Tyre dust pollution

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Tyre dust pollution

Post by Grumble » Sat Jul 04, 2020 10:54 am

I’m thinking hard about getting an electric car, and to that end part of my research has included listening to the Fully Charged podcast. On a recent episode discussing air pollution they were careful to describe electric cars as having zero tailpipe emissions, and went on to say that the exhaust gases cause less than half of the particulate pollution of a typical car - so electric cars don’t get off free by any stretch. I’m going to have a dig around but I’m not aware of any research to reduce tyre wear pollution, and it’s quite a significant contributor to microplastic and PM2.5 levels. Does anyone here know anything about this?

I’m starting my reading here: https://www.emissionsanalytics.com/news ... -emissions
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Re: Tyre dust pollution

Post by minusnine » Sat Jul 04, 2020 1:13 pm

Because I’m reading into this at the moment I listened to the same podcast. The guy interviewed suggested non-exhaust emissions were more like half to two-thirds of total emissions, rather than the ‘1000x’ scare quote in the emissions analytics press release. Here’s an EU report from 2014 which I haven’t yet read in detail but which appears to support the 50ish+% claim.

https://publications.jrc.ec.europa.eu/r ... on%202.pdf

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Re: Tyre dust pollution

Post by Martin Y » Sat Jul 04, 2020 2:02 pm

Thanks for that. I was sure I had previously come upon the "about half" claim but had no recollection of where. It struck me years ago that the rubber missing from worn out tyres didn't just vanish.

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Re: Tyre dust pollution

Post by Bird on a Fire » Sat Jul 04, 2020 2:14 pm

To be clear, I think this is talking about particulate pollution only? Which is already subject to fairly stringent restrictions (in new vehicles) so it's perhaps not surprising that exhausts are providing a small amount of the total - indeed, it reflects past success in reducing emissions.
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Re: Tyre dust pollution

Post by minusnine » Sat Jul 04, 2020 2:36 pm

Yes, sorry, particulate emissions. And he was highlighting the contrast between the, as you say, stringent controls on exhaust emissions in place with the essential lack of controls on wear generated by tyre and brake friction. What would a bit of cash invested in harder-wearing tyres or brake surfaces achieve?

I think he also highlighted the obvious trade-off that a harder wearing tyre might have much les grip on the road, which might be problematic...

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Re: Tyre dust pollution

Post by Grumble » Sat Jul 04, 2020 3:01 pm

Bird on a Fire wrote:
Sat Jul 04, 2020 2:14 pm
To be clear, I think this is talking about particulate pollution only? Which is already subject to fairly stringent restrictions (in new vehicles) so it's perhaps not surprising that exhausts are providing a small amount of the total - indeed, it reflects past success in reducing emissions.
Yes, and he highlighted the disproportionate effect that reducing sulphur content had in reducing particulate exhaust emissions. The thing is that there are no controls on tyre particulates. I don’t know how you would draft them, but it may be that there is something analogous to reducing sulphur content that would make a big difference.
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Re: Tyre dust pollution

Post by Grumble » Sat Jul 04, 2020 3:02 pm

minusnine wrote:
Sat Jul 04, 2020 1:13 pm
Because I’m reading into this at the moment I listened to the same podcast. The guy interviewed suggested non-exhaust emissions were more like half to two-thirds of total emissions, rather than the ‘1000x’ scare quote in the emissions analytics press release. Here’s an EU report from 2014 which I haven’t yet read in detail but which appears to support the 50ish+% claim.

https://publications.jrc.ec.europa.eu/r ... on%202.pdf
Yeah, the “1000x” claim is a bit daft because it relates to mass, which isn’t necessarily the important thing to measure.
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Re: Tyre dust pollution

Post by Martin Y » Sat Jul 04, 2020 3:21 pm

minusnine wrote:
Sat Jul 04, 2020 2:36 pm
Yes, sorry, particulate emissions. And he was highlighting the contrast between the, as you say, stringent controls on exhaust emissions in place with the essential lack of controls on wear generated by tyre and brake friction. What would a bit of cash invested in harder-wearing tyres or brake surfaces achieve?

I think he also highlighted the obvious trade-off that a harder wearing tyre might have much les grip on the road, which might be problematic...
The formulation of car tyres is surely sufficiently mature that there aren't any easy gains to be made on reducing abrasion. As you say, just making the tyres harder gives less grip. As it is, the formulations vary in different parts of the world and between summer and winter models, due to the temperature range they have to cope with. There are all sorts of other compromises to consider such as wet vs dry grip and noise generation by different tread patterns. I remember hearing anecdotally of one model developed for particularly low noise and it worked beautifully where it was developed, in Australia, but was hopelessly noisy on European roads, presumably due to different tarmac/asphalt/concrete surfaces.

