I have a big case of parts and the only things that I've ever broken on the B5 series of cars is steering racks, arms and a T5M body mount. Neither of my SC5Ms have broken since I built them 5 or 6 months ago. As far as spares go I'd keep fr/rr arms, fr/rr towers, ballcups, caster blocks, steering blocks, and a steering set. Its alot of stuff and its doubtful that you'll use most it but those are must haves for a club racer in my opinion. Its easier if you have the whole line up of cars as they share a lot of parts. Its amazing how durable this new generation of cars is.