Street category

Steven Carter · **Posted:** Wed Mar 20, 2013 9:02 pm

My DS WRX may have just gotten camber and two bars with an extra 1" wheel diameter allowance....it just might be competitive!

http://www.solomatters.com/2013/03/street-catagory-proposal-explained/

It will be uh....interesting....to see this unfold.

JamesShort · **Posted:** Wed Mar 20, 2013 9:21 pm

Like

Matt McGrain · **Posted:** Wed Mar 20, 2013 9:29 pm

This to me is the biggest shocker and I don't necessarily think it's a bad idea. :shock:

Quote:
The section likely to get the most attention in the proposal is 13.3, Tires. The proposal would set a 2014 treadwear minimum of 140 and a 2015 minimum of 200. Part of the logic behind this is reducing cost per run. Some will claim that testing and optimizing 200+ treadwear tires will be just as costly as current R-Compound tires. There will always be a faction of our sport that will invest heavily in achieving the greatest pace and it is possible that the treadwear limitations will not result in significant savings for them. However, for the average competitor, the per run cost of autocrossing would be greatly reduced with the higher treadwear ratings as the number of on pace competition runs a tire could produce would meaningfully increase.

Aaron Buckley · **Posted:** Wed Mar 20, 2013 9:52 pm

I saw this coming with the invention of the RT classes... no coincidence I quit autocrossing too. - AB

JamesMilko · **Posted:** Wed Mar 20, 2013 9:59 pm

And oh joy a whole slew of new classes as well.

Steven Carter · **Posted:** Wed Mar 20, 2013 10:14 pm

Yeah, not sure how the limited prep classes will work out. Seems easier just to sell one's stockpile of Hoosiers to an SP driver and buy more wheels and 200TW tires.....lots and lots of wheels and tires.

The RT classes will still remain I suspect. The line between Street and ST may get a lot closer though.

BriceJohnson · **Joined:** Thu Apr 13, 2006 7:33 am **Posts:** 2230

To me, seems like you basically just eliminate the conventional SP classes and the RT classes, and make a category of the ST classes that allows R comps like back in the day. Leave the mod and prepared classes alone.

Chuck Branscomb · **Posted:** Thu Mar 21, 2013 8:52 am

I guess Hoosier lost their grip on the SEB? :lol:

j/k

Sanity is finally prevailing imo. Simply allowing camber and both end sway bars goes a long way to allowing a reasonably fun street driven car to participate. Clearly, the extremes of the sport will now be investigating what types of courses necessitate 45mm sway bars front and rear, etc, but at least you're not left in the cold if you want to simply have fun in a "street" class with a daily driven car.

Looks like there's going to be a good supply of remote reservoir shocks coming to the market if someone is looking for a set for a track car.

JamesShort · **Posted:** Thu Mar 21, 2013 9:13 am

Well I thought about it and I agree that all changes are great except the 2 sway bar allowance. With the rule as it stands (either side but not both), it inherently limits the size of the bar that you put on it since the balancing act only goes in one direction (relative to stock). If you allow 2 bars, then people will just have effectively ST* car (600+ #/in effective spring rates) and absurdly expensive bars that mangle the subframe and hit exhaust etc etc (granted they still with have soft pitch characteristics). If I understand the sentiment right on this new reclassing, I'm assuming it's to encourage people with reasonably modified cars to participate and be competitive and if you need $1000 sway bar and you'll probably damage the mounts/subframe/endlinks etc, then it might do exactly the opposite.

I feel like this is an attempt to alleviate the "IBM Effect" (not due to causes, just effect) that seems prevalent in SCCA autocross: You have a ton of long timers (not necessarily age, but length of time since participating in the sport). Who know the rules in an out and have lots of experience with setups and testing and what works and what doesn't and they continue participating no matter how expensive gas gets or Hoosiers get etc etc. Then you have this crowd of short timers (regardless of age) who come in and participate and have fun but realize the cost and effort to be competitive is quite great (even in a ***STOCK*** classed car) because: they don't have $1000 to drop on a set of tires ever 4 events, $1000 to tow a **STOCK*** classed car to Lincoln, buy $5000 remote reservoir 3-4x adjustable Motons/MCS and yet they still want to drive and have fun in a competitive way. When they realize this is impossible, they stop attending so you have this broad gap of experience in the middle area that seems to be grow year to year. When the former participants 'retire' (ie Lemons/TT/W2W etc) then there is nearly no one left.

Anyway, I have a feeling that though this might piss off a decent number of long time autocrossers, long term its going to be better for the SCCA and overall participation in the sport.

EDIT: I would hope these classes would eliminate RT, no? Would it just be similar to what stands? Super Street, A Street, B Street, C street etc? and all the Stock classes are gone?

