Tram-lining horror

Hi All I have just become a first time 911 owner – a 996 C2 Tiptronic. Generally I like the car especially on a smooth bit of road but unfortunately they are few and far between where I live. The drive is shocking round town with it tram-lining all over the place making it not exactly undrivable but certainly not relaxing. The tracking and suspension has been fully checked so I dont think there is any worries there. I know many cars can be very susceptible to tyre choice and I'm wondering if this could be the case here. My car is shod with brand new Pirelli P Zero Rosso 285 30 ZR18 N4 at the rear and P Zero 225 40 ZR 18 N3 on the front - which seem a popular choice Anyone have any suggestions? I would be 'happy" to change all four tyres even though they are hardly used if it cured the problem. It would be cheaper than changing the car so soon, as I couldn't put up with this for long. Cheers

Are the front brand new as well or just rears? A pedantic but relevant question it reads like you have Rossos rears currently N4 rated (they dont make Assim in 285 now) and you have Assim fronts as these are currently N3 rated? If so I think you'll find this is contributing to the handling issues. They have different treads and different characteristics. I am sure I read somewhere in teh past you cannot mix these. You may find it better to get Rosso fronts too, at least they are cheaper than the rears. Also, who did the check of the suspension/tracking? 911's are different and require specilist setup not just any old place.

If you want to be sure its the tyres, and you aren't a million miles from me, you are welcome to come and try out various different wheel and tyre combinations on your to see the difference they make. Im nr Watford. :thumb:

Hi Chris Yes they are Assimetrico's on the front. The suspension / tracking was done by a Porsche specialist...mind you it was the same place that fitted the new rears so.... You're a reasonable treck from my home but I might take you up on your offer! Thanks for the help.

Hi Smudge - Have you also checked your tyre pressures? 911s are sensitive to changes in pressures. What pressures are you running? When I had my 996 I was running 32psi front and 40psi rear using the same size tyres as yourself. These pressures are below the recommended levels but a lot of people on here seem to run their 996s just a bit below recommendations for one reason or another. Mine was for a more compliant ride. I did once run at the recommended 36 front and 44 rear but this made for a rock hard ride, unpleasant driving experience especially around town and a very rattly glass roof (mine was a Targa). ~ Maxie

Who did the tracking? A full four-wheel geometry check on a 996 is very specific, I would not trust KwikFit. I would ascribe to the recommended pressures if the geomtry is correct. I would also suggest all tyres are the same manufacturer, design and N rating. N rated tyres are designed to comply with specific Porsche high performance requirements. N rated tyres are needed because in the 996 the chassis/suspension development was integrated with the tyre design and in the 996 installation they must pass the following: Compound mix designed to suit the vehicle handling characteristics The rear mounted engine placement poses particular handling issues (there is only so much the suspension design can control without the correct tyres) Designed for factory wheel camber and and toe settings (which put particular stress on middle and inner sections of the tyre). Designed for (relatively) high standard pressures (36/44 PSI F/R) Unlike some other vehicles, which allow mixed axle tyres (same tyres per axle though), Porsche specifically advise against this practice and state the same brand and design should be used on all tyres. See here: http://www.911uk.com/viewtopic.php?t=51071 http://www.911uk.com/download.php?id=10981

GT4 - as you are located quite close would you be interested in a blind tyre testing afternoon sometime? Nothing lairy just switch around a few sets of tyres, including some non-N rated and see if you can notice the difference, on normal roads at relatively normal speeds? I think there is a lot to be said for N rated rears, less so on the front. If the tracking/geo has been done correctly I'd put money on the PZ Asim's being the culprits, mixed with Rossos on the rear.

I agree that is the most important issue. Mix-and-match tyre tread designs on a shopping hatch can lead to handling woes, let alone a precision sports car with its own *cough* - ar$e engined -*cough* "issues". As for a tyre swap, thanks for the offer, but my OCD couldn't cope. Last year my car had new tyres (Conti SCIIs N2 all round), new bushes etc and a full geo. A Porsche tuner I took my car to a month or so later took it for a 20-30 min test drive, he seemed genuinely either surprised or appreciative when he said it was the nicest handling 996 he had driven. I won't be fixing what isn't broken.

