lqcj8
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Factory Sponsored Pro-Crawler, expect Catastrophic Body Damage
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Posts: 601
Carnage 4x4 expect body damage
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« on: July 21, 2008, 08:23:19 PM » |
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with 35" tires & 4:88 gears, how far off is my speedo going to be ;D in a 05 LJ w/6 speed trans
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« Last Edit: July 21, 2008, 08:26:21 PM by lqcj8 »
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 81 CJ8,350,400,4:1 300,60,14,40" MTR's,SOA,OBA Anyone can lead, Not everyone can follow Experience is something you don't get until just after you need it |
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Metal Twister
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« Reply #1 on: July 21, 2008, 09:26:16 PM » |
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Wow, pull out the big guns right off the bat!
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StvDiego
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« Reply #2 on: July 21, 2008, 09:27:29 PM » |
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Just for giggles, here's an over-simplified formula:
MPH=(RPM X Tire Diameter) ? (Gear Ratio X 336)
A more complex, and accurate formula at variable speeds:
MPH=(RPM X Tire Diameter) ? (Axle Ratio X Transmission Ratio(s) X T-Case Ratio)
So first we have to figure the current configuration, add a variable for the tire diameter change and then again for the gear change. We will find that the indicated speed will be a variable based on the actual speed and RPM so you will not be at a set level, i.e., at 60mph you will be off by almost 10mph while at lower speeds you will be off by about 3mph, Give me few and I'll do the math but right now there's a hot tub and a beer calling me
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Metal Twister
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« Reply #3 on: July 21, 2008, 09:35:20 PM » |
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Yep, exactly what I was thinking... ~1eye ??? ~eek sure I was?
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Brink
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« Reply #4 on: July 21, 2008, 10:30:07 PM » |
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Man, I knew this one!!! ;D Just kidding. :(
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lqcj8
M.O.M. Awarded
Factory Sponsored Pro-Crawler, expect Catastrophic Body Damage
Offline
Posts: 601
Carnage 4x4 expect body damage
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« Reply #5 on: July 21, 2008, 10:32:34 PM » |
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Dude your pretty good, only I'm off about 5 @ 60 . Did I mention it's a Rubi. (4:10 stock gearing). The 4:88s brought it back to a real close to stock feel & the speedo is close . Good job
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81 CJ8,350,400,4:1 300,60,14,40" MTR's,SOA,OBA Anyone can lead, Not everyone can follow Experience is something you don't get until just after you need it |
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StvDiego
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« Reply #6 on: July 21, 2008, 11:19:20 PM » |
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Dude your pretty good, only I'm off about 5 @ 60 . Did I mention it's a Rubi. (4:10 stock gearing). The 4:88s brought it back to a real close to stock feel & the speedo is close . Good job
Um no, left that minor detail out about the 4:10 factory ratio which of course makes just a tad bit of difference ~clown ~oops |
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« Last Edit: July 22, 2008, 09:13:12 AM by StvDiego »
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