[Tannaton]

There is only one size of disc and pads that were fitted to UK spec XC90's (including petrol models) so there shouldn't be any issue with getting the correct size. 336mm is the diameter of the disc, if the pads are 156mm width that will be the sideways width not the height - if you see what I mean (i.e. distance measured up and down when the pad is installed, not from the centre of the hub outwards).

I believe Volvo cast their own discs for the XC90, there is no other way of buying the correct quality aside from the Volvo branded part. Most pattern parts for front discs for the XC90 are sh*t including Mintex, National etc. about every 3 months we get a new member with judder, pulling or poor feel on the brakes - invariably cured by fitting genuine parts. And I have personally made that mistake myself and now would not fit anything other than genuine Volvo when it comes to brakes - even on my V40.

Every time I share this I get some stick but I've seen so many times when I've changed brakes, where genuine Volvo parts are being removed the contact surface of the disc is almost mirror like. With the majority of pattern parts the brake disc is invariably scored and looks like the pads were made from rough concrete with old nails in it.

Taking into account fitting, life, total cost of ownership... the cheapest parts are genuine Volvo. So if you do fit the Brembo discs I would still get Volvo pads - a number of sellers do them at trade prices on ebay.