I have installed the 65 tune and I am trying to do the tire parameter. When you go into modify tune it than asks which tune I select 65 and enter. It than goes to next screen: axle ratio, speed limit and actual wheel size. I do not get the fourth selection of factory tire size. If i install actual tire size nothing changes, speedo still off. Called Diablo no answers yet they said no one else is having this problem, funny, I know of three. Any one else having only three selection instead of four.

i got confused when i did it also. the factory tires is what your truck came with factory and the actual is the new ones you just put on. if you go in to the program it will have the actual save in the program

You don't need to program what the original is, just what you are running...

I did put in what I am running and nothing changes Still 5-6 mph off @ 65mph I tried 7 or 8 different tire sizes all off 5-6 mph @ 65. I am going to put the stock tune back in and start over. I installed 65 tune all by itself about a month ago and have been trying to modify that tune. I will install modified tune from stock and see what happens. I still do not understand why some of you are getting 4 selections and I only have 3. Even Diablo is confused. They have no answer yet

Dunno, it works for me. Is your selling dealer close by? Maybe he can help walk you through it.

mine worked great.you need to get to the modify screen type in the old size then enter then the new size enter again then it will ask you if you want to save the modfified performance file press enter and you should uplaod just like the frist time you uploaded the 65 hp tune.its a little trickey

Here's what I"m guessing, cause it happened to me...
The first time in, it asks for your FATORY tire size, then repeats the same screen but this time for the ACTUAL tire size. After having done that the first time, it does not come back and re-ask about the FACTORY size again as you re-tune, or re-adjust tire size.
To get it to again ask about FACTORY size, reinstall the factory tune.. uninstall the Predator completely. Then go back and retune to what you want, and go back to the tire size screen, and it will again ask for the FACTORY tire size the first time only into to that screen, before it moves on to ask for ACTUAL tire size.
I missed the FACTORY tire size screen when I first installed, and this is what I've figured out, and now my speedo is back within 1%, not 8.5%.
Hope this helps... :grd:

Thank You for replies, the selling dealer is right here in stillwater he has suggested the same thing. Go back to stock and start over. I will try it tommorow and post results.

I'm hoping to have enough influence to simplify some of these issue in future revisions, Dmaximus may have hit on something that I've been missing. I always figured it went blank when you selecetd enter after revising tire size, and you needed to Escape. I'll try it again from scratch once.

Either way, I have an idea for a much better way to do this...

Exactly what Dmaximus said. You need to go back and start over. It is kind of confusing actually. It would be nice if they made it a little easier to adjust.

We have discussed adding an interim page between the tire size entry screens because the only difference is the word Factory and Actual which easily slips by a guy.


I'll be the first to admit that I thought the thing reset itself when I hit enter.:shootself

Been discussing many upgrades that benefit the end user...

D_Maximus, thanks for your insight on this, I had mine wrong too. I restored the factory tune and reinstalled with factory size and then actual size with the 65hp tune. It's right on now.:D

Here is the scoop. When I first installed predator I did not want to change tire size. Went right to install tune. I figured I could go and adjust later. This is not the case, You can not adjust parameters once a tune is installed. You must go and install the stock tune and adjust your parameters to your power tune and reinstall power tune. This is what I spent the evening last night and this afternoon loading and unloading programs to see if my theory is right. Take it for what it is worth, I know next time I want to adjust I will put back to stock first and go from there.

2500HD04, Mark

I did mine without going back to stock. You just have to esc back, after modifying the parameters, to a screen asking you if you want to install the modified tune. And then press enter to send the load. You will see it sned the load all over again while having to turn off and on the ignition.

I thougt at first that you would have to go back again, but after playing with mine, it works without it.

is it dead on when you, return it to stock then to load the tune after modifying, with the 285/75/16 data inputed?

I put in 295/70/17 @ 70 mph the gps is at 69.4 to 69.6 that is close enough for me.

I don't know what I'd do without this forum. I went from stock 245's tires to 265's. I adjusted for the tires on the Predator, but the odo. was always ~6% off. I even called Diablosport and they had no clue. I followed the directions in this post, basically starting over and now the odometer is dead on.

:cool2:

Thanks!

My Predator should be here Tuesday for my '05. Funny, but i'm running 285's and according to my GPS, when the speedo shows 65 mph, I'm actually travelling 66.4 mph. I thought it would be off more than that.........

Ok - got my new tires today. Went from 245' to 265's. I currently have the 40HP tune loaded and am going to change my speedo parameter........

If I read this thread right, I need to reload my stock program, change my speedo parameter for the 40 HP tune and then reload the 40HP tune, correct?

If so, do I have to change the speedo parameter everytime I go from stock to 40HP or is the new parameter "saved" forever for the 40 hp tune?

Rob

Modify Tune
Select 40HP
Load Performance Tune, 40HP

Modify Tune
Select 40HP
Load Performance Tune, 40HP

Yep, that's the way it went - mighty confusing though.

Before I modified the tune, per my GPS the speedo was about 2.0 MPH slow at 70 MPH with the new tires (went from 245's to 265's). After modify it is .5 MPH fast at 70MPH. The odd thing though is it's about 1.5MPH fast at 55MPH - 60 MPH. Wish I would have checked it's accuracy when the OEM tires were still on it.

Yep, that's the way it went - mighty confusing though.

Before I modified the tune, per my GPS the speedo was about 2.0 MPH slow at 70 MPH with the new tires (went from 245's to 265's). After modify it is .5 MPH fast at 70MPH. The odd thing though is it's about 1.5MPH fast at 55MPH - 60 MPH. Wish I would have checked it's accuracy when the OEM tires were still on it.

Here's what I found - comparing the dash speedo to the GPS I get the same results as stated above. Using the Predator to monitor the vehicle speed it's within .5 mph of the GPS throughout the 50 - 70 mph range. When I compare the Predator speed reading to the dash speedo, they are off. In short, the GPS matches the Predator - but not the dash speedo. Looks to me that the dash speedo is the inconsistant link and is piss poor for accuracy!

At least it will make a unique excuse. "No officer, see my gps and predator said I was going 80, but I decided the speedometer had to be right when it said 75"