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Discussion Starter #1
So I've had my 19 Limited for a month and have put 2000 miles on it. Averaging 53mpg on paper over those 2000 miles. My only complaint has been road noise. So I decided to step down to 15 inch for multiple reasons. First off I wanted a taller tire to soften the ride and help with road noise secondly I wanted to try to reduce wheel weight and increase gas mileage. I know some of you will ask why I didn't just buy the blue model with 15 inch rims to begin with well that's because I wanted the features that came on the limited I also don't particularly care for how the 15-inch wheels look on the base blue models. I went with 15 by 6 and 1/2 Vision cross Wheels and I put 195/65 Michelin Defender tires on them.

It was an 80 mile trip each way to the tire shop. On the way there on the factory 17's the dash read 57 miles per gallon at 68 miles per hour. On the return trip on the 15-inch wheels the computer said I averaged 59 miles per gallon at 68 miles per hour and I was also driving into a headwind. The car definitely seems to roll easier on the 15-inch wheels and there's a noticeable improvement in ride quality as expected. I'll see how much the gas mileage improved over the next couple thousand miles.

I weighed each set of wheels and tires before mounting them. The factory limited 17 inch wheels with Michelin Primacy tires weighed in at 47 lb per Wheel and Tire. The new 15-inch setup weighs in at 38 lb per Wheel and Tire so 9 pounds lighter per tire. Anyone who knows anything about rolling weight will know reducing rotating mass by 9 pounds per corner is huge which is obviously the main reason the blue model gets better mileage.

I definitely think the car looks better with 17in wheels but I feel the 15 inch wheels suit the car better and are going to give better mileage which is what this car is all about.

Also the Michelin Defenders are noticeably more quiet than the factory Michelin Primacy that came on the car. However it's still a little louder than I want so I'm going to be using Dynamat in the back of the car to help quiet it down just a little bit more.

Here's a few pics of the new wheels and one on factory wheels.
Vision Cross 15x6.5 +38 offset. 195/65 Michelin Defender tires.
 

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Does the new setup have the same diameter as the original setup. I ask because that will affect the speedometer and odometer. The 195 is a lot narrower tire - how is that affecting handling? How much clearance do the disk brakes have? Why did you choose the Vision Cross wheels?
 

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I weighed each set of wheels and tires before mounting them. The factory limited 17 inch wheels with Michelin Primacy tires weighed in at 47 lb per Wheel and Tire. The new 15-inch setup weighs in at 38 lb per Wheel and Tire so 9 pounds lighter per tire. Anyone who knows anything about rolling weight will know reducing rotating mass by 9 pounds per corner is huge which is obviously the main reason the blue model gets better mileage.
The major reason the Blue does better is that higher profile tires are much more efficient. That is a far bigger effect than the reduction in rotating mass, although Hyundai did do some fairly extreme weight loss measures on the Blue. In fact, your car should have less road noise (with the same wheels/tires) than the Blue because of the flimsy load floor on the Blue (I think limited to 100 pounds on top of it).

Reducing rotating mass is more important to race drivers with their acceleration needs than green cars. For regular drivers, reducing a 100 pounds of mass anywhere has close to the same effect on efficiency (yes, lots of electrons burned debating this topic online). Reducing unsprung weight (which the wheels are) can theoretically make the suspension more active. But tires are the more important suspension component, at least for paved road drivers, and those same high profile tires help with comfort too as you noticed already.

Good luck with the Dynamat! Nothing better than a quiet car, but I'm too cheap, umm I mean thrifty/frugal to buy a luxury car.
 

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Discussion Starter #4
Does the new setup have the same diameter as the original setup. I ask because that will affect the speedometer and odometer. The 195 is a lot narrower tire - how is that affecting handling? How much clearance do the disk brakes have? Why did you choose the Vision Cross wheels?
Diameter is nearly identical so not speedo worries. Obviously handling has changed. You can feel the sidewall lean over more but it's not dangerous. I mean standard blue models come with this size. But no I wouldn't want to go bomb a back road with it.
 

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Discussion Starter #5
I weighed each set of wheels and tires before mounting them. The factory limited 17 inch wheels with Michelin Primacy tires weighed in at 47 lb per Wheel and Tire. The new 15-inch setup weighs in at 38 lb per Wheel and Tire so 9 pounds lighter per tire. Anyone who knows anything about rolling weight will know reducing rotating mass by 9 pounds per corner is huge which is obviously the main reason the blue model gets better mileage.
The major reason the Blue does better is that higher profile tires are much more efficient. That is a far bigger effect than the reduction in rotating mass, although Hyundai did do some fairly extreme weight loss measures on the Blue. In fact, your car should have less road noise (with the same wheels/tires) than the Blue because of the flimsy load floor on the Blue (I think limited to 100 pounds on top of it).

Reducing rotating mass is more important to race drivers with their acceleration needs than green cars. For regular drivers, reducing a 100 pounds of mass anywhere has close to the same effect on efficiency (yes, lots of electrons burned debating this topic online). Reducing unsprung weight (which the wheels are) can theoretically make the suspension more active. But tires are the more important suspension component, at least for paved road drivers, and those same high profile tires help with comfort too as you noticed already.

Good luck with the Dynamat! Nothing better than a quiet car, but I'm too cheap, umm I mean thrifty/frugal to buy a luxury car.
Yeah it's really win win to go with this size in this car. No need for low profile tires on it really. I have no intent to drive it hard. These tires are perfect for the car. Added fuel economy and reduced weight.
 

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Kudos to your efforts for increasing efficiency. I believe those are the same size tires on my Blue with Michelin Hybrid tires. Reducing un-sprung weight and rolling resistance are the way to go! I'm debating whether to replace my factory light weight alloy with wheel covers to more conventional and better looking wheels.
 

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'17 Marina Blue HEV Ltd I O N I Q since 25 Jul '17
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Congrats on this! That's quite a fuel savings and weight difference. I have my winter tyres mounted on 15" rims, but of course, that's not a worry in Florida. I had the 15" rims for winter tyres on my previous Elantra, and so I just had them mount new tyres on the same rims for the Ioniq. They were reluctant to do so, as my dealership typically uses a minimum 16" rim size, as they say they were finding premature and uneven tyre wear on cars with 15" rims.

That said, I doubt I'm saving that much weight on my winter tyres as they are steel, so still quite heavy. Haven't actually weighed them, mind you, but if anything, I think they might actually be heavier. Even if not, other factors in winter contribute to lower mpg, such as freezing temperatures and increased drag from the better grip of the winter tyres.
 

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Might be a dumb question (don't know alot about cars) but did you have to do anything with the tire pressure sensors? Buy new ones, transfer the old ones to the new rims?
 
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