0

I currently have 225/65R17 tires on my car. I have noticed that many new electric cars come with larger wheel rim and lower profile tire, such as 235/45R21 tire. I wonder why -- after all, lower profile tires are less comfortable and have higher rolling resistance. Electric cars, if any, should avoid using low profile tires because range is such a critical parameter for them.

If we pick two rims and pair them with tires in such a manner that the rolling diameter stays the same, which is heavier:

  • A traditional tire + wheel rim where the rim diameter in inches is small, or
  • A low profile tire + wheel rim where the rim diameter in inches is large and the tire aspect ratio is modified accordingly to keep rolling diameter approximately the same?

The reason I'm interested is that it seems to be impossible to find any electric SUV with 17-inch wheels. Thus, I'll probably have to accept larger wheel rims (fortunately probably not 21" as 19" rims seem to be available in some limited cases). However, the 225/65R17 wheel+tire combo is already so heavyweight that my muscles ache for a day or two after seasonal wheel swap (where I live, I have to use dedicated winter tires during the winter).

Is the added aluminum lighter or heavier than the eliminated rubber in the low profile tires? (Let's consider only aluminum rims -- steel rims are outdated.)

Improve this question
4
  • 1
    You have a source for the statement, "lower profile tires ... have higher rolling resistance"? To my knowledge and thinking, lower profile tires are harder and therefore should have less rolling resistance. In order for them to support the vehicle, they should be pressurized higher. Short profiles have less squish area, which means less rolling resistance ... at least to my thinking.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    May 9, 2021 at 15:42
  • This observation was made by comparing identical electric vehicles only varying on the aspect ratio of the tire. The low profile tires have less range. Happens for Teslas for example. Yet, now we do have an answer that verifies exactly this effect!
    – juhist
    May 11, 2021 at 17:31
  • Actually, it doesn't answer what I'm talking about. And the answer given is a "guess", not anything derivative (as read in "I believe" seen in the last sentence).
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    May 11, 2021 at 17:36
  • While not derivative, there are multiple examples where high trim levels have larger wheels and have a fuel economy penalty. Regarding rolling resistance, a big soft tire can still have low resistance if it is more "springy" rather than "spongy" if it returns that compressive force back, rather than absorbing it. Another example, early hybrids (that were focused on efficiency, with little styling influence) had small wheels with higher aspect tires, think Honda Insight or 1st gen Prius.
    – masospaghetti
    May 12, 2021 at 16:19

1 Answer 1

Reset to default
2

Typically, a larger wheel and lower aspect tire will be heavier than a small wheel and higher aspect tire.

While not a scientific comparison, you can see on some higher trim level vehicles with larger wheels actually have reduced fuel economy vs base models. Per Car and Driver for the 2021 Accord Hybrid:

[F]uel economy remains practically the same, with the 2021 model's EPA combined estimate remaining 48 mpg and the highway score moving up a tick from 47 to 48 mpg. But that's for the lower-spec models riding on 17-inch wheels. The Touring trim rides on 19s and carries a 43-mpg combined and a 41-mph highway rating.

Car and Driver

It's possible that the touring has stickier tires, but I believe the higher rolling resistance due to higher overall wheel+tire weight is the main culprit for reduced efficiency.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .