STX setup sharing thread (2019)

[Molez93]

^ Thanks for the clarification, sounds pretty reasonable.

[Westen86]

I see a lot of people with only an upgraded front swaybar. Is this a SoloII thing, or is there reason it benefits any track setup? 949 Racing also only has a front bar. Would you guys prefer to run stiffer front coils and this is whats available because not all coilovers have a choice?

[strat61caster]

Seems to me that being much stiffer than about 550# or so on the front the car reacts poorly to shitty/bumpy/broken up surfaces, even at that spring rate a stiffer front bar than stock helps with transitions. Many run softer springs than that (300# to 500#) and up the sway bar rate to keep the car quick through slaloms and offsets. There's plenty of spring rate and damper options available so this isn't limited when it comes to Street Touring setups, more related to the physics of the chassis.

The rear suspension gets most of it's stiffness from the springs, the rear bar is pretty low impact with a 0.5x motion ratio. Just lucky/good design that matching the rear spring for good longitudinal manners to the front also results in a good roll stiffness match with the stock rear bar. Slightly different suspension design (pickup points, arm lengths, mounting points, etc.) could totally change that, but we got what we got. Most people develop on a budget, why spend a ton of money testing when the OE rear matches well with a stiffer front and stiffer springs all around?

949 specifically tests on tracks with crappier pavement and consider autox use (I would be surprised if they didn't do some skidpad testing with slaloms and offsets) so it makes sense to me that they're in a similar ballpark when tuning for the same wider stickier street tires. Add aero and bias towards smooth well maintained tracks and you start seeing stiffer spring rates like what's on track focused Teins or JRZ's with 10k-12k rates.

[Westen86]

Originally Posted by strat61caster

Seems to me that being much stiffer than about 550# or so on the front the car reacts poorly to shitty/bumpy/broken up surfaces, even at that spring rate a stiffer front bar than stock helps with transitions. Many run softer springs than that (300# to 500#) and up the sway bar rate to keep the car quick through slaloms and offsets. There's plenty of spring rate and damper options available so this isn't limited when it comes to Street Touring setups, more related to the physics of the chassis.

The rear suspension gets most of it's stiffness from the springs, the rear bar is pretty low impact with a 0.5x motion ratio. Just lucky/good design that matching the rear spring for good longitudinal manners to the front also results in a good roll stiffness match with the stock rear bar. Slightly different suspension design (pickup points, arm lengths, mounting points, etc.) could totally change that, but we got what we got. Most people develop on a budget, why spend a ton of money testing when the OE rear matches well with a stiffer front and stiffer springs all around?

949 specifically tests on tracks with crappier pavement and consider autox use (I would be surprised if they didn't do some skidpad testing with slaloms and offsets) so it makes sense to me that they're in a similar ballpark when tuning for the same wider stickier street tires. Add aero and bias towards smooth well maintained tracks and you start seeing stiffer spring rates like what's on track focused Teins or JRZ's with 10k-12k rates.

So the limitation is in the front shock not coping with the force of a hard spring? A stiffer front bar makes both sides work for one. Ideally, if you could make it work with less swaybar the added articulation would increase grip, correct?

[strat61caster]

Originally Posted by Westen86

So the limitation is in the front shock not coping with the force of a hard spring? A stiffer front bar makes both sides work for one. Ideally, if you could make it work with less swaybar the added articulation would increase grip, correct?

The damper is not a limitation, you can get whatever you need in this class. More spring makes the car unsettled over bad surfaces while the bar does not. That's just my experience and observation, feel free to experiment and seek other opinions.

[Icecreamtruk]

While "conventionnal knowledge" says that a softer sway bar would net more grip overall (softer more grip but slower to react), the reality is that "it depends". While im sure there are plenty of cars out there that work best with stiff springs and soft bars, or even no bars at all, what I have found in my own car is that, even if you have ridiculously stiff srpings (700+), a stiffer sway bar works better than a stock one. Dont ask me how or why, but the car became much easier to drive after putting in stiff swaybars (keeping a around 200% stiffer than stock in both front and rear). I dont know the effect that only the front bar will have, in theory it should understeer, but again, this is another "it depends" answer.

