Modified Street Tire Classes - What to do?

[Loren]

As anyone who cares has surely noticed, our current "Class E - Modified Street Tire - Under 3 liters" has become a pretty large class lately, often 1/4 of the cars at an event will fall into this class.

That in itself is not a horrible thing, but, the class is typically dominated by high-powered cars, like a certain turbocharged Miata, and several S2000's. Leaving folks who have less powerful cars and are running Modified due to suspension modifications out in the cold most of the time.

Obviously, we need to split Class E. How do we split it? How many classes do we split it into? These are the questions we need to answer.

Share your thoughts.

[Agent]

Pretty obvious who you are talking about, but don't forget the super charged one that has a stock suspension and goes slower than a Yaris on suspension with less horsepower than an S2000 from the factory. You can't loop my driving ability in there with his...

[Loren]

Nope, I was talking about Ron's Miata. But it doesn't matter.

100 HP cars shouldn't be competing with 200 HP cars.

(and I can't believe you just said that a Yaris has a better suspension than a Miata... hah!)

[Native]

If the turbo charged Miata you are talking about is actually a super charged one

Nope. That's not the one he's referring to.

Generally speaking, E encompasses to large of a range of cars, some of which are just not competitive with others. The example Loren offered was just that, an example.

Do you have any thoughts on revising current class E?



edit: I'm too slow at posting, too...

[Anonymous]

How about a class for cars with solid rear axles over and under 3L?

Another class for cars with loud exhaust, and another for cars with no bumpers? When does it end?

but, really can we make one for cars with solide rear axles??

[Anonymous]

Use the Street Prepared Pax to split cars up.

ASP 0.866
BSP 0.859
CSP 0.862
DSP 0.845
ESP 0.846
FSP 0.831

Just split it in half.

1. ASP, BSP, CSP
2. DSP, ESP, FSP

FSP should really be on it's own, but that's a similar situation to the H Stock in Production class issue.

[Agent]

Nope, I was talking about Ron's Miata. But it doesn't matter.

100 HP cars shouldn't be competing with 200 HP cars.

(and I can't believe you just said that a Yaris has a better suspension than a Miata... hah!)

I know, I changed my post above me if you look. I completely forgot Ron was in the same class that I am in since he switched to street tires.

On a side topic, Loren, I would be hard pressed to believe my car handles better than yours. The Yaris and the Miata have almost identical weights and all I have is stiff shocks. I'm not lowered, I don't have crazy spring rates, no aftermarket sway bars, I have shocks, and that's it. I know you are a far better driver than me, and I completely accept that, but you take a turn at the same speed I do and your car doesn't even lean and mine pitches up 6" on a side. Frankly, it doesn't matter to me what class I race in. I'm modifying my car how I want and whichever class I end up in is where I will do my best at to compete. Just like no one told Tim in number 21 to get a Vette to compete in a tight autocross, no one told me to get a Miata or you to get a Yaris. There is no one car that is always the best.

However, I still 100% believe that your car handles better than mine.

[impalanut]

We don't want to end up with too many classes, although there are frequently no cars in B so B and C could be combined. Then you can either make E two classes with an additional motor size split, or you can just take the current class and lower the motor size split, or you can increase the multiplyer for forced induction if these are the only cars that are upsetting the balance. I don't know if we want to become too dependent on the SCCA classification.

[Loren]

How about a class for cars with solid rear axles over and under 3L?

Another class for cars with loud exhaust, and another for cars with no bumpers? When does it end?

but, really can we make one for cars with solide rear axles??

Let's be serious here. "When does it end" is a valid question, but we're nowhere near needing to ask it. We have exactly two Modified street tire classes. The "Over 3" class is staying fairly small at present, and Drew (solid rear axle Mustang) usually finishes first. I don' that class is an issue at this time, though we could incorporate it in whatever change we make.

Nobody's suggesting an "I" class here, where "MY" car is competitive. We're just looking to add some more logical divisions in the classing structure. Something that will break a 15-20 car class up into a smaller classes that are fairly well-distributed and give people better competition within them.

FWIW, my Yaris has a solid rear axle, too.

Jeremy's suggestion of using SCCA SP classing is "almost" good. But, because SCCA SP is a race tire class (our isn't) and doesn't allow the addition of forced induction (ours does), I'm not sure it would work. I think we need a simple formula-based class structure that incorporates displacement, a FI modifier, and a modifier for VTEC and similar active cam timing systems. I'd be willing to consider some minor adjustment for solid rear axle and/or FWD, but that probably wouldn't be enough of an adjustment to affect the classing of most people.

For instance, if we put the displacement points at 2.0, 3.1 and 4.2 (just pulled those numbers out of the air) with a 1.5 FI multiplier, 1.2 for VTEC, and 0.9 for solid axle... a 5.0 Mustang would drop to 4.5 and be in the 4.2+ class. Obviously, who that allowance helps will depend on where the class breaks end up.

