While I was busy adjusting the gear indexing, I noticed something wrong with the front derailleur. It was quite impossible to shift to the granny, despite the front derailleur cage fork nearly hitting the frame. By contrast, it was rather easy to go beyond the outer chainring, despite the limiter screw being correctly set.
Height as well as parallelism of the front derailleur cage fork seemed fine too.
Yet the routing of the derailleur cable didn't look good. @RockiMtn pointed to me that the cable was not sitting within the small grove of the derailleur tab. But even with this fixed and despite other advices from @RockiMtn (thanks again!), the cable was still sliding against the derailleur body when on the granny position.
All this eventually made me wonder whether I was running the correct chainline. Bikepro's Bottom Bracket Compatibility Table [1] lists 122.5mm spindle as compatible with "1993 or earlier" FC-M730 crankset, while also listing 127.5mm spindle for "pre 1994- some chainline applications". Shimano date code PC is etched in my crankset, meaning it was manufactured in March 1991. So both "1993 or earlier" and "pre 1994" apply in my case. Great! So? Should I go with 122.5mm or 127.5mm spindle? And how should "some chainline applications" be understood? Looking at the current setup, the chainline was measured at a mere 45mm with 68 x 122.5mm BB-UN52 bottom bracket. The latter was obviously not an original component, as confirmed by Shimano date code UE (May 1996). Moreover, BB-UN5x references are for Deore LX bottom brackets vs. BB-UN7x for XT.
Height as well as parallelism of the front derailleur cage fork seemed fine too.
Yet the routing of the derailleur cable didn't look good. @RockiMtn pointed to me that the cable was not sitting within the small grove of the derailleur tab. But even with this fixed and despite other advices from @RockiMtn (thanks again!), the cable was still sliding against the derailleur body when on the granny position.
All this eventually made me wonder whether I was running the correct chainline. Bikepro's Bottom Bracket Compatibility Table [1] lists 122.5mm spindle as compatible with "1993 or earlier" FC-M730 crankset, while also listing 127.5mm spindle for "pre 1994- some chainline applications". Shimano date code PC is etched in my crankset, meaning it was manufactured in March 1991. So both "1993 or earlier" and "pre 1994" apply in my case. Great! So? Should I go with 122.5mm or 127.5mm spindle? And how should "some chainline applications" be understood? Looking at the current setup, the chainline was measured at a mere 45mm with 68 x 122.5mm BB-UN52 bottom bracket. The latter was obviously not an original component, as confirmed by Shimano date code UE (May 1996). Moreover, BB-UN5x references are for Deore LX bottom brackets vs. BB-UN7x for XT.
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