Modifying As-Built Data Guide

[zuki_dan]

[MENTION=25607]Spart[/MENTION] Thanks for taking the initiative to try and figure out the tire size in the as-built data. I have been waiting for someone to stumble onto this and your process seems to make sense that they would use revs per mile to calculate the speed. Now I need to take the time to figure out the setting for my slightly smaller tires.

I know while speed shifting my car I have noticed the speedometer increase speed with tire spin so I am pretty sure it is being taken from the rear tires.

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[Spart]

[MENTION=18894]zuki_dan[/MENTION] what is your tire size?

 

[zuki_dan]

[MENTION=18894]zuki_dan[/MENTION] what is your tire size?

My rear tire size is 325-30-19. And using the below site and your calculation I come up with changing mine to 080A. I will see later tonight if I can input this into the as-built data.

http://www.willtheyfit.com/

 

[Spart]

My rear tire size is 325-30-19. And using the below site and your calculation I come up with changing mine to 080A. I will see later tonight if I can input this into the as-built data.

http://www.willtheyfit.com/

I came up with 080F. If it won't allow you to write that value, try 0827 which is the smallest factory value.

ETA: Keep in mind I came up with my nominal tire diameters using this calculator. If you use another calculator, you may get different results (and thus need a different conversion factor.)

 

[zuki_dan]

Well I managed to successfully program 080F into the car. I am going to go on a test drive here in a few with GPS speedometer app set on my phone to verify how accurate the speedometer is. I will post back with results in awhile.

 

[zuki_dan]

Tire Size confirmed working!

:hail:[MENTION]Spart[/MENTION] I just got back from my test drive with 726-12-01 programmed to xxxx 080F xxxx for my rear tire size 325/30/19. I can confirm that this was able to be programmed and it works as you thought it would! Thanks so much for this!!! Now I no longer have to calculate in my head how far off my speedo is when cruising. No more need for the whipple flare device to correct the speedo either.

I tried it out with the cruise set at: 55, 60, 65, 70, 75, & 80 and the GPS speed app on my phone was displaying the same speed I had set the cruise control to.

[MENTION=8977]fionic[/MENTION]This is confirmed working on my car with non OEM size tires. This probably needs to be added to your spreadsheet but I don't exactly know how it should be added based on how Spart is calculating the size and converting to hex value. It will probably need its own tab. Actually it could probably be figured out which standard sizes are used on our cars and have the values placed in a table.

 

[Wally-Bob]

@Zuki-Dan,

I thought you would have tested it 100 MPH, that way if it was off - no difficult math to determine how far off you were!

Mine reads 4-1/2% slow so now with your effort, I can easily fix it.

Good job and thanks for this.

@Spart ,

And thanks to you as well !!!

 

[Spart]

That's awesome! I'm just glad we figured out how to adjust it without a tune.

When I get time, I'm going to play with how extreme it will let you go on either end.

 

[dotJake]

That's awesome! I'm just glad we figured out how to adjust it without a tune.

When I get time, I'm going to play with how extreme it will let you go on either end.

Too bad none of us will live to see the value of these cars go up. If one could set the value so far out of bounds as to "misrepresent" the miles on the odo...

 

[Spart]

Too bad odometer fraud is a felony.

 

[solodogg]

[MENTION=25607]Spart[/MENTION], that is insane that you spent that much time to figure out that it was a dec/hex conversion of the tire size, definitely much appreciated. I would say you are correct that the 50th anniversary car is probably just an oversight on Ford's part, and it appears the EB wheel/stripe pack cars were the same way. Makes you wonder if the 50th GT cars were initially supposed to have a staggered setup as well.

We now have a much cheaper and easier way to calibrate the speedometer!

 

[solodogg]

To make things a bit simpler, here is a fairly easy way to figure out the as-built values for different tire sizes...

Tire size calculator: http://www.rimsntires.com/specspro.jsp
Inch to millimeter converter: http://www.convertunits.com/from/inches/to/mm
Circumference calculator: http://www.onlineconversion.com/circlesolve.htm
Dec to Hex converter: http://www.binaryhexconverter.com/decimal-to-hex-converter

1a.) Using the tire size calculator above, plug in your size (wheel width and backspacing don't matter for this calc).

OR

1b.)If the manufacturer of your tire lists the tire height in inches or millimeters online, use that value for better accuracy. If inches, convert to millimeters using the converter listed above.

2.) Using the circumference calculator, enter the diameter in millimeters in the "diameter" field, then press the "solve others" button.

3.) Take the value listed in circumference rounded to the nearest whole number, and multiply by .967

4.) Enter value from step 3 into the dec to hex converter, this is your as-built value.

example: 305/35-19 has a nominal height of 27.3" or 697mm. Circumference would be 2190mm, and 2118mm is 96.7% of that value. The hex value is 0846. As-built becomes 726-12-01 xxxx 0846 xxxx

 

[Spart]

[MENTION=25607]Spart[/MENTION], that is insane that you spent that much time to figure out that it was a dec/hex conversion of the tire size, definitely much appreciated. I would say you are correct that the 50th anniversary car is probably just an oversight on Ford's part, and it appears the EB wheel/stripe pack cars were the same way. Makes you wonder if the 50th GT cars were initially supposed to have a staggered setup as well.

We now have a much cheaper and easier way to calibrate the speedometer!

Everything I read about the 50Y cars says that they're staggered with the same rubber as the but it was hard to find good info. I couldn't even find the model number(s) of the wheels.

Here's one link that describes the rubber: http://www.autobytel.com/car-ownership/accessories/what-is-the-mustang-50th-anniversary-edition-124858/

ETA: another link http://www.post-gazette.com/auto/2014/04/24/Ford-Honors-First-Mustang-With-50-Year-Limited-Edition/stories/201404240115

Anybody out there with a 50Y car care to chime in?

 

[Spart]

To make things a bit simpler, here is a fairly easy way to figure out the as-built values for different tire sizes...

Tire size calculator: http://www.rimsntires.com/specspro.jsp
Inch to millimeter converter: http://www.convertunits.com/from/inches/to/mm
Circumference calculator: http://www.onlineconversion.com/circlesolve.htm
Dec to Hex converter: http://www.binaryhexconverter.com/decimal-to-hex-converter

1a.) Using the tire size calculator above, plug in your size (wheel width and backspacing don't matter for this calc).

OR

1b.)If the manufacturer of your tire lists the tire height in inches or millimeters online, use that value for better accuracy. If inches, convert to millimeters using the converter listed above.

2.) Using the circumference calculator, enter the diameter in millimeters in the "diameter" field, then press the "solve others" button.

3.) Take the value listed in circumference rounded to the nearest whole number, and multiply by .967

4.) Enter value from step 3 into the dec to hex converter, this is your as-built value.

example: 305/35-19 has a nominal height of 27.3" or 697mm. Circumference would be 2190mm, and 2118mm is 96.7% of that value. The hex value is 0846. As-built becomes 726-12-01 xxxx 0846 xxxx

Is this simpler? I made a Google sheets calculator.

https://docs.google.com/spreadsheets/d/1rNzj0Ibm6pGJZbg-J2szZ0Su0RlTr7FhwR6JxwTo0v0/edit?usp=sharing

 

[jody858]

If I'm doing the calculations right, my hex value should be 858...username checks out. :headbonk:

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