tire height affecting more than speedo?

[usnfenix]

hey i have a quick question regarding tire heights, the factory rear tires on my 14 GT were the 245/45/19s with a height of 27.7 and i have had on there now for a few months 285/35/19 in the rear with a height of 26.9, a difference of .8 and all i have really noticed was the speedo was off by about 2mph but never really bothered me so i never did anything. I was talking to a guy who mentioned that he changed his tire size and his aftermarket tune had its shift points a little off after that, got me to thinking am i screwing with anything bad having not recalibrated for the new height? i have an auto with the mike rousch tune and nothing else. Reason i am asking is i am about to go on a 3000 mile road trip and will reflash to stock tune most likely for the drive (GF will be doing some of the driving as well) and im not sure on how to recalibrate or if i was causing any potential wear and damage when i didnt do it initially.

 

[rotarymagic]

hey i have a quick question regarding tire heights, the factory rear tires on my 14 GT were the 245/45/19s with a height of 27.7 and i have had on there now for a few months 285/35/19 in the rear with a height of 26.9, a difference of .8 and all i have really noticed was the speedo was off by about 2mph but never really bothered me so i never did anything. I was talking to a guy who mentioned that he changed his tire size and his aftermarket tune had its shift points a little off after that, got me to thinking am i screwing with anything bad having not recalibrated for the new height? i have an auto with the mike rousch tune and nothing else. Reason i am asking is i am about to go on a 3000 mile road trip and will reflash to stock tune most likely for the drive (GF will be doing some of the driving as well) and im not sure on how to recalibrate or if i was causing any potential wear and damage when i didnt do it initially.

Considering the transmission shifts based upon speed and not rpm, it could affect it quite a bit. Also if you aren't properly calibrating your speedo then you are also misrepresenting mileage on the vehicle. Not as big of a deal if you're racking up miles more quickly, but if you're showing less miles (over a long period of time) than you've actually traveled then it can cause issues reselling the vehicle. Calling Mike Rousch and getting a revision for the tire height would be the best idea, but... we all know how he is when it comes to customer service lol.

 

[usnfenix]

Interesting i didnt think about the odometer in this case

I have the handheld SCTx4 cant i just calibrate for the 26.9 when i flash to factory tune?

 

[king_13]

Also if you aren't properly calibrating your speedo then you are also misrepresenting mileage on the vehicle. Not as big of a deal if you're racking up miles more quickly, but if you're showing less miles (over a long period of time) than you've actually traveled then it can cause issues reselling the vehicle.

Ive always wondered what's stopping people from tuning for taller tires than they actually have and just use a GPS device for a speedometer.

How could anyone find out besides being told it?


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