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#1
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Strangest Tire Question EVERRR...
Strangest Tire Question EVERRR...
Has anyone ever calculated or estimated the area, in square inches/square cm, of the *surface of the inside* of a tire? Does at least an average exist out there, for broad categories: passenger car, SUV-light truck, and commercial truck? Just curious, Thanks! |
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#2
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Strangest Tire Question EVERRR...
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#3
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Strangest Tire Question EVERRR...
Steve W.:
I went to several tire mfg. sites, but could not find such information. I guess it's time for some E-mails & phone calls. |
#4
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Strangest Tire Question EVERRR...
In response to what > wrote :
> I went to several tire mfg. sites, but could not find such information. I guess it's > time for some E-mails & phone calls. What tools do we have to solve the problem? o Let's start with shape & terminology: <https://tireguides.com/TireTips/TireDocument/9> That gives us these perhaps relevant terms: o Tread width o Section height o Aspect ratio o Rolling circumference etc. Where for now I'll ignore there's a difference between o free (i.e., unloaded), and, o loaded Then, using this tire-size calculator: <https://tiresize.com/calculator/> And ignoring sig fig approximations (so I can just cut & paste numbers)... Assume a P200/50R15 for easy numbers & using only the 1st URL above: o Diameter = 582mm (22.9") o Width = 200mm (7.9") o Sidewall = 99mm (3.9") o Circum. = 1,824mm (71.8") o Revs/Mile = 882 Also noting: o Rim diameter = 381mm (15") Assuming the carcass inside & outside surface is "similar" in both shape & surface area, we easily arrive at a gross _approximation_ of: o Tread area = ~200mm wide times ~1,824mm around = ~364,800‬sq mm o Sidewall area = ~99mm times ~1,824mm around times 2 = ~361,152sq mm Which calculates to... o Total U shaped carcass = ~364,800‬sq mm + ~361,152sq mm Which comes to roughly ~725,952‬sq mm Given the sidewall area is probably more accurately done with donuts: <https://www.spikevm.com/calculators/area-perimeter/area-donut.php> Where the terms appear to be: o Diameter of the Whole Area = 582mm o Diameter of Inside Area = 381mm Which calculates out to: o Area = 152,023.9sq mm o Outer Perimeter = 1,828.4mm o Inner Perimeter = 1,196.9mm o Total Perimeter = 1,196.9mm Using these numbers for sidewall area in the previous calculation: o Tread area = ~200mm wide times ~1,824mm around = ~364,800‬sq mm o Sidewall area = ~152,023.9sq mm times 2 = ~304,047.8‬sq mm o Total U shaped carcass = ~364,800‬sq mm + ~304,047.8‬sq mm Which comes to roughly ~668,847.8‬sq mm In summary, and knowing the inside dimensions must be smaller than the outside dimensions, I'd guess it's around 600,000sq mm to 700,000sq mm. But that's only a gross approximation. o How much accuracy does the OP need? -- Adults gather on Usenet to politely learn via public technical discussion. |
#5
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Strangest Tire Question EVERRR...
Arlen Holder - wow! You went to town on the math!
How precise? Ohh, just an average. It's something I'm working on, so an average sized automobile tire is all I'm asking about. 215/6R16ish. Thanks for the hard work though. |
#6
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Strangest Tire Question EVERRR...
Arlen Holder:
So 725,000 sq mm approximates 1,224 sq in. internal area of your example tire. If a particular vehicle requires 32psi cold air pressure in that tire, that equates to 32 * 1,224sq. in = 39,168 total pounds of air pressure against the interior wall of that tire! Wow! If we increase that 32psi figure by 10%, that's 35.2psi. 35.2 x 1,224 = 39,564 total pounds of pressure against the wall of that same tire. An increase of only 1.01% in the total pressure against it. So much for my theory that each additional pound of air pressure exponentiates the total pressure imposed on the inside of that tire. |
#7
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Strangest Tire Question EVERRR...
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#8
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Strangest Tire Question EVERRR...
AMuzi:
Well, to me, 'per square inch' means exactly that. 35lbs per every square inch of the tire cavity and outer edge of accompanying rim or wheel surface. |
#9
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Strangest Tire Question EVERRR...
In response to what > wrote :
> It's something I'm working on, so an average > sized automobile tire is all I'm asking about. 215/6R16ish. I just noticed something interesting when it comes to 'averages'. o All you need is the tread width & the aspect ratio & rim size. That is... o For a 40 series tire, it's 2x40, i.e., tread area times 180% o For a 50 series tire, it's 2x50, i.e., tread area times 200% o For a 60 series tire, it's 2x60, i.e., tread area times 220% etc. Notice an aspect ratio of, oh, say, 50 is 50% of the tread width. o So the surface area is a function of the tread width & aspect ratio. If the tire is a 50-series tire, the sidewall area is approximately 100% more than the tread area (i.e., 50% times 2 sidewalls). For a 60 series tire, the sidewall area is approximately 120% more than the tread area (i.e., 60% times 2 sidewalls). In short, for a quick mental calculation all you need is the tread area and the sidewall-to-tread ratio, where the tread area is simply the width times the circumference of the tire. So, for your P215/60R16, this calculator tells me: <https://tiresize.com/calculator/> o Diameter = 26.2" o Width = 8.5" o Sidewall = 5.1" o Circumference = 82.1" o Revs/Mile = 771 The area of the tread would be its width time the circumference: o Tread area = 8.5" times 26.2" = 222.7 sq inches Since it's a 60-series tire, the sidewall area is 120% of that. o Sidewall area = 222.7sq inches time 120% = 267.24 sq inches In summary, you just take the tread area and multiply it by the percent: o For a 40 series tire, surface area is tread area times 180% o For a 50 series tire, surface area is tread area times 200% o For a 60 series tire, surface area is tread area times 220% etc. -- Each thread on Usenet should add unique value to our combined knowledge. |
#10
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Strangest Tire Question EVERRR...
Arlen Holder:
So rounded off we'll just say 270 sq. inch of area inside the avg. passenger tire. I think something was wrong with that online calculator I was using last night to convert square mm to square inches. For a similar tire I was getting, if I recall,1,220-something square inches? I suspected something was off! So the air inside the tire inflated to 35psi is pressing down on each one of those 270 square inches with 35 lbs of force. So a more sane 9,450lbs of total pressure on the inside wall of that tire. Probably closer to 7,000ish if you consider that side of the rim which completes the inside of that total air cavity at each corner of our daily vehicles. |
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