BMW i3's Tall Skinny Tires To Boost Efficiency (And Cut Noise)

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BMW i3 Concept live photos, 2012 L.A. Auto Show

BMW i3 Concept live photos, 2012 L.A. Auto Show

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Most people give them little thought, but tires are one of the most important components on a car.

They are, of course, your only point of contact with the road. So ultimately, tires are responsible for everything from performance, through cornering, to efficiency and noise.

Tires of the future will significantly improve the last two factors, and BMW's i3 electric car will be among the first production vehicles to adopt the new breed of tire.

While "round and black" has long been a simplified definition for tires, their design has changed significantly over the years. Most recently, the fashion is for larger diameters and a wide footprint. The latter is a significant contributor to rolling resistance and noise.

High rolling resistance is detrimental to fuel efficiency, while noise can manifest itself as everything from a constant drone at speed to unusual sounds and resonances over different surfaces.

Pirelli is one of the tire makers aiming to change this, says Go Auto. The company is developing tires both taller and narrower than current examples. By 2020, the average tire diameter is expected to grow from 16 inches to 21. At the same time, it'll become narrower.

European regulations on noise, rolling resistance and wet grip are prompting the changes, but the latest breed of electric vehicles, such as the BMW i3, will make best use of the technology to improve range and keep noise to a minimum.

The i3 has used tall, narrow tires since the early concept stage. While they look a little odd at first, particularly from any angle showing the tire's section, they should allow it to be one of the quietest vehicles on the road. And viewed in profile, it lends the i3 larger diameter wheels than you'd expect on a typical small car, improving the car's appearance.

You might think that grip would suffer--and by extension, safety--on these new tires. However, their development coincides with a new trend for cars finally getting lighter. A lighter car doesn't work its tires as hard, and doesn't require as wide a footprint for the same levels of grip. Additionally, these new tires should be more adept at cutting through standing water, without the tendency of wider rubber to hydroplane.

Not every car will head down the tall and narrow route of course, but the ones that do could prove more economical and refined than ever.


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Comments (25)
  1. how will these new thinner tires perform in a city of potholes?

  2. This is still a tradeoff in traction.

    1. Skinner and taller (hopefully stiffer sidewalls) will reduce some of the cornering issues.

    2. Even with lower weight, skinner tires will reduce traction. The tire contact with the road will reduce at a much faster rate than the weight reduction.

    3. Those low profile sidewalls are potentially subject to cuts, punctures and rim damages with the deteriorating road conditions of America. CA is famous for its poor roads. Some of the Northern States aren't much better. I live near the pot hole capital of state.

    4. Doesn't those skinny tires require a larger rim? That will be something really expensive to replace or fix...

  3. 5. Custom side/unpopular size tires will be also very expensive for owners to replace.

  4. And don't forget that a larger (and heavier) wheel does contribute to unsprung weight that has a far greater impact on economy. Even when thinner, a larger wheel obviously weighs more than a larger tire.

  5. How so? If it is both taller and narrower, it should have roughly the same mass as a tire that is shorter and wider. It does take more torque to accellerate a taller tire of the same mass, but EVs have plenty of torque.

  6. I think he was talking about the rim. As it grows taller, there might be more weight due to the larger rim. Some of that weight can be offset by the rim design and type of material.

  7. 1) BMW already uses tires with similar sidewalls, and uses run-flats on most of their cars which have reinforced walls.
    2) They aren't custom tires cars all have different tire specs these will be regular production tires.

    I'm sure BMW and their tire supplier know what they're doing

  8. Run Flat tires are heavier. So all your saving are almost a wash if you go run flat. Sure, they can be production tires but they won't be nearly as popular as standard ICE vehicles tires. That will mean reduced volume which will increase price per unit.

    If you adopt Prius's tires, it will be much cheaper. But of course, BMW will never sink themselves down to the Prius performance level.

  9. Right, the point of owning a BMW is to prove to the world that you have money to waste. So expensive tires are a virtue.

  10. Can't afford one so your bashing them, cute.

  11. I read articles about tall LRR tires long before the i3 was announced. I applaud BMW for adopting this technology and I predict other EV makers will soon follow. If companies also adopt the new airless tires, spare tires and repair kits will become unnecessary.

  12. Those early adoption just mean it will cost more for the early adopters to replace them...

  13. Do you know for a fact that these tires cost a lot of money? Or are you assuming they'll be expensive? There is no evidence that these tires will cost anymore then the tires BMW already uses.

  14. Which BMW current production tire is "narrow" and "tall"?

    If those terms used in the article is correct, then it won't be one of those standard BMW tires. Also, assuming it cares about fuel efficiency, it will use one of those fuel efficient threads patterns as well.

    Those are my basis.

    Want a bet? If those are indeed 18 inch rim and low profile tires, they will be more expensive than your standard 3 series tires for the same speed rating.

  15. The wheels on the i3 are 20 inches, but just because these tires have different dimensions doesn't make them more expensive, tires come in thousands of sizes.

  16. The BMW i3 tires are (155/60 R20) look up similar sizes and price them.

  17. @CDspeed,

    All the tires that I can find don't have 155/60/R20 tires for sale. So, I would say that size would have to be a special order... That alone will limit your choice and raise the price.

  18. There are more comments in this thread
  19. BMW i has a video on youtube that talks about the Bridgestone tires.

  20. I read an article on Fox News today and Pirelli is jumping on the bandwagon as well. They predict 21 inch 125/60 tires will be the norm by 2020. That should definitely bring down the cost.

  21. Funny, a larger diameter wheel will get poorer performance and worse gas mileage than a smaller one. I could see a 14" skinny tire besting a 21" one in MPG's any day.

  22. It's funny that Mitsubishi's I-MiEV came equipped with skinny tires up front and the press went berserk calling the I-MiEV a golf cart. Now that BMW is doing it, it seems to be alright, lauded and a BMW milestone. I don't have the traction problem with the skinny tires on my I-MiEV, even driving in the snow. The tires seem to last as long as any other tire I've driven on. I'm all for these tires - quieter, better economy and great in all weather conditions.

  23. Good article, Antony, thanks for covering this. Many new EV owners might not realize how important tire and rim selection are for the range of the vehicle. While I don't claim to be an expert in this area, and can't really comment on what BMW and Bridgestone are doing, I applaud innovation in this important area. I wasn't all too happy with the tires on the ActiveE and the Ecopias on the LEAF are not very popular with early adopters. Hopefully, we will see significant improvements in the near future. Both in handling and efficiency.

  24. Great to see BMW adopt LRR tires. But this isn't new innovation, the LEAF has LRR Bridgstone tires, Michelin make energy saver tires.

    Presumably the BMW spec is superior in performance and comes at a higher price to boot.

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