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? For all you intellects-
Ray B
Member Posts: 11,822
How far does a car travel per rotation of the tires? You say "Simple"- It's the circumference of the tire. Not so quick-
If I have tires that have diameter 37" on by truck, the circumference of those tires is 37" x Pi, 3.14 is close enough for this question. So the circumference is a little over 116". So one answer is that the truck goes 116" everytime the tire makes one revolution.
But unless I have the tires severely overinflated, the tire sidewall is pressed down by the weight of the truck. The radius of the tire is .5 of the diameter, so a 37" diameter has an 18.5" radius. At normal pressures, the portion of the tire that is on the ground is pushed toward the center of the tire, thus reducing the radius by about 1.5". Since this distance remains constant as the truck moves, then the effective diameter is 34", which result in a circumference of about 106 3/4". So another answer is that the weight of the truck results in reduced tire diameter, so the truck travels about 10" less than the first measurement.
So which did you choose as the correct answer?
If you chose #1, Please answer this: How can a tire with actual radius between the axle and ground of 17" gain the additional distance?
If you chose #2, Please answer this: If the car only travels the distance of the effective radius- what happens to the other ten inches of tire tread?
If I have tires that have diameter 37" on by truck, the circumference of those tires is 37" x Pi, 3.14 is close enough for this question. So the circumference is a little over 116". So one answer is that the truck goes 116" everytime the tire makes one revolution.
But unless I have the tires severely overinflated, the tire sidewall is pressed down by the weight of the truck. The radius of the tire is .5 of the diameter, so a 37" diameter has an 18.5" radius. At normal pressures, the portion of the tire that is on the ground is pushed toward the center of the tire, thus reducing the radius by about 1.5". Since this distance remains constant as the truck moves, then the effective diameter is 34", which result in a circumference of about 106 3/4". So another answer is that the weight of the truck results in reduced tire diameter, so the truck travels about 10" less than the first measurement.
So which did you choose as the correct answer?
If you chose #1, Please answer this: How can a tire with actual radius between the axle and ground of 17" gain the additional distance?
If you chose #2, Please answer this: If the car only travels the distance of the effective radius- what happens to the other ten inches of tire tread?
Comments
If he is a 600lber I think the flat spot in your equation will be a little bigger.
the inconsistency regarding circumference of the two models is resolved when you understand that the extra material of the rubber tire is displaced outwards from where the tread contacts the ground.
the entire tread still has the same circumference, but now the contact area with the ground is flat; the shape of the rest of the tire tread resembles an ellipsoid. the tread near the ground is pushed outwards, while the top part of tread hasn't flexed and is still mostly round.
when such a tire rolls, the part near the ground and in front if the direction of rotation gets sucked underneath the tire, becomes flat as the ground, and has flexed into a different shape. the part near the ground and behind the direction of rotation rotates upwards, unflexes, and becomes round. it's now on top.
al this constant flexing and unflexing is what makes tires get hot. when your tire gets low on air, the effect is exaggerated and your tire may fail mechanically.
a diagram would make the explanation much more easy to understand. but that's the explanation.
quote:choice #1
Please answer this: How can a tire with actual radius between the axle and ground of 17" gain the additional distance?
it's got extra material schmushed outwards near where the tread contacts the ground. you will find that if you roll the car far enough to make 1 complete revolution according to a mark on the tire(to 'gain the additional distance'), the discrepancy between that and the circumference for an ideal disk with a diameter of 17" is the length of actual tread that is out of round.
quote:choice #2
Please answer this: If the car only travels the distance of the effective radius- what happens to the (remaining length) of tire tread?
it hasn't come all the way around yet. put a mark on the tire and a corresponding mark on the ground, roll the car as far as you said, then put a mark on the ground at tht point. then take a tape measure from that point on the ground and measure along the front of the tire and around until you get to the first mark on the tire. that can be used to measure the discrepancy. that isn't the discrepancy, but it is what you would use to figure it. since you said "the car only travelled the effective raduis", you would have to set up an equation to do that figuring I was talking about, but that's how you solve it and I'll leave it up to you to set up the equation.
To put it another way let's look at this. Take a tape measure and loup it around in a twenty inch or so circle. the length of the tape is obviously twenty inches at that point. Now take it and stand the edge on a table top. If you push down on it until the bottom is flattened out to represent the tire tread under load, is it not still twenty inches long? Now, if you mark the spot on the table where it begins it's loup, then roll it one complete revolution while keeping the bottom flattened against the table, it has still traveled 20 inches. Thus, your answer is found.
How far does a car travel per rotation of the tires?The same distance no matter what the load, inflation, ambient temperature, tire temperature, etc. Otherwise you'd have to constantly recalibrate your speedometer as these changed.
it is the tires on the passenger side of the vehicle rotate clockwise as the vehicle operates in a forward motion and the drivers side tires rotate counter-clockwise as the vehicle operates in the same direction.
I like your explaination the best - there's a lot there to reflect upon![:o)][:o)][:o)]
The car will travel a mile regardless of how many turns the tires make. A mile is a mile. Now get a woman and some real problems. Don
Excellent[:D]response[:D]
And the ambient temperature outside the tire, also the internal temperature, which rises with use.
I agree with cubslovers. You ever ran 37" tires down the highway at 55mph? I think you may actually get increased tire diameter....inches per revolution at highway speeds.