FWD vs RWD: Adders, Subtractors, and Weight, Oh my...!

[dickita15]

sorry, i don't take your word for it.

Travis, I like a good Greg bashing as much as anyone but you should trust Kirk on this one

[Tristan Smith]

Coupled to the fact I'm really getting tired of all the silly non-equitor arguments assaulting my patience and intelligence (Tristan, I'm game for adding weight to FWD cars in rainy conditions as long as you agree to add the same amount in the dry. You're writing a letter on that today, right?) GA

If the weight is taken off the FWD cars I will write a letter. If being FWD is such a disadvantage in normal/dry conditions and you get a weight break, and you get the added advantage of FWD in the wet, aren't RWD cars being essentially penalized twice? I think ITR is way too early in it's deveolpment to be predicting which cars are going to be competitive and non competitive. Maybe you have a better argument for ITS. Fair enough, since there is some history to draw from. But whatever happened to the IT credo of you living with whatever strengths or weaknesses of the car you choose to race? I saw no advantage racing a 240sx RWD drive car in ITA as the Integras and CRX's smoked my ass lap after lap.

I thought I was bringing up a somewhat valid point that having an advantage (for either FWD or RWD) is also a bit subjective depending on the conditions. If I raced in Phoenix, RWD advantage. Seattle, FWD.

And Greg, you take cheap-shots all day long at people. Remind me to to ignore you next time I see you.

[lateapex911]

If the weight is taken off the FWD cars I will write a letter. If being FWD is such a disadvantage in normal/dry conditions and you get a weight break, and you get the added advantage of FWD in the wet, aren't RWD cars being essentially penalized twice? I think ITR is way too early in it's deveolpment to be predicting which cars are going to be competitive and non competitive. Maybe you have a better argument for ITS. Fair enough, since there is some history to draw from. But whatever happened to the IT credo of you living with whatever strengths or weaknesses of the car you choose to race? I saw no advantage racing a 240sx RWD drive car in ITA as the Integras and CRX's smoked my ass lap after lap.

I thought I was bringing up a somewhat valid point that having an advantage (for either FWD or RWD) is also a bit subjective depending on the conditions. If I raced in Phoenix, RWD advantage. Seattle, FWD.

And Greg, you take cheap-shots all day long at people. Remind me to to ignore you next time I see you.

Tristan, on the surface, I can see your point about the wet weather advantage, but, don't be too sure. My only ITA wins have come in the rain, and I drove by FWD cars that smoke my little live axled torqueless RX-7 in dry conditions, driven by guys who have ARRC medals..

You'd think that the RX-7, known for it's tail out histerical behavior would be hard pressed (esp driven by me!) to keep up with the more forgiving front heavy FWD Integras, etc, but in our little racing world, that's actually not the case. The FWD cars need pretty significant set up changes to run well in the rain, and often changing weather conditions, limited time and limited crew resources means they race on a compromise setup.

Point being that as an classing body, we need to concentrate on standard conditions and let the chips fall where they may.

You made a point regarding the old IT crdeo of living with your warts.

I think that misses the broader point. If that were the case, we wouldn't bother classing cars, right?

In this case, we are attempting to find an appropriate response to a genre of cars. Now, in so doing, we will of course be cognizant that, as Dick points out, the rules allow a lot of rubber on the road for the ITR cars, and the resultant math will certainly account for that.

But..just because the rules allow 8.5" wide wheels and 275 section tires doens't mean that every ITR car can actually fit them. THAT's where the old credo comes into play. Choose your horse carefully, and live with it's strengths AND weaknesses.

[Tristan Smith]

Tristan, on the surface, I can see your point about the wet weather advantage, but, don't be too sure. My only ITA wins have come in the rain, and I drove by FWD cars that smoke my little live axled torqueless RX-7 in dry conditions, driven by guys who have ARRC medals.

