tire sizes
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yep tired reading it have 0 idea what the hell was said
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wtf... do they still teach math in school ?
the distance a tire rolls in one turn is roughly the same as the circumference (distance around) of the tire. the circumference of a circle is pi * the diameter. The diameter is the distance across the center of the circle from edge to edge. The radius of a circle is the distance from its center to its edge, and is always half of its diameter.
To figure out the diameter of a tire, and thus the distance it rolls in one turn, its easiest to first figure out the radius.
The radius of the tire is made up of three components - the tread depth, the sidewall height, and half the empty space where the wheel goes
You can calculate the sidewall height and the empty space by knowing the tire size. The tread depth measurement you'd need to measure, and i'm not sure what depth is used when the tires sidewall height is calculated, so i don't know of the tread depth is additive or subtractive.to calculate the sidewall height you just multiply the tire width (205mm) by the aspect ratio (55%). To get the distance of "empty space" you just cut the wheel diameter in half (we're talking about radius, remember). Since the wheel diameter is in inches and the section width of the tire is in millimeters, you need to do a unit version between millimeters and inches, depending on what units you want the answer to be in. I chose millimeters because the metric system is awesome and the US system is stupid
once the sidewall height has been added to the wheel radius, can you double that value to get the total diameter, and then multiple the diameter by pi to get the circumference, which is the approximate linear distance the tire will travel in one revolution along the ground.
what would make this more clear? pictures?
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I think what he meant was TMI. Like I stated earlier, most people don't need nor will use most of the info that has been posted. Alot of times, just the basics will do. Hell, if half of my customers knew just that... my job would be a helluva lot easier.
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http://www.rims-n-tires.com/rt_specs.jsp
plug and play what you are looking for, then scroll down for some pretty descriptive details of your selections...
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again all these things are helpful but still dosent explain the reason that the spedometer would change if i put a 235/45/17 on instead of a 245/45/17
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killer69penguin;180542 wrote:
again all these things are helpful but still dosent explain the reason that the spedometer would change if i put a 235/45/17 on instead of a 245/45/17Your fucking kidding right???
What do you not understand???
Going from a 245/45 to a 235/45 the tire diameter is smaller. Le'ts say you drive 1,000 rpm's in drive(1:1) tranny ratio. and you gears are 1:1 your tire will spin 1,000 rpm's too. So to make it easier to see let say the tire diameter is 24". Then at 1,000 rpm your tire will travel 1,000PID = 1,0003.142=6280' in one minute.
Now lets say you put some 4' diameter tires on there.
1,000PiD= 1,0003.144=12,560' in one minute. Your speedo is not measuring the the distance your tire travels but it measures the speed of the tranny output shaft(or whatever on rice??) that is why on some you change the gears on the speedo to correct gear or tire size changes.......
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