The FL2 manual says:

"Ideally, tyres should be replaced in sets of 4. If this is not possible, replace the tyres in pairs (both front or both rear). When tyres are replaced, the wheels should always be re-balanced and the alignment checked."

The FL2 is totally different to the FL1, in which the Haldex can take out the difference in tyre size. Peeps have fitted 2 new on front or 2 new on rear, without problems. Peeps are still undecided if this is wrong, but FL2 owners have been fitting either way for years without problems, on high mileages. Fleel2 peeps are undecided anorl.

Tyre manufacturers state fitting new to rear so yer get under steer as opposed to new on front which can give over steer. Personally I would fit new to the rear if I were to change 2 on a FL2, or any car, but that's down to choice and the under steer option as preference.

My choice is due to when cornering:
Losing the front end with front part warn tyres and rear with new tyres gives you a chance of holding the line. Losing the front end with new tyres on the front and part warn on the rear means the rear won't hold the line as well, as the rear have already gone. Like on wet roads.
 
The FL2 is totally different to the FL1, in which the Haldex can take out the difference in tyre size.
It is very different, but essentially does exactly the same thing using a mechanical/electronic clutch rather than viscous plates. For it to function therefore the tyres must match as it won't take any difference out.
Peeps have fitted 2 new on front or 2 new on rear, without problems. Peeps are still undecided if this is wrong, but FL2 owners have been fitting either way for years without problems, on high mileages.
Well F2 owners must be as thick as shakes then - cos while there's still a lot of older F1s running on original front & rear diffs - there's not many F2s that are older than 5 or 6 years old. - if they had matching tyres, there must be less chance of diff problems surely.
 
It is very different, but essentially does exactly the same thing using a mechanical/electronic clutch rather than viscous plates. For it to function therefore the tyres must match as it won't take any difference out.

Well F2 owners must be as thick as shakes then - cos while there's still a lot of older F1s running on original front & rear diffs - there's not many F2s that are older than 5 or 6 years old. - if they had matching tyres, there must be less chance of diff problems surely.
The haldex varies the connection so it's OK. There are a lot of high mileage FL2's. A lot of the hype like certain reconners saying the diff will fail etc is just hype. Many have never had diff or heldex problems. For every FL on the web with a problem there's many more without that problem. 2006 to 2014 build dates.
 

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