changing the computer for different size tires. [Archive]

duglas

11-10-2004, 08:02 PM

Frist off, unless you work at Chrysler, MB, or a Dodge dealer, please do not reply and say you "think this is not possible"..

I called 2 different Dodge dealers today and asked about adjusting the computer for a new tire size, they both told me the LX cars could change it but there was a limited # of tires in there system..

IS there anyone out there that actually knows what our options are??? I want to put a 255X40X18 on my car to give me some more power off the line, I know I will need to lower it also...

I know it is possible, the dealer wanted $85 just to hook my car up to the computer to see what the options are, then charge me $85 again when I get the tires.....

Again, the dealer said it is possible, so unless you know for sure and do not think or was told that it is not, please do not offer a negative response....

bri

11-10-2004, 08:55 PM

jeez, it's not that bad here, is it?

duglas

11-10-2004, 11:37 PM

LOL, I was not trying to be mean, but I asked about this before and lots of people replied saying it was not possible and had nothing to back it up, but I believed them and did not CHECK with the dealer or anyone else... So when I was at the dealer I just thought I would ask and was told no problem at all... Had I done that first I would of had new tires months ago.....

11-11-2004, 12:07 AM

Funny thing you mention the tire options.......

I went to my dealer yesterday, to have my EVIC updated so the Sirius stations would SHOW up on the display (I added Sirius and NAV). They could not make it work........ The dealer I am going to is relatively small, and has been MORE than cooperative with me. So, of course, I asked if I could play around with the Star Scan!
They left me alone for about 30 minutes to play around with it........
I did get my Sirius to display on the EVIC after about 2 minutes of playing around with the menus. So, that left me some time to investigate other options in the Star Scan "toy"!
I did go INTO the tire size menu, and they list specific sizes and brands of tires. I wish I would have gone INTO the menu to see how extensive the list was, but I didn't. I can tell you that the menu lists only specific tires.... so I don't think you can just enter a size based on what I saw...... Maybe I can get back to the dealer in the next week or so to play around some more. I know I will be there in the next 2 weeks, as I am approaching my next oil change.
If no one gives any additional info, I will post back when I get more info.......

I wish I had 3K for a Star Scan of my own!

--Bo

01-05-2005, 12:53 AM

OK......so it took a little longer than 2 weeks......but here is the info:

The following tire size options are available for the LX in Star Scan...... Star Scan lists some of these sizes multiple times, but with a different brand of tire???....

215/65/17
225/60/18
245/45/20
255/45/20
235/55/18

Of course, you could use one of the online claculators and match one of the above sizes as closely as possible to your specific setup....... I am unsure if the software in the Star Scan I was using is 100% up to date, but I KNOW that these sizes are in the computer, as I pulled the DATA FROM Star Scan myself.

HTH,

--Bo

2003z

01-05-2005, 01:07 AM

great info, thanks!

Zog

01-05-2005, 01:07 AM

Did you manage to disable the speed limiter?

tonyt

01-05-2005, 12:30 PM

Did you manage to disable the speed limiter?

Yeah, I'd like to know that myself. I still would like to know for a fact if the dealerships would do it or not.

tonyt

01-05-2005, 12:31 PM

Did you manage to disable the speed limiter?

Yeah, I'd like to know that myself. I still would like to know for a fact if the dealerships would do it or not.

01-05-2005, 02:56 PM

I looked around for such an option in the Star Scan menu...... but could not find anything that would be "easy".
However, your comment has me wondering........
The tire selcetions in the menu are FROM different manufacturers, and for a couple of the sizes, there are 2-3 choices. Those choices SHOW different speed ratings on the tires. Maybe the speed limiter would be increased if a Z rated tire were selected?? The only bad thing is that I remember that there was no Z rated tire option for the factory size tire...... I will CHECK again during my next oil change, or when my foglight arrives (not too far off with the miles I have been putting on the car!).

--Bo

grinner

01-05-2005, 09:17 PM

I have an appt to have mine done next week (along with a list of other things)
I'll report on this when it's done. Otta be reprogrammed to top at 149... we'll see.

