Why do you run different sizes?
long story.. whew.
since I bracket race the car putting "FAT TIRES" on the front slows down the cars reaction time due to "more tire" being "in the beams" for a longer period of time when you launch.
Since the 245-50's are about 1 inch shorter it puts a wider portion of the tires "Circle" in the beams, thus slowing down the reaction time.
Since the 225-60's "go up in smoke" on the rear of my car, I needed to run the 245's to get enough traction to "launch the car".
with the 225's up front running between 45-50PSI I can use air pressure to increase or decrease my RT.
If my first 3 time trials have RT's in the .050 range I can increase the tire pressure by 5LBS and that .050 turns into an .010.
In my car 5LBS pressure is between .040-.050.
I was using those RT's for an example.
IF I am cutting .050's I AINT CHANGING ANYTHING!
But.. the same formula applies
Say I was cutting .060's or .070's.. increasing pressure by 5LBS will turn that .070 into an .030 or .020 which is "right in the groove" if you ask me.
When I had 245's on the front I would have to "prestage, then stage, THEN bump into the stage beam twice" and HOPE I didn't turn off the "prestage light".
With 225's up front I stage SHALLOW as possible and dont have to do any of that guesswork/bumping into the beams crap.
bumping into the staged beam is a "fix" but it's not "consistant" and can very easily cause you to "deep stage" which at some tracks will disqualify you with a RED LIGHT unless "deep staging is allowed".
So... there you have it.. 225's on the front for better RT's and 245's on the back for better 60 foots.