PCA SDR

Carl,
I was looking at the BRI for the Speedway and it seems like many folks in the top 10 (even 20) have very high BRI placements as compared to their actual times. In my case in order to place in a comparable real time position in the BRI standings I need to run 2 seconds faster per lap (which would be right there with Bill Dawson car) which was not going to happen . Look at John Paynes car and placement of 12 in BRI with a time that is slower than mine. Seems to me that car, in its class ought to kill an old 993 even if it is on slicks compared to Hoosiers on the front straights alone. (Sorry John)

Seems like maybe some tweaking needs to be done or else could it be the nature of the track as compared to others? What do you think?

The BRI does certainly need tweaking, and we should always remain open to suggested ways to improve the system.

The system doesn’t account for track differences (it was developed using AX data and that it works at all on TT results was a surprise to me). If someone can come up with a way to modify the indices for different tracks, that’s great! Might not be too difficult if we limit ourselves to the 5-6 tracks we run regularly, but what do we do about the always-changing AX configurations?

The system is based on the Zone 8 classing system and it has all the problems found there. Since the progression in Zone 8 classes goes from PS to PP to MI to KM, it seemed logical that the index for MI should be somewhere between PP (1.115) and KM (1.120). Not too much wiggle room here.

The problem you mentioned of indexing John Payne’s GT3 versus your 993 is difficult due to the fact that Zone 8 rules allow John to (for example) remove 200 pounds, add wider stickier tires and then run in PP. Now if he took an addition 20 points for removing even more weight, improving his suspension, increasing power, running slicks, etc. then he would be in the same class as your 993. IMHO perhaps a highly modified GT3 shouldn’t be going head-to-head with a similarly modified 993.

The BRI is a simple system and it has lots of imperfections. Until we can figure out some of these problems, it should be taken with all the seriousness of the brass dolphin presented to the winner.

Carl, I understand that it is not perfect and no disrespect intended toward you for putting this together for us.

I just find the classification system to a bit off if I can prepare a GT3 like my 993 and end up in the same class. I know that even in PS for a GT3, I could easily bury my time in my 993 in MI. I can enter turn 1 20 mph faster maybe lower that speed between 1 and 2 (due to tires), and then get back to or even higher than 160 by turn 3. The infield is the same issue, the straights there are worth about 15 mph top end for each straight. That is many seconds per lap even giving up time on the turns for tires that are less than slicks.

That said, the classifcations are clearly flawed which will be the case for as long as we are involved in this sport

I am not sure how we could calculate a BRI for certain tracks, I just know that we are building a pretty good database for time trail that might require us to calculate new BRI indices that are based off of those rather than the auto-x data. Have you tried that already? Are the numbers different?

Even if BRI were more perfect, cars which are not maxed out on points for their class probably shouldn't be high on the BRI in theory. BRI handicap assumes good driver in well-prepared car.

bobbrand wrote:Even if BRI were more perfect, cars which are not maxed out on points for their class probably shouldn't be high on the BRI in theory. BRI handicap assumes good driver in well-prepared car.

Agreed, but for auto-x not time trail. Very different modifications and points needed to be competitive in time trail versus auto-x.

Some time ago I suggested a further multiplier breakdown for classes with big point spreads. For instance, if GP cars can have 7-20 points of mods, they shouldn't be lumped into the same multiplier.
My suggestion was to assign incremental multipliers for every, say, couple additional points. So what's the multiplier decimal spread between the next lower class, GS, and the next higher class, FI? Instead of giving one number in between those two to all the GP cars, divide the point spread into increments.
So:
A GP car with 7 mod points will get a .002
A GP car with 10 mod points will get a .003
"" 13 " .004
" 17 "
" 20 "
Those aren't real numbers, but only an example.
There's a big difference between a 7 point car and a 20 point car.
See what I mean? Sounds simple ?

kary wrote:Agreed, but for auto-x not time trail.

I think that is the key, Kary. The BRI was only developed on the basis of autox results. There should be a separate index for big tracks. The different performance characteristics on high speed tracks of the various classes needs to be indexed differently, I think, and you would need to look at historical data from TTs to do that. Unfortunately, there isn't a lot of historical data for the newer cars, like the GT3, GT2, and 997 variants.

TT

ttweed wrote:

kary wrote:Agreed, but for auto-x not time trail.

I think that is the key, Kary. The BRI was only developed on the basis of autox results. There should be a separate index for big tracks. The different performance characteristics on high speed tracks of the various classes needs to be indexed differently, I think, and you would need to look at historical data from TTs to do that. Unfortunately, there isn't a lot of historical data for the newer cars, like the GT3, GT2, and 997 variants.

