RE: Really Good Gas Mileage in my H3!!!
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 8:38:36 AM
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TexH3
Posts: 224
Joined: 9/14/2007
From: North Texas
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I'm getting 17.5 in my Base I5 automatic, going to and from work 75% freeway. Standard 32" tires. After driving an H2 for 5 years, I am happy with 17.5. Getting that in the Alpha is super.
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Jim --
2003 H2 Red Lux (sold)
2008 H3 Graphite Lux
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 9:10:10 AM
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H34me
Posts: 132
Joined: 11/24/2007
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That's excellent gas mileage. I have the I-5 and just completed a 2,400 mile highway road trip. The vehicle had 2,200 miles on it at the start of the trip and I averaged 18.5mpg cruising between 70-80mph. Stopped calculating mileage halfway through the trip since it was so consistent. If I could've been sure of your mpg I might have rethought the Alpha.
H34me
< Message edited by H34me -- 3/20/2008 9:18:05 AM >
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 2:42:24 PM
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alphadogg
Posts: 358
Joined: 12/30/2007
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quote:
ORIGINAL: rhill20
I don't have GPS in the truck yet, but I put the same tires on that you have Alpha. And everytime that I pass one of those signs that post your speed, it is dead on. WTH?
According to my GPS, the Garman Nuvi 260, my speedo is off by 3 mph. It tells me what street to turn on “by name”, a very convenient feature and it runs on a re-chargeable battery.
SolarFlare,
How come you have 285/75R16's on your Alpha? Mine came with 265/75R16's.
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 3:00:13 PM
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solarflare
Posts: 703
Joined: 1/3/2008
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I have the off road package...do you?
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2005 HUMMER H2 SUV SE
"Never Give Up!"
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 3:11:03 PM
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solarflare
Posts: 703
Joined: 1/3/2008
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That's why then.......
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2005 HUMMER H2 SUV SE
"Never Give Up!"
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 7:03:13 PM
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ALPHA XY
Posts: 123
Joined: 12/9/2007
From: Rockville, MD
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solar...its because you weight 1/2 what we do...lol...driver weight reduction FTW :)
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 7:38:04 PM
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RealJeep
Posts: 725
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AAAAARRRGGGGHHHH!!!!! Tire swaps do NOT change mileage. The tires change the final gear ratio which throws off your speedo. After going up or down on a tire height YOU MUST recalibrate the speedo.
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 8:56:01 PM
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alphadogg
Posts: 358
Joined: 12/30/2007
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We knew that! We just didn't feel like explaining it. Somewhere I have a chart for guys that put monster tires on trucks and it explains what ratio gears are best suited for the size monster tires they use. But someone who increases their tire size to 35", 37" or even up to 44" usually doesn't bother to change their gears. They just recalibrate the speedo.
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RE: Really Good Gas Mileage in my H3!!! - 3/20/2008 9:57:04 PM
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alrock
Posts: 1058
Joined: 5/12/2007
From: Scottsdale, AZ
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quote:
ORIGINAL: RealJeep
AAAAARRRGGGGHHHH!!!!! Tire swaps do NOT change mileage. The tires change the final gear ratio which throws off your speedo. After going up or down on a tire height YOU MUST recalibrate the speedo.
Are you talking MPG? Larger tires generally are heavier tires with larger rotational mass. More mass being turned means more power to turn them, more gas used. It's one reason those econo-boxes have such little wheels. The mpg drop isn't as drastic as it might seem before the speedo recalibration but larger, heavier tires do hurt. Here's one example:
http://rockcrawlermag.com/techreports/superlift_crosstrainer/page4.asp
A good general rule seems to be that each pound of un-sprung mass = 10 lbs of sprung mass. How does this affect our Jeep? Each one of my stock tires weighed 51 Lbs. Each one of the new tires weighs 68 Lbs. This means that my Jeep has to move, stop and turn with the effect of 680 more lbs. of weight on-board. If you check a gear ratio chart you can see what gears you need to change to in order to regain your power and gas mileage.
More info here: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=108
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RE: Really Good Gas Mileage in my H3!!! - 3/21/2008 1:06:50 AM
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HummBob
Posts: 16148
Joined: 5/6/2006
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Your gonna make Impy cry in his Wheaties!!!
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2004 Black Hummer H2
2007 Black Escalade
 
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Drive conversion - 3/21/2008 8:46:55 AM
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RealJeep
Posts: 725
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Here's the formula again... Thanks http://www.4lo.com/ for their EXCELLENT real 4x4 information!
I'm not going to get into rotational masses or the whole tire weight thing. Of course if you have heavier tires the engine has to move more weight thus uses more energy. But the mileage difference is insignificant compared to changing your final drive ratio. Too many people fail to comprehend that when you put on a taller tire your final drive ratio increases.
Here's another
(New Tire Diameter / Old Tire Diameter) * Speedometer MPH = Actual MPH
New 35" Old 33" 55 58
Your vehicle now thinks your're going 55 when you're going 58. If your speedo is off then your odometer is off too so your mileage has not changed but your math has. Someone forgot to tell the speedo that the final drive changed which throws EVERYTHING off.
< Message edited by RealJeep -- 3/21/2008 9:03:43 AM >
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RE: Drive conversion - 3/21/2008 9:14:05 AM
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TexH3
Posts: 224
Joined: 9/14/2007
From: North Texas
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RealJeep,
Your equation in terms of Tire diameter seems right. In your example, however, wouldn't the vehicle think you are going 55 (the speedo reading) when you are actually going 58? You stated the reverse. -- Oh, I see you corrected it.
I would think the vehicle mileage is based on rotations calibrated to tire size. Hence a larger tire size would have you traveling slightly further than your odometer indicated. So if you calculate mpg by dividing odometer miles (e.g. on the trip meter) by gallons to fill up, you get a result that is less than actual -- hence an apparently lower mpg when that's not the case.
Actually it's a bit confusing, but correct me if i'm wrong.
< Message edited by TexH3 -- 3/21/2008 9:20:27 AM >
_____________________________
Jim --
2003 H2 Red Lux (sold)
2008 H3 Graphite Lux
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RE: Drive conversion - 3/21/2008 10:56:52 AM
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CWS
Posts: 241
Joined: 1/7/2008
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All I know is when you get to 88 miles per hour, your gonna see some serious sh!t.
Cliff
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Solar Flare H3 Alpha; adventure pkg, painted grille, sunroof, roof marker lights, rock rails, undercarriage protection, black brush guard, lower grille lights, backup camera, flux capacitor, fender flares, tactical wheels and assist steps.
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RE: Drive conversion - 3/21/2008 11:06:13 AM
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moabxj01
Posts: 39
Joined: 3/13/2008
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I think my flux capacitor is broken...cause when I hit 88 I just see red and blue flashing lights...especially when i'm in a 40mph zone for some reason
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