When do parts break?

76% on chasis for next race, should I replace this? 

Several considerations: one is when it breaks. It won't yet - I got stuff down to 40% and it still does not break. Second is speed - I think worn stuff reflects badly on your speed. Not sure which parts how much - but keep it in mind. Last one is that replacing stuff uses enigneers and mechanics. So if you don't replace anything, all parts might be worn out at the same time, and you would need tons of mechanics to get the car running.
My tactic is to replace worse/most worn parts every race, till I run out of mechanics and engineers (except for the engine - you got a limited amount of those).  After a few races you will find that you need more mechanics to keep your car running.... but by then you should be able to get a larger office and be able to hire more of them.

They don't break until 0% but like Redmeijer said, you slow down with worn parts. Suspension seems to be the worst. Replace that every race.

Tbh I replace everything every race, except engines and internals which I replace every second race (alternating) regardless of their condition.

Good lord, I can't afford that!  :(  Is that just because I am a new team, still getting going?  (Been playing ~a week, just hit level 4)

-Matt

haha yes Matthew, the longer you play the more you will be able to afford. (take a look a Jasons World ranking and you'll see why and how he can replace every race ;))

Oke, thanks guys! :)