Originally Posted by
jimc101
The Op said the Shimano 900 was 2x7, the A70 STI's are 2x7, not seeing where any other compatibility issues could come from, on the basis that the RD/FD worked with the original 7 speed cassette, they will work with the new shifters.
For the FD, that's normally an issue with trying to mix and match between MTB and road groupsets, not an issue in this case.
Jim- Shimano has never claimed that non specific gear systems are index compatible with those that are designed with indexing in mind. The lack of this understanding suggest a youth or lack of exposure to older stuff. Nothing wrong with that except when you're offering advise dealing with the stuff you're not familiar with. There was only about 10 years of Shimano 600 prior to the introduction of indexing as it is designed currently. Now as dabac mentioned sometimes current indexed shifters will work with older preindexed ders and cogs. But I won't make any claims of this being a certainty.
When Shimano first brought out indexed systems (and they empassised the system aspect) it was made known that there are 17 design elements that went into proper performance or indexed shifting. Any one want to give the list a shot?
A real good resource for a fuller understanding of ders is Frank Berto's "The dancing Chain". It's interesting to see design elements that have been claimed by current companies were actually around many decades before. Same to for pedals, anatomical/relief grooved saddles, dual pivot calipers and the list goes on. Speedplay's pedal museum is another cool resource for those who want to learn about history and the repeating of it. Andy.