Printable View
When I put in my new tire size, 28.9 inch with 4.10 gears (original ratio), the calculated tire size goes to 29.32 inch. My brother has HPTuners also and when he put in a tire size of 33.5 with 4.10 gears, it calculated it at 31.8, when I input it on my program it calculates 33.99 inch. Why does the tire size recalculate? And why the difference between our programs?
I would have thought it had to do with a final drive ratio number, but that doesn't explain the difference between the two programs running the same numbers. Unless the two programs are using two different transmissions.
More to the point the number calculation may take in the tire size, gear ratio, and the transmission ratio somewhere.
I'm just guessing though, someone correct me if I am wrong
mine does it too might have something to do with a mean of tire size averages that's my guess
To correct the calculated tire dia; calculated tire dia/current tire dia*trans revolutions/mile. Then close & open the speedo page. Now the calculated tire dia should match the current tire dia. This is very important, as the trans shift speeds depend on the correct calculated tire dia & trans revs/mile.
Russ Kemp