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I have been running a car in AM and have come to the conclusion that PAX has no value as an indicator to gage my performance. I am sure that this is true for most of the mod classes. The improvements in DOT tires should have closed the gap in the PAX numbers.  How many people in modified classes think the PAX numbers work for them? 

Stanley

 

I've run D and E mod for a long time. We don't pay a huge amount of attention to PAX numbers, but they are as relative an indicator of your performance as you'll find.

First, you have to beat everyone at your events on a consistant basis. Once your doing that, you could think about using PAX.

Del Long D/E mod

The biggest issue for using PAX/RTP factors in any race tire class is that race tires go off in less events than DOT legal tires.  That means that those classes on DOT tires get relatively consistent performance out of their tires from event to event until reaching the cord. 

Classes on race tires, however, get their best performance in the tire's first two events and then continuously less performance thereafter.  And in the case of the Hoosier R25 used on my CM car, the rears loose much more grip than the fronts after somewhere between 7 and 10 events depending on various issues.  The durometer backs this up.

BUT, the PAX/RTP factors are primarily based on results from important events.  For these important events, winning times in race tire classes are obtained on fresh race tires.  But as stated above, those results are not obtainable throughout the useage of the race tire.  So the results on which the factors are based cannot be repeated at most local events because those people on race tires use older tires for local events.

DOT tire classes get a much tighter window of performance from their tires as do race tire classes.  This has a signficant affect on how race tire classes will fare on the PAX/RTP factors.  Do  I look at how I finished on the factors anyway?  Of course.

Jim

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Jim Garry

Keep in mind that PAX assumes the very fastest AMod cars in North America. How fast is your car compared to the top few AMod cars? How fresh are your tires? As Jim said, old race tires lose more grip than old DOT or ST tires.

FYI for CMod, I have found that with good tires and a decent surface that I can run with (in PAX) some pretty quick National level drivers in other classes IF I drive well. However to do so I have to be the fastest CMod car and beat all other classes by a bunch (not counting AM, BM, or F125). At local events I may be the only fully prepared mod class car so getting top time raw is "easy". The hard part is being near the top of PAX since there are likely to be well driven fully prepared cars in numerous other classes.

 If you don't have a "top" AMod car and don't have fresh tires, you can always just go for the fastest car on what may be a real bargin budget compared to the cost of MANY of the top Stock and SP cars. :-)

Dick

CM 85

There are some very good points made about this. But if you do the math the very fast AMod cars do not do that well using the PAX system. Currently AMod’s at National Tours are well down the list viewing the PAX listings.  Placed like 155 to 185 for the few listing that I looked at. I don't think all of then are running on old tires.  Last years fastest AMod using the PAX would have place something like 12^th in AS.   I didn’t do the math for another classes but I am sure the out come would be similar. 

Even the Pax numbers between the different Modified classes do not seem coherent. F Mod cars seem to do quite well in Pax compared to many of the higher (A and B mod) classes. F 500's really have gotten faster over the years but the Pax does not seem to indicate that. In the Pro Solo Modified Index class, B Mod for instance gets really whacked with a tough PAX multiplier. Wonder why?

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Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY

PAX has always been a relatively good number to quantify yourself to others provided you are at the top of your game and your car is equally prepared.  It is never perfect and some classes are softer than others.  This can be because of several different factors such as tire development, class structure changes, product development and human error in calculation due to a limited information pool to generate from.  Amod has consistently been number one in PAX at Nationals provided weather was not a concern.  Last year was the first in many that this was not the case.  And that reason was because it was the first year back on asphalt in a long time.  With aero downforce generation and the grip coefficient of concrete, the Amod cars that are truly fast were well above the rest of the pack.  In recent years the index has been adjusted several times to better reflect a balance between Amod and other classes.  But now there may be a change in the opposite direction with the new Heartland Park site

 

Steve O'Blenes

Amod BBR special now for sale including trailer-one of 3 top cars in North America

Come own a top TTD car for yourself.

BProtaryracer:

 

 ... Amod has consistently been number one in PAX at Nationals provided weather was not a concern.  Last year was the first in many that this was not the case.  And that reason was because it was the first year back on asphalt in a long time. 

 

 

The A-Mod index works great on concrete.  Also, between 1996 - 2002, the development on my Phantom project was pretty intense and the car would show up every year at Tour events and Nationals going a second faster than the previous year.  The PAX was constantly being adjusted to chase that forever increasing performance envelope. However, since PAX is basically a reflection of past history and thus always lag behind the real time performance of the car, it was no surprise that the Phantom in those years was always paxing high on the result. 

