Tire rotation...

Can any one tell me how to calculate how fast a 16" tire is turning (RPM) when the vehicle is traveling at 60mph?

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No, they cant.... because there isnt enough info. And "16 inch" tire isnt relevant
Measure from the center of the wheel (axle) to ground as it sits, multiply by 2, multiply THAT by 3.14. That is the WORKING circumference of the tire . And divide THAT by 12, circumference in feet
Divide 5,280 (distance traveled/minute) by that result; equals RPM,
if center of axle to ground is 20", would be about 500 RPM
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Arrghh.. but that'd be one TALL tire.
Make that more reasonable...
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12 inches center to ground
840 RPM, approx
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High school math.... diameter of the outside of the tire (different tires will have different roll-outs) times Pi (your choice... 22/7 or 3.14159) give the circumferance. You will have probably started this exercise using inches...... Divide 63,360 by the circumferance of the tire (63,360 being the number of inches in a mile).... this gives the number of rotations per mile. Conveniently, there are 60 minutes in an hour so, at 60 mph, we are covering one mile per minute..... this number is going to be somewhat theoretical as we have both reduced roll-out if a tire is low and increased roll-out if a tire is subject to growth from physical forces.
If you have an accurate tach, you can figure your rpm at 60 mph in direct gear (usually 3rd or 4th in an overdrive unit, depending) and divide that by the axle ratio - in the case of an automatic, you will want to feel closely for torque converter lock up.
If this is just part of an overall equation, easy bet is Googling "gear ratio calculator".... there are many on the 'net - some better than others but all easy to find and use....

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Robert Bodling wrote:

Try this...
60 mph = 1 mile per minute 16" tire has a circumference of 50.265482456" (16" * 3.1415926535) 1 mile = 5,280 ft. 1 mile = 63,360 in.
Divide the inches in one mile by the circumference of the tire 63,360 / 50.265482456 = 1260.5071493238389698188794800096
So the tire spins at about 1260 revolutions per minute. I just made this shit up.
All the decimal places are due to using Pi to the tenth decimal place. I don't like rounding.
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snipped-for-privacy@optonline.net wrote:

Amazing...
We all got hung up on one thing or another...
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I didn't put much thought into the tire diameter but now I'm wondering would 16" be the inside diameter where it attaches to the rim? In that case I'm way off. More appropriate would be wheel diameter...
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The listed diameter of the tire is always the "rim size" of the tire... 16" tires can go from very tall to very small. on their spec sheets.Many manufacturers will list the "roll out" of their tires

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