Kim Hufty

07-10-2005, 12:49 PM

I had my computer reprogrammed to better fit my 285x50x18 and it only cost $37, once. I would go to anouther dealer that knew what they were doing if I was you.

magnumdude

07-10-2005, 01:17 PM

I know but since I don't work for dc I guess I can't post a reply. Oh well

zonian

07-14-2005, 10:20 AM

OK, not to beat a dead horse...but are there any updates to this thread?

I'm ready for new rubber for my RT (looking at the BFG 255-55-18 G-Force KDW2's)

Regarding the Starscan, curious if anyone knows FOR SURE (I heard somewhere "Bo knows...http://www.lxforums.com/board/images/icons/icon7.gif"):

1) Are more tire "options" added with later firmware versions?
2) Does selection of a specifc "speed rated" tire change or increase the speed limiter?
Paul

07-14-2005, 11:20 AM

The tire sizes listed earlier in this thread were what was actually in the StarScan as options...... I witnessed them with my own eyes! I was wondering, as you were, if there had been any updates to their software. I will be taking my car to the dealer in the next couple of weeks..... and I will hook up the StarScan and find out....

--Bo

zonian

07-14-2005, 11:21 AM

Thank Bo...wish I had a dealer like yours...

Paul

Rockadile

07-14-2005, 04:00 PM

Rev.Hammer

07-14-2005, 04:28 PM

Dammit We Need A Starscan!!

bigdwaters

07-14-2005, 06:17 PM

hey maybe we could do a group buy...........................

BrilliantBlackHemi

07-14-2005, 08:17 PM

I'm in for that and dibs on using it first!!!!!!! :D :D

Fred

07-14-2005, 11:36 PM

Timeshare STARSCAN!!

07-15-2005, 11:48 AM

Yes, I have a VERY cool service dept at my dealer!

I thought about buying a StarScan.... but they run about 3k, and are essentially worthless without direct access to Dealer Connect. All updates and flashes are downloaded from Dealer Connect to the StarScan, then transferred to the car.
I suppose that I don't really need one... until the dealer stops being friendly!

--Bo

sloloco

07-24-2005, 06:58 PM

Cool beans, you answered my question too. I am getting ready to put on 255/45-20's and wanted to be able to adjust it at the dealer as well.

Scarbs

09-20-2005, 02:05 AM

Bo

Can you give us the path to get to thes differant sizes?

09-20-2005, 10:39 AM

Courtesy of fnkychkn in another thread......

"from starscan main menu:
ECU view > FCM (CGW) > misc. functions > program tire size."

HTH,

--Bo

Rev.Hammer

09-20-2005, 01:26 PM

Hey Funky C!
Can we use you as a pipeline for dealer updates? hehehehe

AGGOST

09-20-2005, 08:50 PM

fnkychkn

09-20-2005, 09:49 PM

played with starscan today. EDIT: checked with starscan version 6.02
available tire sizes: A = 2006 magnum SRT8/ B = 2005 300C/ C = 2005 magnum SXT

A-B-C P215/65R17 T A/S ride goodyear integrity
A-B-C P215/65R17 T A/S ride continental CT95
A-B-C P225/60R18 H A/S touring continental CH95
A-B-C P225/60R18 H S/S A/S touring continental CH95
A-B-C P225/60R18 V A/S performance continental
A-B-C P225/60R18 V summer performance pirelli
A-B P225/60R18 W summer performance pirelli
A-B P225/60R18 H A/S touring 4x4 continental contact
A-B P225/60R18 99H S/S A/S touring continental contact
A-B 245/45ZR20 A/S performance
A-B 245/45ZR20 or 255/45ZR20 performance
A-B 235/55R18 MXM4 michelin

maneval69

09-20-2005, 10:15 PM

That sucks.
There are only 4 diameters available
29.0", 28.7" 28.2" and 28.0"
And I'll bet that the 29.0/28.7 and the 28.2/28.0 are the same in the computers eyes as the diameters are so close.
Doesn't the SRT have 245/45R20 on the front and 255/45R20 on the rear?
I know the speed rating is different but that's not as important to me as the speed accuracy.