[Autoxer62]

Hi folks,

This isn't exactly a setup post, but a rules post. The 2019 SCCA rules for STX only list the 86/BRZ through 2017. I assume this is basically an oversight since the 2017 to current cars are virtually identical in spec, so I wrote a letter to the STAC asking them to update the listings.

Of course, the other route would be to run a newer car in STS under the catchall rule and get protested, but I'd rather not

I think it would be helpful if a few other members wrote and asked for the update as well.

[Lincoln Logs]

Originally Posted by strat61caster

More spring makes the car unsettled over bad surfaces while the bar does not. That's just my experience and observation, feel free to experiment and seek other opinions.

This is correct to a certain extent, more bar will always give up some grip over uneven surfaces as well. It allows less independent wheel movement the stiffer the bar you put in.

949s suggestions are track focused but will still work well at autocross. I've been running the stock 2017 sway bars at autocross for a while and it's neutral-loose which I like but would be faster with a bigger front bar. I am currently running 450lb springs F/R with MCS 1WNR shocks.

I do not think you need more than a 15mm rear bar in 99% of use cases. It'll be too much and make the car more difficult to drive on the limit.

[KevBRZ]

Originally Posted by strat61caster

The damper is not a limitation, you can get whatever you need in this class. More spring makes the car unsettled over bad surfaces while the bar does not. That's just my experience and observation, feel free to experiment and seek other opinions.

Thats what i was thinking, i got the SS1s which some may say are not stiff enough for autox, but the 2 lots i run on are pretty bumpy etc. and i daily the car and i like my back and kidneys alot lol, adding the front bar i think helped with planting the car and didn't add punishment to the setup, i am very comfortable with dailying the car and i am old. lol
My complaints with dailying are related to space in the car etc. not so much suspension etc. lol Sometimes i think some setups are more specific for smooth concrete like Lincoln (never been there but i am sure its nice) but i know i will never be there due to don't really get much seat time due to work etc. ( and I suck ) lol Sometimes i wonder why i have this car due to being a 95% daily/5% racer but its so damn fun, thats why!

[steverife]

Another thing in the spring versus bar conversation is adjustability. Most people aren't going to find it viable to swap front springs on an FRZ between autocross runs.

[skylinekin]

Is there an equivalent SCCA time trials class for STX setup FRS?? I know the SSC translates well to TT S6, wasn’t sure about STX.

[strat61caster]

Originally Posted by skylinekin

Is there an equivalent SCCA time trials class for STX setup FRS?? I know the SSC translates well to TT S6, wasn’t sure about STX.

Tuner class roughly aligns with Street Touring
The FRZ86 is classed in Tuner4

I thought there was an allowance for STX -> T4 a la the SSC (some SSC parts aren't actually allowed in Streetk, mostly the camber parts from SPC) but I can't find it now, that might have been eliminated as it's been a good year since I took a close look at the rules.

[bmacfrs]

Yes its tuner 4.
Go to timetrials.scca.com
Click on 'what's my class'


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[tony_r]

There isn't a direct ST > Tuner translation for TT but the ruleset is basically a copy/paste from ST. You'll find that Tuner 5 is STS/STR, T4 is STR/STX/STH and T3 is STH/STU. Rules are locked for another year so this isn't likely to change.

Unfortunately STX cars find themselves in-between the speed of Tuner 4/5, so they don't really have a premium competitive home unlike the Sport classed cars.

There is an "Alt Motorsport" classing but currently it only covers autocross Street class and SSC direct to Sport. The rest of the "Alt Motorsport" is Road Race, etc.

RE: Spring vs Bar in AX; it's better practice to keep the spring rates on the softer side and use adjustments of sway bars to get roll stiffness required. It's much easier to make a change on the sway bar than it is to change springs if there is an issue with surface grip. Since autocross is slower, on imperfect surfaces and has more undulations than track, big spring doesn't have the same benefits. This has been proven in practice more often than not in ST.