There is no reason for you to be paying more than 50/50 then. Fight this, even if you have to pay lawyer's fees you'll still not have to pay the entire cost of auto repairs. In NY, this wouldn't even be an issue for you most likely. Really sucks dude. Email Bob Mionske (ex-olympic cyclist turned lawyer) for legal advice before you pursue anything if you're unsure of the circumstances and their relation to your state's D.O.T's rules.