I wonder how bad it would mess with the computer to be ½ inch bigger or smaller than the tire size loaded in the computer.

maneval69

09-20-2005, 10:20 PM

I know 1/2 inch would make the speedometer off by 3.5% but would it cause problems?

By the way,

Thanks for the info fnkychkn

elcapitan87

09-23-2005, 04:16 PM

A-B-C P215/65R17 T A/S ride goodyear integrity - 746 revs/mile
A-B-C P215/65R17 T A/S ride continental CT95 - 742 revs/mile
A-B-C P225/60R18 H A/S touring continental CH95 - 734 revs/mile
A-B-C P225/60R18 H S/S A/S touring continental CH95 - 734 revs/mile
A-B-C P225/60R18 V A/S performance continental - 734 revs/mile
A-B-C P225/60R18 V summer performance pirelli -
A-B P225/60R18 W summer performance pirelli - 782 revs/mile
A-B P225/60R18 H A/S touring 4x4 continental contact -
A-B P225/60R18 99H S/S A/S touring continental contact -
A-B 245/45ZR20 A/S performance
A-B 245/45ZR20 or 255/45ZR20 performance - 719 revs/mile (Eagle F1 Supercar)
A-B 235/55R18 MXM4 michelin -

I've filled in the revs/mile for the listed tires above that I could find. Find the revs/mile of the tire that you want programmed and match it to the nearest of the above and you should close. Closer than not having the computer updated anyway. That is assuming that you tried to stay close to the stock ratio when you upgraded your wheel/tire combo.

MAGNUM8R

09-23-2005, 06:36 PM

What about the 255/55R-18 109V BFG KDW set up?? Anyone have the right conversion for this?? I am goiing to ask the dealer to adjust to this size and I know they will play dumb!
I'm getting ready for my 30K service and hope to this and flash at the same time.

MattRobertson

09-23-2005, 07:17 PM

What about the 255/55R-18 109V BFG KDW set up?? Tire brand irregularities aside, this is the same size as a 255/45/20.

elcapitan87

09-24-2005, 02:03 PM

Yep, KDW2 are 717 rev/mile. The 20" size in the computer would get you real darn close. .2% off.

Meister

09-24-2005, 03:43 PM

I've filled in the revs/mile for the listed tires above that I could find....

Very helpful addition, elcap--thanks. :thumbs_u:

Kudos to both you & the super chicken for the initial info. :beerchug:

joeb1

10-12-2005, 05:26 PM

I know 1/2 inch would make the speedometer off by 3.5% but would it cause problems?

Only in traffic court. :)

Joe B
Glendale, AZ
Magnum Owners Club
Southwest Chapter
Member # 1015
2005 Magnum RT
Inferno Red Tinted Pearl Coat

Robins_SXT

10-12-2005, 07:57 PM

I've a couple of questions to clarify my understanding of this issue:

1) The speed is measured by a wheel sensor and independent of driveline drive ratios? Which wheel sensor is used?

2) Fnkychkn posted tire sizes available in Starscan by model: Does that mean only the indicated values are available for that model or can any size listed be selected for any model?

sloloco

10-12-2005, 08:12 PM

Yes, but you can use the formula to find the closest overal diam. to the combo you are running.

MikeEast

10-12-2005, 08:14 PM

I just got back from Lanier Tire and Wheel in Cumming, GA and am now the proud owner of a set of 255/55-18 KDW-2's - serious tires indeed.

Nothing like having some big fat tires on your ride - and the cornering is sooo much better than the conti's. The only thing I regret is not having done some serious burnouts and getting video footage of it. The rears on the contil's were -><- this close to showing a solid wear bar.

Mike
(I'd put a picture here, but it's soo dirty I'd be ashamed to have y'all see it :-)

Robins_SXT

10-12-2005, 08:56 PM

Yes, but you can use the formula to find the closest overal diam. to the combo you are running.

