I have a 2008 Specialized Allez with a triple crankset. The large and middle rings were getting worn so I bought replacements of identical tooth counts for them. However, after installing them I found it was impossible to shift onto the largest ring no matter how I adjusted the front derailleur because the space between the middle and largest rings was just too wide.
So I removed the rings and compared them. The new large ring was identical to the old one but the middle ring was not. The tabs where the bolt holes are drilled in the old ring were thinner than the new ring. The result was this made the middle ring stand about 2 mm farther from the large ring, just enough to make shifting upward impossible.
Is it standard for middle chainrings on a triple to be thinner or was that just unique to the crankset used on the bike? (It was the stock, unnamed crankset installed by Specialized.)