel bikes, and electric mountain bikes.

They’re also working with the laboratory of Professor Dr. Christian Laforsch, from the Collaborative Research Center 1357 Microplastics, to analyze environmental samples.

This collaboration will help paint a fuller picture of how microplastics from bike tires interact with the natural world.

While biking remains a greener alternative to driving, this research shows that even our cleanest habits leave marks.

Understanding those marks is a step toward making better choices – and maybe building better tires in the future.

Why microplastics still matter

Even though mountain bikes contribute far less to microplastic pollution than motor vehicles, they still play a role in the broader environmental picture.

The real issue is that microplastics are showing up in places they shouldn’t be – soils, rivers, oceans, and even inside our bodies. And they don’t break down. Once released, they linger in the environment, often for decades.

That’s why every bit of data matters. Understanding how much microplastic comes from different sources – whether it’s cars, clothes, shoes, or bike tires – helps build a clearer picture of where these particles come from and how we might reduce them.

It also helps inform smarter design choices, like new tire materials, better manufacturing practices, or improved trail planning, to protect the places we love to ride.

This study may be about bikes, but it’s also about something bigger: learning how our everyday habits connect to the growing web of microplastic pollution all around us.

The full study was published in the journal Science of The Total Environment.

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