Like mentioned before try harder.
Did the discs on my step mums bora no problem...
On my dads caravelle the calipers where torqued on to about 150NM.
so half inch breaker bar, extended by a jack handle did it in the end.
Also may be worth soaking the bolt in WD40, Penetrant spray, Plus gas or similar (be carefull not to contaminate any discs or pads that are going to be used with the said sprays).
Once you bolt starts to move you'll be laughing...until you remeber youve got another 3 to go ;)
Cal