2F,4:88,37'
- Thread starter SteadyT3ddy
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- Thread starter
- #82
Clearly no one here understands how a radial tire works.
Under inflating a tire does not change its rolling circumference.
As he said. Previously answered. Low tire pressure does not change the tire circumference.
OP. Get a clue.
Under inflating a tire does not change its rolling circumference.
As he said. Previously answered. Low tire pressure does not change the tire circumference.
OP. Get a clue.
As I said, irrelevant. The radius as defined between the hub and ground define the effective circumference as experienced by the truck. Rubber is not dimensionally stable when deflated. If it was, it would not deform when deflated.
This radius defines the thrust at the contact patch, which increases as the radius decreases for a given amount of torque, as does resultant distance traveled.
Maybe this will help illustrate what is going on. The section under pressure compresses. That flat spot reduces the circumference that amount. As you roll and continue to compress each section it debits the aggregate circumference per the effective radius.
Frank
This radius defines the thrust at the contact patch, which increases as the radius decreases for a given amount of torque, as does resultant distance traveled.
Maybe this will help illustrate what is going on. The section under pressure compresses. That flat spot reduces the circumference that amount. As you roll and continue to compress each section it debits the aggregate circumference per the effective radius.
Frank
What he said...
Let's take it to the extreme...if the tire was flat, what's the effective radius? Is it the same as when the 37 inch tire was fully inflated? No...
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hoser
SILVER Star
Many vehicles with TPMS use the ABS sensors to detect low air pressure. How do you suppose ABS sensors do that?
back to the OP question though to make this argument mute how about just inflating the tires to 30ish pounds and see if that changes the RPM.
and by the way i agree that a flat tire has a shorter functional radius but does it actually change the circumference enough to loose 56 inches of traveled distance per rotation? (thats comparing the circumference of a 37 inch tire to a 28 inch tire: 2piR=circumfrence) thats what is going to make the difference in RPM.
(the 28 inch tire is based of a previous calculation suggesting that with the RPM achieved and gear ratios he'd have to be running 28 inch tires)
and by the way i agree that a flat tire has a shorter functional radius but does it actually change the circumference enough to loose 56 inches of traveled distance per rotation? (thats comparing the circumference of a 37 inch tire to a 28 inch tire: 2piR=circumfrence) thats what is going to make the difference in RPM.
(the 28 inch tire is based of a previous calculation suggesting that with the RPM achieved and gear ratios he'd have to be running 28 inch tires)
you ran at 60 mph for an extended amount of time at 13psi in the tires? Not good for anything.
ABS sensors don't measure tire pressure.
hoser
SILVER Star
Stumpalama
Forum Junkie
Stepping in to the s*** show...
OP: Do you smell anything? What year is your truck? Since you could spin the wheel, it sort of debunks my theory about dragging the ebrake but do all 4 tires spin freely when off the ground? When you are at 60mph and you put in the clutch and let off the gas, does the truck slow down very quickly or will it coast?
My point is you might be fighting through dragging brakes.
OP: Do you smell anything? What year is your truck? Since you could spin the wheel, it sort of debunks my theory about dragging the ebrake but do all 4 tires spin freely when off the ground? When you are at 60mph and you put in the clutch and let off the gas, does the truck slow down very quickly or will it coast?
My point is you might be fighting through dragging brakes.
- Thread starter
- #94
No smell! All I smell is the fumes from the exhaust manifold leak. When vehicle off the ground tires spin with no effort locked and unlocked. 60 mph hit the clutch the vehicle will slow down pretty fast, faster then a usual truck. Its an 85'
I'm not sure whether the op is trolling us at this point. Especially with the 13psi nonsense. Are you going to try any of the tests mentioned to help figure out the actual cause. Did you even air up the tires and take it back out for a spin? Do you have to shift into 4th gear at 20mph?!? What speed are you going in 3rd gear at 2000rpm
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You simply do not understand. The example is not applicable. Tires are simply not steel tank belts where you are forced to travel the cord length. Steel belting is irrelevant here where the tire is clasping on itself. And, as the human race discovered before Christ, the circumference IS a function of the radius as defined by the wheel in your example. Change that radius and the final gear ratio will change as well.
BTW, a non slipping wheel IS a gear as far as engineering principles are concerned.
I tell you what, research belt and toroidal CVTs for real world examples of what I am trying to illustrate. You can then see the relationship of angular vs. tangential velocity as a function of the radius at the point of contact.
Yes I am a powertrain engineer. Trust me, I am right. I have to put principles like this in practice daily.
Frank
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BTW, a non slipping wheel IS a gear as far as engineering principles are concerned.
I tell you what, research belt and toroidal CVTs for real world examples of what I am trying to illustrate. You can then see the relationship of angular vs. tangential velocity as a function of the radius at the point of contact.
Yes I am a powertrain engineer. Trust me, I am right. I have to put principles like this in practice daily.
Frank
Sent from my SM-N910V
I am digging this thread - lots of intelligent and educated comments. Since the pot need more stirring...maybe the transfer case gears are not OEM (AA or Marks) and have an under drive output. These are typically 10-15%...which doesn't by itself account for the gap...so i'll just go back to watching the fun unfold...
