My kwaka's tyres had no tyre left on the edges 
I'm too chicken to explore the outer reaches of my tyres

Me too.
I ride within the capabilities of both the bike and myself, and doubt I ever explored the full capabilities of what the bike could do, esp as the ZX10 had some pretty awful brakes

If people want to ride faster than me, thats fine, I have no issue with that.
If people want to say I have a small penis because I don't ride it flat out, or get the pegs down (I don't think I ever got the pegs down on the ZX10, not without falling off, anyway), thats fine.
Thats the one reason I'd never go out on a group ride, as its easy to get encouraged to go a bit too quick for your capabilities. Worse, its too easy to be pressured into going faster than you are comfortable with. I've been out with a few people as very small groups, some faster, some slower, but only on the understanding that they wouldn't get frustrated waiting for me, or that I'd be more than willing to pull over every few miles and wait for them.