Harmonster

Trying to tune some oversteer out of my 997.2 gt3. It rolls more than I’d like so I don’t want to soften up the rear bar. Wondering if anyone has had luck w adjustable coilovers / different spring rates.

For reference
- stock shocks/springs w 35k miles
- dsc
- rear toe rod, rear upper control arms, tie rod ends all spherical from rss
-2.5 f / -2 r camber, 0 / .1 deg toe f/r
- NT01 245 and 305
- one from hard front, middle rear on bar
- guard diff

Veloce Raptor

What track?

Frank 993 C4S

Corner entry or corner exit? High speed or low speed? What do you mean by "It rolls more than I'd like"? What kind of roll bars? Have you tried stiffening the front bar all the way? What does the oversteer limit - Trail braking or throttle application? What tire pressures are you running?

good hands

This was very helpful when I was running coil overs and remote shocks.

https://www.pegasusautoracing.com/pr...yABEgJhiPD_BwE

gbuff

https://speed.academy/how-to-fix-und...-setup-tuning/

jdistefa

Good intro piece. Dave Pratte is a good guy and very capable shoe... and he writes well.

Excellent hint about mid-corner roll coupling

911ted

Anything less than a 265 tire is a battle always being fought against understeer IMO.

smf32s

I've got a set of Motion Control 3 way adjustable dampers with springs with only one weekend on them. I'll cut you a good deal. The owner of Motion Control set them up for me. They are for a 997.2 Cup but should work on your car. I'm sure they would help set you up.

Let me know.

Stu

Harmonster

Thank you for the links and comments - all helpful. To clarify my question, I'm speaking less to 'how do I tune the oversteer out of the stock suspension' and more to 'what real world result did folks get when upgrading to a good motorsport coilover on a 997 track day car'. Hope that makes sense as it's a big investment.

Most notable at Buttonwillow. Bus stop (the entire complex), Riverside, and sweeper are where I feel it most - causing me to lift or be less aggressive than I'd like. Consistently running 1:59.


Re corner entry: Mid-corner and exit. Corner entry car feels good. Mix of mid and high speed as above.

Re roll bars: Roll bars are stock with stock links. As above, 2nd from hard on front and middle on rear. Admittedly I have played less with the bar settings than I should.

Re "Rolls more than I like": This is related to (a) how the car feels in transition (significant body roll during direction change) and (b) a sensation that the car has to roll and plant before it is stable in corners. When I turn in, it feels like the rear needs to roll and squat before there is grip - I'd prefer the car be flatter and not need the squat.

Re Oversteer limits: Oversteer is limiting both trail braking and throttle application - I'm more concerned with the throttle application. I prefer how the car feels on throttle with the diff working so I am generally on light throttle pre-apex. My feeling is that the car should have enough grip to go full throttle much sooner and longer, but the oversteer and roll are sapping my confidence.

Tire pressures are 32/33 hot.

jdistefa

Sounds like you would benefit from adjustable shocks.

Squat is part of the 911 experience.

You need to do sway bar sweeps to understand what they do re. roll coupling and balance, particularly mid-corner.

Being on-throttle before apex is a big hint that a) your Vmin is too slow and in the wrong place, and b) that you feel better with LSD lockup prior to apex likely because you don't feel confident about the rear of the car.

You would probably benefit from having a pro drive the car and help you with setup.

My 0.02

2BWise

Roll angle is actually pretty hard to subjectively evaluate. A car that rolls 2 degrees and one that rolls 3 degrees is pretty much imperceptible. What is more likely is that the roll velocity is what you are picking up on. Generally that means you don't have enough roll damping, especially if you feel as though you have to wait for the car in transition before adding any further inputs. Likely, that means going to aftermarket dampers with either more control or going to an adjustable set.

Frank 993 C4S

^^^^ This

fleadh

What's the diff break away set to?

Everything you posted about your setup sounds like it should be understeering everywhere, IMO. Apart from having a Pro hop in the car and do 1 lap to verify what you're feeling -- if it were me, first I'd make the rear bar fully soft just to see if that has any improvement (it doesn't matter what you feel or think about too much or too little roll). Then I'd add a bunch of toe-in on the rear (and make both L/F the same... you're not driving at Lime Rock). Also, put the car on jack stands and give both rear wheels a hard wiggle/shake left/right and see if there's any movement.

Also, is the balance the same throughout the age of the tire? Have you tried fresh tires?

The ride height on a stock 997.2 GT3 isn't adjustable is it? If it is, lower the rear 5mm.

-mike

audipwr1

Dan just bring it to laguna 4 day event and I'll drive it / they cars do roll and set.

You def wanna be on gas going over bus stop!

Apex996

Nobody answered the questions. Your tuning options on a stock suspension are very limited. Camber, Toe, Sway bars.
And yes a true track oriented set of springs/shocks can dramatically alter the behavior of the car on track. Dramatically, as in addition to a stiffer platform you get the ability to also adjust corner weights, rake, and more with adjustable suspensions.
Something tells me you want this car to retain it's daily driver comfort ? It's a tough compromise if you want to go fast.
With stock springs its going to roll. A lot... Plain and simple. It's going to roll enough that your -2º camber may not be enough to stop the tire from rolling on to the sidewall. Have you marked the tires to check the rollover?

But here is a question... and hear me out on this... How do you KNOW it's over-steering?
The 911 is a unique beast. With no weight over the front and most of the weight behind the rear axle you get a very different sensation when turning the car into a corner.
It's all about roll rates and their timing. As you turn in to a corner the front begins to roll and then the rear begins to roll. No different than a FWD GTI or Front Engined/ Rear Drive BMW at this point.

But at some point as the weight transitions, the light front end will complete it's transfer and therefore stop rolling.... while the rear (wait for it) is still transferring weight and still rolling. This is where it's different than a front engine car.
So while the rear is still rolling (taking a set) your brain may think it's over-steering.. but its quite possibly not ! It's just out of phase with the front and finishing it's weight transfer.

The bus stop is going to be tamed with shocks as shocks control your transient response. The sweeper is going to be spring rates and camber. Shocks do very little in sweepers once the car has finished rolling.