Fast forward to last year's Nationals. I was there crewing for an E-Mod car.  I also competed in A-Mod in the Phantom and let me tell you, the mod cars were having serious problems on the low-grip surface, especially in that cold windy condition.  I remember on Sunday's practice event, my brand new sticker tires were still wearing their stickers after 3 runs.  I am not surprised that the A-Mod winner didn't PAX high at all.  The problem with A-Mod is that, once low grip is encountered, the average speed comes down and lower aero downforce follows. The decrease in speed and downforce feed each other and the resultant increase in lap time can be exponential.  

Having said that, if an A-Mod car is driven on a high grip surface and the ambient temperature is high enough, then there is no reason why the current PAX won't work.  Stanley, I do know that you have no wing on your A-Mod car (I have seen photos but they might not be current), and if you don't mind me saying it, I don't believe you truly realize just how fast a top running A-Mod car really is, and its potential in placing high on PAX result. My new car is finally done and I will be at the Packwood Tour event with Milligan.  If you want to gauge your lap time against a potential national winning A-Mod car, that might be your best chance. 

Joe 

My point about the PAX is that it is not the system that can be used to figure how fast at some course I should have been. Lets say that I run a course at 39.063. But the top PAX times come out to be 35.161, that works out to indicate that I would need to pick up around 4 seconds. I realize that I need to get faster, but 4 seconds is huge. This just makes me question every thing that I have done, which is a good thing, But I do not think that the PAX system is giving me the real data. If the PAX system uses numbers from years past to get an average, then it does not indicate, or give enough weight to the current course locations and improvements in tires, cars, so on. If I take the same run times from above and use a PAX number figured from just last years nationals then I am only about 2.5 seconds off.

I know that the weather conditions and track surface have a big effect on the performance of a Amod. I also so know that with the faster I can go (because of good conditions) then it is not just a little bit quicker, is a lot quicker. I have not run this year in what I would call good conditions without some kind of problem. But I would like to think that I am only 2.5 seconds off, not 4 seconds. Either way 2.5 or 4 seconds I have a lot of work to do.

Stanley

An index computed from a single event, especially Nationals, is worthless.  The RTP/PAX is computed from over 200 events held last year.  It is impossible for the PAX to take into account new tires, new cars etc.  It can only use existing data and there is no data for new tires or cars.  You are taking the PAX way too seriously.  And if you don't have wings and a full developed car, you can easily be 4 seconds off.

---

2002 Mercedes C230k, retired, 2005 Nationals STU DFL

1969 Beach Solo Vee and 1985 Lynx B Solo Vee

Stanley,

 As Joe Cheng and Lynn pointed out, fully developed A Mod cars are fast.  No, wait. That's wrong.  "Fast" doesn't describe it.  How about "really fast".  No, that's way off the mark.  Watching the few fully developed A Mod cars in the world run at Nationals can mess with your mind.  There's just no way a car should be able to get through a slalom that quickly.  They go around a course so blazingly fast that it's hard to believe. 

So if you're only 4 seconds off the pace with no wings, you're doing really good.  You've got one of the toughest factors to deal with.  Just have fun and take satisfaction in watching your factored time improve over the season and from year to year.

 

 

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Jim Garry

"Really fast" isn't good enough to describe what a top tier AM car is.  I've been autocrossing in F125 for 5+ years now, and I've usually been on pace when mechanical issues don't intervene. In 2005 I got the incredible chance to drive a top tier AM car at Peru concrete.

 There is something weird that happens (to I think every driver) that at some point the speed of the car exceeds the ability of the driver to provide the intended inputs to the car. When I drive a slower stock class car, I'm always "ahead" of the car, and my intended inputs are almost always executed when I want, and I never feel like I'm "catching up" to the car. The problem is I usually am intending apparently the wrong input ! 

 My first couple of events in F125 ( a huge step up in speed from severely underprep SM i started in) - this wasn't really the case. Some parts of courses I was merely along for the ride and I was reacting to gates and cones, not planning inputs and executing them. There is a crucial difference : the chance for a time-costing driver error goes up dramatically. However not always - sometimes I'd realize that I had braked too late - only to react and find that I still could hit the apex perfectly - as I better learned the envelope of performance of the F125. Most of the time however a time-costly error was the result of "reactionary driving".

 
After several years in F125, almost always, I'm well "ahead" of the kart, and planning my inputs and never in "hang on reaction mode".

