B arry's Tire Tech

This is a series of articles on the technical aspects of tires, their care and usage.

My primary purpose in these articles is to help people understand tires and thereby reduce the risks we all face every day.

..........and since tires is just about the only thing I know about..........

Please drop me a note if you have a topic you want to see:

Barry@BarrysTireTech.com

EV Tires:

Here's what you should get from this article:

  • EV's don't require special tires.
    • They can use regular tires, but the compromise for regular tires isn't always what an EV owner might want - in particular, a drop in range. I explain below.
    • By the same token, EV tires can be used on regular ICE vehicles.
  • Tires for EV's aren't as special as some try to make them out to be. I explain below.
  • There is no EV rating for tires. If you hear the term, it was made up by the marketing department of a tire manufacturer.

First some definitions:

  • When I use the term "EV", I mean "BEV" - Battery Electric Vehicle - that is, vehicles which only have an electric motor for propulsion.
    • This does not include hybrids where there is an on-board engine, such as an "ICE" - an internal combustion engne that is either the source of the electric power or is used in part to power the vehicle.
    • BEV's require a charging system.

There are a number of things peculiar about EV's:

  • Range is EXTREMELY important - much more than for a gasoline or deisel fueled vehicle.

  • Weight: Yes, EV's are heavier.

  • Low Speed Torque

  • Noise for an electric vehicle is lower than for a fueled car.

I'm going to take each of these individually.

Range:

Where tires play a role here is in rolling resistance.

Unfortunately, the rolling resistance of a tire is improved by sacrificing treadwear and traction, especially wet traction. That means that the tire design has to balance those 3 things aiming to get the proportion correct. It is my opinion that rubber chemistry plays a huge role here - meaning that R&D can improve this 3 way technological triangle.

This also means that there will be significant differences between brands, largely depending on how much money is spent on R&D. Larger tire manufacturers generally spend more than smaller manufacturers. That's why they are large!!

The net effect is that tires from large manufacturers are generally better for RR than comparable tires from smaller manufacturers.

What I find most interesting when talking about the range of an EV is that with fossil fueled vehicles, we don't talk very much about how many miles we go between fuel fill ups. I suppose that's because filling stations are literally everywhere.

Plus a fillup only takes 5 minutes, where an electrical charge is much, much longer.

That means the rolling resistance of a regular tire is much less important - and since changing tires is such a hassle and costly, people tend to buy long wearing tires - and that means tires that have high RR values.

Weight:

Yes, EV's are heavier, but the load carrying capacity of a tire is defined by its size and inflation pressure. That is reflected in the vehicle tire placard, which lists the original tire size and inflation pressure. That means if you read something that implies the tires can carry more load because they are EV tires, you can be sure that is BS. I go into more detail on tire load carrying capacity here:

Barry's Tire Tech - Load Tables

Low Speed Torque:

Electric motors make the most torque when they are starting off. This translates to the potential for a tire to slip when it is taking off.

I suspect EV manufacturers have a controller that reduces the amount of electrical power supplied to the motor at zero speed. Nevertheless, some consideration for a tire for an EV has to be given to traction, especially wet traction. Keep in mind that traction, wear, and rolling resistance are tradeoffs!

Noise:

It is common for OE tires for EV's to have a foam insert on the inside of the tire. This reduces the echo effect inside the tires which amplifies certain noise frequencies.

These foam inserts don't seem to make it to aftermarket EV tires. I suspect there are a number of reasons:

  • The foam is not very effective.
  • Other noise reduction techniques are much more effective.

However, the things that reduce noise also hurt wet traction and snow traction.

I've talked about need for wet traction above - so a compromise has to be made to the tire itself.

Again, the balance between properties is important here. I talk about noise here:

Barry's Tire Tech - Noise

General Comments:

EV tires can be used on ICE vehicles - AND - regular ICE vehicle tires can be used on EV's. It's just that EV's have some peculiarities that can be helped by modifying the tires. But those modifications have the same effect on ICE vehicles. It's all about the compromise.

There is no EV rating test. Unlike a Snow Rating (3PMSF), or Speed Rating (H, V, Z, etc), each of which has a test associated with the rating, if you see adverts saying the tires are "EV Rated" - well - that's just some BS some marketing department made up.




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