I took NY's comment to refer, more specifically, to your speculation that your husband might be upset because you want to replace a bike that he gave you as a gift. I think that's an issue worth discussing with your husband as it doesn't appear that you already have. Perhaps that's what NY was getting at. Beyond that, I think you need to switch gears from trying to talk him into the bike to explaining your hurt and confusion over what feels like a lack of support from him. As lph suggested, the issue between you and your husband really goes beyond the bike itself and you'd be well advised to approach it as such--if you really want to get to the heart of why he has objected to the purchase.

I'd also say that I don't think a car ride is the best time to have a difficult discussion. Yes, you have a captive audience. But you're also both trapped if the conversation goes south.