On the other hand, there's probably good reason to think that electric cars with regenerative braking will reduce the wear on brake pads simply because they'll use the mechanical brakes so much less.

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Re: Tyre dust pollution

Post by bolo » Sat Jul 04, 2020 4:41 pm

Martin Y wrote:
Sat Jul 04, 2020 3:21 pm
The formulation of car tyres is surely sufficiently mature that there aren't any easy gains to be made on reducing abrasion.
Given that reducing abrasion means selling fewer replacement tires, I am not entirely confident that manufacturers are laser focused on this.

Tires are rated by, among other things, how many miles they are expected to last. So lower abrasion ones do exist, at least to some degree. They are just more expensive.

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Re: Tyre dust pollution

Post by Grumble » Sat Jul 04, 2020 5:08 pm

There may be a way of changing how quickly the particles break down once more surface area is exposed, for example. Or how they behave when bonded to bitumen - in the podcast I linked to Dr Gary Fuller says that the particles tend to be half tyre compound and half road compound.
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Re: Tyre dust pollution

Post by dyqik » Sat Jul 04, 2020 6:23 pm

Brake dust is probably also a chunk of particulate emissions. Hybrids and EVs do help a lot there though, as they don't use their brakes much at all.

There's no real way to reduce tire particulates except to make vehicles lighter. Grip requires adhesion between the tires and the wide variety of road surfaces, and that inherently produces particulates.

To improve matters, you'd have to adapt all road surfaces to work with something more resilient than tire rubber. And at that point, you're probably building a railway...

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Re: Tyre dust pollution

Post by dyqik » Sat Jul 04, 2020 6:26 pm

bolo wrote:
Sat Jul 04, 2020 4:41 pm
Martin Y wrote:
Sat Jul 04, 2020 3:21 pm
The formulation of car tyres is surely sufficiently mature that there aren't any easy gains to be made on reducing abrasion.
Given that reducing abrasion means selling fewer replacement tires, I am not entirely confident that manufacturers are laser focused on this.

Tires are rated by, among other things, how many miles they are expected to last. So lower abrasion ones do exist, at least to some degree. They are just more expensive.
Thing is, the difference in price between low abrasion tires and regular tires is less than the price differences between brands with the same mileage rating. The problem is that low abrasion tires are not really all-season capable, and struggle in cold rain or light snow.

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Re: Tyre dust pollution

Post by Bird on a Fire » Sat Jul 04, 2020 6:28 pm

The press release mentions that tyres "from a budget range" could give off even more particulates - is there any merit in the idea that cheaper/older (retreaded, perhaps) tyres are dustier?
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Re: Tyre dust pollution

Post by Grumble » Sat Jul 04, 2020 9:01 pm

dyqik wrote:
Sat Jul 04, 2020 6:23 pm
Brake dust is probably also a chunk of particulate emissions. Hybrids and EVs do help a lot there though, as they don't use their brakes much at all.

There's no real way to reduce tire particulates except to make vehicles lighter. Grip requires adhesion between the tires and the wide variety of road surfaces, and that inherently produces particulates.

To improve matters, you'd have to adapt all road surfaces to work with something more resilient than tire rubber. And at that point, you're probably building a railway...
Does grip require adhesion? It requires friction but that seems to be slightly different to me. Racing tyres shed bits like buggery though.
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Re: Tyre dust pollution

Post by Martin Y » Sat Jul 04, 2020 11:19 pm

Bird on a Fire wrote:
Sat Jul 04, 2020 6:28 pm
The press release mentions that tyres "from a budget range" could give off even more particulates - is there any merit in the idea that cheaper/older (retreaded, perhaps) tyres are dustier?
At a guess, it's probably cheaper to make tyres that grip at the expense of wear than to make tyres which grip and also last a long time.

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Re: Tyre dust pollution

Post by minusnine » Sun Jul 05, 2020 10:22 am

Grumble wrote:
Sat Jul 04, 2020 9:01 pm
dyqik wrote:
Sat Jul 04, 2020 6:23 pm
Brake dust is probably also a chunk of particulate emissions. Hybrids and EVs do help a lot there though, as they don't use their brakes much at all.