Yes, I agree, but then again we are told over and over that you can't use race results as a basis for rules changes. You may be a brilliant rain driver! Those other guys may have gone out with their dry set-up. And while I have never seen you drive, I am sure you ARE a brillant rain driver! But that is just my opinion.

In this case, we are attempting to find an appropriate response to a genre of cars. Now, in so doing, we will of course be cognizant that, as Dick points out, the rules allow a lot of rubber on the road for the ITR cars, and the resultant math will certainly account for that.

But..just because the rules allow 8.5" wide wheels and 275 section tires doens't mean that every ITR car can actually fit them. THAT's where the old credo comes into play. Choose your horse carefully, and live with it's strengths AND weaknesses.

Your right about the tire issue. No argument there. But we seem to be trying to fix issues (and this more related to ITR) before they have been proven to be a problem. My point in this is that a case has been made that all FWD cars are at a disadvantage. Yet when I made a broad statement that FWD cars have an advantage in wet conditions I am quickly told that I can't make a broad statement like that. And that that shouldn't be a consideration. Well if we are going to change rules, shouldn't all things be factored in?

I just want all factors to be looked at before we start changing things.

[Knestis]

I don't think I see an issue, Andy, substantial enough for that later accusation. Or maybe I'm influenced by the fact that I have some frustrations similar to Greg's about this discussion. Or maybe I just missed something but I think that generally speaking, Greg is agreeing with the first principles that Mike is expanding on...

Or maybe, since Greg made it clear several pages before that he was basing his judgment on his experience, and since he was subsequently told that wasn't enough, he figured there wasn't much point in continuing to say over and over what he'd already said.

If we went back through this discussion and deleted every single post that made an assertion without "evidence" (your word, Andy), this thread would be about one page long. Mike posts Lapsim numbers and a half dozen people say in essence, "That doesn't feel right to me" (too much of a weight break), but they tend to be "anti-new idea." Sometimes "because I said so" seems to be OK, and sometimes it isn't, but the distinction appears to be dependent on the extent to which someone appears to agree with the position stated.

And I share what I *think* are Greg's frustration with what seem like disingenuous arguments...

But this is the Internet.

K

[Knestis]

>> ...when I made a broad statement that FWD cars have an advantage in wet conditions I am quickly told that I can't make a broad statement like that.

I don't think anyone said that. The response -and I share the sentiment - is that we make our decisions on the conditions that we see the vast majority of the time across the country (dry) and not considering outlier tracks, that disproportionately reward particular features (a la Daytona). You can make those statements until the cows come home but the ITAC's got to establish braod guidelines and assumptions - every one of which is a compromise of some kind, where exceptions to the rules are concerned.

K

K

[ekim952522000]

Despite everything else I still feel like this was a very valuable discussion.

I should try to clear up where I am coming from, basically I agree with Greg I feel like he is using sound logic and experience to make a request that he feels will help all FWD cars become more competitive within ITS.

BUT I needed to find to find something else to help back up Greg. So I thought that Lapsim would help me back up his theory.

To me Greg's theory was that the more power a FWD car had and the greater the mass of a FWD car the larger weight deduction it would need in order to make the lap times equal with a RWD car of similar design.
(Note: This may not actually be Greg's theory this is just how I took it)

I never intended Lapsim to give us the weights I just wanted to see if it backed up Greg's theory, and it did (twice). The question I then had to ask myself was given what a experienced racer and Lapsim are telling me what do I think a good "guess" would be for weights so I thought about it and said this.

Let's say that the FWD subtractor for ITA is correct. What that means then is that it is possible that the subtractor for ITS is correct, it is not likely that the subtractor is correct for ITR, ITB, or ITC.

Which made me think "assuming" the weights for ITS, and ITA were correct that the weights should probably look something like this

ITR - 150
ITS - 100
ITA - 50
ITB - 25
ITC - 0

But then there was this question.

