Bill,I have 30 chipped cars,all a little bit different,some with magnets in pockets in front of chassis and standard tyres, a lot of nascars(inlines)with lowered magnets, silicone tyres a little bit of weight in front,some with no magnets a little weight up front. I wanted another class of four cars that offered something else.Looking on forum its looks like no one has hadproblems cooking chips with motors of rpm of 20,0000...So on this basis I installed scaleauto ball bearing 20.0000 rpm motors into 4 scalextric nissan skylines,magnets in the front pockets and a liitle bit of lead over guide plus new sprung guides.... These are great fun,a little tail happy around corners but predictable,punchy acceleration,and they make a fantastic motor noise a real sense of speed.So far no cooked chips,and I run 4 at a time in some hectic SSDC racing.Hope it helps cheers mikefi