If you fill your tires with air, they will have 80% nitrogen in them. The gas you use to fill your tires has no effect on your gas mileage.
Nitrogen is lighter than air, if my truck tires weighs 100 lbs by filling it with nitrogen it may only weigh 97lbs because the nitrogen is trying to lift the tire.
@WheresRick: Seriously, Google “elemental composition of air”. Atmospheric air is 78% nitrogen to start with, so any weight reduction gains are negligible. And the nitrogen filled tires aren’t lighter because they’re lifting the truck more, geez; they’re lighter because Nitrogen molecules weigh less than the other molecules that comprise regular air.
If your truck actually gained 2 MPG then it wasn’t due to nitrogen. It would probably be due more to new properly inflated tires and dual straight exhaust pipes which not only opened up the exhaust system but may have also unknowingly replaced a partially clogged converter.
Any perceived MPG increase may be a false numbers game due to the dinking around with the speedometer
The problem is not Hondas, timing belts, or Trailblazers. It’s lack of maintenance.
The weight of air is miniscule. Three pounds of air in one tire? Hee, hee.
I cannot tell you how much air weighs, except that a 15 mile high pile of it, one inch square, I believe, weighs 14.7 pounds.
“a 15 mile high pile of it, one inch square, I believe, weighs 14.7 pounds.”
Let’s do a little cipherin’:
One inch square by 15 miles is 79,200 cubic inches.
So the median cubic inch weighs 14.7lb / 79,200 = 84 milligrams (mixing English & metric, yea!)
Let’s say the cube at the bottom weighs twice the median: 168 mg
And the tire is inflated to 3 atmospheres (44 psi).
That’s 504 mg per cubic inch.
My rough guess for the volume in the tire is 1800 cu in (6" high x 10" wide x 30" circumference)
So the air in the tire weighs ~2 lb.
Fill your tire with helium and you might save a pound.
Interesting math. But, 15 miles high, one square inch is 950,400 cubic inches. 5280 X 12 X 15. However, 15 miles was sort of flippant on my part, sorry, because air pressure at 29,000 feet (Mt. Everest) is already down to 4.4 psi. And, at 5,000 feet it is 12.5 psi.
Thus, the entire 60,000 cubic inches between sea level and 5000 feet will weigh 2.2 pounds total, or average .0000366666 lbs, per cubic inch, with the cubic inch at the bottom weighing slightly more than the one at the top of the 5,000 foot column.
I did some interesting Googling, and found answers all over the place.
The most likely correct answer is at http://answers.yahoo.com/question/index?qid=20080328130315AA5juKa
It says 1.2 Kg for one cubic meter at sea level. A cubic meter will be around 35 cubic feet. (39.37 X 39.37 X 39.37 = 61023 cubic inches) He simplified it down to .01 lb/gallon.
A gallon I remember as 231 cubic inches. So, a cubic foot will be around .065 lb at one atmosphere. At 3 atmospheres, that will be around 0.195 lb per cubic foot. Your estimate of tire size if correct will be slightly over 1 cubic foot (1728 cubic inches.)
Thus the air in a tire a bit over one cubic foot at 3 atmospheres will be about 3 ounces, not 2 pounds.
I notice with interest if you divide your 2 lb. figure by 12, the number you accidentally left out, your answer is pretty doggone close to correct, .17. Good job, actually.
You shoulda’ seen some of the answers I found. One person even claimed that one cubic inch weighed 14.7 pounds. Hee, hee.
In agreement with this, one man said he works in a place where they have a $10,000 scale, and he actually weighed a tire full and then empty, and could not detect the difference. I assure you that changing to pure nitrogen will also not be measurable.
Note that a fixed container (a flexible tire changes volume under pressure) with one atmosphere in it the air has no weight because of the buoyancy of the container. To weigh it accurately you would need to weigh it in a vacuum.
Also notice that one man said a scuba tank loaded to 3000 psi, or around 200 atmospheres, weighs 6 pounds more when full than when empty. Scuba tanks have an internal capacity around 0.64 cubic feet when empty. This is a good double check on these calculations. If it were one cubic feet, that would be 9 pounds. 9 / 200 = .045. Not exact but a good rough check on calculations.
So, you can see changing to nitrogen does not reduce weight any measurable amount, for a car tire.
Well Im not a scientist but when I put 35’s on I got better gas mileage.
Dang! Forgot to go from feet to inches. Factor of 12.
I suspected my number was high, but I had to go do some real-life stuff.
My rough estimate was 14.7 psi at sea level falling to 0 psi at 15 miles, half pressure at half height.
My tire circumference estimate should have been 60", not 30".
I did consider buoyancy. That’s why I used 3 atmospheres gauge pressure vs 4 atmospheres absolute pressure.
So factoring in feet to inches and doubling the circumference (and thus tire volume) I get .33 pounds (5 ounces).
or the civic which has a unreliable timing belt and gets 37mpg.
Lots of car makers are going back to chains these days. As cars age and need their belts changed out, people don’t want that $600+ maintenance bill(VW’s are usually $1k+) and ditch the car as soon as they can; which was a likely scenario with the Civic’s previous owner.