Honest question: there seems to be some agreement here that ITS and ITR FWD cars need more of a break due to the problem of higher horsepower cars putting too much stress on the front tires because of weight distribution and the front tires doing all the work. There is also a feeling from some R cars will need more that S cars. Is this higher need by the R cars at all mitigated by wider wheels and by extension tires allowed in ITR?

Which set off a lightbulb in my head about something that had been bugging me all along. Why does the -50 seem to work for both ITB and ITA? That did not follow what everything else had been telling me. But Dick seemed to point out the answer, at least to me.

Which leads me to believe that again assuming the ITS "adder" is correct that maybe it should look something like this.

ITR - 8.5" -100
ITS - 7" -100
ITA - 7" -50
ITB - 6" -50
ITC - 6" -0

Well look at that, I think that is what we have. (not sure about ITC) But I am starting to think we have the "pattern" close enough.

Then this was posted

....... we seem to be trying to fix issues (and this more related to ITR) before they have been proven to be a problem. .........

This post concerned me because I think it must have looked like I was talking about ITR getting a weight reduction the whole time (I was, in a way, but let me try to explain) basically what I was trying to say was given the data IF we change the subtractor for ITS, to for example 125lbs then at a minimum ITR should be 150lbs. But after Dick made his post talking about tire sizes, now I feel like at the very least the subtractor for ITR should be the same between ITS, and ITR.

I also think that a adjusted pw/wt ratio would be a even better way to handle this but have no idea how the ITAC is supposed to answer when people say they want everything to use a adjusted pw/wt ratio instead of the simple adders and subtractors. So I understand using this method is very unlikely.

I think we should be using 150lbs minimum for both ITS, and ITR, But I have no way to prove that 150lbs makes anymore since then 100lbs.

Also of note is finding a way to work this out would go along way towards finding a solution to classing AWD cars. (Which I do think IT will need to do one day)

Sorry for the very long winded post but I wanted to summarize.



One last thing I am not clear on. Why is GSR currently classed using a 150lb subtractor. I'm guessing it was not adjusted during the great realignment do to the 100lb leave it alone rule and the math just happens to work out that way? If that is the case then it appears after the ITAC run all cars to within 5lbs of the process that the GSR will be gaining 50lbs.

[Andy Bettencourt]

One last thing I am not clear on. Why is GSR currently classed using a 150lb subtractor. I'm guessing it was not adjusted during the great realignment do to the 100lb leave it alone rule and the math just happens to work out that way? If that is the case then it appears after the ITAC run all cars to within 5lbs of the process that the GSR will be gaining 50lbs.

Mike,

Many thanks for all your hard work. I don't recall anyone thinking this theory was bogus, we just needed to try and drill down and prove that there were 'better' numbers out there than 3x50 and 2x100.

On the GSR, it didn't get it's +50 for double wishbones when it was classed for some reason. That is why it ends up where it is if you re-look at the weight using the -150lbs for FWD.

Onto the ITR number. While Dick's thought process is 100% valid IMHO, I also feel like there aren't many FWD'ers that will be able to really utilize the 8.5" rim. I am betting most RWD guys will be able to try out a 275mm tire...255 for sure. I would doubt that any FWD car could stuff a 275 under the fenders with the current bodywork rules we have. So we need to compare the differences inside the class. I think there should be a difference when you look at it practically.

[tnord]

Onto the ITR number. While Dick's thought process is 100% valid IMHO, I also feel like there aren't many FWD'ers that will be able to really utilize the 8.5" rim. I am betting most RWD guys will be able to try out a 275mm tire...255 for sure. I would doubt that any FWD car could stuff a 275 under the fenders with the current bodywork rules we have. So we need to compare the differences inside the class. I think there should be a difference when you look at it practically.

yeah but then you're getting into chassis specific allowances, and that's just not cool.

even accepting all of the downfalls of the FWD layout, i want to know why it makes more sense to arbitrarily pick a number for weight break rather than doing it as a % of min weight.

