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Mopar1973Man

Tire Pressure Calculator

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Well after playing around with Excel and doing some thinking. I figured out how to figure exactly how much air pressure you need in each tire. The thing is that you need to get your truck weighed on a truck scale. The calculator needs front axle and rear axle weights. Then you'll need the weight rating of your tire and maximum air pressure rating. Then you plug the information into the calculator (blue boxes) and it will figure out when your optimal tire pressure is. Since I just weighed my truck I left my figures in the boxes as samples...

Information

Front Axle 4,420

Rear Axle 3,040

GAWR

Front Axle 5,200

Rear Axle 6,084

Tire

Max Tire Weight 3,042

Max Air Pressure 80 PSI

Calculation (Axle Weight / 2) / Tire Max Weight x Tire Max PSI = Inflate Pressure

Front Axle = (4,420 / 2) = 2,210 / 3,042 = 0.72 x 80 = 58 PSI

Rear Axle = (3040 / 2) = 1,520 / 3,042 = 0.49 x 80 = 40 PSI

Tire Air Pressures.xlsx

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I am not sure about that. I don't know the weight distribution on mine but I am betting the back tires would calculate out to be in the 30's. I think there is a tire stance calculation that needs to be figured in, as in at say, 10psi, the tire would be very flat and wear very unevenly. I believe the only way to know for sure where the tire pressure needs to be is have a cross sectional weight scale thing on the part of the tire contacting the ground and get it to where there is equal weight distributed along the entire width of the tire. That would obviously require a million dollar machine, but I just think the way you did it has some flaws. There is also the fact that when cornering, a flatter tire is going to roll on the sidewall more. I can tell when mine get low because of this, therefore I keep the fronts at 80psi at all times. I still don't like the feeling and wish I had bigger wheels so I could cut down on the sidewall height. Try saving them all in xls too, I figured out not many people have excel 2010+ and xlsx is not very compatible with free spreadsheet programs.

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Well I would NOT suggest doing below manufacture designed air pressures listed in the owners manual of the truck. Like currently I've been running 60 PSI in the front and 40 PSI in the rear for some time now... It was alway strange because I typically inflated for profile appearance of the tire vs. weight anyways. I grab the camera and give you all a few photos...

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I didn't download your sheet so I don't know if you just did a plain ratio, but I'd assume so. I expect reality might match that for the top 70% of the tires' capacities but I don't think it's a simple proportion below there. The "proper" way for tire wear is to take your fresh tire, air up to sidewall pressure, and then chalk or paint the tire or use a patchy wet parking lot to see when the tread pattern becomes even and square as you drop pressure. Once the shoulders of the tire contact the pavement (even wear of the chalk across the tread) drop about 3psi further and you're at optimal pressure for tread wear. Depending on profile/ rim width/ aspect, that may be high or low for handling but should be very close an will give your optimal tread life.

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Found your topic , searching Google for tire-pressure-calculator.

Been busy with calculating that with use of the European formula, I once got hold of and worked out.

Learned myself Excell, to make spreadsheets for it and translated a few from Dutch to English to go worldwide with it.

What you do with your calculation is not so wrong, gives slightly higher pressures then absolutely needed.

For much lower loads then maximum even a lower pressure is save for the tires.

https://skydrive.live.com/?cid=a526e0eee092e6dc#cid=A526E0EEE092E6DC&id=A526E0EEE092E6DC%21128

Yus look around on my public map of skydrive wich belongs to my hotmail adress with the same username as here. Many spreadsheets and articles. One of an American J.C.Daws. with new system and comparison with the old power formula and its diferent used powers in Europe and America

You can navigate yust as in a forum . and if you want to download a document click at the end of the line on I in blue and on the rightbarr click download . Then open it in Excell or compatible program to use it.

The browser cant handle it because of sheetprotection and datavalidation I used in most of them.

Greatings from Holland

Peter

--- Update to the previous post...

To fill in the exactly weighed loads on per tire in the formula is somewhat dangerous.

You always have to use some reserve for misreadings of weight and pressure, but also for incidental extra load or loadshifting and pressureloss in time.

But if you take to much reserve, things go bouncing.

That is why I introduced the load-percentage or gripp-percentage.

This is what the real weight is of the weight you calculate the pressure for.

Example : assumed "real"weigt 850 lbs/kg watever, wanted Load% ( L%) 85%, then calculate the pressure for 850/0.85= 1000 ( coincidently? no?). then the percentage of the surface on the ground is also 85% as it would beif 1000 was on the tire at that pressure.

Never go over 100% L% , gives tiredamage at higher speed.

100% gives maximum gripp and comfort , without damaging the tires.

95% gives the least tire-wear.

90% gives a little more tire-wear, the same as 100%

85% is the border under wich discomfort begins by bouncing.

80% is as low I dare to go for trailers with no persons or animals in it. Lower screws come loose.

Mind that this is my own estimation, concluded by reactions.

The lower the L% the less fuel-consumption , comfort, and gripp.

The higher the L% the more gripp and comfort , and also more fuel consumption.

A tyre-specialist in Holland , Profile, writes that 25% to low pressure gives 10% more roling resistance, and by that 2% more fuell- consumption, so what are we talking about.

I work with L% and not with % higher pressure, because it gives a better idea about the gripp-surface. For lower L% you need higher pressure, mayby somewhat confusing.

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well i had some time ago a chat with the michelin general manager for latinamerican operations (it includes mexico, brasil, argentina, and a lot of latin american countries) and he told me that in their test grounds they always inflates the tires to a maximum of 90% of what the manufacturer recomends, it means that if your tire says 80psi you can inflate them at 72 or 70 psi, that would give a 10% of heating inflation (at least where i live in the summer is always 98*, 100* or a little more:mad: ) when i travel as soon as i get where im going (usually 3 or 4 hours of higway) i check mi tire pressure and it reads around 5 more psi than the begining of the trip. This is what usually happens when a tire is used without the proper care, like never cheking if they're inflated correctly, it's just happened to me last week when i was testing the raptor on the highway, i was running 70 and cheking the truck at WOT, when i stop to check from 0 to 60 mph (well 80 mph:lol:) when my truck hit 70 miles, the tire thread hit my fender, door and front bumper, those tires were given to me by my big brother, he used them in a tow truck and he told me that he never check the tire pressure. So please check your tire pressure and any weird mark that your tire have on the side wall. post-11078-138698179391_thumb.jpg

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I always run max., it's safer here in tx heat. Besides I have been know'n to pull 30k :lmao:I wonder what happen to the last motor I had :shrug:

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I've been running 50psi front and 45psi in the rear and have been getting excellent wear and it also gives a good ride.

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