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GRs in STU autocross
GRs in STU autocross
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Old 02-28-19, 01:47 AM   #661
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Default Re: GRs in STU autocross

Looking forward to meeting folks at the Pro & Dover.
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Old 05-15-19, 08:11 PM   #662
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Default Re: GRs in STU autocross

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

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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Old 08-30-19, 09:14 PM   #663
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Default Re: GRs in STU autocross

Originally Posted by brapp View Post
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.

Last edited by Pault1; 08-31-19 at 09:46 AM.
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