Strommen95
Well-Known Member
After upgrading tire size, shifts will be off for a bit of time, yes. This is because of the extra "load" of the tires. The bigger the tire, the worse the shifting will be initially, but the ECU will adjust to the added load of the tires. For 33s, OP will barely notice a difference once the ECU adjusts. With 35s, hitting 8th is greatly reduced compared to 33s. Depending on driving habits, might not see 8th at all with 35s. Personally, 35s is where I would regear and definitely would for anything above that. We have so many engine choices now though that this has become a gray area to broadly answer.@Strommen95
OK, I hear you.... I'll stand corrected... especially after input from Joe Z. you linked to.... 8-)
Guess my comments were pointing to... if you change tire size dramatically and the trannies shift points will be off til the transmission relearns over time, if possible for relearn if change is minimal... or you do a re-gear. Am I ok saying it like that?
In short, it's accurate to say upgrading tire size will negatively affect shifting but it's temporary. With much larger tires, the long term negative impact is the added weight of the tires, not the ECU potentially having a wrong calibration.
For the record, gearing needs to be properly calibrated for the ECU, which often gives people a false impression tire size needs to be calibrated correctly too. To put it at simply as possible, gearing is part of the mathematical equation for the transmission to determine speed, so it's vital for gearing to be accurate.
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