TT

I think we could extrapolate the newer cars off the the earlier car data since there is history with those cars. Then as the year progress we can modify as needed.

On a track like Fontana, power to weight says a lot for how a base class will perform - I think more so than all of the trick suspension and well balanced cars that are faster on more technical tracks (auto-x or time trial).

[quote="kary"] Look at John Paynes car and placement of 12 in BRI with a time that is slower than mine. Seems to me that car, in its class ought to kill an old 993 even if it is on slicks compared to Hoosiers on the front straights alone. (Sorry John)

I appreciate your position, Kary (meaning, behind me in the BRI).
Isn't your one line comparison of our cars a little simplistic? What does your car weigh now? Mine is 3350 lbs. incl. me and a 1/2 tank. With your weight to contact patch (a little known ratio created by Hoosier Daddy), I know you're coming out of the final turn faster than I, and I'd bet, regardless of our respective power to weight ratios (which may not be that far apart), that you would lead me all the way down the front straight to turn #1, and then you'd kill me in the turns with your weight/contact patch.
The system may need some tweaking, but before you can seriously gripe about our respective positions, we'd have to do a little more analysis, don't ya think?

bobbrand wrote:On a track like Fontana, power to weight says a lot for how a base class will perform - I think more so than all of the trick suspension and well balanced cars that are faster on more technical tracks (auto-x or time trial).

Bob, FWIW, the guy in front of me in the older 911 race car with slicks (I don't know who it was) killed me on the oval. My power/weight allowed me to pass him on the straight, but when we came to turn #1, he was all over me and passed me like I was standing still. But the big difference and the major reason why I wound up with a better time than his was brakes. Even though he was far ahead of me appoaching the turn to the infield, I was braking so late, I nearly ran into him. I wouldn't minimize the importance of brakes nor weight to contact patch. Say you have two cars, one with a better power to weight ratio. But, the other car weighs 1000 lbs less and is running slicks that are much larger. Which car would you rather be in going around the oval? Even at Fontana, I believe the lighter car with the big slicks has the advantage unless we're talking about a huge difference in power/weight ratios.

JHPGT3 wrote:

kary wrote: Look at John Paynes car and placement of 12 in BRI with a time that is slower than mine. Seems to me that car, in its class ought to kill an old 993 even if it is on slicks compared to Hoosiers on the front straights alone. (Sorry John)

I appreciate your position, Kary (meaning, behind me in the BRI).
Isn't your one line comparison of our cars a little simplistic? What does your car weigh now? Mine is 3350 lbs. incl. me and a 1/2 tank. With your weight to contact patch (a little known ratio created by Hoosier Daddy), I know you're coming out of the final turn faster than I, and I'd bet, regardless of our respective power to weight ratios (which may not be that far apart), that you would lead me all the way down the front straight to turn #1, and then you'd kill me in the turns with your weight/contact patch.
The system may need some tweaking, but before you can seriously gripe about our respective positions, we'd have to do a little more analysis, don't ya think?

John, no griping here, just factual data. The previous year at Fontana, a GT3 with MPSC, stock set up, ran through the banking at 170 mph. That car is the same as yours (without hoosiers) and is capable of far faster times than my car regardless of tires. I max out at 145 mph in the same turns. I have driven other GT3's at other tracks and I can tell you I beat my time in a lap in the GT3 without even pushing to the limit over my 993. I believe Jack Miller did the same with your car at SOW when he went with you. The GT3 is a sweet car and is capable of a lot. Remember, car capablitlity does not mean driver capability for any of us.

Weight you say, with me in the car and a half a tank I am at 2890 + 225 + 70 for a total of around 3185. So I will give you the 150 pounds and you give me the 100+ horse power with a torque curve that is longer than my entire 993 RPM range, then we will see who is gripping about the BRI, ok?

Well, I just read some of today's comments, don't know what you guys are talking about in regard to BRI, guess I'd better do some research on that. By the way, how come know one is complaining about me or my times? I feel left out!

jsimone wrote:Well, I just read some of today's comments, don't know what you guys are talking about in regard to BRI, guess I'd better do some research on that. By the way, how come know one is complaining about me or my times? I feel left out!

John, I did not complain, I just adjusted your transponder because you complained about it all weekend

Kary, my friend. I was at Fontana last year, remember? (Don't answer that!!) I don't recall any GT3 ever approaching 170 mph on the bank. Believe me, as an owner of a GT3, I am keenly interested in that sort of thing and it would forever be fixed in my memory.
If you're thinking of Todd, I drove with Todd in Joe's car. You thinking of Joe's car? He might have hit 140, but no more.

Simone, you did really good out there. Feel better? Now get off the WEB and get back to building my car!!