I have been looking at a Shimano MF-HG50, 11-38. The components on the old bike are Shimano Exage, not the top of the line but will do fine for now. Any idea of the width of the MFHG50? The chain rings are Shimano Biopace 42 and 52t. What would you recommend as replacements? The local terrain is rolling hills and flats. Thanks for the comments. Spkt