2004 C4 Tyre size question

OK- this is probably a numpty question, but I'm confused about recommended tyre sizes! Currently I have 285/30/Z18's on the rear (Conti's all round) and need to replace them. All the 'enter your reg number' tyre sellers come up with 265/35/Y18 as the standard size. So- I understand what all the figures mean but which is correct for my C4, and can 265's be put on instead of the current 285's. Would there be much difference in day to day driving? Mine is a 'general commuter' car most of the time. 265's are a lot cheaper and I could probably afford to do all 4 to avoid mixing makes front to rear.

265's were used on the pre-facelift 996's, and 285's on the facelift cars. I would stick with 285's if I were you.

Richard, any particular reason why sticking with the 285's? I purchased my 996 Facelift model last year and replaced the rear tyres this summer. They had Conti 295/30/18 however the road noise was ear drum breaking. Being my first Porsche I thought this was normal until after chatting to my buddy about the noise in my car being more than his, he's running a 993 C4S with PZero Rosso's, I decided to try out the PZero Rosso 265/30/18 which as mentioned were considerably cheaper and have not seemed to have altered the handling at all. The noise level reduction was amazing though! Cheers

You should be using 295s on a C4S, as they are 11" wheels as opposed to the 10" on a C2/C4. 265's would be a helluva stretch. IMO it is best to stick to the tyre sizes specified by Porsche, purely from an insurance point of view. When I changed from N rated tyres to the Yokohamas on mine, my insurers said that they had no problem with that, provided I used tyres of the same size and speed rating as those specified by Porsche.

Thanks to both for those replies! Richard- as always I'm amazed at your font of knowledge! It's interesting that you have found the 265's quieter Sean. My Contis are very noisy especially on 'stone chip' roads as opposed to tarmac. Of couse, you have the S model which has even wider tyres than mine! I never push my C4 to the handling limit (that's MY limit not the car's ) so it may still be worth considering 265's. As the profile is slightly higher it may also improve the ride on our diabolical Essex/Suffolk country roads!

Hi Both, very interesting, when I changed the rears they (National) did mention that they were 11" and not 10" however didnt really mention it might be an issue. Now I'm worried they might be dangerous! What do you think?

The recommended wheel width for a 265/35/18 tyre is 9" to 10". I think you are stretching them too much putting them on 11".

Thanks Richard I appreciate your advise.... My fronts are due so I think I will change back the rears as well to be safe. Cheers

do not mix brands !! i say again do not mix brands, my c4 1999 was on contis , due to quick wear i changed to pirellis on rear , bad news , handling terrible, psm coming on at about 40mph, changed fronts to pirillis , all normal again , you have been told ! ps 285 on rear 75pno

Thanks 75pno, although I was told mixing on the same axle was not to be done although not ideal between front and back was tolerable! Think I will just revert back to the original setup ASAP.... Cheers

I seem to remember that changing tyre sizes on a 4wd 996 has all sorts of complications regarding the drive system- possibly PSM issues.. I'm sure Richard will know if it has any credability... I wanted to change my rear tyre size but it was highly recommended not too..[&:] garyw

I recall reading something a while back that messing with the tyres could affect the ABS or 4WD reaction?? I use 285 Sport contacts and don't find them too noisy. Maybe its different tastes or you're not driving it fast enough [ ]

I must admit I've not noticed any handling issues although to be fair I havnt driven the car hard since changing the tyres! Perhaps I should try the faster approach, like your style Craig I'm more worried the tyres will fall off the rims at the moment never mind affect the PSM or 4WD! Have you seen the article in Porsche911 about the Michelin Pilot Super Sport developed in conjunction with Porsche, I bet there expensive! But sound good... I see you've got the slow Meridien Silver colour on your car[ ][ ][ ]

I've decided to take best advice and replace like with like! It's going into PSR Automotive on Monday for the 2 rear 285/30/Z18 Conti 2's at £218 each fully fitted then a full geometry setup at £200 inc VAT. (the n/s rear was badly worn to the inside part of the tyre) Should drive better with the geo adjusted!

Hi all, unfortunately now in the market for a full set - N3 295/30s & 225/40s, currently on Pirellis with no issues but just wondering if a different manufacturer would give less road noise. I've seen on the forum that Conti's wear quickly so have decided to disregard these but the best price I can get is £830 for Bridgestones. Any views would be greatly appreciated.. Mark