I apoligise if this is a dumb question..... I am currently running 13/50. I don't want to put a little 12 up front. I want to go up 3 teeth on the rear. The only one I have found is aluminum. I want steel if at all possible. Is a steel 53 available? From whom? How many links will I have to add? Will the chain guide need to be modified? Replaced? Thank You, RJ.