Chuck Branscomb · **Posted:** Thu Mar 21, 2013 9:23 am

James we are on the same boat here...they should ponder some formula that limits sway bar size as a percentage of stock diameter. They should also have some words to the effect that interference with other suspension parts through range of motion is illegal. I realize this all starts opening up a can of worms, but it will be about 10 minutes before people are out testing those massive custom bars to see how much loading stock control arms and chassis mounting locations will take. I have no clue what the "hot ticket" will be in terms of bar rates with stock springs, but damn this did just open up a whole new realm of stuff I'm sure people are already looking to test.

It does seem unlikely that a set of sway bars available for purchase now will turn out to be the optimum sizing, doesn't it? I wonder if they included non-stock brackets?

Steven Carter · **Posted:** Thu Mar 21, 2013 9:39 am

It seems sorta redundant to keep RT, but on its face it appears the parts cost for Street has gone up while the tire costs have been mitigated. This may make RT remain as a lower cost alternative, but that's up to SCCA to decide if that class gets folded in or not.

In re swaybars...this is where I get confused. Previously, we had big fat front swaybars on supergrippy R-comp shod cars where a few (not a lot, but enough to notice) cars had swaybar mounts tear off. If you move to street tires, the tires *should* break grip before the stress on the swaybar mount becomes excessibe, correct? If so, that risk may be less overall.

JamesShort · **Posted:** Thu Mar 21, 2013 9:42 am

Also, to those who are annoyed about having to 'relearn' setup/prep for the various stock/street classes (as opposed to following 30+ year old formulas), I say get over it. It will add another interesting element to car prep if you have to hone in on setup almost every year due to small changes (think F1).

I will say that expect Super Street and F Street's PAXs to plummet (relative to the others) unless the EPST mfgr, start making 300+ mm 140/200 TW tires. I'd expect that B Street will be as fast or faster than Super Street with the current set of street tire choices.

Chuck Branscomb · **Posted:** Thu Mar 21, 2013 9:45 am

The stiffness of a cylindrical bar in torsion changes with the fourth power of the diameter. Hence bar stiffness increases in a hurry with diameter. If a stock bar is say 25mm, and someone can fit a 45mm bar in its place, stiffness goes up ~ a factor of 10. Hence it will be easy to rip off mounting parts pretty quickly with increasing bar diameters in many cars. The standard engineering factors of safety used in the design of the bar mounts, mounting locations, unibody/frame loading, etc, etc, all never expected such potential craziness as massive bar diameters like above. Perhaps it won't be an issue since it won't work from a handling perspective anyway on most cars. I have no idea.

Picture a control arm sway bar end link mount. Now picture said mount with a bar with a 10x stiffness. Now add a pothole or bump to the equation.

JamesShort · **Posted:** Thu Mar 21, 2013 9:47 am

Steven Carter wrote:

In re swaybars...this is where I get confused. Previously, we had big fat front swaybars on supergrippy R-comp shod cars where a few (not a lot, but enough to notice) cars had swaybar mounts tear off. If you move to street tires, the tires *should* break grip before the stress on the swaybar mount becomes excessibe, correct? If so, that risk may be less overall.

I see your point, but with your 800f/700r STR springs (might have made that up), I'd hypothesize (though I could do the math if I get the ARB motion ratios and dimensions off the S2000) that if you had 200/200 #/in stock springs to get the same roll rate, you'd probably need a 40+mm sway bar front and rear.

The tires breaking grip before the stress on the sway bar only applies on the traditional Stock class "I have a TLLTD percentage of 90/10 due to my monster FSB" but with front and rear bar allowance, you can keep a reasonable TLLTD and take advantage of the full grip the tires can offer on both the front AND the back.

JamesShort · **Posted:** Thu Mar 21, 2013 9:50 am

Chuck Branscomb wrote:

The stiffness of a cylindrical bar in torsion changes with the fourth power of the diameter. Hence bar stiffness increases in a hurry with diameter. If a stock bar is say 25mm, and someone can fit a 45mm bar in its place, stiffness goes up ~ a factor of 10. Hence it will be easy to rip off mounting parts pretty quickly with increasing bar diameters in many cars. The standard engineering factors of safety used in the design of the bar mounts, mounting locations, unibody/frame loading, etc, etc, all never expected such potential craziness as massive bar diameters like above. Perhaps it won't be an issue since it won't work from a handling perspective anyway on most cars. I have no idea.

Picture a control arm sway bar end link mount. Now picture said mount with a bar with a 10x stiffness. Now add a pothole or bump to the equation.

While true, most of these humongous bars would be hollow to capitalize on the higher torsional constant (J) per unit mass/density. Though if brackets/mounts are NOT allowed, then smaller diamater, solid bars would be required to fit the constraints of the OEM mounts/brackets.

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