Doug H

I have 8/32s PZeroes. I typically do not like PZereos so it could just be tires with less than optimal grip in the front. Well after turn in and in the middle of long, high speed sweepers, my fronts start grabbing for traction/understeering way, way, way before the back end even thinks about coming loose. My previous street 997s, including turbos with the wider rear track, generally slid pretty neutrally.

Anyone else notice this in the GTS be it cab or coupe? Does a larger front help and has anyone tried to dial out some of the safety net toe they put in these 997s?

Honestly, it feels like crappy front tires when I throttle steer it through some hard sweepers. The rear has tons of grip though and they are the same tires.

porscheralph

Might check your front tire pressure.

qikqbn

How old are the tires? If the tires are several years old they may be drying out and losing a lot of grip regardless of how much tread is left. I am a big fan of the Michelin Sport 4S if you ever need new tires.

If new tires don't cut it, then I would recommend a stiffer rear sway bar. I dialed out a lot of understeer with a thicker GT3/GT2 spec 25mm adjustable sway bars made by Eibach and designed for the 997 Turbo car, but should fit on wide body GTS as well.

The 25mm Eibach bar thickness is the same thickness recommended for GT3 or GT2 stock. With this bar you have to use GT2 Bushings as well in order to work with the 25mm bar thickness. I also purchased new oem droplinks just to keep things fresh back there. Car turns in much sharper now and a lot less understeer.

-REAR ANTI-ROLL Kit (Rear Sway Bar Only) 7217.312 Rear Sway Bar is Tubular and 3 Way-Adjustable. 25mm
https://eibach.com/us/i-2419-rear-an...-bar-only.html

-GT2 rear sway bar bushings required in order to fit around fatter rear 25mm sway bar. Part # 997-333-792-95

Tcc1999

FWIW, I have had the same issue with P-Zeros (stock suspension). Playing around with tire pressure helps a little, but I think you are on the right track (sorry for the pun) is placing a good deal of the blame on the tires.

platinum997

How are you entering the corner? If your hard braking and immediately turning in, the springs are unloading and because of weight transfer can cause a bit of understeer. Trail braking to keep load on the fronts or giving the car a bit to settle before turn in will help.

If your hard in the throttle all the way through, lift the throttle a bit to "rotate" the rear. Lifting shifts weight back to the front which gives more traction up there and loosens the rear.

Outside of that, tire pressures, increasing front camber and toe in will help.

Doug H

Thanks, but as indicated above this well after turn in and during throttle steering so I am at absolute limits of the car and using tiny adjustments in throttle to slightly alter balance, grip, arc, slip angle and etc.

i think the tires suck and are a tad over-inflated. The car handles remarkably well for a street car. It’s more of a manner in how the front tires feel when exceeding the limits and the manner in which it is communicated through the steering wheel.

I usually take the Porsche oversteer safety net toe out to make them more neutral. I will probably ditch the PZeroes and put some new tires on here and get a more neutral alignment. Makes front tires last longer and I rather have a bit of oversteer tendency than understeer.

Petza914

If you're RWD and and AWD, you can also go up in section width to a 245 or even a 255. I looked at front and rear clearance on my particular c2S with the custom Forgeline wheels and my next set of tires will be another set of Nitto Invos, but in a 255 35s on the front and 325 30s on the rear. The slightly larger rolling circumference might also correct the 2 MPH speedo error that Porsche builds into all their cars. Front wheels are 8.5" and rears are 12". The current 305s are too stretched on the 12" wide rear even though that's Porsche GT3 fitment spec and I want a straighter sidewall and more rear traction for the HP I'm putting down. Because of that I need to recreate balance at the front and that's why the 255s.

In your case, leave the rear size as is and increase the front

Bruce In Philly

2009 C2S 145K miles

Back when I was tracking my 2000 Boxster S, the car had fairly persistent understeer using factory alignment and tire pressures. To remove the understeer, I just changed the front tire pressures. They guys at the track knew exactly what to do and gave me the exact pressure to use. The car became perfectly neutral. I was shocked and how much understeer could be effected... a real education on the importance of tire pressure on traction. I would experiment with pressure before spending any money. Again the amount of change was profound with just a few pounds.... oh and tire temps were also very important... you had to get some heat in the tire first before you can judge. If you are doing this on the track, you need to heat them up first... on the street... well maybe setting them neutral at cold temps is the way to go as we don't get much temp into our tires from normal or even aggressive street driving (in my experience).

Peace
Bruce in Philly

roadie13

I second modifying the tire pressures first before looking at hardware.

I started tracking my new to me 997 this year and, coming from an E90 M3, I had a horrible time with understeer.
Ultimately, I found out that the tire pressure advice I had received from various sources (including a motorsports shop) were just plain wrong.

What worked on my 997.1 S with 245/305 RE71R tires is 32/38 hot; the rear must be significantly
higher in pressure than the front. With this combo the fronts are wearing to the triangles and the rear end is mobile enough to give fairly neutral handling.

So I would adjust the front hot pressure using the same method (wear down to triangles) and then bump up the rear until happiness ensues. I would not be afraid of hot rear pressures in the 40s if that is what is needed.

Good luck and keep us posted!

semicycler

Sounds like roll steer effects due to a lowered car. Is your car stock?

Doug H

Perfect info. I was wondering if others put 245s on front to balance the wider rear track. Did I read correctly the rear track on the GTS is 44 mm wider than the C4S?

I think getting new and better tires along with dialing out the factory toe/understeer will be even better. It was a strange push feel in the steering wheel like bad tires when limits are exceeded.

The car drives and handles amazingly otherwise. This could very well be one of my favorite all around cars I have owned.

Doug H

Yes. Completely stock suspension and wheels. Thanks for the input though.

Doug H

Thanks much for the input. If tracking, the best way to tell ideal tire pressures is using a pyrometer to measure temps across the entire surface of the tire after a session or after they are hot. This will let you get dialed in to keep optimal contact patch when tires are hot.

Doug H

Yes, I can generally feel simple tire pressure issues on fronts by how they communicate through the steering wheel in how they behave hot or cold at the limits. These tires reminded me of a dry rotted inconsistent, grabby feel and not a smooth release I typically get with better tires. That would be indicative of bad tires or how Porsche sets up their street cars to understeer as a safety net for 99% of those buying 911s.

Took toe out of my wife's 997.2 C2 and the car was completely neutral and would slowly, gently and smoothly slide neutrally once 10/10s was in the rear view mirror. It was so easy to let the tail out and keep it there as long as you wanted. Not looking to shred my GTS tire yet, but I doubt very seriously I could get it there without an abrupt lift mid corner.

Petza914

Yes, others have run 245s or 255s on the fronts, especially some of the GT3 guys. The GTS being a widebody has a wider rear track but the tire seciton widths are the same as the NB, the wheel offsets are just different so the total track width is wider, but the contact patch size is the same when running standard sized tires or the same size tires between a NB and a WB.

You could certainly go to a 245 without any drama or concern. A 255 might require some clearance measurements at full lock and load if running standard wheel offsets.