[bfgeek]

To add to this, (from what I remember reading the study at the time) it was basically racing a car around a track (think lots of tyre squealing around corners), and found that the tyre wear was very high. I haven't seen a study which actually simulates somewhat "normal" driving (presumably because the wear is so low driving like that it's difficult to measure). Also didn't factor in a bunch of different stuff - tyres are effected by lots of things; compound, temperature, pressure, surface abrasion, etc. There might be an effect! But this study was very bad.

[chongli]

A normal driving test was (famously [1]) done to measure the effect of axle load (vehicle weight per axle) on road wear. This is where we got the “fourth power law” of road wear.

I think as a starting point, I would expect that tire wear should remain roughly in proportion to road wear, given the same tires on each vehicle. From this, I would expect car makers to use larger, thicker, heavier tires on heavier vehicles in order to compensate.

Thus I think we shouldn’t accept claims about the replacement lifecycle of tires without knowing these details of their construction. If an electric car is twice the mass of an older ICE car then the fourth power rule would predict a 16-fold increase in road wear. I would then expect the tires on the EV to have 16 times more rubber in order to last the same duration, unless they’re made of some newer compounds which are more durable.

[1] https://en.wikipedia.org/wiki/AASHO_Road_Test

[bfgeek]

> I think as a starting point, I would expect that tire wear should remain roughly in proportion to road wear

IMO this would be a suspect assumption to make w/o data to back it up. You've got two dissimilar materials interacting (in very different modes). E.g. rolling a metal ball bearing on a wood surface would obviously cause the wood to degrade far more than the ball bearing, (and even a wooden ball rolling on a wood surface would wear substantially less due to the mode difference).

(If I had to guess the road has a higher wear as the surface has a tensile stress around the contact patch of the tyre, causing most of the damage, but this is just armchair engineering at this stage).

[chongli]

You quoted me out of context by cutting off a very important qualification to my statement:

given the same tires on each vehicle

I don’t endorse the broader statement which would imply the same wear regardless of tire material. That claim is clearly false.

[bfgeek]

The point I was after to make is that you can't assume that road wear scales the same way as tyre wear (I was assuming same material fwiw, just different loads). They are being worn under very different modes/scenarios.

[chongli]

Given that roads and tires experience the same forces under driving conditions (Newton’s Third Law guarantees this) I think it’s a reasonable prior assumption to start from. There are of course other environmental factors that accelerate road wear (rain and water erosion, freeze thaw expansion) but those conditions were not included in the study that produced the Fourth Power Law.

[_benedict]

This assumes that road wear and tyre wear are caused by the same mechanism, but tyre wear is presumably caused predominantly by friction, whereas road wear is at least in part (and perhaps predominantly) caused by compression, creating pot holes by causing the earth underneath to move.

[ndsipa_pomu]

It's quite noticeable (to me at least) that the areas with highest wear are usually places that have heavy vehicles (buses and lorries) braking and accelerating. Traffic lights and bus stops will often have bumps/dips that seem to demonstrate a shearing force between the road surface layers.

[_benedict]

I have always assumed it was just due to the uneven distribution of weight by vehicles often being stationary in the same spot, so those points are subject to more compression forces than the surrounding road surface.

If it were acceleration and deceleration I’d have expected the effect to be less localised, as breaking and accelerating happens over a much longer distance.

But, I have no actual idea. It’s just probably not friction…

[ndsipa_pomu]

I'm surprised there isn't more info available to compare vehicles/tyre wear. There's plenty of real-world driving going on, so you'd think someone would have measured tyre replacement frequencies.

[seanmcdirmid]

Tires and driving styles vary a lot, so it would be really hard to come up with some aggregate numbers. Maybe you could compare the same very popular tire on different cars that still have enough data points to average out differing factors?

[ndsipa_pomu]

I reckon that the different driving styles could be partially dealt with by considering different classes of car. E G. Fast "prestige" cars will tend to share certain driving styles and be quite different to cheaper run-arounds.

Ideally, it'd be great if insurance companies made a big push to get some kind of standardised "black box" that drivers could fit. As well as providing extra stats, I think they'd be great for detecting illnesses. A simple driving ability stat could be produced from the typical acceleration/braking timings - smoother is better as it shows good anticipation by the driver. If their stat starts decreasing more than expected due to aging etc. then the driver could be alerted that they should consult a doctor as it could cognitive decline, eye problems etc.