Is it definitely tramlining (front end getting pulled around by camber or longtitudinal ruts) or does it feel like the rear is unstable leading to you having to make lots of steering corrections? If it is tramlining I very much doubt it would be due to mixed N ratings front to rear. If you're absolutely sure the alignment is spot on I'd look at the following... Tread depth on the insides of the front tyres... mine tramlines like a bitch at the moment as the far insides of the front tyres are right at the legal limit. It's fine on rubber with a bit tread depth. Front suspension bushes (in the bottom arms)... worn bushes allow unwanted movement in the suspension when under load. Like GT4, I had all 4 bottom arms replaced and a full 4 wheel alignment (at a Porsche specialist) at the beginning of this year and it transformed the handling. Do you have any squeaking over speed bumps (a usual sign of worn bottom arms... but could also be worn top mounts)? Tyre pressures... IMO, the factory recommended tyre pressures (36/44 cold) are far too high. I run mine at 30/38 cold. The car rides better, feels far more settled under higher speed cornering and improves steering feel and weight too. Hope you get it sorted as a well set up 911 should be a joy to drive.

Cars that have track orientated settings with adjusted cambers and toe-in do tramline a lot. If you have bigger wheels and lower profile tyres it make matters worse Best thing to do after checking the pressures/tyres is to get the geo checked and put back to std(if applicable) Even on std settings a 911 driver will still get more tramlining than usual.

Hi Smudge, Until last week I had similar symptoms with my 996C4 with 5 year old pZero Rossos. The rears had only 3mm left but had been much the same with 5mm. I don't know if the wheel alignment had ever been checked. On Friday I had 285/30R18 and 225/40R18 N4's fitted and filled with Nitrogen. The pressures were set at 36/44 and I had the wheel alignment checked and adjusted to within 'tolerance' (ie not to exact 911 standards but done using the Corghi laser equipment I've seen at ordinary main dealers). Yesterday I did the 160 motorway round trip to Windsor and the ride was superb. The car tracked straight and true and all the jitters and tramlining had completely gone. It was like driving a much newer car. Obviously I don't know how much of the improvement was down to each thing but it was certainly £750 well spent.

Very interesting post GT4 Basically to add to GT4's advice I would check if everything conforms to factory specifications. Has aftermarket suspension been fitted? Has the car been lowered Has aftermarket bushings been fitted Has wheel sizes been changed from standard? Then make sure that the camber, ride height, toe settings, Castor and alignment are all within factory tolerances. If you ensure that all the above are returned to factory recommendations then I would feel confident that your problems will be solved!

As already said by many, I'd bet if you changed the fronts for new PZero Rosso N4's your problem would be cured. I run PZero Rosso N4 all round and have no problem with the ride or tramlining. I did notice prior to changing the tyres that the car tramlined quite a lot on the old worn PZero Rossos. When I fitted the new tyres the improvement in ride was remarkable. I've seen this on other cars too - previously I've had a Honda Accord Type-S which tramlined badly on very worn Bridgestone Potenza's but when the tyres were replaced the ride was perfect. I know there's been a lot of debate on tyre pressure but I find the Porsche recommended pressures best.

+1 I had new Rossi N4's all round last week and had the geo done and my car has no sign of tram lining at all

Thank you Thank you all for your replies. I am genuinely surprised at how helpful people have been. So much for all 911 drivers being ********s ! :thumb: I bought the car from RSJ Sports cars ( I'm sure some of you will know them ) so everything "should" be fine apart from the tyre choice. I will get back to them to see what they say regarding the tracking and / or their tyre choice. I had hoped it will be something as simple as incorrect tyre matching as I would go as far as saying my current set up makes it drive like a pig! I was always a Ferrari man (before children) and I had hoped this wasn't just part of the 911's 'character" !