Will swapping tires change shift points?
Thread Starter
Racer
Joined: Nov 2007
Posts: 441
Likes: 3
From: Huntsville Alabama
Will swapping tires change shift points?
Here is the question.
I run as a daily tire a 315/35/18 Drag Radial, and that tire is 26.8" tall.
If the car has a tune on it to shift at 6600 rpm with those tires, will it still make the 6600 rpm shift when I swap out at the track a drag pack set up with a 275/40/17" rear tire that is 25.7" tall?
I run as a daily tire a 315/35/18 Drag Radial, and that tire is 26.8" tall.
If the car has a tune on it to shift at 6600 rpm with those tires, will it still make the 6600 rpm shift when I swap out at the track a drag pack set up with a 275/40/17" rear tire that is 25.7" tall?
Melting Slicks
Joined: May 2007
Posts: 2,014
Likes: 48
From: Dayton Ohio
You guys need to quit hustlin on the forum 
OP,
I'm not a big auto guy but as long as the tune is for rpm and not certain speed then yes it would. Your speedo will likely be slightly off and car would just shift sooner than before due to the smaller tire ( less mph per gear).
OP,
I'm not a big auto guy but as long as the tune is for rpm and not certain speed then yes it would. Your speedo will likely be slightly off and car would just shift sooner than before due to the smaller tire ( less mph per gear).
Thread Starter
Racer
Joined: Nov 2007
Posts: 441
Likes: 3
From: Huntsville Alabama
Tune
Thanks for any input. I am no tuner for sure, but I think there is a RPM/MPH % that factors in to make a shift. Again, I really do not know this and that is why I am asking.
Here is the biggest reason I am asking. As of right now the shifts points are off in the car, and my tuner is planning to this afternoon dial them in this afternoon.
My car is shifting 1-2 @ 5500 rpm, and 2-3 @ 5600 rpm. This past Sunday at the 1/8th mile track, the car ran 103 mph shifting on its own by leaving it in 3rd, and when I shifted it manually, ( lucky I did not hit the rev limiter) I shifted @ 6600 rpm, and the car went 108 mph on that pass.
I would like to make sure if possible when we tune it, it is still going to make the desired shift with tires that are over 1 inch shorter.
Here is the biggest reason I am asking. As of right now the shifts points are off in the car, and my tuner is planning to this afternoon dial them in this afternoon.
My car is shifting 1-2 @ 5500 rpm, and 2-3 @ 5600 rpm. This past Sunday at the 1/8th mile track, the car ran 103 mph shifting on its own by leaving it in 3rd, and when I shifted it manually, ( lucky I did not hit the rev limiter) I shifted @ 6600 rpm, and the car went 108 mph on that pass.
I would like to make sure if possible when we tune it, it is still going to make the desired shift with tires that are over 1 inch shorter.
