Tyre tracking

Would you expect the tyre wear to be even across the front tyres.Looked at mine and both inner edges are worn equally across the first two inches.Is because of RWD or something else needs a check

If you don't know if its been done, its worth spending some £££ on a proper 4 wheel geo check, either at OPC or better still Chris Franklin at Centre Gravity. Not only will it mean that the tyre wear can be checked out, but you'll know its handling as it should, and 911s are sensitive to small geo changes.

handling "problem" over a ton I have a 996 C4 and it is plain scary over 100 MPH. I bought it with 19 inch wheels and it was made with 18 inch and I am told that this could be the problem. Do you think the geometry could make this better or tyre pressures ?. I am at my wits end as the car is lovely below this speed but I would like to find someone brave enough to drive it over the ton and feel safe. I have spent a fair bit getting it really nice with ALL parts like toolkits, compressors, manuals and spare keys as well as a good service, fitred missing under tray and air ducts. It is my dream car but my last car ( Alfa) was much safer at speed. I could cry right now as no one seems to be able to answer with authority and that includes the Porsche centre. Thanks in advance

1. Inner front tyre scrub is normal, absolutely normal. Boxsters and 996 rub in this way and it's the standard (and correct) set up 2. I wouldn't recommend (and nor would Porsche) having a Geo done to "correct" the inner tyre scrub as it adversely affects the handling. 3. 19" wheels are not recommended on the 996 (and a little known fact is that the 997 wasn't designed for 19" wheels either and were only added after pressure from the marketing department), but 19" wheels should not cause the instability problem at higher speeds on the 996. Floaty front end is usually tyre pressure, or tyres low on tread (ie. less than Porsche recommended 3mm wear). Experiment with the pressure and try slightly lower PSI than Porsche specification. It might be balancing, but this is usually seen as a vibration affect through the steering wheel. Check to see if your wheels have lost any of their weights. It could be the Geo setup and on an older car, I'd recommend getting this completed anyway. Finally, don't rule out tyre manufacturer, as this also has a bearing on the performance. Michelin Pilot Sports are highly recommended, as are Continental. Pirelli have mixed reviews, but are N rated and wouldn't provide the results you are experiencing. I run Yokohoma's and I think they are great tyres. The only problem is that they don't manufacturer these as 285/30 (only 265/35, winter specification or pre-facelift 996).

Re: handling "problem" over a ton Have you got an aerokit rear spoiler or something - without the matching front spoiler? This would make the car quite dangerous at high speed. If you have the standard spoiler - make sure it is lifting at speed: If it isn't you will have very significant aerodynamic lift and will cause the car to 'float' - again very dangerous at high speed. Also, check tyre pressures (as above) I don't think geo alone would give these symptoms, as it would feel strange at all speeds, with poor steering feel, etc... The high speed only nature points at an aerodynamic problem IMO.

Re: handling "problem" over a ton :? what is the significant difference between a rear aerokit and standard spoiler in terms of performance? A car with the standard spoiler can be driven fast without a front spoiler. TB

reply to answers Thanks to you all, I do not have an extra spolier and only have the one that lifts automatically and I'll double check to make sure it is opening. I would be surprised that this could be the problem to be honest but am here to learn from moire experienced people. I will get the geo checked anyway but, like I said, it drives beautifully below a ton and has no sterring wheel vibration at all or drift in any direction. I hope somone can help as this is truly getting to me and is making me quite obsessive and upset. I had the tyres at 30 psi FRONT and 44 rear and have lowered to 30 front and 34 back, it is a better ride, less hard but still floaty at speed. Thanks for your answers Jools

Personally I think that's too much PSI drop. I wouldn't do much more than 10-15% within spec...and it's the front you want to experiment with, not the rear. The spoiler on the 996 isn't really a spoiler, it's just to aid cooling to the engine. The GT3 rear spoiler changes the airflow of the car and should be fitted with side and front aprons to ensure the the front gets a similar ground suction as the rear, as Wattie points out. Otherwise the front feels floaty.

PS if that doesn't help, suggest you get a geo done.

Very strange cause every Porsche I've ever owned has felt far safer over 100 than under when you can feel the aerodynamics come into play. You don't say where you are but I would take it to a good Indy who does geometry set ups (cause they more likely to have come across the problem before) rather than a OPC. I'm guessing there is a simple solution so don't give up.

Sorry GD, but you are wrong there - at high speed the lifting rear spoiler is absolutely critical and has virtually nothing to do with cooling the engine really (it is water cooled remember, and has no cooling fins on the block or anything) Ask the families of those killed in early Audi TTs if you don't believe how much difference a small spoiler makes at high speed... Absolutely - all the larger rear spoilers (especially those with winglets of any description) massively increase rear downforce and if you don't increase front downforce to match they will effectively lift the front wheels off the ground at very high speeds - which doesn't help very much with the steering

Re: reply to answers Those pressures sound much too low to me? On 18" wheels they should be 36 front and 44 rear, and I would be surprised if they should be less for the bigger lower profile tyres... I would have thought higher if anything :?: The ride quality on correctly inflated 19" wheels is terrible IMO: Having just had a 24 hour test-drive in a 997 fitted with them, I found it totally unacceptable - the car was bouncing around all over the place on bumpy roads - but I wouldn't describe it as 'floaty'. Check your rear spoiler though - if that isn't lifting, that will definitely cause the problem. Also, are the tyres N-rated? If not, maybe the sidewalls are not stiff enough (which will be compounded by low pressures)

I had the pleasure of taking my car down to, and around "The Ring" earlier this year and I found my car got more stable the faster I went...I am perfectly happy with the standard aero on my car with 44psi in the rears and 36psi in the fronts. I never felt floaty once - light headed with the thirll of it...but never floaty Sounds like your flip up spoiler isnt flipping up and/or incorrect tyre pressures or (forgive me for sounding patronising ) you are not used to driving a sports car at speed.

Oi - Getting back to the question!!! I don't think the inner two inches should wear on a standard car - to me that shows camber has been added and I suspect your car may have been set up for the track?? LOJO

Thanks to all I took her to 160 MPH today, naughty but nice. I felt a considerable difference AFTER 120. Maybe the aerodynamics come into play after that speed ? I do not know but it was lovely. I added a little pressure to the front wheels, 34 PSI and then 38 at rear. It's a labour of love as our speed limits don't allow to try but I am going to Germany next month so needed to know I am safe. Thaks to all Jools