Understeer Problems

Hi Guys I wonder if I could call on your vast knowledge yet again?:thumb: Now the snow has finally gone I have ventured out of the garage. I'm new to driving Porsches but I would guess the driving / steering would be pretty pin point accurate?? Although when I turn my car into a corner the front seems to slide and not grip, then all of a sudden grip and turn in?! Surely this isn't right.......is it? Also when at considerable speed (150mph) the front becomes very light......is this because I've got the big carbon wing on the back, although I do have the MK1 GT3 front bumper? I've got the car booked in for 4 x Pirelli P Zero Rosso Tyres (it has these on already) on Saturday and the car has just been geometrically laser aligned. What can I do to combat these problems? Please help....... :worship: Regards Lee

Lee, What tyre pressures are you running and who carried out the geo? I always have my car set up to dial out some of the inherent understeer that exists within the 996. I also never run anywhere near the manufacturers recommended tyre pressures. On my 996tt I run the fronts at 32/33 and the rears at 38/39. With regards to the light feeling at high speed (track or autobahn of course) this is quite characteristic of the car but in your case may be made worse by the aerokit you have on .

hmmm.....the rear aero kit looks to have a tad more downforce than the std GT3 so yes it is possibly affecting the lift on the front. used GT2 type front PU's can be had for about £200 and offer more downforce(but will slow you cars top speed by 3/5 MPH). This "may" be an option/fix. I have previously written on here about having/ensuring balance between the front and rear aero units above 140mph so do a search if interested. Trial and error can often be the norm when you step out of the official/tested/approved Porsche aero kit arena. You "may" have an aero imbalance but it's a difficult one to confirm. Q: What suspension are you running? A lowered car will usually sit/behave better at high speed. Try running the fronts at 29/30 psi. I run Rosso's with KW's and the front grip is excellent.

+1 for the lower tyre pressures. 911 sport lowered mine on a back to back run from thier place and this has transformed the handling. i have Pzero Rosso's all round, not too sure if i like these tyres yet though as i dont use the car too much.

Thanks Dave I put 34 in the front and Imperial Tyres of Swindon did the laser alignment. I'll try lowering the tyre pressures and let you know.

Thanks Wizard993 I'll check out your thread, got to be worth a try!! The car has the M030 factory fitted suspension, I think It's 30 mm lower not sure what shocks it has on there, as not looked. Although for a start I'll try lowering the tyre pressures. When you say 'used GT2 type front PU's' do you mean the complete front bumper from a GT2? Are they deeper or have a larger skirt? I'd love to sort out this problem because at 150 mph my car feels like there is plenty left! But feels just to unstable to give it anymore...... :dont know:

Thanks for the reply deccle what tyres would you recommend then? I've read up about the P Zero Rosso and it say on the blurb that you get a lot of feed back from the tyres and there is normally some warning before the back end suddenly breaks away......Ooh er!!! I've got continentals on at the moment, but I lost the back end the other day with no warning at all........although in their defence they are at the end of their life.......so not really sure now???? :?:

I would say you need a proper geo, not just laser alignment. You should also get the ride height checked, I wonder if you are running a bit nose up to create this result. Someone like Chris at Center Gravity will check and correct all of this. With regard to tyres I had Rossos on my car, a 993 in my case when I got it. I can't speak with authority about 996s, but the day those tyres came off was a milestone in the handling of my car. I will certainly never have them again. Finally regarding understeer into corners, pretty much all 911s do this to some extent (though yours sounds excessive) but technique can overcome it, if you trail brake into the corner and keep more weight over the front wheels you will keep the fronts loaded up and significantly reduce understeer. I used to think I had an understeer problem until I learned to drive ...

Absolutely agree with lowering the tyre pressures .I have done so on all my past 911s to good effect. On the 996 I run about 30 front 33 rear. It stops the car skitting about at the front on turn in in bumpy roads. seems to give more grip, and has the side benefit ob being far more comfortable

RE understeer, have you thought about changing your anti roll bars to the GT3 type? You can 'dial' out understeer but adjusting the droplink positions. This worked for mine, I also run lower tyre pressures 34f, 38r. A good geo will also dramatically improve the understeer and high speed stability. Also, I would have thought your aerokit wouldn't cause this light front feeling. Your front PU produces almost as much downforce as the RS style PU which matches your wing. Like others have said I'm going with tyre pressures again. :thumb:

Thanks Tertius for the help I'll definitely look at 'Center Gravity' any ideas on cost? But I love the quote at the end. You may have hit the nail on the head :floor: I wondered where I was going wrong :worship:

Thanks again Stuart :thumb: Do you mean I should change this part '996 Anti Roll Bar Kit ( Sports M030 option )' Pardon my ignorance but my mechanical skills are very limited. I'll go with the general consensus first of all and lower the tyre pressures, then I'll see about swapping the anti roll bar & get the cars geometry checked, because when you look at it from the front the front does seem to sit higher than the back.:nooo: I'll keep you all posted on the findings & outcome and thanks for the help yet again. Looks like the beers are on me when / if I meet any of you! :thumbs:

Well as it happens I was sorting through my invoices this morning and have my CG bill in front of me ... last year he charged me £450+VAT for a full geo, setup, ride height adjustment and corner weighting. However, at the same time he fitted new suspension (obviously at extra cost) so it may be different if you are just having your existing suspension checked. Call Chris on 01827 718800 and have a word. He is incredibly helpful.

911 sport changed them to 28 front and 32 psi rear. its a lot lower, but made the rear a lot more stable. asked the usual questions about tyre wear, but was reassured that this would be minimal. spoke to an old 911 driver about this who rolled round laughing that i was still on the 'factory' settings and told me the lowering the pressures was well known in 911 circles (made me feel about 1" tall!!) Dan

center gravity i had same problem with my c4 with aero kit,fitted m030 suspension and had it set up for welsh roads by chris at center gravity,not cheap but totally transforms the car mo30 i believe lowers by 10 mm mine is awsome now and handles like a go cart,turns in as fast as you can blink.