You're saying the tire selection is independent of model; SE, SXT, RT, & SRT? If this is so I'm wondering why Fnkychkn posted the sizes available by model....

fnkychkn

10-12-2005, 09:04 PM

You're saying the tire selection is independent of model; SE, SXT, RT, & SRT? If this is so I'm wondering why Fnkychkn posted the sizes available by model....
the sizes i posted were the ones listed on the starscan menu for each model that i checked.
starscan is now running version 6.03. one of the updates to this software is a modified routine to only display 20 inch tire sizes for SRT8 vehicles.

MCaesar

10-12-2005, 10:11 PM

fnkychkn

10-12-2005, 10:27 PM

1) The speed is measured by a wheel sensor and independent of driveline drive ratios? Which wheel sensor is used?
IIRC, the average of both rear wheel speed sensors is used to determine vehicle speed.

Robins_SXT

10-13-2005, 06:00 PM

the sizes i posted were the ones listed on the starscan menu for each model that i checked.
starscan is now running version 6.03. one of the updates to this software is a modified routine to only display 20 inch tire sizes for SRT8 vehicles.

Then you have to select a model and it only displays those choices associated with that model; I.E. no 20 inch tire sizes for an SE, SXT, & RT? If so, could you select the SRT model and load it on a SE, SXT, or RT anyway?

I'm just trying to understand if all choices are available or if you're limited by the model. Thanks for clearing up the wheel sensor question.

fnkychkn

10-13-2005, 06:11 PM

Then you have to select a model and it only displays those choices associated with that model; I.E. no 20 inch tire sizes for an SE, SXT, & RT? If so, could you select the SRT model and load it on a SE, SXT, or RT anyway?

I'm just trying to understand if all choices are available or if you're limited by the model. Thanks for clearing up the wheel sensor question.
when i hook-up starscan, it knows what vehicle i'm working on. when i select "program tire size", several choices come up but some models have more choices than others.

Robins_SXT

10-14-2005, 07:12 AM

Many thanks knowledgable chkn

JMatt

11-24-2005, 12:44 AM

That sucks.
There are only 4 diameters available . . . . Doesn't the SRT have 245/45R20 on the front and 255/45R20 on the rear?
I know the speed rating is different but that's not as important to me as the speed accuracy.

Very interesting indeed! I have the SRT-8 with the 255's on the back. According to tirerack the 245's are 729 revs per mile, but my 255's are 719 revs per mile.

Why is this VERY interesting? Well - I checked my speedometer against a GPS unit. I found it curious that my actual speed was consistently about 1% higher than indicated regardless of speed. I checked the speedo at speeds from 35 to 80 in 5 mph increments, holding each speed on level ground with cruise control to make sure the GPS speed had stabilized.

The difference between 719 and 729 revs per mile suggests my actual speed would be 1.3% higher than indicated. That number is well within my margin of error, given that even the digital speedo in the EVIC display only shows whold miles per hour, not tenths.

Conclusion? DCX uses the same setting for the speedo regardless of whether they use the 245 or the 255 rear tires.

VanillaRT4me

11-24-2005, 03:50 AM

hey bo can you tell me the current tire sizes on the 6.03 version of the starscan. I am looking for the 255/45r20 for a 300c but the curent one I saw does not have any 20" wheels at all. Anyone else have answers please post.

What we all need to do at this point is determine the diameter of the particular tire we wish to put on our cars. Then, find the diameter of the tires available on the computer that most closely match it.

Forget about the diameter of the wheel because that is irrelevant at this point! Likewise, don't bother looking at revs/mile, it is a troublesome measurement. Just go by overall tire diameter.

Using 255/45-20 as an example, the tire diameter is: 29.03 inches. If this tire size is found in the computer, then I can use it in place of my 265/35-22 tire.

It is that simple.

StarJack

11-24-2005, 09:11 PM

when i hook-up starscan, it knows what vehicle i'm working on. when i select "program tire size", several choices come up but some models have more choices than others.

