| From | Message |
Daddy-D
Gen III
 
12/28/2001
10:42:13
|
 Subject: Speedo Calibration
IP: Logged
Message:
Having changed from the wierd 235/70/15
tires to 255/60/15, the 1"-smaller tire diameter
theoretically will cause my speedo to be off
(indicating faster than real speed).
I called the dealer, they told me my '98 has to
go to a speedo shop for calibration - they don't
do it at the dealer (scary).
What's involved? Change a little gear - or is it
electronic and self-calibrating (I cannot see
how)?
Of course, my Haynes book doesn't even
mention the speedo - how is this done?
TIA
'98 DakSport C/C 3.9 2WD A/T
|
JohnBen
Dodge Dakota
12/28/2001
11:16:13
| RE: Speedo Calibration
IP: Logged
Message:
Amazing! I was just about to post this exact same question about my 99 Dakota. I assumed that the tire's rolling diameter was simply programmed into the truck's computer, but surely the dealer would be able to do that...
If the tire diameter IS programmed into the computer, does anyone know how to display it?
JohnBen
|
CW
GenIII
12/28/2001
14:23:44
|  RE: Speedo Calibration
IP: Logged
Message:
aren't the tires a 255/65R15 from the factory? If it is the 235/70R15 is the same diameter.
2001 4.7 5sp 3.92 LSD sport plus
Ported throttle body, IAT adjuster, 3" flowmaster cat back, TPS @ .76v, 4" cold air, Roadmaster active suspention.
|
Daddy-D
Gen III
12/29/2001
00:54:21
|  RE: Speedo Calibration
IP: Logged
Message:
My '98 came with crap Goodyear Eagle LS
235/70/15s on it (28" dia). Although my new
Pirelli Scorpion Zero 255/60/15s (27" dia) are
smaller, my speedo is still accurate!
These Pirelli Scorpion Zeros are sweet!
'98 DakSport C/C 3.9 2WD A/T
|
dodgedogjb
Dodge Dakota
12/29/2001
01:35:38
| RE: Speedo Calibration
IP: Logged
Message:
The easier factor to measure here is the circumfrence of the tire. Most vehicles have room for error built into the initial calibration to account for tire wear, loading, and tire pressure changes. I believe the error to be somewhere between 3-5% on most autos, but not positive. This error range on vehicles with larger initial tire sizes allows for a bigger change without affecting the speedo. You may not even need to change the speedo unless the difference is pretty drastic???
The best way to check is with a good GPS if you know someone that has one. Also there are often mileage check points on highways but I'm not sure if it would show up in the five miles or not unless its pretty far off where as a few mph might show on a calibration unit.
Hope this helps.
|
Daddy-D
Gen III
12/29/2001
11:22:34
| RE: Speedo Calibration
IP: Logged
Message:
Yes, I did several highway mileposts - my
speedo is still accurate.
'98 DakSport C/C 3.9 2WD A/T
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