Honestly, I don't think the solid rear axle is that much of a hindrance for autocross. You can still get a limited slip diff with your solid axle... and THAT would make a difference.

(a lot of Miatas have an open diff... ask them about how well that works for them... even with independent rear suspension)

[Native]

I don't know if we want to become too dependent on the SCCA classification.

+1

[Dave-ROR]

at some people.

[Jamie]

Honestly, I don't think the solid rear axle is that much of a hindrance for autocross.

...and VTEC (or any other variable cam system) isn't that much of an advantage, given the number of times every course forces you to drop back to the "slow" cam. The power's all at the top end, and the torque differences between otherwise equivalent VTEC and non-VTEC engines is pretty much nil.

The solution may be simpler than it appears -- increase the FI modifier to 2, or drop the displacement crossover between Class E to Class D to 2.5 liters. The other big division would be FWD and RWD/AWD, but I don't think that's as much a difference as boost.

[Loren]

Remember, Jamie... those VTEC guys (S2000's, Integra R's, etc) DO make every effort to stay in the high revs. For instance, yesterday, where you and I were running the course at the bottom of 2nd gear, they were running it in 1st. Don't kid yourself. They are capable of making more usable power, and a good driver will know how to use it.

Look at it this way, though... let's say we have a 2.0 and under class with no differentiation on VTEC. Now, let's compare a 1.8 Miata and a 2.0 S2000. A turbo will bump either of them out of the class, so that's not an issue. Both cars can be set up to handle (arguably) equally well. But there's no way you can get a stock-engined 1.8 Miata to accelerate like a stock-engined S2000. Are you saying that it's that 200cc's of displacement that makes the difference? I don't think so. VTEC is what gives the S2000 the edge over the Miata.

While we don't want to class "for" specific cars, we do need to use real-world examples, and it makes sense to look at the most popular cars and try to adjust the classing to fit them somewhat. S2000's and Miatas are very popular autocross cars, we're seeing more and more of them in the mod classes. We should have a class that each of them can compete in. (and without requiring forced induction)

It would be nice if there was a class that the lesser non-sports cars can compete in, not just for myself, but for all the folks who show up with something like a Civic or a Focus with light suspension mods. That could very well be the same class the Miatas compete in... as long as we keep the turbos out.

[Anonymous]

Remember, Jamie... those VTEC guys (S2000's, Integra R's, etc) DO make every effort to stay in the high revs. For instance, yesterday, where you and I were running the course at the bottom of 2nd gear, they were running it in 1st. Don't kid yourself. They are capable of making more usable power, and a good driver will know how to use it.

I did the whole course in 2nd gear and I was .1 off of scratch FTD.
And the PAX index disagrees that a modified s2000 is faster than a modified Miata.
BSP 0.859
CSP 0.862

I would like to hear some specific examples of why the SP pax won't work. I think you need to split out FSP and everyone's goals will be met.
So we go to 3 classes instead of 2, and hopefully things will be more evenly distributed, but at least I can guarantee they will be more fair.

Class 1 - ASP, BSP, CSP
Class 2 - DSP, ESP
Class 3 - FSP

doesn't allow the addition of forced induction (ours does),

Maybe bump up one class for forced induction, although personally I say since everyone has the opportunity to add forced induction there should be no penalty for it.

But, because SCCA SP is a race tire class (our isn't)

Street tires vs race tires in street prepared is kind of irrelevant, because everyone will be on street tires.

[Loren]

To have a class structure that allows forced induction that allows FI without penalty is to have a class that REQUIRES FI (or at least a certain amount of HP). It's just like the classic race tires in stock class SCCA argument. To allow race tires is to require them because you can't compete without them.

Color me educated on the difference between BSP/CSP (and thus the theoretical difference between 1.8 non-VTEC and 2.0 VTEC). There's still a lot more at play, however. Your national class-winning Miata is nowhere near the kind of car that shows up at our events or the kind of car that most people would drive on the street. They strip the weight down to about 1950 (from 2200ish for the typical Miata), and put 13x10" wheels on them. As I said before, our "mod street tire" classes are not really that close to SCCA SP.

But, you asked for specific examples of why PAX on SP classes won't work for us. Let's use the same example. If we lump BSP and CSP together, we've got all the Miatas and all the S2000's in the same class. Now, in theory, if they're all equally prepared, there should be parity as the PAX is very close. But, what happens when you put a turbo on the Miata and bump it from maybe 140 hp to something like 250-280 or more? Assuming there's a good driver behind it, it's going to make a difference.

