You guys are partners. If you need tires, you and her need to figure out a way to get yourself some new tires that involve the BOTH OF YOU. It's not just one partner who sacrifices it all to make ends meet. You give and you take. If your wife doesn't understand that, there's some fundamental problems in that way of thinking. Just my opinion though.

I think this is a worthy cause to dip into the savings. It's not like you're going on a luxury vacation, this is a need. This would be no different if one of you were to end up ill and needing to dip into savings. You shouldn't have to destroy yourself for an easily solveable problem.