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Street Touring Hatchback (STH) discussion/setup

xXDavidCXx

Drag Racing Champion
Car(s)
2017 GTI SE DSG
I’ve been chasing front end grip from day one on track.
Put on better tires and added a 034 RSB. Less understeer but still easy to lose front end grip. Lack of front end feel and responsiveness at turn in.

Fast forward fall last year. Re-valved my Ohlins for 8k/12k springs and dialed in -3.4 front camber and some front toe out. The front end was much more responsive.

I have been following this thread closely. Auto-X and Track/HPDE are to very different disciplines. Auto-X set-ups being more extreme, but overall because it is the same car it is directionally correct.

I have been against stiffer swaybars. Preferring to use spring rate to support the car and to control roll. The stiffer the bar, the less independent your suspension becomes. I’m starting to come round and thinking that a stiffer front sway may be in my future and potentially going back to a stock rear sway.

I’ve under-estimated the impact of camber loss in roll, to front end grip. Dialing in -3.4 of static camber has helped. Most probably need a little more. Need to get my tire pyrometer out and re-check tire temps. I’m also thinking that I need to adjust my driving style and reduce my usage of apex curbs which pitches the car further over.

I’m not bound by your Auto-X rules, so have had much more flexibility on suspension mods. The Verkline front LCA will give all sorts of adjustments. Given that I can dial in all sorts of front camber. I most probably will need to cap that at -3.8 for the track.

David, based on 450lb/672lb and an 034 RSB set on the softer of the two settings, what size front swaybar would you recommend?

I’m curious about going back to my stock RSB for my next event at VIR. It’s an easy swop on rhino ramps.

Also, I have more headroom to go to stiffer springs without needing a re-valve.

The current discussion isn't as much about the FSB, that is more of a GS setup discussion, but having a stiffre FSB does make turn-in crisper in STH trim.

As far as what you should do, I don't have enough data to know what front/rear roll couple we should shoot for right now. I'll post up later today what I think the stock vs my current roll couple is and maybe we can make some observations.

Until I have better (more rebound or DA) shocks, I may have to go back to last years spring setup in order to keep the car a daily driver that I don't hate.

However, I think having more front camber, higher front tire pressure, a stiff front bar, and rear toe-out will keep the car happy-ish.
 
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bfury5

Drag Racing Champion
Location
CT
However, I think having more front camber, higher front tire pressure, a stiff front bar, and rear toe-out will keep the car happy-ish.
I think the one trend most people can agree on is front camber, the more the merrier in almost every case with these cars.

The tire pressure thing I think might also be a result of building to STH rules. With being limited to 9" wheel and the 200TW measured widths getting out of control, pressure is really just a crutch for not having enough wheel width for how much tire we can legally run.
 

xXDavidCXx

Drag Racing Champion
Car(s)
2017 GTI SE DSG
I think the one trend most people can agree on is front camber, the more the merrier in almost every case with these cars.

The tire pressure thing I think might also be a result of building to STH rules. With being limited to 9" wheel and the 200TW measured widths getting out of control, pressure is really just a crutch for not having enough wheel width for how much tire we can legally run.
I don't think there is much correlation between tire width limitations and required tire pressure.

I think it has to do more with axle weight and load transfer.

1000 lbs per front corner plus 1.2Gs of load transfer adds up quick.

Its very easy to overload the front tires with too much load transfer not enough tire pressure to support the load.
 
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JackRabbitSLIM

Go Kart Champion
Location
OHIO
Car(s)
MK7 GTI
I think the one trend most people can agree on is front camber, the more the merrier in almost every case with these cars.

The tire pressure thing I think might also be a result of building to STH rules. With being limited to 9" wheel and the 200TW measured widths getting out of control, pressure is really just a crutch for not having enough wheel width for how much tire we can legally run.
I think you should try 40+ in the front just to see and to get your opinion on it. On the GS Si, I ran 40F/30R and always liked it and was very competitive. I'm kind of sticking around there until I figure it out more.

@xXDavidCXx have you ever asked Ron Williams what pressures he runs on his Si?
 

RacingManiac

Go Kart Champion
Location
MI
I can theoize why you got the test results you did, but did you ever test toe-out on a stock rear bar?

I've got plenty of data that shows how bad the front loses camber, which is why I think that should be the focus. Create front grip, don't reduce rear grip, untill you have to.

Case in point, I ran STH light in 2018 with stiff front and rear bars on stock springs (stock alignment though) and did great locally and okay at Nats.

I started my MK7 setup with 0 front 1/8" rear toe out and 0.5deg rear camber with the 26mm H&R. Before I got the Proparts damper setup, I move back to 0 rear toe pretty quickly because the car is just too nervous in the slalom. After I got the damper on the car thats when we did the test with the bar because Sam Strano sent me his bar after I gave him my stock bar for the prototype. We compared that with the H&R at the 0 toe setup, the way was way pushier with the Strano bar vs the H&R. Potentially I suppose a soft rear bar with rear toeout might move in the same direction, but playing with toe wasn't as easy as turning shock knob. Rear camber by the end was more up to 1-1.5* range to help with rear grip for stability as well. Once I got the dampers on the car we can do damper setting and tire pressure to shift the balance pretty readily for surface and condition. Only really bad outside of window conditions were those April PittRace events....

I think its also arguable with the front bar you are still killing front grip and also reducing inside front tire load which is useful for the traction even with the VAQ in place. Shifting the roll torque distribution with a rear bar adds load to the inside front tire for acceleration as opposed to inside rear for no real gain. Ideally to my mind you want rotation to the point you can add power to exit corner. With GS trim limit on ESC Sport as well you want rotation up to some point before the car kills it.

