I'm planning on changing the front discs on my 997.1 standard 3.6 and am aware that the diameters are different from the S model.
You're right to be cautious about which ones to order but assuming you are replacing your 'standard' or factory fitted ones, then take a look at EBCs web site, where
they list each model of car and appropriate discs for it, click here to see, when you're on that page, press 'CTRL' and 'F' on your keyboard (means find on this page) then type in your cars specific mode (Eg. 997 or GTS), your browser will/should highlight the model you have typed in on the page to aid you with narrowing down your search.
Ps. I knew the Carrera and Carrera 'S' models have different diameter discs but looking at EBC's web page (in the link above) there are all sorts of different diameters of discs for the range of models of the 911
So you do have to be careful when handing over your credit card details in case there is a re-stocking fee or difficult to return policy in place. Not to mention the inconvenience of having taken yours apart only to find out the discs (and pads) are the wrong size.
While we're on here. I have seen several discs and pads on eBay. For example these
MEYLE PLATINUM DISCS for just £92 a pair (fronts). Does platinum (coating I suppose) have any advantage over other types?
And what about the Brembo discs
PORSCHE FRONT DRILLED BRAKE DISCS BREMBO PADS at £179.99 (with 25 pairs already sold). These look very attractive to me and are what I'm considering.
Can anyone please say if these discs should be avoided for any obvious reason and if so, is that because they are simply not as good/wont last as long (due to different materials) or simply because the manufacturers are not reputable companies?
Having said that, here is a
PAIR GENUINE PORSCHE 997 C2 C4 FRONT BRAKE DISCS NEW up for sale at £377 , again not very economic compared to EBCoption you are contemplating or the above options.
Good luck.