My Coworker: Chris, can I borrow your bike Saturday to see if I will like riding?
Me: Sure, can I borrow your Mustang Saturday night to see if I like Fords or not.
He's never asked again.
Yes it's just a bike, but it's my bike, it's expensive and if something happened to it, it would be hard for me to replace at this time in my life. Not to mention if something happened to him while riding it. That would be terrible for everyone.