You're absolutely right. As of 2000, the following tire sizes are
programmable to the CABS. These sizes are related to revolutions per mile
for each specific tire/wheel combination. Any other size and they can come
close to one of these listed sizes.
1) P215/75R15 760 rpm (revolutions per mile)
2) P235/75R15 XL 729 rpm
3) P255/65R15 755 rpm
4) P255/55R17 750 rpm
5) 31x10.50R15 LT 689 rpm
If your dealer says he can't, bring it to another.
Ron
00 SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Kenneth Eng
Sent: Sunday, October 01, 2000 8:11 PM
To: dakota-truck@buffnet.net
Subject: RE: DML: RE: More.....big tires 'n backspacing
Ron,
Bernd has determined that the 98 and up no longer uses a speedo gear change
to correct for a change in tire size as the PCM needs to be reprogrammed
instead. I went from the 235/75-15 to 255/65-15. Both of these tire sizes
come directly from Dodge on the Daks. I also assumed that since these are
standard tire sizes they should available as a selection on the device used
to reprogram the PCM. The change in tire size is small but if there is a
way to set my speedo to correct for it I would still like it corrected. I
guess I need to call another dealer.
Ken
------Original Message------
From: "Ronald Wong" <ron-wong@home.com>
To: dakota-truck@buffnet.net
Sent: October 1, 2000 4:00:11 AM GMT
Subject: RE: DML: RE: More.....big tires 'n backspacing
Either it can re-programmed or it uses a speedo gear. If it can be
re-programmed there are only specific sizes it can do. Unless you get
radical the dealer should be able to come close. With the tires you changed
to your difference is negligible. Your old diameter was 28.88", your new
one is 28.05".
Ron
00 SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Kenneth Eng
Sent: Saturday, September 30, 2000 8:08 PM
To: dakota-truck@buffnet.net
Subject: RE: DML: RE: More.....big tires 'n backspacing
Last Wednesday I brought my 98 4x2 Auto to get the PCM reprogrammed as I had
changed from 235/75-15 tires to 255/65-15 tires. The mechanic told me that
he couldn't reprogram the PCM as they are individually configured at the
factory for a specific tire size. To correct for the new tire size he told
me I would need to buy a new PCM module for that tire size. He even took
the reprogramming device to my truck to try it out and still couldn't
reprogram it. Is this true? Has anyone actually had their PCM reprogrammed
for a different tire size?
Ken
------Original Message------
From: "Bernd D. Ratsch" <bernd@texas.net>
To: dakota-truck@buffnet.net
Sent: September 29, 2000 12:01:16 PM GMT
Subject: DML: RE: More.....big tires 'n backspacing
I had changed the speedo-gear to match the setup I have (Differential
Gears/Tire combination). Otherwise, no PCM change required on my truck.
- Bernd
-----Original Message-----
From: owner-dakota-truck@buffnet.net
Subject: DML: More.....big tires 'n backspacing
Hey, thanks to all of you that gave me some input about this whole tire
thing. Every bit helps.
Bernd, thank you for your more detailed experiences. I guess it's off to
find some wheels.......but, not a whole lot of selection out there!!!
Actually think that the only 3.75 backspaced wheel I even saw on various
mfg's sites was the style that you have ---hell, I don't want to be a copy
cat!! ;>
Did you need to make any adjustments to the PCM.
I'm lifting it primarily to get some decent clearance when I haul the
bikes out to the desert----that's why I'm not doing a body lift.
Thanks again to all for your input,
Ken H.
"The shortest distance between two points is a straight line"
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