I bought a new WW tire for my Heritage about 6 months ago . I can't seem to get it clean it looks like it is yellow. I have tried loads of products and they don't work. (bleach white, simple green, and a magic eraser). Any other ideas would be greatly appreciated. I love my white walls but this one looks bad. I don't want to by a new one. It is a Harley Davidson tire. Thanks again.