Tire and RIM weight - Page 4 - Kia Niro Forum
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post #31 of 42 (permalink) Old 03-26-2019, 06:49 PM
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I like my 18's way more than the 16's is why I was wondering so I'll stick with them. 46lbs not enough weight for a change for me.
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post #32 of 42 (permalink) Old 03-27-2019, 07:37 AM Thread Starter
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Thanks for the info guys...I think I will stick with the 18s....maybe I will think about again when comes to time to replace tires.
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post #33 of 42 (permalink) Old 03-27-2019, 09:51 AM
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Yeah I calculated it would cost $600 plus for new wheels alone and I'd save maybe $50 a year in fuel 50x10 years is $500 still doesn't cover the cost. And where I live fuel may be cheaper anyways we are at $2.25 now and was at $1.65 in the winter.

And I like the 18's!!
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post #34 of 42 (permalink) Old 03-27-2019, 09:56 AM
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To change the wheel size for the sake of it doens't make mathimatical sense. When the 18" wheels wear out and they will, you can look at the cost of selling your 18" rims and buying 16" with the lower cost tires and it might make sense. Then again it might not as I haven't run the numbers.

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post #35 of 42 (permalink) Old 03-27-2019, 04:36 PM
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Also the 18's may actually handle better than the 16's and despite KIA doing a good job making the 16's look decent, the 18's IMHO, look better.
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post #36 of 42 (permalink) Old 03-27-2019, 11:56 PM
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Originally Posted by Mal View Post
Also the 18's may actually handle better than the 16's and despite KIA doing a good job making the 16's look decent, the 18's IMHO, look better.
I agree the 18s look great. Dealer wanted $500 each for just the 18 wheels. I passed and bought good enough 16in after market for $120 each installed.

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post #37 of 42 (permalink) Old 03-28-2019, 09:13 AM
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Originally Posted by charlesH View Post
However, the stiffer a tire is the less it will deform thus less heat is generated thus less rolling resistance.

Consider why a underinflated tire has a higher rolling resistance than a properly inflated tire. The reason is the sidewall is less stiff and the contact patch is larger for the underinvested tire, resulting in more flexing of the sidewall and tread resulting in more generated heat thus higher rolling resistance.
When a tire hits an impact, a tire must deform to a certain extent. When sidewalls are flexible, the tire deforms easily over the irregularity with the vehicle losing little momentum. With stiffer tires, they flex less but the impact now has to be absorbed with wasted heat. In addition, road irregularities cause micro (sometimes gross) air or the tire leaving the road. Every small loss of contact creates higher rolling resistance, again as wasted heat from increased friction.

Sure, and overinflated tires reduce rolling resistance on smooth roads by reducing contact patch area. Hypermilers will use narrow overinflated tires and ride the ridge or painted lines to take advantage of increased smoothness where their choice of tires and inflation have a clear advantage. Smooth roads (with the ultimate being your beloved steel rails) are where this strategy wins. On other surfaces, it loses in every regard, rolling resistance plus handling, comfort, braking, and tire life.

The ultimate example of this are off road tires. Road tires will be skipping and hopping at their normal pressures. A coast down test down a rocky bumpy hill will quickly reveal that those large low pressure tires actually have lower rolling resistance under those conditions. Road tires are designed for the middle between those two extremes of off road and steel roads and have design criteria considerably different.

Bicycle tires are a different animal and it is difficult to directly compare them. Yet I have a constructive example. Wider road bicycle tires (to a point) are routinely known and tested to have lower rolling resistance (has to do with lower pressure and how the contact patch interfaces with road surfaces). Tradition and air resistance stop road racers from using wider tires with pave racing or cyclocross being exceptions. I often go out on group road rides with local clubs where I'm the only one with one and a half inch tires - the rest on around one inch high pressure tires. Not really any noticeable difference in coasting down hills with the group (we would just be talking a few seconds over 10 miles, less at higher speeds due to the aero advantage of skinny tires). But where the effects were dramatic where we had to do a quarter mile on gravel surface. Everyone but me immediately dropped speed and had to work hard to maintain that pace. I just floated along, not as in a smooth road, but far easier than my fellow riders.

If we had car tires with skin walls, they would have lower rolling resistance but higher rates of failure from the tire sidewall touching obstacles minus a protective rubber coating. Bicycle riders have that choice, and tires without that stiff rubber side coating roll better, but of course fail more from sidewall damage.

Besides the issue of sidewall suppleness and rolling resistance, tire compounds also contribute greatly to rolling resistance in a comparable way. They are the point of contact with the road, and the better they conform to the road surface, the lower the rolling resistance as they don't skip or deflect forward and back which creates wasted heat.

Bias ply tires are obsolete. They were lucky to last 15,000 miles. Any tire rotation was creating heat trying to tear the bias layers apart. Radial tires greatly reduced rolling resistance by guess what! Increasing suppleness, the ability of the tire to conform to the road surface with substantially less heat than standard tires. I was around for the Michelin radial introduction and bought a set of tires (much more costly than standard tires at the time) and they did last for the advertised 40,000 miles. Radials have improved over the last forty years, had a set last 85,000 miles on my last car. Rolling resistance improved as a result, otherwise there is no way tires could last so long if they created as much heat as previously.

Efficient green tires are designed for low rolling resistance. While tire design is incredibly complex, these tires are more supple by design. This costs them for some other attributes such as handling, but they are a good compromise for non boy racers and their effect is more noticeable mounted on more efficient cars. But feel free to go no compromise your way and start riding on bare rims.

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post #38 of 42 (permalink) Old 04-12-2019, 08:23 AM
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The 16 inch rims are actually milled steel under the hubcaps, not black-painted aluminium. (:

I do know everything, just not all at once. It's a virtual memory problem.

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post #39 of 42 (permalink) Old 04-12-2019, 01:41 PM
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Yticolev's chart is accurate for either one particular tire model or an average of tires that size. There is some subtle variation on the overall diameter, width, and weight of tires of the same size. The variation is in the range of 1-2%

I'm a bit of a tire geek as I consider them on of the easiest, least expensive things one can change that will significantly affect multiple areas of a cars behavior. Those areas include road noise, ride comfort, cornering, and most importantly stopping under various conditions. Living in the PNW, one of my primary concerns is how well a tire stops in the wet - both when it is new and has 30,000 miles on it. The link below from CR provides measured data clearly shows how dramatically different well known, "premium" tires can vary. https://www.consumerreports.org/tire...ires-are-worn/

Tirerack is the best place to find size info (including revs/ mile), real data and consumer impressions of tire performance in various conditions.

For my rainy area and money, Michelin Crossclimate and Premier AS are the best. But YMMV
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post #40 of 42 (permalink) Old 04-12-2019, 06:52 PM
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There is zero data on the linked article. I think you have to have a subscription and be logged in to see anything of real interest. I do have online access via my library but this article is not available yet. A similar article from 2003 probably has similar information but no specific tire model recommendations or data. In wet, half worn tires hydroplaned at lower speeds, and had longer stopping distances. On dry roads, worn tire performance was better than new tires. That seems to be the entire takeaway.

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