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Bump from the dead!!!

ASP was fun, but SM beckons. I'm curious if anyone had any insight on optimal spring rates for big sticky Hohos :D

From my (most likely incorrect and horribly applied) math on motion ratios and effective wheel rates, I think that a range of 750lbs/in to 950lbs/in is going to be solid, and my starting point will be around 850f/900r with close to stock diameter anti-sway bars. Tires will be 315mm A7s initially, and I'm machining front and rear uprights to bring roll center and bump steer correction into spec for a 1.5-2.0" ride height drop.

What do the experts think?
 

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SMS is not an "official" class. But it might be a local class. Different local regions sometimes tweak rules to suit the local environment. Most likely it's just SM (Street Modified) with a tweak or two. SM is a whole different beast with tons of stuff allowed. For example... there's a 06 STi built for SM class in one region I run in... it has 650whp, sequential gearbox, 305 section Hoosiers, lots of aero... etc etc.

Haven't made it anywhere near thru all 7 years of this thread.
Changes at SCCA since thread started: now no limitations on what you can do with the ECU, but still no changes to fuel reg, pump, BOV etc. allowed. Still should be smog legal. Other clubs may use different rules of course.
SMS class mentioned may be like one of our local classes that is Street Mod prep but with Street tires (200 treadwear).

FWIW on the amazing surface at Crows Landing CA airport, my STU legal car pulls slightly over 1.3 g (not calibrated, that is using an Android tablet with Solostorm software) lateral.
Approx stats: as much negative front camber as I can get is ~3.9 / 4.1 IIRC. Whiteline plates. 600#/550# f/r. 23/27 mm f/r swaybars. KW variant 3 double adjustables. I was using old Kosei TS 17x9/45mm but one cracked when I was forced into a curb by a bozo. New wheels are Motegi 17x9.5 45mm, slight rub on the KW reservoirs so am using a spacer on that wheel for now. 255/40-17 BS RE71R's. 2006 GD STI. Tread temps are almost equal across the tread after a lap so camber pretty close to optimum.


p.s. I understand that the tread was GR originally but if anything that chassis is stiffer than the GD so the change might be that you would get even better wheel control with my setup on GR. FWIW I am starting to think that a little more spring might be beneficial based on what some setup guys have commented w.r.t. body roll.
p.p.s. Last year a GD won STU Nationals. The car is still competitive though some hot drivers have won with M3's, Evo IX, and 370Z, and the C5 Vette is now allowed in the class and a couple of them have been moving up the lists. I wasn't able to get 265/35-18 to fit though some people have, maybe they used more creative inner fender rolling.
 

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I can’t decide if GR STi’s aren’t competitive in B Street or if people Just can’t resist the urge to mod their cars and end up in STU. Or maybe the best drivers just opt for cars in B Street that are cheaper to buy and cheaper to replace consumables.
 

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I can’t decide if GR STi’s aren’t competitive in B Street or if people Just can’t resist the urge to mod their cars and end up in STU. Or maybe the best drivers just opt for cars in B Street that are cheaper to buy and cheaper to replace consumables.

Well, given that the only STI in B Street this year was like 40th at the Nationals, my money would be that the cars are not truly competitive at the sharp end. Someone did get a Focus RS high into the trophies, so it's not like boost buggies cannot roll, but the STI's handling just isn't quite there and the weight increases that improved the chassis stiffness slowed it down some. It's not winning comparo tests any more. A good driver can still win locally of course.



Not saying that running a Porsche is cheaper, but the 06 Cayman S blue book is around $18K. Yes, most people who can't resist a mod or ten will immediately end up in STU or beyond - the rules are very strict on engine mods, so a blow off valve and decatted pipe will put you into Street Prepared or Street Mod instantly, and things like that are often the first changes. "Yo, my car has big street cred, listen to my loud exhaust and BOV!" If stance is the reason for your chassis mods that is fine, but being focused on autocross is a different path than most will take.
 

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I can’t decide if GR STi’s aren’t competitive in B Street or if people Just can’t resist the urge to mod their cars and end up in STU. Or maybe the best drivers just opt for cars in B Street that are cheaper to buy and cheaper to replace consumables.
The GR STI is buried in B-street. It needs to be in D-street, like the Focus RS (16-17) and Civic Type R. It will likely still be buried in D-Street...

If you want to run B-street, there were 8 different cars in the top 9 at Nationals this year... none of which were a Subaru.

Focus RS (2018)
BMW 1M
BMW M2
Porsche Cayman
Mustang (Shelby)
Camaro (SS 1LE)
Tesla Model3 (non performance) ... winning car
Lotus Evora
 
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