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quick tire question


 
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erther
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Joined: 14 Jul 2005

PostPosted: Sat Sep 17, 2005 3:42 pm    Post subject: quick tire question Reply with quote

I just upgraded from 30s to 31s. is there a spedo adjustment, or am i fine the way it is?
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IBTJn
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Joined: 31 Dec 2004
Location: Just Outside of Portland, OR

PostPosted: Sat Sep 17, 2005 3:50 pm    Post subject: Reply with quote

When I did that on my '02 TJ, it made very little difference. MAYBE a couple mph on the slower side...meaning I was going faster than the speedo' showed.

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ThePhantum
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Joined: 23 Jan 2004
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PostPosted: Sat Sep 17, 2005 3:50 pm    Post subject: Reply with quote

You can replace the plastic gear under the speedo sensor on the t-case to correct the speedometer. I'd check it first to see how far it's off.
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'drack
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Joined: 01 Jan 2004
Location: points that way...

PostPosted: Sat Sep 17, 2005 5:42 pm    Post subject: Reply with quote

I never bothered checking it (and it's wayyy to late now), but people have said that the speedo is closer to being accurate with the 31's than the 30's (if they were the original equipment). If that's the case, ya should be fine as is.
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AggieDog
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Joined: 16 Jul 2004
Location: Northern California

PostPosted: Sun Sep 18, 2005 3:25 pm    Post subject: Reply with quote

I never checked mine either, but going from 30's to 31's didnt seem a problem. Going on to 32's was.
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Wed Sep 21, 2005 8:53 pm    Post subject: Reply with quote

I have 32's on mine, I know that these weren't stock tires, I just found out how far off my speedo was. With my GPS and cruising at indicated 60mph, the GPS read 63mph. And as far as odometer miles at 10 miles indicated I’m going 10.8.
Check in to a hypethec chip, they say you can recalibrate your speedo to the tire size with a computer.
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02' Apex Edition,
2" BB, 31" BFG AT's
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'drack
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Joined: 01 Jan 2004
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PostPosted: Wed Sep 21, 2005 10:36 pm    Post subject: Reply with quote

TJ Apex wrote:

Check in to a hypethec chip, they say you can recalibrate your speedo to the tire size with a computer.


Problem with the TJ's (other than the Rubicon's) is that they use a gear in the tcase that calibrates the speedo. That needs to be replaced with one with the proper tooth count to get things all matched up. If it was electronic, then those chips and computers would do the trick.
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Thu Sep 22, 2005 3:52 pm    Post subject: Reply with quote

I'm not sure if the dash pods changed from year to year, but I know my 02' has an electronic type dash. there's no cable going from the back of the dash to the t case. so the chip should work.
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2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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ehirner
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Joined: 01 Jan 2004
Location: Eastern PA

PostPosted: Thu Sep 22, 2005 5:37 pm    Post subject: Reply with quote

TJ Apex wrote:
I'm not sure if the dash pods changed from year to year, but I know my 02' has an electronic type dash. there's no cable going from the back of the dash to the t case. so the chip should work.

The non-Rubicon speedometers are a hybrid. There isn't a cable that runs to the dash, but the speedometer is mechanical. There is a speedo gear in the tailhousing of the transfer case that is spun by the main shaft of the t-case. An electronic sensor monitors the speed at which the gear turns and converts the mechanical gear into an electronic signal.
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Fri Sep 23, 2005 6:54 am    Post subject: Reply with quote

I did do some research on the hypertech and jet chip site's and did find that the power programmer they sell will not correct for tire size.
The copyed and pasted the text below from the hypertech site.

Part # Year Make Model Engine Shift Pts/Firm Eng. Tuning Rev Limiter Top Speed Tire Size* Dual Fuel DTC's
96-04 Jeep Cherokee, Grand Cherokee, Wrangler 4.0L N/A Dual Fuel Yes Yes N/A Yes Yes

*The following applications use the Kelsey-Hayes ABS controller and will also include the Tire Size Adjustment feature: 1998-2001 Ram (all), 1997-2000 Dakota 4X4, 1998-2000 Dakota 4X2,1998-2000 Durango (all). Tire Size feature for Part #50008 is available only for the 2500/3500 models only.
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2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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