[dj10]

Mike,

Onto the ITR number. While Dick's thought process is 100% valid IMHO, I also feel like there aren't many FWD'ers that will be able to really utilize the 8.5" rim. I am betting most RWD guys will be able to try out a 275mm tire...255 for sure. I would doubt that any FWD car could stuff a 275 under the fenders with the current bodywork rules we have. So we need to compare the differences inside the class. I think there should be a difference when you look at it practically.

As to date I've seen only the Porsche 944S2 able to use 275.40.17's and have not even seen 255.40 on any cars including the BMW's.

[Knestis]

...even accepting all of the downfalls of the FWD layout, i want to know why it makes more sense to arbitrarily pick a number for weight break rather than doing it as a % of min weight.

That's the part of this that I'm still not getting. The only real responses I've HEARD (irrespective of what's been meant) are that "we can't do it perfectly, so the way we do it is fine," and suggestions that if we try to be more precise - more granular - about the FWD subtractor, then we'll somehow have to change policy to include additional factors into the weight-setting process.

I used the term disingenuous earlier but I think specious is a more apt term. But for consideration (one last time)...

1. We think drive layout is a consideration - That's a binary, yes-no decision that applies the follow-on math

2. Our theory is that mass and power aggravate the situation - do we have much dissent on this point?

3. We use power to set the weights - by a function, not in XX pound chunks decided upon subjectively...

4. Therefore, it's completely sound to set the FWD subtractor as a function of weight, power, or both.

Arguments against doing so also pointed out specific examples from math models that were being played with, where the outcome OF THAT SPECIFIC CASE, APPLYING THOSE SPECIFIC ASSUMPTIONS seemed "wrong."

Ultimately, I continue to get closer to the conclusion that we collectively WANT to be able to do what feels right - to do math reserving the right to reject it if the specific case outputs don't fit our preconceived notions. I also KNOW that six different people will have six different notions in any situation like that, unless they are purposefully picked to have matching priorities, goals, and interests around whatever is being discussed.

I'm also understanding more and more that I'm in the tiniest of minority of people worried about this.

K

[Andy Bettencourt]

yeah but then you're getting into chassis specific allowances, and that's just not cool.

But isn't that the whole point behind a FWD 'adder'? I am thinking that FWD cars won't be able to utilize the additial wheel width - therby negating the theory that ITS and ITR cars should have the sames adder.

Just bouncing it around.

Here is where I am at currently:

ITR - 175
ITS - 150
ITA - 50
ITB - 25
ITC - 0

On edit: I think a % of min weight is a great idea - but in reality, wouldn't we be picking that % based on a pre-conceived number from charts like above? For example:

The base weight on a GSR is 2741...call it 2740. 150lbs is roughly 5.5%. So should we use a 5.5% subtractor for ITS?

Base weight on a typical ITA car is 2445. 50lbs is roughly 2%.

Wouldn't we be pulling these numbers out of asses? To me its real similar. In the 'static' method, lighter cars will have more % of loss but have less hp. In the 'dynamic' method, everyone gets the same % off but its based on hp numbers.

Show me the methodology behind determining the %'s...

[tnord]

That's the part of this that I'm still not getting. The only real responses I've HEARD (irrespective of what's been meant) are that "we can't do it perfectly, so the way we do it is fine," and suggestions that if we try to be more precise - more granular - about the FWD subtractor, then we'll somehow have to change policy to include additional factors into the weight-setting process.

ok fine.....i accept that we can't do it perfectly.....but an arbitrary 200lb weight break is much riskier than an arbitrary 50, 100, or whatever it is these days. why? because what we have hasn't created any "overdogs" yet, and despite all the complaining, the cars aren't THAT far off. we know the GSR and Prelude can be competitive in ITS, and ITR is WAY WAY WAY too early in it's life to really determine anything.

I used the term disingenuous earlier but I think specious is a more apt term. But for consideration (one last time)...

1. We think drive layout is a consideration - That's a binary, yes-no decision that applies the follow-on math

agreed.

