Looking around different forums, I ain't found nothing on folks reprogramming different tire size in Hummer H3s so that the speedometer & odometer read correctly. Are folks not fixing this when changing tire sizes, or are they just not talking about it? This correction doesn't just ensure the speed & mileage shown on the dash are right. It also affects ABS behavior (and I imagine traction control + stability control + the simulated limited-slip action) to ensure they all function correctly.

I simply want to confirm what methods are available aside from mailing the computer back to a shop (or buying a crappy handheld generic tune module). We're happy with our PCM of NC custom tune, which corrected for our current 285/75-17s (33.8"), but I'm eyeballing some 255/80-17s for our next set (32.8 to 33.3", depending on the model). Of the stealerships here in town: one quoted $110 for 1hr of computer flashing, and the other said it'd be ~$350 for GM to write a custom flash & them to download it to the truck... which is absolute horses#!t because I did my previous 99 GMC with a friend's Tech2 in about 10min after changing to 33s.

I obviously don't still live near that friend and ain't sure if the E38 PCM is as easy as a 0411 to update the revolutions per mile for the VSS. Thoughts?

 

PS: It ain't worth buying HPT or EFI credits on my own... and I ain't buying a Windows computer just for them programs, neither.

 

Ask PCM of NC. Since you have their tune they might just do it for free.

And yes, A F A I K all the ECM cares about is revs per mile; doesn't give a damn about tire size, gear ratio, or any other things that affect it. Only their cumulative outcome.

 

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