Tyrolit Grinding wheels all the way!
I have used many different brands of grinding wheel in the past and in my opinion the best by far is a manufacturer called Tyrolit. They are a swiss company but I think to date they are one of the biggest manufacturer of abbrasive and super abbrasives in the world. They are a company within the swarovski (crystal) group, you must have heard of that! they really know their stuff when it comes to abbrasives.
The type no. for both the 3,2mm wide wheel and the 4,5mm wheel are as follows:-
740908 size 140x3,2x12 88A54K5AV217
244477 size 140x4,5x12 88A54K5AV217
They are pink wheels and if dressed regularly with a diamond stick etc once they look black, they cut with no burning and hold the radius form very well.