Such a thing as narrow, low-profile tires? - Fuelly Forums

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Old 11-03-2007, 06:29 PM   #1
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Such a thing as narrow, low-profile tires?

Does anyone know if there is such a thing? I have never heard of anything but wider, low-profile tires. But a narrow AND low-profile tire would be the ultimate fuel economy tire. Unlike high-profile tires, low-profile tires flex less as they turn, which decreases internal losses. This is why road bikes (bicycles) ALWAYS use narrow, but low profile tires (unlike mountain bikes). Also, low profile tires handle better. Not only does this make a car more enjoyable to drive. It also allows you to take turns faster, which decreases losses that result from braking before a turn, and needing to re-accelerate afterwards. Of course, despite these advantages, I have never heard of such a tire. To the best of my knowledge, ALL narrow tires are ridiculously high-profile.
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Old 11-03-2007, 06:40 PM   #2
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I know on Honda-tech I stumbled across a thread about someone who put very short tires on the VX wheels to make his gear ratio better for the 1/4 mile. The only problem with doing this on a small wheel like a 13 inch, is that it would make the overall diameter of the tire too small to make the speedometer very correct, and would make your gearing worse for MPG. On the other hand, if you got a larger wheel, such as a skinny 15 in steel wheel, you could get a lower profile and skinny tire to fit it.
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Old 11-03-2007, 07:28 PM   #3
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Pay a visit to this tire size calculator:
http://www.wickedbodies.net/Tire-Size-Calculator.htm

Using the calculator you can find outer diameter tire sizes for nearly any wheel diameter. With correct outer diameter your speedometer and odometer stay accurate. Calculator will let you input a 15 or 16 inch wheel and keep trying different tire size combinations till you find the ones that match the oem tire diameter.

If you don't know what the different numbers in the tire size actually mean you can read about that at tirerack.com. Shopping Tools - Tech Center - Tire Size Information.
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Old 11-03-2007, 08:15 PM   #4
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I guess that ideally, you would probably want something like a 175/50/16. This would give an overall wheel diameter similar to a 175/70/13, and a sideall height similar to a 205/40/16. But I doubt such a tire (or wheel) exists.
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Old 11-03-2007, 08:26 PM   #5
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I should add that a 195/40/16 DOES exist. This tire would have a similar overall diameter to a 175/70/13, AND a shorter sidewall than a 205/40/16. I just have to wonder whether the rolling resistance would actually be LESS than, say, a 175/70/13.
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Old 11-03-2007, 09:14 PM   #6
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If I'm not mistaken, width of the tire has nothing to do with RR. The type of rubber and the air pressure is all that matters.

I know it's counter-intuitive, but with a narrow tire, the contact patch is longer but narrow, but with a wider tire, the contact patch may be wider, but it's also far shorter.

So it doesn't matter the width of the tire, the contact patch is always the same size if the pressure is the same.
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Old 11-03-2007, 09:29 PM   #7
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Quote:
Originally Posted by StorminMatt View Post
I should add that a 195/40/16 DOES exist. This tire would have a similar overall diameter to a 175/70/13, AND a shorter sidewall than a 205/40/16. I just have to wonder whether the rolling resistance would actually be LESS than, say, a 175/70/13.
Good question. I think the 195/40 might have higher RR based on the loose correlation between the tires speed rating and it's stiffness. In other words, I'm assuming the low profile tire would have a higher max speed rating than a 175/70 tire. See http://www.sullivantire.com/tires/speed_rating.aspx

significant quote;
"An "S" Speed-Rated tire (max 112mph)will give a more comfortable Ride compared to "H" Speed-Rated tire (max 130MPH), and a "H" Speed-Rated tire will give a more comfortable Ride compared to a "Z" Speed-Rated tire. The Ride Comfort Characteristics can be attributed to the tire's Overall Stiffness. A tire capable of running at High Speeds requires a more stiff construction, in order to provide the necessary high speed stability & durability. "

A stiffer tire has thicker sidewalls, which means there's more rubber to flex and absorb power. Bicycle tires with the lowest RR have extremely thin sidewalls and tread. Here's a good read for bike fans http://www.rouesartisanales.com/article-1503651.html
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Old 11-03-2007, 09:35 PM   #8
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Keep in mind that the apect ratio is all relative to each other.

Tires almost always go wider as they go lower profile.To go narrow and lower profile would a) be a nightmare in terms of ride comfort b) be a nightmare in terms of having enough sidewall to protect the wheel c) look really strange.

a 50-series tire is 50% as wide as it is tall. A 40-series tire is 40% wide as it is tall, etc...

I'd say that 195/40-16 that StorminMatt quoted is about as extreme an example as possible. Possibly the strangest size I've ever heard of.
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Old 11-03-2007, 09:36 PM   #9
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Thanks for the bike link!

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Old 11-04-2007, 06:12 AM   #10
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I would argue that given the same rubber and construction, a wider tire will generally have a lower rolling resistance. This is because the contact patch shape changes, and with it, the amount of sidewall distortion.

As the tire sits or rolls along, the contact patch will always be centered around a line below and parallel to the axle axis. For a narrower tire to maintain the same contact area, it must distort the sidewalls for the contact patch to extend more ahead of and behind this axle line. As the tire is adjusted wider, the amount of distortion - and consequently tire heating and resistance to rolling - is reduced.

So with all else the same, a wider tire will always have a lower rolling resistance, but the tradeoff is aerodynamic drag.

I don't have a calculator or formula handy, but consider that a 1 inch difference in width on something like a pickup could amount to up to 2 feet or more of increased frontal area - and that is going to have a significant impact on Cd.

My thought is that if nearly all of your driving is going to be done on streets with speeds of 45 mph or less, go wide. Mostly highway driving suggests leaning toward the narrow.
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