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Tracking / Autocross / HPDE / Drifting What these cars were built for! |
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05-15-2023, 08:10 PM | #1 |
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RCE SS-2 for '23, spring rates ?
I'm about to install RCE Superstreet-2 coilovers on my '23 BRZ. Spring rates are 7kg/mm all around. I'm thinking about getting softer springs for the front to keep wheel rates more in line with front/rear weight distribution and to mitigate the inherent understeer this car seems to have (my '17 did anyway, on 4.4 kg/mm front and 5.3 kg/mm rear springs).
The car will be my daily-driver, but I'll also compete in time-trials with it with COMSCC. Competition is stiff at the sharp end of my class, so willing to compromise streetability for tenths of a second! Tires will be either 225 A052s or RT660s. Target alignment specs -3.5 front, -2.5 rear camber, zero toe all around. Ride heights -30mm front, -25mm rear Competition weight 3050-3100 lb. No aero Thinking I'll go 5kg/mm front with 7kg/mm rear. But maybe 7F/9R... I may just try the 7 all around they come with as a baseline but honestly it just seems like it will be an inherently understeery setup, with wheel rates of ~6.3 front and ~3.9 rear, YUK... Anyway, expert opinions welcomed! TIA... |
05-16-2023, 11:23 AM | #2 |
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Why so little front camber?
I do agree with changing up spring rates though.
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05-16-2023, 11:31 AM | #3 |
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Base line them but make sure you have your ride height with .25" of rake with the rear being higher. It makes a significant difference in balance. After that make changes as you see fit.
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05-16-2023, 11:31 AM | #4 |
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Will a pair of 10k's work? I have a full set of 6k, and 9k, but I planned on selling those with my T2's.
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05-16-2023, 11:53 AM | #5 | |
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I'm not worried at -3.5 or -3.25 even, but it better be more than -3! |
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05-16-2023, 11:56 AM | #6 | |
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The '17 was about -35 all around, I'm thinking that's where some of my understeer was coming from (super-low rear roll center). |
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05-16-2023, 11:58 AM | #7 | |
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It is my street car so keeping it a bit on the soft side is preferable. I've historically done pretty well with softer-sprung track cars anyway. Ability to curb-jump comes in particularly handy at Palmer CW! |
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05-16-2023, 12:00 PM | #8 |
Try it first!
Would probably not go softer in front for you, maybe stiffer in rear. Your old car with relatively soft rates was likely still using the bumpstops quite a bit in cornering even if they were trimmed. - andrew |
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05-16-2023, 12:14 PM | #9 | |
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But yeah, still could well be a factor in my '17s understeer... |
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05-16-2023, 12:23 PM | #10 | |
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Agreed with going stiffer rear and not softer front
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05-16-2023, 04:47 PM | #11 |
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Listen to RCE. 7K is pretty decent. Are these for a new GR/BRZ? If so remember the new chassis is stiffer so you can afford to be a bit softer on springs.
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05-21-2023, 11:29 AM | #12 |
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9kg/mm springs for the rear on the way, thanks @NoHaveMSG !
Running the numbers, I get 2.1 Hz both front and rear running 7kg/mm front springs and 9kg/mm rear. We'll see how it goes in a couple of weeks at Palmer! |
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05-21-2023, 10:24 PM | #13 |
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Your valving, alignment, and tires will make a big difference too. I don't have Racecomp coilovers, but I dropped my rear spring rates on my MCS setup to 400 lb/in front and rear (7kg/mm), and the car is much better suited for street and track usage. 400F/500R was decidedly not fun over big expansion joints while in a turn, nor as the weather got cold.
I suspect a lot of folks that understeer on 400/400 with lesser coilovers are likely riding front bump stops, sending rates sky high. Don't lower the car too much.
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05-22-2023, 10:25 AM | #14 | |||
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Honestly I don't think it's going to make any profound difference in handling balance. I'm just trying to mitigate understeer, I still expect to get some. I will be *very* surprised if 7F/9R results in an oversteery car but we shall see. Will go over this with RCE, but plan to lower the car something like 32F/25R. RCE SS-2 include rear top mounts which I *think* increase bump travel so less worried about bottoming the rears too soon which could result in unexpected oversteer. |
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