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You always hear about the negative side of people putting massive, heavy setups on cars, and how that leads to poor gas milage and braking and accel...

But I'm looking for ACTUAL numbers of increases.

Not technicalities.
Not guesswork.
Not even mathwork formulas.

I want to know, when you lost rolling mass... have you experienced any increase in fuel economy? Please post how much weight you lost per corner, and how much, or little, of an increase you noticed.

I just picked up a fully loaded '07 and was looking into replacing the factory wheels with some centerline forged wheels (17x7") that weigh in at 16lbs.
 

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i know mathmatically it should be a big difference, but personally think there is very little change in accelleration.
i took off my speed3 wheels(48lbs) and replaced them with a 17" 38lb wheelset. i thought it was going to be a huge difference. it is hardly noticeable. when i track my 3 i run a 45lb wheelset and accellerate just as fast as everyone else.
 

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I got lightweight wheels a while back (15 pounds supposedly) and noticed quite a difference in the low end acceleration. I also keep logs of my fuel mileage each time I fill up. I could check that to see if it shows anything, although in all honesty, this will be a hard question to pinpoint an answer on. Fuel mileage can vary so much anyways, based on different driving conditions and other factors.

I have a scan tool that shows current MPG updated every second. It also logs the fuel mileage for the current trip, the day, and the tank. The best way to answer this would probably be to find someone with this scan tool who also has two sets of wheels/tires. They could go out for a little drive on the highway, with the cruise set at a constant speed, check their fuel mileage, and then switch the wheel/tire set and take the same trip back, then compare the results.

With that said, I think that the biggest difference will be driving around the city. It's a lot easier to keep an object moving that is already moving, so there's not as big of a difference on the highway. However, there's a lot more work required to get an object into motion from a stop, so your city driving will probably see the biggest improvement. Sometimes I've gotten 27-28 MPG in the city if I drive VERY gently. That's also with an intake, though.
 

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[quote author=unique3 link=topic=71438.msg1256519#msg1256519 date=1173376862]
with some centerline forged wheels (17x7") that weigh in at 16lbs.
[/quote]

mine are cast and weigh like 16 lbs... 17x7.5

Anyways, the difference will not be that drastic, but i have been able to do like 30 kms more on my tank. The car steers easier ans brakes a little better as also with acceleration. Spinning inertia makes a BIG difference of the way the engine puts down the power. Ahh... physics :D
 

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Discussion Starter #5
"mine are cast and weigh like 16 lbs... 17x7.5"




I bet you paid more then $157 per wheel for those beauties! I am slightly jealous, though. Those are some sharp wheels, and they fit your car perfectly.

I'm more interested in fuel economy improvements than anything else. I don't track the car, nor do I drive it spiritedly. It's just a slick daily driver that I want to get the full potential out of. Too bad the navigation is useless around Clearwater!
 

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[quote author=unique3 link=topic=71438.msg1256757#msg1256757 date=1173383585]
"mine are cast and weigh like 16 lbs... 17x7.5"




I bet you paid more then $157 per wheel for those beauties! I am slightly jealous, though. Those are some sharp wheels, and they fit your car perfectly.

I'm more interested in fuel economy improvements than anything else. I don't track the car, nor do I drive it spiritedly. It's just a slick daily driver that I want to get the full potential out of. Too bad the navigation is useless around Clearwater!

They cost around 330$ CDN per wheel. You'll have better fuel economy if you just slack off the pedal :p
[/quote]
 

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I calculate my mileage for every fillup, which for me, is 3 to 5 times a week. I have a 170 mile round trip commute. My OEM wheels, which are used for Winter, are 22 lbs. My (old) Summer wheels, 5Zigen FN01R-Cs, weigh 16 lbs. When I swap them, there is a 1 to 2 mpg change in fuel efficiency. Acceleration is noticeably quicker with the summer wheels, but I obviously have no numbers to back that up. I'm confident that this is not placebo, since I notice it when I go to pass someone on the expressway and I'm not even remembering that I have swapped the wheels. However, with my previous Summer wheels, they were slightly lower profile, so that's also going to result in slightly lower gearing, so I'm not sure how much of the acceleration effect is due to that. My new Summer wheels and tires will match the total wheel and tire diameter perfectly.

