Tire Size Change Question - Page 3

stryker6040 · #21 Mon, May 25th, 2009, 01:18 AM

Jack the number you gave me was almost dead on. just a little more fine tuning and everything should be as close to prefect as we can get thanks a lot for the help!

***Jackpine*** · #22 Mon, May 25th, 2009, 01:50 AM

Quote:

Originally Posted by stryker6040

Jack the number you gave me was almost dead on. just a little more fine tuning and everything should be as close to prefect as we can get thanks a lot for the help!

You're most welcome! Glad we could help you out.

- Jack

Mexico Dan · #23 Sun, June 7th, 2009, 11:42 AM

I just got my custom tunes, took it out for a 250 mile drive this weekend. I don't have a gps, but using the mile markers on the freeway, my odometer flips about 150 feet before each mile marker. I also feel "slow" driving the same roads I'm used to. Decrease tire size a little? I have 285/75/16 Terra Grapplers, max psi 65, and running them about 43. Is this too low?

***Jackpine*** · #24 Sun, June 7th, 2009, 04:05 PM

Quote:

Originally Posted by Mexico Dan

I just got my custom tunes, took it out for a 250 mile drive this weekend. I don't have a gps, but using the mile markers on the freeway, my odometer flips about 150 feet before each mile marker. I also feel "slow" driving the same roads I'm used to. Decrease tire size a little? I have 285/75/16 Terra Grapplers, max psi 65, and running them about 43. Is this too low?

Your 150 feet in 5280 feet is about 2.8% in error. You COULD try subtracting 2.8% from the current circumference you are using. The pressure seems all right to me - are you using OEM sized tires and wheels? If so, there should be stickers on the truck recommending the tire pressure. However, since the max pressure is 65, I doubt you'd hurt anything using 50 psi cold.

When I enter your tire size in Bill's Gear Ratio Calculator in Pegasus and use a 7% rubber squish, I get a circumference of 2525 mm. What are you currently using?

- Jack

Mexico Dan · #25 Mon, June 8th, 2009, 07:38 PM

These aren't stock tires. I usually run them around 41-43 then up them to 50 when I tow the boat.

The custom tunes came with the value 2550. I just dropped it down to 2449. There is one of those parked cop things that displays your speed, I'm going to drive by that a few times to get it where it needs to be.

***Jackpine*** · #26 Mon, June 8th, 2009, 09:02 PM

Good! I just subtracted 2.8% from 2550 and came up with 2479. I suspect 2449 will be much too low. I'd try something in the 2500 range as a start.

- Jack

Mexico Dan · #27 Wed, June 10th, 2009, 09:08 PM

Argh, when I change the tire size and it goes throught the 4 stages, it doesn't save the change when I restart the truck. What am I doing wrong? I did the same thing before custom tunes and it stuck.

***88Racing*** · #28 Thu, June 11th, 2009, 12:20 AM

When I go into check the tire size or any other changes. I do the following.

Open CO menu.
Then load previous settings.
Then to tire size usually says 2484
Then to gear ratio usually says 3.73
Then save changes/done. Or follow this link:
http://dygytalworld.ehost-services13...newpost&t=1101

Lars

***Jackpine*** · #29 Thu, June 11th, 2009, 12:18 PM

Quote:

Originally Posted by Mexico Dan

Argh, when I change the tire size and it goes throught the 4 stages, it doesn't save the change when I restart the truck. What am I doing wrong? I did the same thing before custom tunes and it stuck.

Follow the directions Lars gave you in the post just above this one. I suspect you are not "Loading Previous Settings". Follow the link he gave you for an explanation of all the custom options idiosyncrasies.

- Jack