I need some schooling on Chainrings
I have a double chainring up front a 42/53. I want to replace the 42 with a 38. The current 42 is a shimano sg 42. This is being used on a 7 speed bike. When I look at chainrings I see that there are different types like type b and I think that I saw a type c. What is the difference between these types? The bcd on the chainring is 130mm and it looks like the ring is about 2mm thick and the teeth appear to be centered on the ring. Do I need to steer clear of 9 and 10 speed chainrings?
Where can I get a plain Jane chainring that will work on the bike? Is the 15 tooth jump on the front chainrings going to cause extreme shifting problems? Are there any other things that I need to take into account when I make this change?