Tire pressure for the 2 types of tires we ran with the car varied by type as well. We run ~30/28 for REs and ~35/32 for BFGs. This was also done in T&T to just kinda get our preferences in.
 

xXDavidCXx

Drag Racing Champion
Car(s)
2017 GTI SE DSG
I'm really surprised by your low tire pressures (30/28: 35/32) I tried this on RE71Rs and was understeering everywhere.

Also, I really don't think the front bar is killing front grip via inside tire lift, because It's also reducing front roll, which reduces grip loss to the terrible camber curve, and I already run a much higher spring rate than stock. I used to think the front bar was hurting me, but after the first event this year with all the changes, including the front bar, I'm not convinced it hurts when the rest of the front suspension is happy.

STH allowances change so much of what we collectively "know" about what works with the GTI under certain constraints.
 

RacingManiac

Go Kart Champion
Location
MI
STH you can certainly optimize the car way better than GS trim can. So I really don't know ultimately where everything ends up. I was just more commenting on the idea of using front vs rear bar as the first knob to turn, especially if you are limited in the available knobs.

Its not really the inside tire lift that's reducing the grip, its just you are shifting weight away from the inside tire of the given axle when you add more roll stiffness anyway. Roll bar always takes more overall combined grip away than what they add at the one tire being gained from maintaining its camber, you are also moving more to the diminishing return side of mu vs normal force curves for the outside tire. Same reason why you are killing rear grip with a stiff rear bar. The G-Stock day Hoosiers are before my time and I am curious to know how that worked, I always wonder if they used to run super pinched hoosiers and stiff front bar because normally they can't get to the limit of those tires otherwise.
 

JackRabbitSLIM

Go Kart Champion
Location
OHIO
Car(s)
MK7 GTI
I think TCS and XDS change the balance of RacingManiac's car quite a bit and I've seen him say that he and Kenny had to drive around that a lot. BTW this car had 2 second place finishes at Nationals. One for Jen and one for Kenny I think.

I'm not claiming to know that high tire pressure is best, I'm just +1 for trying it.
Shifting the roll torque distribution with a rear bar adds load to the inside front tire for acceleration as opposed to inside rear for no real gain.
This is true if the rear tire stays on the ground. I'm guessing the change in balance you guys experienced was more related to the timing of the rear lift and electronic intervention rather than change in roll couple. The rear tire probably came off the ground in both cases, right?
 

RacingManiac

Go Kart Champion
Location
MI
Yeah the tire comes up pretty often in the car with the fat bar. I think Its plausible I think that we might upset the car more but by not doing things to provoke it after it tend to stay complaint. The issue happens more when you do over drive the car and it complaints by cutting power on you. I drove it the car a lot differently once Ken sorta figured out what was happening.

We played with pressure for that reason as well, because its so different from everyone's experiences. Ken leans on going low on pressure but he said both in his STX days or his BS Corvette days the trend was the same. So we try that and it helped. And the first time I went low on REs was when John Laughlin was codriving my car and he suggested that first(I used to run ~35-ish on the RE, then after that I dropped it a lot). One of the even when we were really hurting on tire wear(almost cording the fronts) we up the pressure to help the wear and the car immediately got way pushier and we just went back down and just forget about the cording....lol

I think normally the behavior of our car when it was fast was it was pointy but never really sliding, once you can get the nose pointed you can really hammer the throttle on the car with the diff and it just sort itself out most of the time. Going into Type R after was quite different in that respect, but we still sorta drive it similarly as the GTI and it still kinda works.
 

RacingManiac

Go Kart Champion
Location
MI
Also in general I am super interested to see how STH setup shakes out. I kinda want to do STH before but with the clutch thing wasn't cleared I wasn't gonna go that route. Now though it seems to be an interesting place. I think GTI can be a super fun STH car. And in theory you can right all the wrongs with the stock trim.....
 

SonicBloom

Go Kart Newbie
Location
Bay Area, CA
Car(s)
2017 GTI S
I think you should try 40+ in the front just to see and to get your opinion on it. On the GS Si, I ran 40F/30R and always liked it and was very competitive. I'm kind of sticking around there until I figure it out more.

@xXDavidCXx have you ever asked Ron Williams what pressures he runs on his Si?

I have an event on Sat and I’m going to try your suggestion of 40F/30R.
 

bfury5

Drag Racing Champion
Location
CT
I think you should try 40+ in the front just to see and to get your opinion on it. On the GS Si, I ran 40F/30R and always liked it and was very competitive. I'm kind of sticking around there until I figure it out more.

@xXDavidCXx have you ever asked Ron Williams what pressures he runs on his Si?
I'll give it a shot, last year I started at 38ish and boiled down to ~36 front. I never had any sidewall roll over or push so I just didn't have a reason to go higher based on what the car felt like.

Edit: I see the need for increased tire pressure in a GS trim car, to prevent tire rollover with a stock spring setup / pinched tires, just haven't seen that same need (in my experience) during my STH adventure
 

xXDavidCXx

Drag Racing Champion
Car(s)
2017 GTI SE DSG
I'll give it a shot, last year I started at 38ish and boiled down to ~36 front. I never had any sidewall roll over or push so I just didn't have a reason to go higher based on what the car felt like.

Edit: I see the need for increased tire pressure in a GS trim car, to prevent tire rollover with a stock spring setup / pinched tires, just haven't seen that same need (in my experience) during my STH adventure
What's your normal surface like?
 
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