alright... do yourself a favor and find out the revs/minute @ 45MP/H figure
for the tires.. that is a universal figure that is used to calibrate your
mp/h on the computer. the figure should be on the BFG website in some kind
of file... you have to look around. the number for michelin LTX M/S in the
size you want is 706, which is under the allowed value for 4x2 pickups (at
least for the 1998), which is 723. now, with that number, the dealership is
able to enter "custom" tire sizes on your PCM.
the size of the tire is not what the computer looks at, its that value.
when i switched my tires from the 215/75R15 to 235/75R15, i had to have my
PCM recalibrated. i think it was off about 8% for about 8-10k miles. also,
you may have to pay to have the computer recalibrated. if they want to
charge you, don't let them charge you for more than 1/2 an hour. it
literally takes 5 minutes for someone to do it. i had a guy who had never
looked at the programmer and he was able to program my PCM in 10 minutes.
hope this helps.
Gabe Couriel
http://frontpage.tripod.com/fijigabe0
--- 1998 Dodge Dakota Club Cab Sport 3.9L V6 5-Speed Manual Transmission (AX-15) 3.21 Open Rear End-----Original Message----- From: owner-dakota-truck@bent.twistedbits.net [mailto:owner-dakota-truck@bent.twistedbits.net]On Behalf Of Korey Atterberry Sent: Wednesday, November 06, 2002 11:15 PM To: dakota-truck@dakota-truck.net Subject: DML: Tire size - speedometer recalibration
Hey all-
I'm looking to replace my 255/65/15's with 30x9.5x15 BFG AT KO's, and my concern is that my odometer/speedometer, etc. will be off. The stock tires are 28" tall, and the 30's are actually 29.5", so I'm looking at a 5% difference. BTW - I drive a 2000 2WD.
My concern is that I'll have problems when I go to sell the truck for the odometer misreporting. Is there a "legal" limit? 5% too much?
I called three different dealerships. One didn't know the first number in P-metric tire sizes means the width, the second thought 1/4" difference in height would cause a 5mph difference, and the third didn't know the Dakota was sold with the 255/65/15's. Needless to say, none of them could tell me if 5% was too much out of spec, and if it were, whether a computer flash was required (or available) or if I needed to change the speedo gear.
I've also heard going up a size or two can cause problems with the ABS computer, but I don't really see how, since I'm getting a set of 4. I kinda figured the truck's computer would just figure that I'm driving a little slower and hauling a little more load and adjust accordingly.
Any thoughts, Korey
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