There's no real way to reduce tire particulates except to make vehicles lighter. Grip requires adhesion between the tires and the wide variety of road surfaces, and that inherently produces particulates.

To improve matters, you'd have to adapt all road surfaces to work with something more resilient than tire rubber. And at that point, you're probably building a railway...
Does grip require adhesion? It requires friction but that seems to be slightly different to me. Racing tyres shed bits like buggery though.
This:
https://www.racecar-engineering.com/tec ... tyre-grip/
says both mechanisms contribute - adhesion and roughness/indentation deformation. I can’t immediately remember/find anything that estimates the proportion each contributes, I assume the formulations of rubber for hard-wearing vs winter grip tyres change that balance.

I think the point Gary Fuller makes in the podcast is about regulations- we regulate exhaust emissions but not tyre/brake particulate emissions. There are some good reasons for that, including the trade-offs we’ve mentioned. Certainly a regulation that led tyres to have less grip, resulting in increased traffic deaths, would be immediately unpopular, and would probably have to be coupled to stringent behavioural restrictions (on speed etc.) to somewhat mitigate the greater accident risk. But I wouldn’t assume the market solves these problems by itself, or necessarily take at face value the industry’s assertion there’s nothing to be done - would we have hybrids and EVs without regulations on exhaust emissions forcing the industry’s hand?

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Re: Tyre dust pollution

Post by minusnine » Sun Jul 05, 2020 10:31 am

Oh, and here’s something saying a lot of that:
https://friendsoftheearth.uk/plastics/t ... vent-wheel

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Re: Tyre dust pollution

Post by Boustrophedon » Sun Jul 05, 2020 11:11 am

Driving the family car gently on mainly country roads, means that I use the brakes so little, the discs are rusting away. I shall have to replace them for the MOT. The tyres show no wear after a year either.

I find the FOE article, as always, disingenuous to the point of being lies. It is well established that tyre grip and tyre life are reciprocal, you can have a grippy tyre or a long lasting one but not both. The statement that they would like to see the tyre companies address this is stupid, what do they think tyre companies have been doing for the last 100 years? As to the statement that "It’s sometimes suggested that improving the wear rate can reduce tyre grip and therefore safety, but there’s no clear correlation between these two for tyres on the EU market." I shall simply say Bollocks, they need to cite their sources before I'll let them get away with that.
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Re: Tyre dust pollution

Post by Martin Y » Sun Jul 05, 2020 11:15 am

Clearly the manufacturers have an incentive to sell more tyres, but they have to match their competitors on tyre wear or lose market share. Reminiscent of the gentlemen's agreement among early light bulb makers that a bulb should last 1000 hours. They only need to be as good as each other.

My anecdotal experience with chatting to our local tyre fitters is that a big chunk of their market just want budget tyres. They buy on price and don't factor in that a more expensive tyre might save money on fuel economy or longevity, or might be safer in the wet or quieter. People are open to being persuaded by such benefits, but it's a lot of information to juggle and when it's an annoying and significant expense right now, people tend to go cheap. So yes, there might be benefits to taking the fastest-wearing tyres off the market to save us from ourselves.

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Re: Tyre dust pollution

Post by Martin Y » Sun Jul 05, 2020 11:23 am

Boustrophedon wrote:
Sun Jul 05, 2020 11:11 am
Driving the family car gently on mainly country roads, means that I use the brakes so little, the discs are rusting away. I shall have to replace them for the MOT.
On my old MX-5 the rear brake pads last 100,000 miles. The lads* who take them to trackdays can use a set of pads in a day.

*Not all younger than me, and certainly not all male.

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Re: Tyre dust pollution

Post by dyqik » Sun Jul 05, 2020 11:35 am

Martin Y wrote:
Sun Jul 05, 2020 11:23 am
Boustrophedon wrote:
Sun Jul 05, 2020 11:11 am
Driving the family car gently on mainly country roads, means that I use the brakes so little, the discs are rusting away. I shall have to replace them for the MOT.
On my old MX-5 the rear brake pads last 100,000 miles. The lads* who take them to trackdays can use a set of pads in a day.

*Not all younger than me, and certainly not all male.
The rear brake pads on our Prius last about 50k miles, while the front ones lasted 95k. Some owners have reported the front brake pads lasting 220k miles.

The rear brakes are used so infrequently that the calipers rust and freeze onto the discs every 4 years or so, requiring new pads, discs and calipers.