 Driving the AM the first lap was almost entirely backwards. This car had roughly 3-4x the power to weight ratio of a kart, proper suspension and huge wings. First lap  I was NEVER planning an input - it was all unconscious reaction. The time was about 10% faster than I had gotten in my kart on the same course, but that 10% pace increase had totally thrown me out of my "comfort" zone. I drove the car at 2 events each run raising my comfort level in it, but even my last lap (which was by far my best driven lap in the car) had several moments of reactionary driving mixed in with some "planned" inputs. The car took top index at what at the time was the largest National Tour ever. I felt like I  could have dropped 1s per day with a couple more events in the car. Every single run I took on a course dropped time from my previous as I probed the limits of both car and driver.

I later drove a really fast CM in a Pro and at Nats that year, with fairy good results (2nd place at Nats) and not once did I ever feel like I was "behind" like I felt much of the time in the AM. The speed through gates and slaloms was fast, but so much slower than AM as to feel like HS on street tires vs SS.

 Ever since that day, I've been trying to figure out why my kart feels dog slow, driving AM literally was the most amazing experience driving I've ever had.

As for PAX : its a best guesstimate, course dependence is huge. I competed in my first national event in a year this weekend on on first day was 176 or so out of 250 on pax in F125. I was .026 behind the kart owner (national trophy winner and experience F125r) with what I felt was a pretty good lap perhaps  0.5secs off a nearly ideal lap. It was > 3s behind pax leaders. This was in a nationally competitive kart in what is essentially a spec class, running the best tires. The 2nd day I know we did better, but the difference would be in course not the kart (which actually had some mechanical issues).

However earlier this year a kart took top PAX at a national tour. So this is how difficult Ricks job in picking the right pax is : 2 former national champs in F125 pax #1 and 3sec off respectively in Tours the same year. 

In F125 I usually try to compare first to CM regulars (several consistent yardsticks in my area) , as usually kart slicks and CM slicks perform more similarly compared to DOT R's. However CM especially performs well in the sections of courses that F125 does terrible on, so there is a large course dependency.

Dan Cyr

 

underpaidslave:

"Really fast" isn't good enough to describe what a top tier AM car is.  I've been autocrossing in F125 for 5+ years now, and I've usually been on pace when mechanical issues don't intervene. In 2005 I got the incredible chance to drive a top tier AM car at Peru concrete.

 There is something weird that happens (to I think every driver) that at some point the speed of the car exceeds the ability of the driver to provide the intended inputs to the car. When I drive a slower stock class car, I'm always "ahead" of the car, and my intended inputs are almost always executed when I want, and I never feel like I'm "catching up" to the car. The problem is I usually am intending apparently the wrong input ! 

 My first couple of events in F125 ( a huge step up in speed from severely underprep SM i started in) - this wasn't really the case. Some parts of courses I was merely along for the ride and I was reacting to gates and cones, not planning inputs and executing them. There is a crucial difference : the chance for a time-costing driver error goes up dramatically. However not always - sometimes I'd realize that I had braked too late - only to react and find that I still could hit the apex perfectly - as I better learned the envelope of performance of the F125. Most of the time however a time-costly error was the result of "reactionary driving".

After several years in F125, almost always, I'm well "ahead" of the kart, and planning my inputs and never in "hang on reaction mode".

 Driving the AM the first lap was almost entirely backwards. This car had roughly 3-4x the power to weight ratio of a kart, proper suspension and huge wings. First lap  I was NEVER planning an input - it was all unconscious reaction. The time was about 10% faster than I had gotten in my kart on the same course, but that 10% pace increase had totally thrown me out of my "comfort" zone. I drove the car at 2 events each run raising my comfort level in it, but even my last lap (which was by far my best driven lap in the car) had several moments of reactionary driving mixed in with some "planned" inputs. The car took top index at what at the time was the largest National Tour ever. I felt like I  could have dropped 1s per day with a couple more events in the car. Every single run I took on a course dropped time from my previous as I probed the limits of both car and driver.

I later drove a really fast CM in a Pro and at Nats that year, with fairy good results (2nd place at Nats) and not once did I ever feel like I was "behind" like I felt much of the time in the AM. The speed through gates and slaloms was fast, but so much slower than AM as to feel like HS on street tires vs SS.

 Ever since that day, I've been trying to figure out why my kart feels dog slow, driving AM literally was the most amazing experience driving I've ever had.

As for PAX : its a best guesstimate, course dependence is huge. I competed in my first national event in a year this weekend on on first day was 176 or so out of 250 on pax in F125. I was .026 behind the kart owner (national trophy winner and experience F125r) with what I felt was a pretty good lap perhaps  0.5secs off a nearly ideal lap. It was > 3s behind pax leaders. This was in a nationally competitive kart in what is essentially a spec class, running the best tires. The 2nd day I know we did better, but the difference would be in course not the kart (which actually had some mechanical issues).

