Tire question

1badbitch

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I am about to bring my car to the track it's a stock 2014 6r80 mustang GT only thing done to it is flowmaster outlaw axel backs. My question is my buddy has a set of drag radial that I am going to borrow but they are 275/50r15 nitto 555r. I keep seeing how you are supposed to change the tire size with a tuner but I want to see how fast the car will go before I put a tune in the car. And by the way yes I searched but didn't really find anything.
 

fourdegrees11

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Changing the size on a tuner is just to adjust your speedo. That rear size is over an inch smaller then your front tires should be, not sure how/if that effects anything?
 

redfirepearlgt

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^^^ El wrong-o stick shift owner. On modern day transmissions such as 6r80's, and 5r55's everything has to be right for the car to shift where it is supposed to. The days of C4's and C6's have come and gone with the exception of trannys like the 4R70 and Power Glide used in big number cars. Therefore Tire rotation, and axle ratio are critical on 6R80 cars for much more than speedometer calibration.

OP - The 6R80 shift calculation is rather complex, unlike the days of yore of C4's FMX's, C6's and AOD's. You can run a shorter tire without changing the Rotations per mile but at WOT it won't shift at the same point actual speed point, it will only think it will. The 275/50 is a shorter tire than the factory wheel without even knowing what your factory tire is. At least 1" shorter if not more depending on if you have 18's or 19's.

I suggest staying on the factory tires for your test passes. The car should run 12.70's easily on the factory tires on your stock vehicle. The 6R80 is a faster car than the MT82.

Below is a time slip between my stock 13 GT manual and a friend with his stock 13 GT auto. He drove around me in spite of my perfect light 000. We were both on street tires. Best of luck to you.

2alDQb3.jpg
 
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1badbitch

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Thanks for the reply !!!!!!! I will give it a shot with the stock tires ...
 

redfirepearlgt

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No big burn outs. Drive around the waterbox if possible. Just scuff the tires to clean them off and stage up.

Once you start modding, and a hand held with a tune will likely be at the top of that list, then you start looking at wheel options with a 6R80 setup.

Best of luck and don't get frustrated if you aren't running 12.5's like the guy on the other side of my ticket did. He made a lot of passes in that car. That was one of his better passes. Most were 12.6x passes. He sold it for a GT500 before he got around to modding it.
 

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