Tire Size not Changing
 

I've upgraded my tires to 295/70R17s (33.4") and my speedo is reading 9% slow. This is GPS vs what the Gryphon says. I had the same problem when it was the stock edge, I can adjust all the other custom settings, but the speedo is always off no matter what numbers I put it. I've tried from 2500 to 2800 and its always reading slow. ex says I'm doing 55mph while gps shows 60mph...

Any idea how to fix this?

All right, this sounds like you're not going into the load tune state after you've entered the Tire Size (TS), or the your Gear Ratio (GR) value is wrong. BOTH will have "default" (placeholder) values when you first open the custom options menu that may or may not be correct.

I can't hep you with the GR value, you have to get that off the VIN sticker. But I suggest a TS value of 2573mm. Your unloaded tire circumference is about 2653 and reducing it by 3% for the flattening effect of weight gives 2573.

Now, when you open the Custom Options Menu: scroll to GR and put in the correct figure if it's not already there. Hit [Enter] to "save" it. Scroll to TS and put in 2573. Hit [Enter] to save it. If you push the [Menu] button in either case, you will "back out" without saving. Then, scroll to "Done" and hit [Enter] to load your tune and those values into your PCM.

Test your speed after you get the tune loaded. If the Gryphon still says you're going slower than you really are, increase your TS. But, this time (and any future time) you open the Custom Options Menu, scroll to "Load Previous Settings as the very first step you perform!. Hit [Enter] to retrieve your previous TS and GR (and any other changes you made. Now, when you scroll to TS, you should see a value very close to what you last used - it won't be quite the same due to "rounding", but the difference will be minor. You can change it as needed.

If you don't see the proper TS after loading previous settings, or if you skip the "Load Previous Settings", you're doing things wrong. Re-read these instructions.

- Jack

ok, I'll give that a shot and see what happens.

Thanks

The easiest way I have found to get the tire size accurate with a GPS is to set your tire size to something you know is wrong, like 2400, clear the odometer on your truck and on the GPS, drive 10 miles then input the numbers as shown.

(GPS Miles/Truck miles) X 2400 = New Tire Size

So I started at 2573 with my gears of 4.10 and was showing 51mph while travelling 55. Shut the truck down, loaded previous settings, and changed the TS to 2774, speedo didn't change. Loaded previous settings again, upped TS to 2900 and speedometer was still off by 9%....

OK, do it again. This time, tell me what your Tire Size value is right after you "Load Previous Settings" (before you enter anything new). Also, if you DO have 4.10 gears installed, tell me what the Gryphon shows for Gear Ratio after the "Load Previous Settings" step.

If you're doing things right, you should see a TS value that is "close" to 2900 and a GR that is 4.10 at this point. Tell me what you find and we'll go from there.

- Jack

My TS says 2905 and GR is 4.10. My truck has the heavy duty package and came stock with 4.10s.

Well, that surprised me. The TS and GR are definitely stored in your "customized" tune file. This leaves only ONE possibility, you are not loading them into the PCM.

So, do it again, for whatever tune you want to use. Scroll to "Load Previous Settings". Check the TS and GR if you'd like, hitting [Enter] after viewing each setting, then scroll to "Done" and hit [Enter]. At this point, you should see the usual progress display telling you that the PCM is being programmed. At the end of this, there should be a "click" under the dash and a "programming complete" message (as I recall).

A TS of 2905 should make your Gryphon and dash speedo read MUCH faster than the GPS. I would think that would show a +9 mph error at a true speed of 70.

And, if you've followed my directions exactly and still have the same problem, I'm out of ideas - except :doh: what year is your truck? I've been working on the assumption it is an 04-08 model. Is it possibly a pre 99 model? If so, you cannot adjust the speed with a programmer. You will need to change the VSS on the rear axle if you mount non OEM tires. Edit: Nevermind - I see from your User Profile that you have a 2007 truck.

- Jack

I'll give it one more shot, but I dont' have much hope either lol This is a first gen Edge and I've never been able to change the tire size since I got it.

Have you checked for any firmware updates? To do so, return your truck to stock, then start Pegasus on your PC. With Pegasus running, plug in the Gryphon. Click on [Updates]->[Gryphon Update Manager] and apply any firmware and calibration updates you find. Then, click on [Updates]->[Custom File Download] to reinstall your custom tunes. After that, try reloading your tune with an adjusted TS. You MAY need to adjust the GR too - the updates may wipe out your "Previous Settings".

- Jack

Jack, just in case you missed it, his truck is an 07. And an update is all I can think of that you could do to fix it.. if that doesn't work, call edge and ask them what's wrong...

Yes, I DID figure out his truck was an 07. If, he in fact was loading the tune after making the Custom Option changes, then the speed should have been corrected. And, maybe the update I suggested will take care of things too.

He's already talked to Edge and they seemed to be of no help. Possibly Bill can figure out what's wrong if the update doesn't do it for him.

And maybe, Bill can adjust his custom tune so that the correct TS and GR are loaded too, if a firmware update doesn't fix it.

- Jack

I just got my Gryphon and custom tunes a week ago. But I'll give the update a shot tomorrow. If that doesn't work, then I'll get a hold of Bill and see what he thinks. It'd be nice to get this fixed cuz my winter tires are a 31" but I'm running 33s right now, and would like to upgrade to 35s next summer lol

So something weird happened. I uploaded my custom tunes from Bill and didn't go through the custom menu or anything. Now my speedo is reading fast lol It shows 58mph while I'm actually going 55.

OK, that's not so weird. I think Bill has input a TS value in your custom tunes. But, you did not say "which" speedo is "reading fast". If the dash speedo is showing 58 when you're actually at 55, you are very close to being "dead on". The dash speedo is normally going to read 3% fast when the odometer is giving accurate mileage. But, if the Gryphon speedo is 3 mph fast, then he has the TS value set too high.

Trouble is, you can't figure out what value he used. If you want to try to correct things again, start with a TS value of 2573 and make sure your GR is 4.10. Make adjustments from that TS value.

- Jack

It was the Gryphon digital speedo vs my GPS digital Speedo. I know that the dash analog speedo reads fast no matter what. I'll try adjusting the TS through the custom menu again and hope it works this time.

good luck! :)

Didn't work... Had the TS read 2574 and the speedo was back to being 9% slow. I guess I'll email Bill and see what he says.