Can you tell me what menu the 'program tire size' option is under? What outer menu? My SM is great, not only did he not charge me for turning on the DRL's, he refused rather strongly my attempt to give him some money! It took him several minutes to figure out how to turn on the DRL's though, so I'd like to able to shorten his journey when I ask him to adjust my tire size. (245-45-20). I'm going to show up with hot Krispy Kreme's this time though! :p

Thanks for any guidance you can provide!

fnkychkn

11-24-2005, 09:16 PM

Can you tell me what menu the 'program tire size' option is under? What outer menu? My SM is great, not only did he not charge me for turning on the DRL's, he refused rather strongly my attempt to give him some money! It took him several minutes to figure out how to turn on the DRL's though, so I'd like to able to shorten his journey when I ask him to adjust my tire size. (245-45-20). I'm going to show up with hot Krispy Kreme's this time though! :p

Thanks for any guidance you can provide!
from starscan main menu: ECU view > FCM > miscellaneous functions > program tire size.

StarJack

11-24-2005, 09:33 PM

from starscan main menu: ECU view > FCM > miscellaneous functions > program tire size.

That is too cool. Thanks Man!:thumbs_u:

da BoMM

11-25-2005, 02:58 PM

This thread is enlightening -- now my questions:

Swapped my Contiseals/ RT wheels for Daytona wheels (really identical wheel) / Michelins: went from 225/60/R18 to P235/55/R18/99V TIRES

1) I've determined that the Michelins are slightly smaller dia (28.17 vs 28.62) and new revs per mile are 738.3 vs 726.7 (from 1010tires.com referenced earlier in this thread)
Speedometer diff is 1.596% too fast (60.9 vs 60 MPH actual) --
do I need to have the computer changed, or can the computer even change such a small difference?

2) Since the new tire is V rated,
can I get the speed limiter bumped up?

Thanks.

Meister

11-25-2005, 08:42 PM

...1)...do I need to have the computer changed, or can the computer even change such a small difference?

2) Since the new tire is V rated,
can I get the speed limiter bumped up?
...Refer to post #31, BragonMyMag.

1) It's your call as to whether or not to change it (I would, personally). If you do choose to change it there is an exact size match in starscan for your tires. (Refer to Funky's input back in post #31.)

Any starscan unit with CD update v6.02 or higher applied will list your tire size. Take Funky's starscan tire size change checklist with you to help your tech go directly to the change page with no wasted time spent looking for it.

2) Not currently, no. This is one of many settings that MF will be looking at hacking.

da BoMM

11-26-2005, 12:38 AM

Refer to post #31, BragonMyMag.

Thanks, Meister --
As to thread #31, can anyone explain why some tires with the same specs have different REVS per MILE? (???)

The two P215/65/17's are different and one of the P225/60/R18's is 782 while all the others are 734 (???) what am I missing?

fnkychkn

11-26-2005, 12:56 AM

tire circumference will determine revs per mile. two same size tires can have different circumferences depending on thread depth. also, as tire wears, revs per mile will increase.

Scott

11-26-2005, 04:18 AM

1) I've determined that the Michelins are slightly smaller dia (28.17 vs 28.62) and new revs per mile are 738.3 vs 726.7 (from 1010tires.com referenced earlier in this thread)
Speedometer diff is 1.596% too fast (60.9 vs 60 MPH actual) --
do I need to have the computer changed, or can the computer even change such a small difference?

My Nov 05 build Magnum speedo indicates almost 2 mph less than actual speed at 60 mph. So that change would improve my accuracy, at least according to police radar. Most speedos are off a bit, the question is yours too fast or to slow?

If you are trying to be exact, measure the circumference yourself with a flexible tape measure and divide by pie to get diameter.

Scott

Scott

11-26-2005, 05:09 AM

1) I've determined that the Michelins are slightly smaller dia (28.17 vs 28.62) and new revs per mile are 738.3 vs 726.7 (from 1010tires.com referenced earlier in this thread)

Lately, I've been looking at a lot of data on tire circumference and revs per mile. The revs/mile at 1010tires site looked wrong, so I ran the numbers myself and calculated 716 and 704 respectively. I also checked a few other online calculators and they are all within a few tenths of a rev/mile of my numbers.

Nevertheless, 1010's method at least showed the relative difference between the tires.

Scott