Also, I don't know that you can expect the same fuel efficiency change as I get, since my driving habits will be different from yours, and so are my other modifictions. I drive 70 mph with cruise control, with the occasional exception (like to blast through expressway ramps in third gear at 2 to 3 times the posted recommended speed limit). I also have a Quaife ATB differential, SPEC Stage 2 clutch, Exedy chrome-moly flywheel, and NSN taller fifth gear.
 

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[quote author=colorblindtyler link=topic=71438.msg1256654#msg1256654 date=1173380687] The best way to answer this would probably be to find someone with this scan tool who also has two sets of wheels/tires. They could go out for a little drive on the highway, with the cruise set at a constant speed, check their fuel mileage, and then switch the wheel/tire set and take the same trip back, then compare the results.
[/quote]

At a constant speed, wheel weight is not going to matter much at all. It's when you are accelerating and decelerating that the change in unsprung weight causing increased angular inertia makes a difference.
 

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[quote author=Deucer link=topic=71438.msg1257217#msg1257217 date=1173397915]
[quote author=colorblindtyler link=topic=71438.msg1256654#msg1256654 date=1173380687] The best way to answer this would probably be to find someone with this scan tool who also has two sets of wheels/tires. They could go out for a little drive on the highway, with the cruise set at a constant speed, check their fuel mileage, and then switch the wheel/tire set and take the same trip back, then compare the results.
[/quote]

At a constant speed, wheel weight is not going to matter much at all. It's when you are accelerating and decelerating that the change in unsprung weight causing increased angular inertia makes a difference.
[/quote]

That's why I followed up with
[quote author=colorblindtyler link=topic=71438.msg1256654#msg1256654 date=1173380687]
With that said, I think that the biggest difference will be driving around the city. It's a lot easier to keep an object moving that is already moving, so there's not as big of a difference on the highway. However, there's a lot more work required to get an object into motion from a stop, so your city driving will probably see the biggest improvement.
[/quote]

But you're right, we should stress that the biggest difference will be during city driving, with not much of an improvement at all on the highway.
 

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dropped about 12 pounds a corner here, some of that is because the tire is lighter too....noticed a huge difference in braking and handling more than acceleration and fuel economy, but maybe got another 20~30 km on a tank of gas.
 

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[quote author=colorblindtyler link=topic=71438.msg1257349#msg1257349 date=1173403542]
[quote author=Deucer link=topic=71438.msg1257217#msg1257217 date=1173397915]
[quote author=colorblindtyler link=topic=71438.msg1256654#msg1256654 date=1173380687] The best way to answer this would probably be to find someone with this scan tool who also has two sets of wheels/tires. They could go out for a little drive on the highway, with the cruise set at a constant speed, check their fuel mileage, and then switch the wheel/tire set and take the same trip back, then compare the results.
[/quote]

At a constant speed, wheel weight is not going to matter much at all. It's when you are accelerating and decelerating that the change in unsprung weight causing increased angular inertia makes a difference.
[/quote]

That's why I followed up with
[quote author=colorblindtyler link=topic=71438.msg1256654#msg1256654 date=1173380687]
With that said, I think that the biggest difference will be driving around the city. It's a lot easier to keep an object moving that is already moving, so there's not as big of a difference on the highway. However, there's a lot more work required to get an object into motion from a stop, so your city driving will probably see the biggest improvement.
[/quote]

But you're right, we should stress that the biggest difference will be during city driving, with not much of an improvement at all on the highway.
[/quote]

Sorry, didn't mean to be nitpicky, but I could just imagine someone going out and doing what you said, then coming back here and posting, "LOLZ, my 60# 19z gets teh same milage as jur wimpy 16s, I ownz jooooo!!!111" :lol: :lol:
 

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Yes, I was surprised to find my city mileage go up considerably with my lightweight flywheel. I rarely ever have a tank of purely city driving to tell what effect my flywheel or my wheels have on purely city driving, but my mileage started taking a much smaller hit when I had a weekend of city driving on a tank after the flywheel went on.
 
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