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Re: Tyre dust pollution

Post by minusnine » Sun Jul 05, 2020 12:06 pm

Boustrophedon wrote:
Sun Jul 05, 2020 11:11 am
Driving the family car gently on mainly country roads, means that I use the brakes so little, the discs are rusting away. I shall have to replace them for the MOT. The tyres show no wear after a year either.

I find the FOE article, as always, disingenuous to the point of being lies. It is well established that tyre grip and tyre life are reciprocal, you can have a grippy tyre or a long lasting one but not both. The statement that they would like to see the tyre companies address this is stupid, what do they think tyre companies have been doing for the last 100 years? As to the statement that "It’s sometimes suggested that improving the wear rate can reduce tyre grip and therefore safety, but there’s no clear correlation between these two for tyres on the EU market." I shall simply say Bollocks, they need to cite their sources before I'll let them get away with that.
:D The FoE article is, yes, a masterpiece of campaigning literature and I’ll not defend every sentence or suggestion in it, though I’d quite like to hear your argument for why it is so much more misleading than your n=1 anecdote of your never-wearing tyres - are you accepting that tyre/brake wear occurs and contributes to harmful particulate emissions, or not?

Where the FoE article has some merit is in considering mitigations other than new supermaterials for tyres - such as collecting or absorbing wear particles from or into the road surfaces. I’ll admit that my first inclination is to think up science fiction ways in which we can solve these problems with new materials etc., and only secondarily consider the boring old behavioural and systemic design approaches that are probably more feasible and effective to implement.

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Re: Tyre dust pollution

Post by Martin Y » Sun Jul 05, 2020 12:20 pm

I wondered about their suggestions of using porous tarmac to absorb particulates for later disposal. They presumably mean the surface getting dug up and replaced. Wonder how much tyre debris a porous road surface can absorb before it stops being porous and what the cost (in price and pollution) would be of replacing the road surface every x years. Roadsweepers which clean along kerbs and suck debris out of drain gulleys are a practical necessity to keep drains working, but I'd like to see some wet-finger-in-the-air numbers comparing the benefit of more sweeping against the cost of the roadsweeper trucks spending more time on the road.

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Re: Tyre dust pollution

Post by Boustrophedon » Mon Jul 06, 2020 7:32 am

dyqik wrote:
Sun Jul 05, 2020 11:35 am


The rear brake pads on our Prius last about 50k miles, while the front ones lasted 95k. Some owners have reported the front brake pads lasting 220k miles.

The rear brakes are used so infrequently that the calipers rust and freeze onto the discs every 4 years or so, requiring new pads, discs and calipers.
Indeed. The old Alfasud had the handbrake on the front wheels, many owners drove a long way before discovering at MOT time that the rear brakes were not working at all.

The problem with modern front wheel drive cars is that the majority of the weight is over the front wheels, particularly in small hatchbacks, and the EU construction and use directives mandate that the rear wheels must never lock up before the front (even in the event of ABS failure.) This can result in the rear brakes doing virtually nothing. I have seen it argued that given the marginal effect that rear brakes have on stopping distance, that the money spent on fitting them would better be spent improving the front brakes instead and leaving the rear ones off entirely, but the law does not allow this.
The older marks of VW Golf and Polo cornered with one rear wheel in air (As did my Passat...) leading VW to contemplate removing one of them too and building a three wheeler, they made some very convincing prototypes, one of which was driven by Setright in CAR magazine. The rear brake was extremely tiny. Setright tested it to extremes and found it was marginal as to whether the locked rear wheel could hold the parked car on a hill or would just slide.
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Re: Tyre dust pollution

Post by Boustrophedon » Mon Jul 06, 2020 7:37 am

Martin Y wrote:
Sun Jul 05, 2020 12:20 pm
I wondered about their suggestions of using porous tarmac to absorb particulates for later disposal. They presumably mean the surface getting dug up and replaced. Wonder how much tyre debris a porous road surface can absorb before it stops being porous and what the cost (in price and pollution) would be of replacing the road surface every x years. Roadsweepers which clean along kerbs and suck debris out of drain gulleys are a practical necessity to keep drains working, but I'd like to see some wet-finger-in-the-air numbers comparing the benefit of more sweeping against the cost of the roadsweeper trucks spending more time on the road.
Experiments on self draining roads with subsurface drainage by Shell and others, in the 70s established that porous tarmac clogged too quickly to be useful on roads, it does find use in carparks and similar places with low actual driving usage.
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