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I have a Shimano FC-T551 triple chainset that should be fitted with 26/38/48 rings but it had no inner ring when I purchased it. I put a 22t ring I had spare at the time just as a short term fix but want to get a bigger inner ring now. How specific do I need to be with the type I use, I know it needs to be a 64BCD 4 arm but can I for instance use a 28t instead of the 26t. I have seen a shimano m675 version cheap but it says it is for a double set up, as its an inner ring is this critical? It also states it as an AJ type which I am not familiar with. I understand the different codes give different shift ramping so looking at compatible rings with this now older version chainset.
If it fits, it'll pretty much work fine, i've never met anybody that's actually noticed poorer shifting if the codes haven't matched up, though i'm sure there are theoretical disadvantages.
As above, it'll work fine. Some rings need the locating tabs filed down slightly to fit, but I think that's just later model rings on earlier model cranks. Just takes a few minutes work with a file.
Other way round, earlier rings had the tabs that cleared square taper BB's, but wouldn't go over external HT2 BB's.
Thanks for the replies. Yes I did try one which had really long tabs but I had borrowed that one so gave it back, as mentioned I could have filed it down as I am using it with the Hollowtech 2 BB which needs clearance so the tabs are an issue without treatment. I did notice this SLX m675 ring has a weird shape to it around the bolts but I guess as long as its 64BCD then it should still do the trick. I could run without it but the 22 is a big jump off from 36 and its an older 9 speed set up as I know many newer set ups are mostly single ring now.
Other way round, earlier rings had the tabs that cleared square taper BB’s, but wouldn’t go over external HT2 BB’s.
Yeah, that makes sense. Just takes a bit of work with a file to get them to fit.