*puts on flame suit*
Sorry, but grooved discs that remove mythical gases which build up under braking are pretty pointless. Well, actually, they might be pretty, but thats about it really! The grooves have little to no effect on a road car, and especially on something like a 172. All they do add is more noise. Changing the pads will have a much greater improvement in braking. Or, fitting larger discs with better pads. But, I have to say, the 172 brakes (even on the track) are superb, and well balanced for road use. Ive driven AKs car (with Tarox front brakes) and they are much sharper, for sure, but thats not to say the std 172 brakes arent any good - theyre bloody marvellous!
*takes off flame suit*