Originally Posted by
dedhed
Not aware of that, but it's just plain stupid to not have these backward compatible with existing 8-9-10 stuff when everything in those speeds had been cross compatible.
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There is a very good reason why Tiagra 4600 and 4700 groups use a different pull ratio and it mostly has to do with shift cable routing under the bar tape. When Shimano first introduced this type of cable routing with the 5700/6700, and 7900 series there were numerous complaints about shifting issues. Simply put, those shifters pulled too little cable per shift for precise shifting and also with cable friction. The previous 5600,6600, and 7800 series drivetrains worked better. Shimano solved that when they went to 11 speed with its revised shifters and derailleurs. They also used the same pull ratio as 11 speed when they introduced Tiagra 4700 so as not to repeat their error. I would not be surprised to see Tiagra move to 11 speed in the near future and it would be fully compatible with current 11 speed groups