I had a really good idea for a structural part on sportbikes a few years back.
Everybody I talked to said "Man, why didn't I think of that" or "I'll give you a cash down payment now until they are ready".
Then, I started checking into liability, what it would cost to insure and start an LLC to do it, and my idea withered into the dust.
The thing you have to take into account, especially if you are building something that is considered a structural or key element of a vehicles stabilty (like a suspension component) is that IF somebody get's injured or dies and sue's you - whether by their own fault or your product's failure, you can lose everything you have.
In todays litiguous society, it's all too real and makes me wonder how many great ideas die on the blackboard.