Error in HPTuners Speedo Calibrate window

[shimp]

I have this error in my speedo calibrate. Original tires were 235/75/16 now I have 235/70/16 and need to change the speedo because my GPS used to be dead-on with the truck speedo, now the truck speedo is reading 1-5mph fast depending on speed. But I can't because of this error. It won't let me click the commit button. And since I am 5 speed do I need to change any of the shift tables or whatever else on this screen?

How tall are my new tires? 29.0 inches doesn't seem right.


Here's a screenshot of the error:

[shimp]

My Girlfriends file lets me change gear ratio and tire size. Can I just change it in hers to match my current setup then paste the numbers into my file and write the PCM? And not save it in my GF's PCM of course....

[Bill@HPTuners]

can you post your file?

[horist]

How tall are my new tires? 29.0 inches doesn't seem right.

not sure about error (like bill said post your file)

but 29" is indeed correct
235mm / 25.4mm = 9.25"
9.25" * .70 (aspect ratio) = 6.48
6.48*2 (2 sidewalls) + 16 (diameter of wheel) = 28.95 which rounds up to 29.0 fine

(original tires were 29.88")

[shimp]

So if I use the numbers for a 29.0" tire and the speedo still doesn't read right (like it used to) then should I just keep trying smaller or larger tire sizes in small increments like .10 inch till it's right?


Here's my hpt file for the 2004 Silverado.

[horist]

the difference between 29" and 28.95" is negligable so using 29" is fine

Have you emailed support w/a copy of this .hpt file? I just tried with 2.1.15 beta and got same thing as you.... HPT guys should be able to fix you up quickly I'd think (support \()#*/ @\hptuners /*\dot(.)/\com is always the preferred first step ...

[shimp]

I didn't email the file, I just posted it here as an attachment.

[EC_Tune]

1st:
Check your roll-out in inches.
Mark the tire & the ground (at nomal tire temps after driving).

Rotate one or two revolutions (divide that value in inches by 2 if you do 2 revs ). Then mark the ground where the tire mark makes it's 1st or 2nd revolution. It should be ~91.11" If it's different, time to rescale.

Here's the math on how to do the speedo rescale assuming a 29" tire:

Tire revolutions/mile = Inches per mile / Tire Circumference Inches
Tire Revolutions/mi = 63360 / 91.11 --- based on (29" tire * Pi)

Trans revolutions/mile = Tire revolutions/mile * Gear ratio

Your values:
(63360" per mile / 91.11" tire circumference) * 3.42 gear = 2378.4466 Trans Revs-Mile

Take that value and multiply by the Rev-Trans value (40 in *most* cases) to get the VSS Pulses/mile = 95138

Put your values in the appropriate places and your speedo's dead on. Check again with your GPS if you have doubts.

EC

[shimp]

Thanks for that info, greatly appreciated. I'll check that roll-out today or tommorow and get it setup correct.

About the tires, I went with the 70 series tire because the price was right, and because I wanted a little stiffer sidewall than the 75 offered. You can barely tell the difference looking at the truck, but you can feel it when you drive. Thinking about lowering the truck 2-4 this year too.

[Lucky13]

I dont even get the option to change my gear ratio in my HPtuners it just gives me an error everytime. I guess I have to change it doing the roll-out. Here is a screen shot of mine. Is this because its a 98 tune?

[Bill@HPTuners]

I dont even get the option to change my gear ratio in my HPtuners it just gives me an error everytime. I guess I have to change it doing the roll-out. Here is a screen shot of mine. Is this because its a 98 tune?

http://www.thetuningdoctor.com/HPTun...gearchange.swf

Just look at what the window itself says Tire/Gear which means Tire divided by Gear.

[Lucky13]

Guess I am just a moron. Thanks

[shimp]

I sent an email using the contact us page about my issue, and pasted a link to this thread into the message, have not heard back yet. It's not a big deal, just wondering if I should have sent a regular email to [email protected] or [email protected] rather than using the contact us form.

[EC_Tune]

Shimp,
Some vehicles have multiple configurations within one operating system for the speedo calculations (IIRC diesels are another one). So because there are multiple configs, an Error is shown in the speedo section. Notice that the Calculated Tire Diameter still works.

Just use the instructions I posted at the top and you should be good to go. You can still use the Manual Scale to rescale your transmission tables. Just calculate New Diameter / Old Diameter click Commit one time and you should be good to go.

[shimp]

I didn't put the calculated tire size in there. It was in there already the first time I loaded my file. And I can't click commit. It won't let me. I have to manually put in those pulses per mile numbers and all that manually. Do I need to rescale transmission tables even with a 5 speed? The software doesn't show my gear ratios. It show those of a 4L60E. for instance, 4th gear is .90 or something. My trans 4th gear is 1.0:1, not overdrive. 5th gear is overdrive.

[EC_Tune]

You don't need to rescale as you get to select your own gears with the 5-speed.

Sorry, didn't know which truck in your sig.

[shimp]

I did end up getting around this problem. By using the tire calculator in my Girlfriends file the 2002 Sierra and setting my tire size and my gear ratio I was able to copy and paste those numbers into my file and write calibration and got the speedometer dead on with the GPS. However temperature dropped the next few days 10-20* and now the speedo is 1mph fast.... I guess my tires are a hair taller on hot days than cold? I will go back later and find a happy medium number. The tire size I had to use ended up being 28.1" or so. Far below 29.0 like the math says the tire height should be. I will check the pressures in them while cold and make sure they are at least 32psi.

I also was wondering if they are ever gonna fix this speedo calibrate problem? I downloaded 2.1.16 and same problem as 2.1.14.

[EC_Tune]

Some calibrations apparently don't have enough info in them to calculate the tire size correctly. Looks like yours is one of them. Bummer.

[shimp]

It's probably because my truck is 5 speed. Not very common these days. I would guess 99% out there are automatics.