R/T doesn't affect anything with the ET or MPH. It simply shows how much time passes from the green light to the time that your car breaks out of the beams. There's lots of things that will affect ET & MPH though. A lot of tire spin will usually show as a higher MPH but worse ET. That's because you're getting a running start of sorts towards the finish line. ET/MPH can also be affected quite a bit by where you stage in the beams. Shallow staging will result in quicker ETs & 60' but slower reaction times. Staging deep in the box will result in slower ETs but quicker R/T. Just try to be as consistent as possible in the way you make your runs and you'll be better able to compare the timeslips from run to run.
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Jeff Chambers
Trophy Stock #3
11.462 Seconds / 117.43 MPH
Chambers Racing Team