Hello,

I have a Trek FX 7.4 Hybrid with a Shimano FC M-391 crankset (170 mm - 48t x 36t x 26t – square taper) . I have close to 12K miles on the bike and have noticed some wear on the cassette (9 speed) and middle chainring (which I use most of the time) but I am not sure if they are bad enough yet to replace. (see attached photos) Last season, I would occasionally have what appeared to be a chain skip but it seemed to be after a shift or when I increased power suddenly. Again, it was only occasional and made me think that at least part of it may be caused by rider error. (By the way, I replaced my chain at about 8K so I have around 4K on this one and it appears to be in good shape at least in terms of chain “stretch”.)

To give you a better idea of my riding (if that matters), I ride primarily a flat gravel trail (fine/hard packed) when the weather permits but will ride roads occasionally also. I ride at a pretty consistent pace and average around 15-15.5 MPH over a 30-50 mile ride.

From a little searching, it looks like the Shimano chainring part # is Y1LD98090 (middle ring) and could be a little challenging to find. I also have considered changing the entire crankset as it might be a more economical option.

Do you think there is enough wear to replace either of these components? If not, any idea how much life they have left? What would you suggest in terms of a replacement if I replace the whole thing? I have the chain guard on mine but have noticed many replacements don’t have it. I would prefer to keep it (not sure why) if possible.

Thanks for any comments or suggestions you may have.