I've got the HPI S and M compound tires and BOTH are a LOT grippier than the kit tires I have!! The KIT tires are HARD and smooth and DON'T grip at all. The soft tires I put on the rear---and I'm trying Mediums on the front--haven't races it yet at Westcoast---but may get some practice there next Tuesday. I'll probably pick up some S fronts also just in case I need more steering.
FWIW
Tim