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Tire revolution question
Topic Started: Jan 2 2011, 06:44 PM (1,097 Views)
dayle1960
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Fastest Hampster EVER

Will a 13" tire on a metro traveling at 40 MPH turn the same number of revolution through a mile as a metro traveling 70MPH?

If yes, why?

If no, why?

Mrs. dayle1960

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Stately
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Geo cheerleader

Unless you're skidding or burning rubber doing it--the same.

As long as there is no slippage, doesn't matter how fast as long as tire maintains same diameter.
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Kik
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<<<Will a 13" tire on a metro traveling at 40 MPH turn the same number of revolution through a mile as a metro traveling 70MPH?>>>

Yes.

<<<If yes, why?>>>

Because there would be 886 revolutions per mile for the 155/80r13 stock tire due to the 71.5 inch circumference. 886 x 71.5 = 63349 inches divided by 12 = 5279. feet or approx. 1 mile

However...if you have 155/80R13 tires on the front axle and 155/60R13 tires on the rear, the shorter tires on the tail would require 992 revs to make up that same mile due to the circumference of 63.8 inches vs the 71.5 of the 155/80's. Still along for the ride at 40 mph or 70 mph but the revolutions change, not the velocity.

The exception would be if one or more of the tires were laying on the roof of said Metro as opposed to being mounted on the wheel hubs. Still traveling at said speed but the revolutions would change substantially.

***If this has caused someone in the house to lose a bet and have to do the dishes for all of 2011, or if mwebb says otherwise, I withdraw all the above information.***
Edited by Kik, Jan 2 2011, 07:18 PM.
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MR Bill
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Did anyone over look tire growth due to increase in speed?
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Jezza
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Boost Junkie

hruehl
Jan 2 2011, 08:48 PM
Did anyone over look tire growth due to increase in speed?

:hmm :ermm:
Edited by Jezza, Jan 2 2011, 08:52 PM.
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Kik
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Key word here is "negligible". Not so much in road tires on a Metro. Drag racing...slicks...yes.

neg'li-gi-ble, adj. too unimportant to matter

:nfs
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bogs
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Duct tape heals all wounds

Kik
Jan 2 2011, 09:19 PM
neg'li-gi-ble, adj. too unimportant to matter - see 'bogs'

:nfs
Bogs - [bog, bawg] Show IPA noun, verb, bogged, bog·ging.
–noun
1. wet, spongy ground with soil composed mainly of decayed vegetable matter.
2. an area or stretch of such ground. –verb (used with object), verb (used without object)
3. to sink in or as if in a bog (often fol. by down ): We were bogged down by overwork. —Verb phrase
4. bog in, Australian Slang . to eat heartily and ravenously.
----------------------------------------------------------------
What happened to my thread? It got bogged down during the hi-jacking :lol
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Jim-Bob
Junkyard Engineer

You have to see it in terms of mathematics. The change in diameter relative to speed should be within the standard deviation, so let's just ignore that. Now assuming the same wheel and tire at the same inflation pressure for both tests, you come down against two mathematical constants- the circumference of the wheel and the length of a mile. The length of a mile does not change and neither does the circumference of the wheel/tire, so it is a simple division problem to determine the number of revolutions per mile it will see. Speed does not play into it. If you wish to decrease the number of revolutions per mile you need to increase the circumference of the tire. To increase the number of revolutions, decrease the circumference of the tire.

It's simple mathematics really when dealing with a modern radial ply tire. As noted with drag slicks however, bias ply tires can be another case all together. This is because bias tires put all of their reinforcement on the bias, or sidewall of the tire, thus the tread portion changes shape under centripetal force. Drag cars actually use this to their advantage as it changes the effective gear ratio with speed, giving it, in effect, another gear ratio. of course this doesn't apply to drag radials, but I can go into a lot of permutations here that would contradict the generally accepted axioms regarding tire construction. I'll save them for the thought experiments I do while delivering pizzas...
Edited by Jim-Bob, Jan 3 2011, 04:35 AM.
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Kik
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Jim-Bob...you're making my head hurt.

Bogs...wrong dictionary. Mine says "bogs" - purveyor of all GEO related goodness, to include historical data review, comedic interventions and sticky stuff that will withstand 100+ mph velocity
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Jezza
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Boost Junkie

Kik
Jan 3 2011, 11:00 AM
Jim-Bob...you're making my head hurt.

Bogs...wrong dictionary. Mine says "bogs" - purveyor of all GEO related goodness, to include historical data review, comedic interventions and sticky stuff that will withstand 100+ mph velocity
Thats the one right there ... ^o) :lol :lol
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bogs
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Duct tape heals all wounds

Yah, dang that Merriam Webster guy, you show him kik :lol :lol :lol
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