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Technical Forum The main forum for jeep related discussions. Mechanically Inept... |
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#1
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Tire size vs. crawl ratio
I've been thinking about this and i'd like some educated feedback.
Why doesn't tire size equate into the final crawl ratio? Larger tires will rotate slower but cover more ground per rotation than a smaller tire with equivalent gearing. Smaller tires should be condusive of more power and torque with everything else remaining the same. For a nice slow crawl; wouldn't smaller tires with a 100:1 crawl ratio crawl slower than a larger tire with same ratio? In other words....small tire rotates faster but covers less ground and larger tire rotates slower but covers more ground. The smaller tire would actually be traversing ahead slower. No? Tire size is taken into consideration when determining ideal gear ratio for a given rpm. Why isn't it considered in the final crawl ratio?
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Life's journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting, "...HOLY $HIT...what a ride!" |
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Re: Tire size vs. crawl ratio
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Brian |
#3
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I think you may be taking it a little too literaly. Think of a transmission. Say you have a 3.14:1 first gear . . . but is that 3.14:1 with 28 inch tires, or 37 inch tires? So what is the actual ratio? Its still 3.14:1. I think anyway.
I guess you could start the "corrected" crawl ratio movement. |
#4
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my axle gears work well for on road driving with the tires I'm running.
my transfer case gearing was based on the the maximum reduction I could get out of one box at the time I bought it. with the ax-15 my final crawl ratio is somewhere near 90:1. This, with 35s mind you, is somewhat acceptable while playing in fairly large rocks. if I were running 37s i doubt I would be happy with the on road characteristics of my axle gearing. if I lowered that, my final crawl ratio would follow. in the end, your Jeep is either set up so it works or it isn't. you (or the people that watch you drive) are best qualified to make that decision.
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Brian |
#5
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Re: Tire size vs. crawl ratio
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#6
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Re: Re: Tire size vs. crawl ratio
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__________________
Life's journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting, "...HOLY $HIT...what a ride!" |
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Re: Re: Tire size vs. crawl ratio
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#9
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I put together a little tool of my own:
http://www.dfw-tx4wd.org/gears.html I have a bunch more transmissions to add when I get around to it.
__________________
1977 Cherokee: 360/TH400/QT/D44/D44 - Beavis 1984 CJ7: 401/SM465/Atlas/D44/9" - In progress 2004 Pontiac GTO: LS1/T56/M80 - My Free Gear Ratio Calculator (In Metric Too) |
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Cactus Kid |
#11
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There is crawl ratio.
There is crawl speed. This is the one where tire size is considered. |
#12
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Quote:
__________________
Life's journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting, "...HOLY $HIT...what a ride!" |
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__________________
1977 Cherokee: 360/TH400/QT/D44/D44 - Beavis 1984 CJ7: 401/SM465/Atlas/D44/9" - In progress 2004 Pontiac GTO: LS1/T56/M80 - My Free Gear Ratio Calculator (In Metric Too) |
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Cactus Kid |
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Cactus Kid |
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Cactus Kid |
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