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Old 08-14-2008, 09:08 PM   #1 (permalink)
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Is there an easy way to figure out what speedometer gear I need? I've changed tire size and rear end gearing. I'm running 245/60R15 tires and 3.25 rear gears behind a wide ratio trans. This is on my 69 Mach 1. Thanks.
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Old 08-14-2008, 09:21 PM   #2 (permalink)
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What is the Outside diameter of your tires?
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Old 08-14-2008, 10:39 PM   #3 (permalink)
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Here is a good web site that should be able to help you out. Speedo gear calculator
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Old 08-14-2008, 10:49 PM   #4 (permalink)
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The NPD catalog has a calculator printed on the same page where they list speedo gears.
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Old 08-14-2008, 11:18 PM   #5 (permalink)
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Quote:
Originally Posted by cmayna
What is the Outside diameter of your tires?
26.55"
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Old 08-16-2008, 12:28 AM   #6 (permalink)
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Looking at the gear chart in CJ Pony, it is showing the same 16 tooth gear for both the 3.00 and the 3.25 unless theres a difference in F70-14 and FR70-14 tires? How can that be? The F70-14 tire is 24.78" tall, I'm running 245/60R15s that are 26.55" tall. I'm assuming with the bigger tires I would need maybe 1 tooth larger gear? I'm not that good with math, I just know my speed is about 15 MPH to fast right now and would like to get right with out buying and swapping a bunch of gears.
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Old 08-17-2008, 08:56 PM   #7 (permalink)
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Any ideas? Does the chart in NPD give you gears for different size tires or just the factory specs like CJ ponys?
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