Originally Posted by
icyclist
Can an Ultegra 11 speed brifter be used with a 9 speed cassette?
No - indexing will be off.
"11 speed ROAD shifters
They work with Shimano 11 speed
road RDs and with Shimano Tiagra 4700 10 speed road RDs.
By data, they should also work with old Campagnolo RDs, but I haven’t tested this. Old Campagnolo RDs come in 8, 9 and 10 speed variants. They should work with 8 and 9 speed old Campagnolo RDs, as long as the cassette used is Shimano 11 speed
road one."
https://bike.bikegremlin.com/1339/bi...compatibility/