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2012 BRZ/FR-S Stock Class Autocross Discussion
This is probably a little early as the BRZ/FR-S hasn't been classed yet, but it seems a good idea to have a single thread for those competing in stock class autocross.
Here's a quick run down of the hight points of the rules: Link to 2012 rules -Stock sized wheels (17x7) with +/- 0.25 in (6.35mm) of offset allowance -Shocks with up to two external adjustments (with stock springs) -Substituion/removal of either the front or rear sway bar (but not both) -If offered by the manufacturer, crash bolts are legal (Please Subaru/Scion!) -Provided it passes sound, exhaust is free after the cat. -A few other odds and ends Tires: The 245/40/17 A6 seems like the natural fit. 225/45/17 and 225/40/17 are other options if the front inboard strut clearance proves too tight. Any thoughts? |
I'll be competing stock class if/when I no longer have a seat in the solstice. I'm reserving all decisions on modifications until I atleast have the car, take some measurements and take a few runs. I dont like making changes until I have a baseline... The only exception to that is wheels... Which as mentioned in the other thread, not a lot of options at the moment. Though I will say i anticipate the 225/40 being fairly useless, sounds like the car is gearing challenged and a shorter sidewall will make it worse.
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Stock Class Legal Wheels
I'm copying over some info from another thread. I'll do my best to keep a running list of some of the stock sized wheels that would work well for autocross.
The stock class rules allow +/- 0.25 in (6.35mm) in offset. So any offset between 42 and 54 is legal. Spacers can be used to acheive maximum offset allowance. Given the relatively tight inboard clearance to the front strut and the fact that you'll want to stuff as much tire as possible in there, I'm thinking that shooting for a 42-43mm offset is probably a good idea. Lightweight Wheel Options in 17x7, 5x100, ET 42-54: -Kosei K4R (14 lbs) -Buddy Club P1 Racing SF (17.4 lbs) -Team Dynamics Pro Race 1.2 (17.3 lbs)* -Motegi Traklite 1.0 (14.5 lbs) *These won't be in stock in the right size, but TD will custom make individual orders to your specs with a 6-8 week lead time. They're reasonable priced, and 17.3 lbs. |
Following bill's lead, you do have some rota options...
GR-A, Boost, and circuit 10 are available in +48 Subzero in a +45 Ill edit this Post if i find others. |
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So this means that you cannot go to a 17x8 wheel in the stock class?
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Bill |
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So what class would this boot me to? Theoretically
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Sorry I posted too soon. Thanks Scooby South
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Would it be a good idea to get an oil catch can? I heard that the boxer engine has an especially hard time with blow-by. Any thoughts on this?
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Bill |
I have never been one to race in stock class... just not in my nature... but If I were to compete in Stock class.. Here would be my take:
-Koni's with stock springs... Depending on what spring rate the FRS has Vs. BRZ I might change the springs out to one or the other. -17x7 Light as possible wheel... maybe the Kosei with a 50 with a 5mm spacer to bring the tire back out away from the strut. -not sure if 245 A6's will fit due to them running wide...might go with a Goodyear if that were the case. -Swaybars are gray area right now on this vehicle.. have to wait and see the data. -Lightweight Exhaust or my personal favorite is the JW2 Exhaust Turn-down..that completely eliminates the muffler... weight saved = about 40 pounds. -Lightweight battery -start with a base model FRS for weight savings..since weight is enemy in stock classes. -crash bolts for front Camber if they become available. -performance alignment...would definitely have to tinker with that to get optimum balance/turn-in/predictable agility that would get me started.. Bill |
The damper rule has a loophole in it the size of a hangar door. You're allowed only two usable adjustments. Adjustments to damper's gas portion are not counted, and any hydraulic adujstments above two just need to be glued in place. So if you want to spend a crap-ton of money on dampers you can. Just put a dollop of a silicone sealer on the least used adjustments before you bring the car to tech.
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Also I dont have my hopes up for a TSB from subaru for crash bolts. Its not something they typically do afaik. Technically the lame part of it all, if toyota offers them and releases a tsb and subaru doesnt, you will only be able to use crash bolts on the frs. Last comment, you will want a smaller offset, positive offset puts the hub outboard of wheel center which drives the wheel more under the car. A +42 total offset will likely be optimal for stock class to get the most tire without rubbing the strut |
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So this is all stock legal? |
Lightweight battery would also technically be protestable because blatant weight reduction is against the stock rules
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Any performance related accessory, even if it is sold from the dealership which is not original equipment as part of an option or trim package is illegal unless it meets the modification guidelines. This includes TRD accessories.
Examples: Legal: Trd front swaybar (provided you dont install a trd rear swaybar and vise versa.) Illegal: dealer installed TRD springs. Unless Scion offers a TRD performance variant of the car as an option code. It that case you would need every piece of that equipment package. If the option package came with different seats and springs, you couldnt install the springs without the seats. |
So removing the exhaust and adding the shorty pipe is probably a no no.
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No more than two separate external shock damping adjustment controls are allowed. This permits the use of shocks which originally came with more than two external adjustments, which have been converted to double-adjustables, only if the additional adjustment controls have been permanently disabled (e.g. via weld-ing, epoxying, grinding off). Gas pressure adjustment is not con-sidered a damping adjustment. The key is "permanently disabled." I don't think a dab of silicone or glue counts. Moreover, I doubt you'll find many competitors trying to find an excuse to spend more money on triple adjustable, stock class legal shocks. The sipirit of the rule is a cost containment measure. You're right about the gas pressure adjustment though: tuning gas pressure is one way of working around OEM spring rates. |
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If its after the cat its legal per the exhaust allowance if it replaces or removes or is in front of the cat, yes it is illegal. I am not aware of the part you are referring to so im not 100% what it does.
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Since last year, there is an additional rule for national (and some local) events that cars must also pass sound requirements. This is <100 db at 50 ft. It's usually tested at an area of WOT. In a stock car, with cats in place, I don't think there will be any problem passing sound just a turn down. Personally, I'll be looking for the lightest, single exit cat-back I can find. |
I will probably leave it all alone because changing weight will change the handling characteristics of the car.
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Since I'm pretty sure I'm getting a BRZ, I'm hoping we 1) don't need much static camber due to low roll, and 2) I'm right about no FR-S TSB :) |
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Less weight is always a good thing. (so long as it doesn't compromise safety, structural integrity, etc.) |
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hmmmm..sorry.didnt know the omplete stock ruleset....but I would expect lots of griping about this car
...already hearing rumblings of the Miata contengent bitching about it....and 3/4 of a degree is better than nothing...:) Bill |
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Kosei K1-TS avail now in ET50 - listed at kosei's website in 42, but can't find a source in that offset |
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Bill |
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If you take off the same amount from the front of the car you would be back to the origiional distribution. I bet you could drop about 100lbs. from the rear without trying very hard. Spare tire and tools along with the exhaust, truck carpet. Might get you close. |
trunk junk has already been weighed at 35lbs...muffler is about 40lbs..
Bill |
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Not bad How about rear seat? The fold down and seat itself. |
Cant remove seats. You will be reducing the yaw moment by removing trunk junk and muffler weight but slightly moving the cg location forward. In the grand scheme of things, you wont be able to tell from a vehicle dynamic standpoint.
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Seats
Per class rules??? |
Per class rules, you can't remove seats. You know, you could actually download the rule book in its entirity from SCCA for free. And the stock section isn't that long, only about 9 pages (if you don't count all the clarifications and classing pages).
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That book gives me a head ache. I currently am going through a build and the SCCA rule book makes me go cross eyed. durrrrr
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