Another tire recalibration thread...

[jwmaier1215]

Okay guys, I inputed JJ's number, 2709 and 3.55 GR. Alls I have to say is WOW, WOW, and WOW. What a difference inputing the right data makes! lol

It's sooooo freakin close, idk if it's worth messing with it. The mileage was dang near spot on. The MPH was dang near spot on. Here's the breakdown:

55mph truck = 56 mph GPS
15.1 miles in truck = 15 (getting ready to turn 15.1 miles) on GPS

In fact the miles may have been equal, I didn't reset my trip meter (anxious to see MPG improvements and couldn't wait for a full tank to be ran, lol). So the miles were virtually equal, and the speedometer is only off about .5 MPH on the gryphon. I think I can live with that!

But good lord, here I was 2 years later still not seeing a huge improvement with a gryphon vs. no gryphon, but man does this thing have some pep to it's step again! May all be just because the speedometer is virtually right now.

Is it even worth tinkering with again, or is that about as right as it's going to get? Because to me, I can definately live with that and am just impressed with the improvement.

@Shotgun, yeah I was almost empty. I had about 1/8th of a tank when I filled up with the 92 octane. I'm going to run a full tank of it, and then run a full tank of 89 and see mileage differences. If 92 gives a lot better gas mileage, then .20 a gallon isn't too shabby (It'd take 5 gallons to equate $1 and 25 gallons to equate $5....what's $5 if you get 2-3 more MPG).

[Jackpine]

I doubt it's worth messing with, but you COULD add just a bit to the Tire Size. Maybe try 2715, since your speed on the Gryphon is just a bit low. Trouble is, the odometer in the truck seems to be just a tiny bit high, which would say to reduce the TS.

You really need to test over a long distance (about 100 miles) to get a more accurate comparison (which is what I did on an interstate trip). And, if you want to base the correction on speed, try to get on a straight stretch where you can hold a constant speed for 10-15 seconds. That lets everything stabilize.

Realize too, that your Gryphon MAY have been seeing 55.4 mph and the GPS may have been seeing 55.5-55.6, but due to "rounding" it would look like a full 1 mph difference.

However, I doubt you're going to get much better than what you have now. And yes, by correcting the speed, the part throttle shift points are happening when they should, since they are based on both vehicle speed and throttle opening.

- Jack

[jwmaier1215]

Yeah, I think I'm just impressed enough right now that 1mph or a fraction of a MPH isn't going to make me much difference. Right on, goovey!

Thank you again shotgun and JackandJanet!

[Longshot270]

Glad you got everything ironed out. Just in case you are wondering I used 2400 in that post because I was making a guess at my tire size for 265/70-17 and then rounded down to the nearest hundred. To help lower your % error it is best to use an initial tire size that is way off from what you should be getting. Since most people are looking for the TS of a 35" tire 2400 just seemed to work.

Here is an example of why I start overly low:
If your tire size is 2715 but you start with 2700, your % difference is .5% Your odometer will not pick that up without going 50+ miles.

Now if your tire size is still 2715 but you start with 2400, your % difference is 11.6% and the difference will show up within 10 miles. I'm guestimating on numbers but your truck will be reading a little over 10 miles when the GPS will read 9.
10.2/9*2400=2720. Dang, I guessed pretty close.

[jwmaier1215]

Lol, yeah LS! I just wanted to make sure 2400 was a guess at whatever tire size you had and not a "standard" number to use. Which is why I kind of got confused/knew something was wrong when I came up with a number greater than what a stock 35in tire should be. Luckily JanetandJack and shotgun are A-M-A-Z-I-N-G with this sort of stuff. I used JJ's number and it's so close, I'm not even going to fool with it! I was extremely amazed running the expressway at 5pm (rush hour galore) and being able to go from 60mph-70mph with a snap of the finger, truck never use to accelerate like this! BTW, the SL on the expressway is 50-55mph (varies) and at one point the entire stretch of road (all 3 lanes going east) from as far as I could see, to as far back as I could see was running 70+ and I was in the slow lane! Crazy stuff. You'd think I'm from Chicago or something, but I'm only living in Evansville, Indiana (pop. of 250k).