its ok putting new discs on,if you make sure the hoses,fluid and calipers are all in top condition,sticking pistons cause drag,enough to heat up your disc,only to give it a hot spot at the next lights.

make sure its all well,.

tip., ,when replacing the seals in your caliper,remove the hose,and the pads,now,the pistons will be set back,ahh,dont reach for the air hose, loosen the bleed nipple,and block the hose hole with a suitable threaded bolt(as not to damage the thread),and pump in the grease from your gun,this wil pump out the pistons ,ready for your new ons,lean out as much grease as you can then wash with warm soapy water ,before reconditioning your calipers,by painting,then new seals.

or just go to your motor factors,for around 85 quid,youll get as new .garranteed ,calipers as swapsees!