I'm glad I could help.

Knuckles are pretty much straight blue groove tires... so hard packed that rubber actually gets layed down ontop of it. For topsoil you want a little more of an aggressive tread. Something where the tread is fairly space apart and a little deep so the tread grabs the ground more. Crime fighters are a pretty good tire but they wear out quick. Badlands are an awesome tire that will last a long time but you might get to much side bite and traction role... also the mug shots are a good tire for top soil and they wont give you to much side bite but if you get into more hardpack clay they get a little loose. Multi spike is another good one... Just look at the tread and it will tell you what they are made for. Close tread with wide flat topped knobs are good for very hard packed conditions because they give you a lot of tire contacting the hard surface... but if you get into loose dirt the tire will float ontop of the surface instead of digging in (like the knuckles). A deep and spaced out tread will let dirt pack in between each knob which lets it dig in and get the traciton on loose dirt (like the multi spike and badland tires).

The SP2 is an awesome buggy if you like lots of steering... the SP1 had more steering but the SP2 is still extremly aggressive and you need to pay attention when you drive it. With all of the MP777s the harder you drive them the better they handle too. I race the normal MP777 and I love it... over my old hyper 7 I cut off over a second from my laps times with the stock settings and as I changed things acordingly the buggy is letting me drive it faster and faster each weekend. It will bite back at you if you aren't focused though because the rear end swings around pretty quick.