That doesn't mean that using SP classes as a basis won't work, but we do need to address certain things that WE allow that SCCA doesn't. Forced induction is the big one. Bumping up one class might be a solution.

Help us out, Jeremy. What are, say, the top 3-4 "spec cars" for each of the SP classes? And the PAX for each class.

[Jamie]

Remember, Jamie...yesterday, where you and I were running the course at the bottom of 2nd gear, they were running it in 1st.

I don't know what I'd have run that course in, since I wasn't there. But my assessment comes from a fair amount seat time in nearly identical VTEC and non-VTEC Preludes. The H22 and H23 engines used in the '92-96 cars were identical except for 100cc difference in displacement and the VTEC head. Same torque, 30-40 horsepower difference. No difference in autocross performance.

...there's no way you can get a stock-engined 1.8 Miata to accelerate like a stock-engined S2000. Are you saying that it's that 200cc's of displacement that makes the difference? I don't think so. VTEC is what gives the S2000 the edge over the Miata.

I'm saying there are other factors in the engine design that also make a difference. VTEC -- basically a system that allows better engine breathing at high revs without sacrificing low-rev performance -- is not going to deliver the 100-110 horsepower advantage an S2000 enjoys over a 1.8 Miata. Beyond acceleration, there are other factors in the S2000 chassis that make a difference, too.

It would be nice if there was a class that the lesser non-sports cars can compete in, not just for myself, but for all the folks who show up with something like a Civic or a Focus with light suspension mods. That could very well be the same class the Miatas compete in...

If the SCCA's STS and STS2 are any yardstick, then you'll need to split 'em up. Of course, that's all getting away from the very large circles we knowingly drew around performance to start with. Popularity breeds complexity. :shock:

[Anonymous]

I don't really follow SCCA classing anymore, and I never followed SP, so I don't really know much about them. I do know that recently they changed the rules to legalize boost mods, so that's why you see some turbo cars higher than they should be.


ASP
C5 Corvettes, Elise, Porsche GT2, M coupe, M Roadster, M3 (E46), MR2 Turbo, Solstice GXP

BSP
C4 Corvettes, s2000, Lancer Evos, STi, M3 (E36), 350Z, 240Z, 300Z Turbo, MS Miata, RX-7 turbo, RX-8, Boxter, Supra Turbo

CSP
NA Miatas (all), MR2, CRX / 88-91 Civic, RSX, M3 (E30), SRT-4, NA MR2, Solstice

DSP
BMW 3 series, Integra (all), Civic VTEc 96-00, Impreza 2.5, Neon, 240sx, Sentra, Focus SVT, Prelude, VW Golf/Jetta, Mini Cooper S.

ESP
Trans Am, Camaro, Mustang, G35, Mazdaspeed 6, WRX, Legacy GT

FSP
Focus (non-svt), Civic non-vtec, VW, NA Subaru NOC, Mazda 3

[Loren]

For our purposes, if we're going to take our current D and E classes and make three classes, I think something like

Class 1: ASP/BSP/ESP (.862, .858, .856)
Class 2: CSP/DSP (.842, .841)
Class 3: FSP (.833)

With an "if you've added forced induction to a car that didn't come with it, you bump up a class" rule.

Not sure what our current population of such a structure would be, though. I think Class 1 would cover our existing Class D and bump the S2000's and turbo Miatas into that class.

The middle class would be what's left except for the dog-slow FWD cars that would go into the third class.

So, from the last event, out of a total of 24 Mod Street Tire cars, about 10 would go in the first class, maybe 6 in the third class, and the remaining 8 in the middle class.

That could work. We're already using SCCA classing as a basis for our "stock" classes, why not?

If anyone wants to look at the class lists in greater detail, Here's the 2008 SCCA rulebook. The SP car listings (whcih are all we'd be using, NOT the prep rules) start on page 185 of the PDF.

And if anyone involved in this discussion doesn't understand what the PAX numbers mean, just ask and someone will explain.

[Anonymous]

For our purposes, if we're going to take our current D and E classes and make three classes, I think something like

Class 1: ASP/BSP/ESP (.862, .858, .856)
Class 2: CSP/DSP (.842, .841)
Class 3: FSP (.833)

You've got some numbers mixed up.

Class 1: ASP/BSP/ESP (.862, .858, .841)
Class 2: CSP/DSP (.856, .843)
Class 3: FSP (.833)

[Loren]

Right you are.

With that, the proper mix would be
ASP/BSP/CSP
DSP/ESP
FSP

Which is pretty much where you started, wasn't it?

Using the SCCA SP base classing solves a lot of problems for us. It addresses VTEC/Non-VTEC, Sportscar/Non-Sportscar, drivetrain and suspension differences, etc.

We'll definitely need an "added forced induction" bump. Is there anything else that we allow that would need to be considered for a class-bump?