Calibration for large tires with Forscan (No CEL)
#16
05-17-2018, 10:13 AM
Awesome to see that this actually works. I had thought about trying this at one time but got side tracked.
Two things to ponder....
I initially tried using the tire vendor provided height as a reference for my calculations. But they always seemed off. Then someone asked me to try the "running tire size" and that seems to work perfect for me. Running/loaded tire size is determined by measuring your tire radius from ground to center cap, then doubling this number. My 37's are claimed to be 36.6" tires on the nitto website, but the loaded tire at 70psi is closer to 35.6".
I was helping one person via PM adjust his tire size and we tried several values greater than the ABA maximum, and he never threw a CEL. Have always wondered if he typed something wrong or if all Canadian based trucks don't have this limitation in the TCM. The check engine light comes from the value the TCM learns via the BCM (what we are programming). But typically the TCM has a soft coded limit and once our tire size goes greater than that value the CEL is triggered via a mismatch.
Two things to ponder....
I initially tried using the tire vendor provided height as a reference for my calculations. But they always seemed off. Then someone asked me to try the "running tire size" and that seems to work perfect for me. Running/loaded tire size is determined by measuring your tire radius from ground to center cap, then doubling this number. My 37's are claimed to be 36.6" tires on the nitto website, but the loaded tire at 70psi is closer to 35.6".
I was helping one person via PM adjust his tire size and we tried several values greater than the ABA maximum, and he never threw a CEL. Have always wondered if he typed something wrong or if all Canadian based trucks don't have this limitation in the TCM. The check engine light comes from the value the TCM learns via the BCM (what we are programming). But typically the TCM has a soft coded limit and once our tire size goes greater than that value the CEL is triggered via a mismatch.
One could always draw a chalk line on the tire, drive forward and measure the distance between the two as well.
#17
05-17-2018, 10:14 AM
Awesome to see that this actually works. I had thought about trying this at one time but got side tracked.
Two things to ponder....
I initially tried using the tire vendor provided height as a reference for my calculations. But they always seemed off. Then someone asked me to try the "running tire size" and that seems to work perfect for me. Running/loaded tire size is determined by measuring your tire radius from ground to center cap, then doubling this number. My 37's are claimed to be 36.6" tires on the nitto website, but the loaded tire at 70psi is closer to 35.6".
I was helping one person via PM adjust his tire size and we tried several values greater than the ABA maximum, and he never threw a CEL. Have always wondered if he typed something wrong or if all Canadian based trucks don't have this limitation in the TCM. The check engine light comes from the value the TCM learns via the BCM (what we are programming). But typically the TCM has a soft coded limit and once our tire size goes greater than that value the CEL is triggered via a mismatch.
Two things to ponder....
I initially tried using the tire vendor provided height as a reference for my calculations. But they always seemed off. Then someone asked me to try the "running tire size" and that seems to work perfect for me. Running/loaded tire size is determined by measuring your tire radius from ground to center cap, then doubling this number. My 37's are claimed to be 36.6" tires on the nitto website, but the loaded tire at 70psi is closer to 35.6".
I was helping one person via PM adjust his tire size and we tried several values greater than the ABA maximum, and he never threw a CEL. Have always wondered if he typed something wrong or if all Canadian based trucks don't have this limitation in the TCM. The check engine light comes from the value the TCM learns via the BCM (what we are programming). But typically the TCM has a soft coded limit and once our tire size goes greater than that value the CEL is triggered via a mismatch.
That was my only reservation actually, that the TCM would use the axle ratio for something but my knowledge there isnt very good ill admit. So far it doesnt 'seem' to be a problem, I havent noticed any issues but that doesnt mean theyre not there of course. BTW im running GDP 150 hp tune with TCM flash. So far so good...
#18
05-17-2018, 10:18 AM
The Barometer Story
#19
05-17-2018, 11:31 AM
#22
05-17-2018, 12:16 PM
#23
05-17-2018, 12:30 PM
#24
05-17-2018, 12:34 PM
#25
05-17-2018, 12:52 PM
Ive created an excel calculator (attached to the original post) that will help calculate the values to achieve. Give it a shot and if you have any questions post here and ill be happy to help.
#26
05-17-2018, 12:57 PM
Thanks brotha! I've gotten such great info from people on these forums over the years, im very happy to be able to give back when I can...
#27
05-17-2018, 03:07 PM
#28
05-18-2018, 02:52 PM
I use the code of ABA (largest possible without CEL) and I am spot on when the tires are set at 65psi... but
at 80 psi im about 2mph off at 80mph.
#29
05-18-2018, 10:30 PM
0AAE code for about 1500 miles now and its very close with my (36.5) 37 nitto G2's I would say within 2-3% of actual maybe a little closer. Like even hard to tell when watching GPS close.
Have you figured out a code for larger tires then that with no CEL?
Kubotaorange76 posted about 0AAE while back as the largest code to work without a light.
Have you figured out a code for larger tires then that with no CEL?
Kubotaorange76 posted about 0AAE while back as the largest code to work without a light.
#30
05-19-2018, 08:58 AM
