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Big Wheels & Low Profile Tires - Why

Pardon the audacity of an almost 72-year-old for asking, but why have car-makers developed a fascination for cars with the combination of a larger diameter rim coupled with a lower profile tire? In reading entries on car owner forums, I get the impression that while such combinations may look 'cool' to style and marketing types, they are distinctly impractical on the pot-hole prone streets of many US cities. The lower the profile of the tire, the greater is the likelihood that the sidewall will be damaged beyond repair and perhaps the rim, too, when the owner encounters the inevitable and perhaps unavoidable (think in-motion bumper-to-bumper traffic) pothole.

Such a combination is especially egregious in a vehicle in that growing class that is sold unequipped with even a doughnut spare and jack. My first experience with such a combination is the Nissan Leaf (P205/55R16.) Perhaps some MIT trained engineer will be able to explain how this combination improves the miles/kWhr. I believe it is the case that a P205/70R 15 would have the same circumference and hence revolutions/mile. I think it would decrease the risk of a pothole flat and consequent tow and tire replacement.

Please help me understand.

baumgrenze
«1345

Comments

  • Consumers sometimes have a "fashion over function" mentality. This is simply a good example of this. You can't blame the automakers too much for providing what people are buying right now.

    You're correct that these tires are often impractical. Although low-profile tires do offer better handling, the tradeoffs generally don't make sense, in my opinion. Something in the medium-profile range would probably provide all the handling most people need while reducing the drawbacks quite a bit.

    For what it's worth, when purchasing a new car, it's often possible to trade a lower-profile setup for a higher-profile setup from the base model of that car.
  • I don't think a R205/55R16 is one of the major offenders on large wheel on small sidewall tire front. In general, a larger wheel allows for a larger disk brake making for more efficient braking and more stopping power. Mostly the very large wheels are way bigger than the brakes and it is marketing and cool factor and perhaps some handling advantages to the combination. You give up ride quality and durability to get the cool look.

    On a Leaf they are looking for the best rolling resistance they can obtain so you get more miles before needing a recharge. The stiffer sidewall means less flexing and less rolling resistance. In the Leaf the tire is selected by performance criteria over the "cool" look.
  • I think you have hit on the reason, but are just having trouble internalizing it.

    Cars are sold based on emotion - not logic. Big wheels look cool and that triggers the emotion. The car designers know that. They don't care if that creates a problem - that's for the engineers to fix!

    And here I am going to disagree with Uncle Turbo - All this business about rolling resistance can be applied to ANY tire. Low profile tires aren't any better for RR than high profile tires.
  • I didn't mean to say that low profile tires have less rolling resistance in general. I meant to say that the particular tires selected for OEM fitting from the factory on the Leaf (a total electric car) will be a low RR tire. I don't really see the tire size given by the OP as one of the ridiculously low profile tires that I've seen mounted on things like Cadillac Escalades.
  • My Toyota Matrix has 205/55R16 tires and I wish it had come with 65 or 70 profile.
    I think the ride would be a little smoother.
  • Just like 200 hp used to be 'high' (now I guess it's 500 hp), 'low profile' is no longer 70 or 60 series. 50 series seems to be the point below which tire and wheel damage becomes more common.
  • IMAGE-IMAGE-IMAGE, the three most important facets in marketing cars. And most other devises and appliances. The Ford Mustang was nothing but a repackaged Falcon but set sales records. Only emasculated men drive mini vans. And the horsepower wars are getting silly. A true 300 horsepower engine would pull a loaded 18 wheeler at a sustained speed in excess of 70 mph. It is unlikely that the Nissan V-6 engine could do that. But then we seem to be VAIN-VAIN-VAIN. And the marketers can play us for all we are worth. The political marketers are sizing us up and picking the IMAGE to paint their man to get our attention and vote with little regard to his real qualifications. Given the choice of a 177 I-6 Mustang or a 260 V-8 Falcon most people went with the Mustang. I hope we do better in up coming elections.
  • I've seen wheel sizes go down and up. My first car, a 1947 Pontiac, had 6.50 X 16 tires. My next car, a 1955 Pontiac had 7.10 x 15 tires. My 1965 Rambler Classic 550 had 6.95 x 14 tires. I thought that the Rambler had a better size than the Ford Falcon which had 13 inch wheels. The 1957 Buick bucked the trend and stayed with 15 inch wheels. The reason was that someone in the design studio thought that the car "looked better" with 15 inch wheels as opposed to 14 inch wheels. I thought I would never see 17" wheel sizes as that on my 1950 Chevrolet 1 ton pickup truck, but my 2011 Toyota Sienna has 17" wheels. Maybe we have hit the peak again and wheel sizes will go down.
    I drive a minivan by necessity since I manage a chamber orchestra and am always transporting musicians and their instruments. I thought I would like to have a Mazda Miata, but Mrs. Triedaq thinks that the Miata is a car for wimps. She thinks if I want a sports car that I should find an Austin Healy Sprite. She says that real men don't mind getting out and pushing their cars out of traffic when they break down.
  • edited March 2012
    They're good for DRY PAVEMENT traction and handling. They're bad for every other kind of condition. As other point out the handling advatage is seldom utilized by those wuho buy these cars. But they are eye-catching.
  • I think it's mostly style.

    I do, however, suspect that a wheel/tire combination that provides a specific tread width and rolling circumference might be lighter if using a lager alloy wheel and lower aspect ratio tire than it would be using a smaller wheel and larger aspect ratio tire to obtain the same tread width and rolling circumference. That lower rotating mass would contribute to higher mileage.

    I've never confiirmed this theory, but would like to. If I had a tire shop I'd probably weigh the two options and find out once and for all.
This discussion has been closed.