You mention unreliable as a reason not to fix the car, yet you own a Chevy truck? Everyone I’ve known with a Chevy truck hasn’t had very good luck with it, so you must have found a diamond in the rough.
"Well Im not a scientist but when I put 35’s on I got better gas mileage. "
Did you regear it? So many people halfass the job of lifting a truck and don’t do the supporting mods you should. For 35’s your probably did a 4-6 inch lift. A double damper steering stabilizer, and 4.10 -4.56 gears would be a appropriate.
If you didn’t regear it the only way your fuel mileage would go up would be if you did mostly highway driving and it had an engine powerful enough to keep the transmission from downshifting constantly whilst on the highway.
When you put the 35’s on did you recalibrate your OD?? If not then you may NOT be getting better gas mileage.
As for the timing belt…It lasted way longer then it should. You complain about the belt because it broke…but if you changed the belt when you SHOULD HAVE…the engine would be fine.
And where do you live that you NEED 4wd. I only know a few places in the country that 4wd is needed. Here in NH…4wd is NOT needed…if you know how to drive in the snow you can easily get by with a good fwd with all season tires.
@fodaddy No I didn’t regear it, I had the speedo re calibrated by my buddy.
@mikeinnh I live down in a holler in southern indiana, if it snows we are screwed.
Please tell us you have braided steel brake hoses instead of those flimsy surgical rubber tubings and you are replacing tires with puncture proof steel tracks.
Though I prefer a steel chain over timing belt, rubber parts on a car work just fine so long as they are replaced as necessary
…Or, you can get a car that has a timing belt but a non-interference engine.
@mikeinnh I live down in a holler in southern indiana, if it snows we are screwed.
Southern Ind…you get at MOST 10" a year…We get that in one storm. And wife has NEVER had a problem any of her fwd vehicles. You don’t live in an area that NEEDS 4wd. Nice to have maybe.
...Or, you can get a car that has a timing belt but a non-interference engine.
The BEST situation is to have a chain with a NON-INTERFERENCE engine. With a interference engine…you have to replace a belt 3 times for the first 400k miles. If you plan on keeping a vehicle to over 300k miles and it has a chain…when the chain starts to rattle it means it’s stretched…and time to replace it before it slips a tooth or two. Chain slipping on a interference engine will DESTROY your engine. And replacing a chain is 3-4 times the cost of a belt replacement.
@MikeInNH-- I live in east central Indiana and we have had 10" or more of snow that occurred in one storm. Everything is flat here, but when this has happened, I was glad to have a 4Runner. In one of these occurrences, I got through by putting the 4Runner in four wheel drive low, and pressing the button that locks the differentials. Southern Indiana is quite hilly.
Blowing and drifting snow also make things difficult in snow storms. I attended a country school and was one of the big kids on the school bus. There was another kid about my size and when we had a snow storm, we got to sit up in the front seat of the bus where there was heat. That was the good news. The bad news was that we were in the front seat so that when we came to corner or other spot in the road where the snow was drifted, our job was to shovel the snow out of the way so the bus could get through. If the weather was cold, but no snow, we rode in the back of the bus where there was no heat. I also remember when I was growing up in the country helping my dad put chains on the rear wheels (the cars back then were all rear wheel drive) so that he could get into work. Four wheel drive has all but eliminated the need for tire chains in my part of the country.
@MikeInNH-- I live in east central Indiana and we have had 10" or more of snow that occurred in one storm. Everything is flat here, but when this has happened,
And how often do you get 10" of snow in one storm… 2-3 times a decade. According to the website below that area of Indiana averages 15" of snow a year. Area’s that you’d NEED a 4wd vehicle for are places like the NH white mountains or the snow belt between Syracuse and Watertown who’s average snowfall is more then 20 times what Southern Indiana. Even here in Southern NH we average more then 3 times the amount of snow Southern Indiana gets…and we don’t NEED 4wd. Wife has NEVER EVER been stuck in a snow storm with her fwd vehicles.
@MikeInNH–we live in an area where our road is the last to be plowed out. We even had a 10" snowfall this year the first week in April. We had a big snowstorm earlier in the season as well. The worst part is the drifting of the snow due to high winds.
Averages snow fall doesn’t mean a lot if the snow drifts or it comes all at once. It also doesn’t mean much when the roads aren’t plowed. I’ve had several occasions where we used 4 wheel drive low on the 4Runner to get to work and back home. Before they passed, my in-laws were in an assisted care facility 50 miles away. I did make it through some heavy snow drifts in the fwd Oldsmobile 88 we had at the time, but my wife decided a 4 wheel drive was better so we bought the 4Runner. One nice feature is that it has “selectable” 4 wheel drive. It can be run in 4 wheel drive high all the time. However, most of the time we run in 2 wheel drive. The feature is particularly nice when our roads aren’t plowed. I can leave the house in 4wd high and when we get to the main road that has been plowed, I can leave it in 4wd high. It performs as an all wheel drive vehicle. Of course, 4wd low is a completely different range.
I used to live further out in the country and had only rear wheel drive vehicles. I carried a snow shovel and a bag of kitty litter which I did use, so I suppose 4wd is not an absolute necessity. However, at my age, I would rather have the 4wd to go through the drifts than get out and shovel. I’ve done enough of that.