I often stop and help people. I think it's a 50/50 shot that if they don't have what they need to fix a flat, they might not have the knowledge either, so I'll ask first if they have done it before. If not I'll go ahead and do it, but explain what I'm doing and why. So far I don't seem to have made anyone think I was talking down to them, they are generally all smiles and will sometimes ask what they need or brands or other relevant questions.