Rear tyre wear

Hello, I have a 53 reg 04 model yr 996 C4 31k mls with MO30 suspension 225/40/18 tyres on front. 285/30/18 on rear all Michelin N1 Had mot at OPC today. Rear tyres are wearing on the inside again despite supposedly having geometry set up when last new tyres were fitted at the OPC due to rear tyres being down to canvas on insides. Have been told at OPC that geometry can go out within a fortnight due to our poor roads etc- a good excuse!!! and that it needs doing again. I treat the car like a baby, missing potholes and walking pace over speed humps etc If the geometry is set correctly should the rears wear even or scrub the insides off??? It is a wicked shame to have to keep changing tyres due to only the inside 30mm being worn whilst the rest is ok All comments and help appreciated. Many thanks, Chris Chappell R7

Hi Chris. I have a C2 996 MY 2003 with M030, 23k miles. The car is used for high days and holidays and always driven very carefully, I've owned it for 5 years. I had exactly the same problem as you have when I first bought the car - from an OPC. As you probably know, part of the 'deal' of buying from an OPC is that they sort everything out and service the car, 111 point check, blah, blah, rip-off, blah, blah..... Following covering just 1,200 miles in the car the inner shoulders of my rears disappeared (all tyres are same dimensions as yours). I only noticed this as I was washing the car at the rear and was washing the underside of the car. I was horrified. To cut a very long story short, it tuned out that the the OPC had not done a four wheel alignment at all. This was [not] recorded on their pre-sale check list so it was pretty easy to [not] spot - if you get my meaning. Anyway they ended up footing the bill for two brand new rear PS2 tyres and a new four wheel alignment at my local OPC (the one that I bought the car from is hundreds of miles from where I live). Following this my OPC then set the car up for an X74 (-30mm) lowered suspension geometry - this was despite my asking the OPC technician to come out to the car with me so that I could personally show him the car and explain that it didn't have standard suspension but M030. I was only able to see that they done this because I asked for a print out of the pre and post geometry measurements and I could see that they were wrong. In particular, they had dialled in far too much negative camber on the rear - they'd set it up for a GT2 or GT3 911 that have the X74 set up. I then gave up completely, refused their offer of 'having another go at it' and took the car to a wheel alignment and tyre specialist about 50 miles from where I live. When I got there the owner took me under the car and showed me that the near side locking nut that secures the alignment adjusters for that side was completely seized. He stuck a long reach ring spanner on it and hung off the spanner with his feet off the ground. "I'd say that hasn't been moved since the car was made" he told me. Great. He then made me a coffee while we soaked the nut in Plus Gas and other wonderful stuff to get it shifted. It worked and we sorted it out. He charged me £70. I'd already spent £150 (discounted price) at the OPC but by this point I just didn't have the wherewithal to go and get my money back. Crooks in suits and lying bas**ards too. When all was said and done I asked the OPC why they'd set the car up for X74 and not the M030. Their answer? "It was the closest match to the M030 that we could find on the geometry machine, sir". This is not a lie. There's a tech Guru on here called Richard. He sent me the PDF files for the correct settings for M030 and X74 so that I could compare and contrast. If you don't get them from him send me an email and I'll forward them to you. Sorry for the long winded reply. I don't know where you live but there's a very well known and reputable wheel alignment specialist here: http://www.centergravity.co.uk/ if you can get there. I plan to make the journey one day! All the best. Let me know how you get on. Adrian.

Excessive inner shoulder wear is very often caused by incorrect rear toe. Rear camber has much less of an effect on wear IME. Take it to Chris at Centre Gravity and you'll be amazed at the difference.

Hi Adrian and Nick and thanks for your replies. Why is it that these OPCs are supposed to be the best thing since sliced bread but still seem to cock things up time and time again?? It is about two years since my geometry was supposed to have been set so I suppose I have little hope of them sorting it out but I am left with footing the bill for new tyres. You can bet that the geometry has never been set up just as yours wasnt Adrian. I will probably print your story out and present the OPC manager with it as it is a dead ringer for my experience, or maybe I would be better off forking out yet more money to sort out their cock up and go to somebody who knows what they are doing Of course if the OPC is accused of such negligence, they will deny any such wrongdoing and emphasise their expertise and state of the art equipment. Best regards, Chris (Leeds)

Think of it like this: you wouldn't go to a GP if you wanted heart surgery, would you? An OPC can't hope to compete with somebody who does nothing but geometry every working day. 911's are very sensitive to geo and although it's not impossible for a mechanic with the right tools (which OPC's do have available) to set a car up accurately, it's quite rare by all accounts. Chris has OCD & this is a definite advantage when doing geo on a car where minutes of a degree can have a significant difference. 2 years is a long time between geo's - mine gets two a year!

+1 on Center Gravity. The best customer service I have ever encountered, has not yet been matched by anybody else - not even close. Chris is a brilliant guy and completely transformed my car, and despite being a 300 mile all-round trip for me up there, it was worth every mile.

Hi Chris echoing the above this isnt how it should be my C2 996 didnt chew up tyres like that On the rears i would get up to 12000 miles more on the fronts with even wear Sadly persuing the opc is likely just to give you a headache I would save your self the hassle take a packed lunch and sleeping bag and go see Chris at centre gravity Nick thank you for your erudite analysis of the medical profession You might need us one day

Hardly an analysis; more like an exaggeration to make point, I'd say Personally, I try to stay as far away from doctors as possible...