2. Our theory is that mass and power aggravate the situation - do we have much dissent on this point?

nope, not from me at least.

3. We use power to set the weights - by a function, not in XX pound chunks decided upon subjectively...

4. Therefore, it's completely sound to set the FWD subtractor as a function of weight, power, or both.

it's much better than "i think it should get AT LEAST 200lbs, let me go come up with some math to try and support it.

Arguments against doing so also pointed out specific examples from math models that were being played with, where the outcome OF THAT SPECIFIC CASE, APPLYING THOSE SPECIFIC ASSUMPTIONS seemed "wrong."

Ultimately, I continue to get closer to the conclusion that we collectively WANT to be able to do what feels right - to do math reserving the right to reject it if the specific case outputs don't fit our preconceived notions. I also KNOW that six different people will have six different notions in any situation like that, unless they are purposefully picked to have matching priorities, goals, and interests around whatever is being discussed.

I'm also understanding more and more that I'm in the tiniest of minority of people worried about this.

K

and this is exactly what i don't like....."this math doesn't fit my desires, let me go find something else." that's totally bunk. whatever math is used, if anything ever happens with this, should fit a couple known quantities (like the ITA integra), but beyond that it shouldn't matter if some people don't like the way it plays out for their cars.

you might be in the minority kirk, but you have to include me too.

[Knestis]

But isn't that the whole point behind a FWD 'adder'? I am thinking that FWD cars won't be able to utilize the additial wheel width - therby negating the theory that ITS and ITR cars should have the sames adder.

Just bouncing it around.

Here is where I am at currently:

ITR - 175
ITS - 150
ITA - 50
ITB - 25
ITC - 0

On edit: I think a % of min weight is a great idea - but in reality, wouldn't we be picking that % based on a pre-conceived number from charts like above? For example:

The base weight on a GSR is 2741...call it 2740. 150lbs is roughly 5.5%. So should we use a 5.5% subtractor for ITS?

Base weight on a typical ITA car is 2445. 50lbs is roughly 2%.

Wouldn't we be pulling these numbers out of asses? To me its real similar. In the 'static' method, lighter cars will have more % of loss but have less hp. In the 'dynamic' method, everyone gets the same % off but its based on hp numbers.

Show me the methodology behind determining the %'s...

Broaden your thinking, Andy. An adder doesn't have to be a set number of pounds. We don't "add" 20 hp to the stock power to represent "IT power" - we ADD a number of pounds based on a factor. This idea just applies the same approach.

And we don't NEED a "methodology" to establish the math. It should just be a representation of our first assumptions about what we're trying to accomplish. Picking 5% for all S cars, based on a subjective assumption applied to ONE make/model, isn't necessarily a super-scientific way to get there but if we're comfortable with that as a first assumption, it's a hell of a lot better than picking a chunk to apply across the board.

MAYBE the only issue that's at play here is whether the same math has to be applied to all classes. I confess that I sort of assumed that to be the case but never really went that far in the calculations, because the roadblocks went up before I got to that point.

But I AM confident that applying -175 to all FWD R cars does a different thing for the Celica GTS (-7%) than it does for the Legend (-5%). And the error is in the wrong direction if our theory is that FWD hurts more as cars get heavier...

How about this, Andy - if you're confident with the numbers you list, plot each as a percentage impact on the weight (or power) outliers in each class and use the mean...?

K

[Eagle7]

How about this, Andy - if you're confident with the numbers you list, plot each as a percentage impact on the weight (or power) outliers in each class and use the mean...?

K

And if that works, see if you can combine five equations into one that's class-neutral. Something as simple as

fwdsubtractor = (multiplier * itpower) - zerofactorpower

or some other equation that fits the data points for all the classes.

BTW, Kirk, I'm solidly in your minority.

[tnord]

The base weight on a GSR is 2741...call it 2740. 150lbs is roughly 5.5%. So should we use a 5.5% subtractor for ITS?

