A couple coats should give a nice thick white line but how long it would last? Who knows.
That's what scares me most. let's assume that i do it right the first time and get a nice finish (which would probably not be the easiest thing in the world). i'm not sure if it last. unless anyone has personal experience with the product lasting, i'll probably just cruise around on my black tires until I get magically rich and can afford white walls. black would look better than messed up whitewalls.
thanks