Tire Rolling Resistance Increases as the temperature drops!
 

From Tire Business May 8, 2023

How does temperature affect rolling resistance?

By Erin Pustay Beaven

GREENVILLE, S.C.

Range can be a very tricky thing. Electric vehicle range is, simply, inconsistent.

It changes over time, across driving conditions and with temperature fluctuations. And while there are a number of factors contributing to the fluctuation in range, it’s understood tires play a role. Especially when it comes to colder temperatures.

And that leaves a lot of questions to be answered. Questions such as: Exactly how much of an EV’s drop in range can be attributed to the tires? And how does temperature fluctuation impact rolling resistance?

That’s exactly what Smithers is working to solve, according to Matt Kent, technical director of the Smithers Tire & Wheel Center in Ravenna, Ohio. Because answering those questions — among others — gives the industry the leverage it needs to design tires better targeted for new mobility.

“Electric vehicles show a significant decrease in range in cold temperatures,” Kent said during his presentation at the recent Clemson University Global Tire Industry Conference in Greenville. “But current test standards only evaluate rolling resistance at room temperature — it’s actually 24 degrees C. And understanding rolling resistance performance at cold temperatures could provide an opportunity for tire design improvements to support an increase in range.”

When it comes to testing and ultimately understanding the ways in which cold temperatures impact rolling resistance, Smithers is turning to its Suzhou, China, facility, which houses a cold chamber rolling resistance machine.

This machine, Kent said, is capable of testing tires at temperatures ranging from 40 degrees C to -40 degrees C.

“It has been really interesting seeing the data and seeing them bring this thing online,” Kent said.

Using a torque method for the study, Smithers tested four different tire brands, each of them at four temperatures—35, 25, -10 and -20 degrees C.

What the team found, Kent said, was “the trends were all the same. But the big difference was they all performed very differently down here at the lower temperature.”

Each of the tires showed significant increases in rolling resistance as the ambient temperatures dropped. With each drop in temperature, the rolling resistance increased.

Tire rolling resistance performance is strongly influenced by temperature,” Kent said. “RRC increased as temperature decreased and is more sensitive at low temperatures as opposed to high temperatures. So clearly, we have a lot of data at 24 degrees C, and around that range there’s some difference, but they are not hugely substantial.”

In the Smithers study, the best performing tire showed a 56% increase in rolling resistance between the highest and lowest temperatures, while the worst performing tire, Kent said, saw rolling resistance increase by 116% between the highest and lowest temperatures.

And this, of course, is just the start. Smithers plans to take its testing further and expects to have further data compiled by the summer of 2023. Additional tests, Kent said, include examination of EV-specific tires that are a mixture of original equipment and replacement tire fitments.

In my ID3 road testing I could see changes in consumption when outside temperatures raise in the morning and if there came clouds and tarmac tems started to go down.
2 celsius outside temp change was 0,1kwh difference which was in my case 0,6%.

Been a while since we had Capri share tire knowledge. Interesting findings.

I would assume tire pressure is even more important at colder temperatures so that less tire deformation is required.

Did they name [brand]names?

No. Here's the data:

http://barrystiretech.com/RRvsTemp.jpg

http://barrystiretech.com/RRvsTemp.jpg

I drive a leaf, I know.

That would explain why I was getting 100 miles per gallon driving around Phoenix at night last month in the city…

I never would have guessed this. I would have guessed a colder tire would be firmer (less pliant) reducing rolling resistance. Racing cars need their tires warmer to increase grip. In racing a warmer tire is ¨stickier". You´d think a sticky tire would have more rolling resistance? This test might be a good example of my perception differing significantly from reality.

Was the tire pressure equalized at the different temperatures? If the pressure was set at one temperature and only the temperature was changed for these tests, what would the tire pressure change be at the various temperatures? I know the pressure would reduce as the temperature falls. Did tire pressure play any part in these differences in the test?

Here´s a little tidbit I checked recently. I drove from NM (6500 ft elevation) to Pensacola, FL (60 ft elevation). I checked the cold tire pressure at both locations at similar temperatures and found 40 psi when I began the trip in NM and 39 psi in Florida the morning after I arrived. I have seen larger changes in tire pressure in my truck driving between similar elevation changes.

temps & R-R
 

* In SAE Paper 780613, they found that 'ICE' vehicles could see up to a 67% mpg variability between 20F and 100F on short 'cold-start' trips, in which the cars never achieve thermal- equilibrium temps for their respective ambient temperatures.
* Tire losses are part of this calculus.
*As mentioned, the SAE considers 70F 'COLD.'
*And R-R can be 40% greater 'cold', compared to when fully up to thermally-equilibrated temperature ( CAR and DRIVER, page-72, August, 1979 ).
* Also, the lower the ambient temperature, the greater the time/distance necessary to achieve equilibrated temperature is required.
*Rubber hysteresis values for both sidewall and tread-block surface are directly impacted by temperature.
* It's no mystery why pre-green- flag race cars are seen racking their front wheels to 'scrub' as much heat into them before the flag drops. It aids both coefficient of friction ( traction ) and lower rolling-resistance ( coefficient of power absorption ).;)

If that is your picture on your pages are you able to make lines sideways to make it easier to interpret?

That test is done at rolls so only tire temp is effected on those results?

So less air drag will come on top of those savings yes or no?