Base weight on a typical ITA car is 2445. 50lbs is roughly 2%.

Wouldn't we be pulling these numbers out of asses? To me its real similar. In the 'static' method, lighter cars will have more % of loss but have less hp. In the 'dynamic' method, everyone gets the same % off but its based on hp numbers.

Show me the methodology behind determining the %'s...

we should use the same % across all classes, but i think it's a big no-no to just pick a number that your gut says "will get these cars competitive" (when some FWD cars already are).

the classes everyone is complaining about is ITS and ITR.....so if the 50lbs for ITA is right, then use that as your baseline, and since we accept the problem gets worse as weight increases, using the same % as ITA gets in all classes, and as their weight goes up, the weight break they get should go up as well.

i'm not so sure that power should be considered. tire abuse (but rear tires instead of front) goes up with power levels on RWD platforms just the same as it does on FWD, and even on ITA miatas you can't just stand on the throttle from turn in all the way out of the corner.

yes, even with some mathematical methodology you still have to arbitrarily pick your starting point. but you can't tell me that giving a 2500lb Integra a 200lb break and a 2800lb (or whatever) Mitsu 3000GT will have the same outcome.

[lateapex911]

Mike,

Many thanks for all your hard work. I don't recall anyone thinking this theory was bogus, we just needed to try and drill down and prove that there were 'better' numbers out there than 3x50 and 2x100.

I'm with you here. I really appreciate Mikes and Gregs and Travis' and everyones contributions here.

Onto the ITR number. While Dick's thought process is 100% valid IMHO, I also feel like there aren't many FWD'ers that will be able to really utilize the 8.5" rim. I am betting most RWD guys will be able to try out a 275mm tire...255 for sure. I would doubt that any FWD car could stuff a 275 under the fenders with the current bodywork rules we have. So we need to compare the differences inside the class. I think there should be a difference when you look at it practically.

But I'm really NOT with you here, LOL. Tough nuggies if the wheel doesn't fit. The class allows it, we assume ...and when you pick your car, it's a factor the smart racer takes into consideration. IF we were to give breaks to FWD cars based on the assumption that they can't fit the allowable tire, then the RWD cars that also can not are getting the dick sandwich.

No, all cars are classed on the same assumption, and it's up to the driver/builder to do his homework. We must remain "blind" to model specific tire issues.

[lateapex911]

Ok, just thinking out loud here.

ITR:

I chose a median weight for an ITR fwd car as 2880.

Since we use power to output weight, I think using weight is fine as a function. So I solved for a 175 adder at that median weight and got 6.0736%. Rounded up to 6.1%

Then i ran down the list:

Using Mikes list with weights from IT power already calculated
--------------------------------------
Toyota Celica GTS (00-02) ------- 2531- 154 = 2377
Honda Prelude (93-96) ------------2672 - 163 = 2509
Acura Integra Type R (98-01) -----2633 - 161 = 2472
Honda Prelude (non SH) (97-01)--- 2813 - 172 = 2641
Acura Legend (91-95) -------------3234 - 197 = 3037 (3135 process weight)

Then of course we do the adders and such.

net result, for ITR (I gotta go to work so ITS could be done later) is that heavy cars lose more, light cars less. Using that "bogey point" (admittedly chosen from the LApsim data and my 'gut (!) ) we get additional losses of as little as 54 pounds and as much as 97, but hovering in the 60 -70 range for most.

Thoughts?

[tnord]

why does a roughly 2% weight break work perfectly for ITA but is apparantly 100lbs or so off in ITR?

[JoshS]

But isn't that the whole point behind a FWD 'adder'? I am thinking that FWD cars won't be able to utilize the additial wheel width - therby negating the theory that ITS and ITR cars should have the sames adder.

It doesn't seem logical to me that FWD cars naturally have bodywork that's more restrictive than RWD cars. What is the basis for a statement like that?

Also, I prefer the fixed adder/subtractor approach than the math.