However earlier this year a kart took top PAX at a national tour. So this is how difficult Ricks job in picking the right pax is : 2 former national champs in F125 pax #1 and 3sec off respectively in Tours the same year. 

In F125 I usually try to compare first to CM regulars (several consistent yardsticks in my area) , as usually kart slicks and CM slicks perform more similarly compared to DOT R's. However CM especially performs well in the sections of courses that F125 does terrible on, so there is a large course dependency.

Dan Cyr

 

underpaidslave:

 

 ...driving AM literally was the most amazing experience driving I've ever had....

  

 

If only more people have the chance to experience what you had, I think there will be more drivers entering A-Mod.

I got the chance to meet Stanley at Packwood.  Just happened to be the largest A-Mod field in years for NorPac Division at that event.  A few of us AM guys had the rare chance to talk about lots of things. The problem with running an A-Mod car is that most of us are usually running in local events with no other competitor in our class.  It's very easy to lose reference on a national scale in terms of performance envelope.  Overall, PAX is a great way to gauge the car/driver combination potential.

Joe 

Now that the National PAX has been posted, I am sure that it is off.  If the PAX indicated the correct performance adjustment for each class then would appear that all the 1^st place drivers in each class should be near the top of the PAX standings. Looking at Nationals PAX-RTP-Final.pdf it appears that adjustment between Amod and others is not really as large the PAX gives them. I wonder what next years PAX will be like. Will F125 now be the (1.000) class.

Stanley

The RTP/PAX is not based on a single event on a single ( and non-typical) surface.  Rick uses over 200 events from all over the courntry to compute the PAX.  This is the first Nationals where the F125's have been faster than A.  This is due to the design of the courses and the surface conditions.  The courses at this year's Nats were too tight to allow the AM's to use all their power.  I would guess the course design and the slick surface also takes away some of their aero advantage.

F125 will not be the top index class because the RTP/PAX is based on so may events.  Rick has told me that most classes will be adjusted upwards next year.  Some classes will be adjusted a lot. 

---

2002 Mercedes C230k, retired, 2005 Nationals STU DFL

1969 Beach Solo Vee and 1985 Lynx B Solo Vee

Another advantage for F125 is that since they are so small, they actually have a choice of lines within the narrow band of clear asphalt on HPT courses.  In other words, most cars (including AM) are wide enough so that they have a non-sandy line of approximately the width of their car plus a little.  F125 on the other hand have a non-sandy line that is about 3 or 4 times their car width.

 

 

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Jim Garry

lightning:

Now that the National PAX has been posted, I am sure that it is off.  If the PAX indicated the correct performance adjustment for each class then would appear that all the 1^st place drivers in each class should be near the top of the PAX standings. Looking at Nationals PAX-RTP-Final.pdf it appears that adjustment between Amod and others is not really as large the PAX gives them. I wonder what next years PAX will be like. Will F125 now be the (1.000) class.

Stanley

Except that many T/W competitors had to deal with rain, and early heats dealt with colder weather, and it's one event on one surface. No significant statistical data can be generated from a single event.

-Mike

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Mike Shields
1993 BMW 325is | 92/192 DSP

Jim G:

F125 on the other hand have a non-sandy line that is about 3 or 4 times their car width

How wide do you think a kart is?  Mine is about 54" track width at the rear.  The rules allow up to 55".  Strangely, that's the same maximum as F-Mod F500 cars are allowed.  How wide is a Formula Ford?  F125 significantly outperformed FM and CM at Nationals on PAX.  I don't think it was a width issue.

Short wheelbase on a "wiggly" course is a HUGE factor.  Especially on the East course.  Very slalom intense.  In fact I was flat out all but 4 small places.  There wasn't a slalom on either course that I couldn't flat-foot once I turned in for the first cone.  I didn't get a chance to watch CM, but FM, as a class, was struggling with the East course.  No one could smoothly make the slalom up the hill from the turn-around.  It was ugly.  I think their wheelbase was just too long to make that tough offset gates.

 I am suspicious that tight slaloms and low-speed are two factors that helped F125 beat A-Mod.

 

LM

I just measured my relatively small CM FF:

Overall width (outside to outside of tire sidewalls) is about 69 inches.

Overall "relevant length" (front of front tires to rear of rear tires at axle height) is about 115 inches.

 Wheelbase is about 93 inches (relatively short)

Dick

85 Van Diemen RF-85