Tire and RIM weight - Page 3 - Kia Niro Forum
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post #21 of 42 (permalink) Old 03-25-2019, 03:30 PM
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Train wheels on steel have zero relevance to pneumatic tires on roads. Their compliance or non compliance has nothing to do with rolling resistance of steel on steel. You could easily make a compliant steel wheel but the compliance will have no impact at all on the rolling resistance.

Pneumatic tire compliance has a direct impact on all aspects of a tire's performance on different surfaces. Off-road tire's are large with low inflation pressures. Tire's for cars racing on very smooth surfaces are at the other extreme. Consumer vehicles are in between. They all need different compliance to fit intended use.

Rather than just making stuff up, a few minutes of reading about tires would save you from appearing ignorant. Read about pneumatic tires, not solid steel ones.

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post #22 of 42 (permalink) Old 03-25-2019, 06:00 PM
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Originally Posted by yticolev View Post
Train wheels on steel have zero relevance to pneumatic tires on roads. Their compliance or non compliance has nothing to do with rolling resistance of steel on steel. You could easily make a compliant steel wheel but the compliance will have no impact at all on the rolling resistance.

Pneumatic tire compliance has a direct impact on all aspects of a tire's performance on different surfaces. Off-road tire's are large with low inflation pressures. Tire's for cars racing on very smooth surfaces are at the other extreme. Consumer vehicles are in between. They all need different compliance to fit intended use.

Rather than just making stuff up, a few minutes of reading about tires would save you from appearing ignorant. Read about pneumatic tires, not solid steel ones.
Frankly, I don't know what you are talking about. What is a compliant steel wheel? Is a compliant car tire just a soft tire?

Ask yourself do you disagree with this statement?

"underinflated tires with less stiff sidewalls have a higher rolling resistance than overinflated tires with stiffer side walls"

Rolling resistance is the energy required to move the wheel forward. It is determined by the energy absorbed by the tire and the road surface. Softer tire sidewalls (e.g. underinflated) and softer treads (e.g. snow tires), snow covered and gravel roads all absorb energy thus result in higher rolling resistance.

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post #23 of 42 (permalink) Old 03-26-2019, 08:17 AM
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Ask yourself do you disagree with this statement?

"underinflated tires with less stiff sidewalls have a higher rolling resistance than overinflated tires with stiffer side walls"
Wow! The straight answer to a stupid question is it depends. You apparently don't understand what tires do. They conform to imperfect road irregularities. To do this, they must deform. This causes heat which is wasted. Tires made for efficiency must be more supple as they will deform easier causing less waste heat. Tires built to handle well with narrow less compliant sidewalls are not as efficient when it comes to rolling resistance. Most road tires perform really badly off road with even more irregular surfaces and a huge increase in rolling resistance compared to purpose built tires. Those same off road tires have much higher rolling resistance than road tires on the road despite relatively supply sidewalls.

There are a ton of variables in how tires perform in various categories. Some you can isolate in a short discussion. But to say that train wheels are more efficient because they are less compliant is not only completely wrong, but does not apply at all when talking about tires.

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post #24 of 42 (permalink) Old 03-26-2019, 10:10 AM
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Wow! The straight answer to a stupid question is it depends. You apparently don't understand what tires do. They conform to imperfect road irregularities. To do this, they must deform. This causes heat which is wasted. Tires made for efficiency must be more supple as they will deform easier causing less waste heat. Tires built to handle well with narrow less compliant sidewalls are not as efficient when it comes to rolling resistance. Most road tires perform really badly off road with even more irregular surfaces and a huge increase in rolling resistance compared to purpose built tires. Those same off road tires have much higher rolling resistance than road tires on the road despite relatively supply sidewalls.

There are a ton of variables in how tires perform in various categories. Some you can isolate in a short discussion. But to say that train wheels are more efficient because they are less compliant is not only completely wrong, but does not apply at all when talking about tires.
You are half right here. When tires deform they do generate heat which results in rolling resistance. However, the stiffer a tire is the less it will deform thus less heat is generated thus less rolling resistance. The ultimate example is a train wheel on a steel track. Very little deformation thus very little heat generated thus very low rolling resistance. An example at the other extreme is a balloon tired dune buggy on a sandy beach. A lot of deformation in tire and surface thus a very high 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.

I think you are assuming a stiff tire must flex just as much as a soft tire as it rolls thus since its harder to flex a stiff tire more heat is generated with a stiff tire. The error in your thinking is assuming a stiff tire flexes just as much as a soft tire. It doesn't.

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post #25 of 42 (permalink) Old 03-26-2019, 10:11 AM
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Interesting how things taken to extremes well describe even small differences. The train wheels are a good example. While tire mechanics are a complex subject, it's generally true that a less complient/overinflated tire will offer less rolling resistance thus greater mileage than a more complient/under inflated one.

Having said that, chassis are tuned for the pressure reccomendations usually appearing on the door frame or in the owners manual......normally for multiple good reasons.
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post #26 of 42 (permalink) Old 03-26-2019, 12:33 PM
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Ok so the OEM 18" wheel and tire weighs 49.5 pounds. Now awaiting the 16" weight.
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post #27 of 42 (permalink) Old 03-26-2019, 02:18 PM
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Ok so the OEM 18" wheel and tire weighs 49.5 pounds. Now awaiting the 16" weight.
phev lx stock 16in wheels with snow tire sans wheel cover, 38lbs


We put stock tires with new wheels on the car.

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post #28 of 42 (permalink) Old 03-26-2019, 03:28 PM
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phev lx stock 16in wheels with snow tire sans wheel cover, 38lbs


We put stock tires with new wheels on the car.
Ok thanks not much of a difference. 46lbs total.
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post #29 of 42 (permalink) Old 03-26-2019, 04:06 PM
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Ok thanks not much of a difference. 46lbs total.
Whoa!
Jaxterra said: " the OEM 18" wheel and tire weighs 49.5 pounds."
Charles H said "phev lx stock 16in wheels with snow tire sans wheel cover, 38lbs"
Back in the day that was a 11.5 lbs difference. Seems like a Big Diff (24%) to me. Am I missing something?

Somewhere else someone said stock wheels were 19 lbs. Stock tire accord to TireRack is 21 lbs, so 38-40 sounds about right.
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post #30 of 42 (permalink) Old 03-26-2019, 06:01 PM
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You're not missing anything, that is indeed a considerable difference. Heavy wheels and tires create a double penalty. Just the added weight is a small detriment in acceleration and braking additionally that weight has to be overcome in angular momentum. Finally the suspension has to handle the additional weight complicating damping and control. Good to avoid unsprung weight where practical. Certainly worse than adding the same weight in cargo.
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