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Old 07-27-2016, 06:48 AM   #1
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Default Street Tire PAX adjustment proposal

Rick Ruth has maintained the PAX factors for nearly two decades. He uses times from national tour events (formerly called divisionals) and the nationals to continually adjust the factors to account for new cars and class changes of cars. While the factors do not reflect the changes in car performance caused by Reno's altitude, nor the problem of unfairly classed cars, the factors are still remarkably close, considering the vast number of variables, for judging driver performance and car preparation across the spectrum of classes.

I used the 2014, 2015 and 2016 PAX factors to arrive at the following numbers. You are welcome to redo the math and/or comment on the logic used.

Just prior to the 2014 season, Rick came up with PAX adjustments for each of the stock classes in anticipation of the move to street tires for those classes. His initial adjustments averaged .72 seconds on a 60 second course. This proved too small of an adjustment and over the next two years tweaked the PAXs for the stock classes until they now average .91 seconds for a 60 second course.

Of interest is a general trend showing the PAXs for higher powered cars were adjusted down more than the lower powered cars. SS changed to 1.50 seconds for a 60 second course as opposed to HS changing a mere .036 seconds. That faster cars were moved into HS and GS over that time period only partially explains that variance.

If we adopt the average, .91 seconds or .985 (.90 seconds) expressed as a PAX factor, this would give a .6 second advantage to race rubber in SS, and a disadvantage of .54 seconds to race rubber in HS and GS. I have not entertained making a PAX adjustment for each class due to the ongoing complexity that would be involved.

While using a blanket PAX adjustment of .9 seconds (.985 PAX) is imperfect, it still gives some relief to those needing or wishing to use street tires in the r-comp classes and it cannot be argued that the adjustment factor is subjective or not based on volume data. Other than the variance between classes, it is as objective as the entire set of PAX factors.

Subjectively, I believe the PAX adjustment should be 1.25 seconds for a 60 second course. My reasoning is that the adjustment factor is applied to classes in which modification are allowed to the cars, thus making them faster. The trend of the stock PAXs appears to show that faster cars benefit most from r-comp tires.

For clarification, the adjustment factor is only applied to drivers using street tires in classes that allow r-comps. The intent is to level the playing field for drivers who must drive their cars to the event and/or cannot afford the approximately 2.5 times higher cost of r-comps. We have never used the street tire PAX adjustment in the classes that already specify street tires.

Last edited by ylwtulp; 07-27-2016 at 07:03 AM.
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Old 07-27-2016, 08:36 AM   #2
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Sounds reasonable. Is this a change that would happen in 2017 or looking to change this year?
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Old 07-27-2016, 08:56 PM   #3
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Originally Posted by k-dogg39 View Post
Sounds reasonable. Is this a change that would happen in 2017 or looking to change this year?
It would be for next year as we can't change the rules for this season mid-season.
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Old 07-28-2016, 10:33 PM   #4
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John's analysis seems pretty solid.

I don't have a horse in this race, but my opinion would be to err on the side of a smaller adjustment. Folks that pony up for the r-comps feel cheated when beaten by the factor, and the idea behind the street tire option is to help out budget racers or folks that ran out of tires, rather than to give them an advantage over those that do use r-comps.

In racing, you almost always get beat by the folks willing/able to spend more money. So, if you can't make a per-class factor, stick to the smaller factor which gives the faster cars on faster tires an advantage rather than giving the slower cars on slower tires the advantage. I think you'll have less unhappy people if the understanding is that the factor helps if you're on street tires, but leaves you still as an underdog.
Slow cars make faster drivers... at least that's what I'm telling myself.
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