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Old 08-03-2006, 10:36 PM   #1
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speedo

alright...i went up to 32" tires today and i know that the speedo should be off by at least 5 mph...but the speedo said 50 when i was drivin and it still felt like 50...how do i know if its off or not?? as long as i know how much it's off i don't mind it...and is the odometer off too?

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Old 08-03-2006, 10:40 PM   #2
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It's off. By quite a bit, too. I live with it myself. I never have worried with it, but there's a geqar you can change for your speedo to be correct. It's been talked about a bit here, but I wasn't paying attention, so I don't know exactly what you have to do. I think if you look, you'll find the thread.

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Old 08-03-2006, 11:09 PM   #3
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yeah...i have a catalog that has that available to order...it is something that has a certain amount of teeth for your gear and tire size...but i don't want to buy it and i actually don't mind it...i just wanted to make sure it was off cause i don't want the speedo to say 55 and then im actually goin' faster and then i get pulled over by a copper...thanks
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Old 08-03-2006, 11:53 PM   #4
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Quote:
Originally Posted by bigjeep
yeah...i have a catalog that has that available to order...it is something that has a certain amount of teeth for your gear and tire size...but i don't want to buy it and i actually don't mind it...i just wanted to make sure it was off cause i don't want the speedo to say 55 and then im actually goin' faster and then i get pulled over by a copper...thanks
i punched your tire info into an online tire calculator and this is what i got.

Tire diameter 703 mm (27.7'') 809 mm: <---stock tire size
(31.9'') 106 mm (15.1%) taller. <----your ~ tire size

When speedometer reads 60mph (96.6km/h) actual speed will be 69mph (111.1km/h): 15% faster.

Hope that helps.
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Old 08-04-2006, 07:09 AM   #5
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thanks for doin that man...that helps a lot
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Old 08-04-2006, 08:38 AM   #6
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That sounds about right. The way I calculated mine was to drive on the interstate for about 25 miles. I simply used the mile markers and the odometer reading and did a ratio. I have 31's on my jeep and I came up about 10% different. So when I am doing 60 on the speedo, I assume I am actually doing 66.
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Old 08-04-2006, 11:28 AM   #7
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also mind you that since you speedo is off your odemeter is going to be off too. what ever % your speedo is i what you will be off. i put 31s on my bronco and to go 1 mile on my odemeter i would actully only go 1.15 trues miles and i my tires where about 12.4% off. so you are actully going farther then your odemeter says. i think that is right its been awile since i did the gps for it, if i am wrong someone please say,and i am going to have to get my gps back out and make sure. its either this or just the oppsite.
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Old 08-04-2006, 11:35 AM   #8
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You are on the right track mswilder, his odometer will show less miles, than actually traveled. The taller the tire, the less revolutions it takes to go any said distance.
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Old 08-04-2006, 12:52 PM   #9
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Cool, I was going to look into or ask this same Question cuz I have been running 31's for a few years now and never gave it any thought. I made a slow progression from 28's - 30's then 31's so the Speed never Felt any different, but I recently passed one of those Check Your Speed Signs and it was 5mph higher than my speedo.......... We'll now I know.
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Old 08-04-2006, 02:48 PM   #10
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well how much will my odometer be off by??? i don't want to miss my oil changes because it's been more miles then what it says
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Old 08-04-2006, 04:03 PM   #11
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There may be a couple of things to consider there. One, you are turning less revolutions to go further so theoretically you are more efficient. Two, It is harder to turn the bigger tires so you are putting more wear and tear. Is it a wash? Probably. I doubt if it would make enough difference to alter your oil change schedule.
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Old 08-04-2006, 04:39 PM   #12
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alright so its not that big of a difference? and what do you mean by "is it a wash"?? i might should know what you mean but maybe i'm not awake from my nap yet...well anyway right now i'm not understanding what you mean by "is it a wash"?
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Old 08-04-2006, 05:48 PM   #13
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I don't think the calculation saying 60 gets you 69 is right. I'm running 35's with 3.73 gearing and real world experience tells me I'm going 66 when my speedo says 60.

Here's the speedo gear chart from another thread in the forum. Looks like you are in need of a 32 tooth speedo gear. They are way easy to change and only run like 6 bucks or so also if it ever gets to bothering you.

http://www.raingler.com/jeepReference/speedoChart.html
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Old 08-04-2006, 09:03 PM   #14
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Quote:
Originally Posted by bigjeep
alright so its not that big of a difference? and what do you mean by "is it a wash"?? i might should know what you mean but maybe i'm not awake from my nap yet...well anyway right now i'm not understanding what you mean by "is it a wash"?

Do they cancel each other out, so that it makes no difference?

Maybe I'm showing my age... using a term not familiar to these younger whippersnappers. (don't even ask what a "whippersnapper" is)
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Old 08-04-2006, 09:27 PM   #15
coilovers are damn flexy
 
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31" tires will not make enough difference to worry about the service intervals, if that is your concern.
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Old 08-04-2006, 10:01 PM   #16
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actually its 32's
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Old 08-10-2006, 01:53 AM   #17
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have 32's as well . need part # or source for 3.07 gears thanks!
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Old 08-10-2006, 10:07 AM   #18
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4wd sells the new speedo gears with a chart...check out their site

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