Predator Tire Resizing

[ZR1BANDIT]

ANYBODY else have to enter false tire sizes to get odometer to read what gps shows for true speed. have 285's on 2005 truck and had to tell computer a diameter size of 36" tires to get spedo to right on when in fact the actual diameter of tire is 33". whats up with this ??????????

[cabletech]

There was a problem with the early Preators. If you use the metric tire size it will work right. This is corrected in the latest release V1.16

Edit:
I missed the year of your truck, so the version doesn't apply. I had problems with my 2004 not being right on using inches, but was closer with metric sizes.

[DmaxMaverick]

My 2001 speedo was off quite a bit before any changes (from the factory).

Now, I program the stock size as 275/75/16, and the actual size as 285/75/16 (actual tire size). Puts it dead on. Your results may vary.

You can also reprogram the running gear ratio (differential) for an effective final drive to get it accurate, while leaving the tire sizes unchanged. Some work with this, and some don't.

What year is your truck, and what software version is your Predator?

[ZR1BANDIT]

my truck is a 2005 and the predaator is #U7185--------------have tires set at 290-90-16 with an actual tire size being 285-75-16---according to gps my spedo reads correct now but the dic has some readings that are off. mpg and gallons used. any ideas-----------??

[DmaxMaverick]

my truck is a 2005 and the predaator is #U7185--------------have tires set at 290-90-16 with an actual tire size being 285-75-16---according to gps my spedo reads correct now but the dic has some readings that are off. mpg and gallons used. any ideas-----------??
Your DIC will be off. The programming has to "lie" to the OEM programming to get it to do what it does, and it skews the algorythm that calculates fuel consumption.

When you say "actual tire size", are you referring to the actual you program, or the actual size on the truck? Are you programming 245/75/16 as the "stock" setting in the programmer? Something isn't right if your spread is 245/75 to 290/90. Your speedo error would have been off by about 9% from the factory, which is more than the difference of the 285 and 245. You may have the programmed figures wrong. 290/90/16 is about a 36.5" diamater. So, if you start with a 33" dia. (the 285), and increase it up to 36.5", the difference is about 3.5", which would be pretty close to the actual difference between the 245 and 285, including OEM inaccuracy. It would be best if you walk through your programming process step by step for us, to be sure you are plugging in the correct #s.

[ZR1BANDIT]

OK---heres what I have done so far. TRuck came with 245's as we all know, I have installed 285's and had the dealer redo tire calc's for me. The spedo was still off so I decided to get my own Predator to play with and reset my own size tires. First I will say that I have experienced that I have to use different seetings for the tires size in different HP modes. Makes no sence to me but is whats happening. No I did not reset to factory specs before I started to reprogram myself. Do I need to do this ???? I understand that when I am using a HP gain program that the DIC will be off, but I didn't think the tire re-sizing would affect the DIC except to make it more accurate. Yes you are right in saying the 290-90-16 is a 36.5" diameter and the 285's I have on now are 33" diameter. Seems like I have to increase tire diameter to in crease spedo speed---confused there ???????---- If i reset all parameters back to original then resize to 285's do you think it will read accurate on the GPS ???? thanks again for the help-------------------Greg

[DmaxMaverick]

OK

On your Predator, select and install the factory tune, just to start with a clean slate. Be sure your truck is up to operating temp before trying any programming. You will have issues, if it lets you at all.

Now, go into tuning mode, and select troubleshooting (I think), and select "Build Diablo Tune". This will reset the tool back to original. Disconnect the tool for about 15 seconds to clear volitile memory.

Make sure the coolant temp is up to at least 140

[ZR1BANDIT]

Thanks ----------will give it a try and let you know how I made out---thanks again------------Greg

[ZR1BANDIT]

RESET everything to stock and started fresh. set original tires at 245's and set new ones at 285's and spedo now reads almost perfect, maybe 1 mph high-----thanks for all the help----------------GREG