Originally Posted by
Doug64
I can see one problem: The post 4403 Tiagra FDs can not handle a tooth difference between the large and middle chainrings less than 11-12 teeth. The 4403 will handle down to a 10 tooth difference. The rear cage of 4503, which is an outstanding FD, is too large and interferes with the middle chainring on cranks like 46/36/24, 48/38/28, 42/32/22, etc . Middle to small chainring tooth differences does not matter if the difference is not too large.
We use the 4503 on several bikes that are running 44/32/22 cranksets, and it shifts very nicely.
Look in Shimano's Tech document site, and you may find the info there.
SHIMANO Dealer's Manual / User's Manual
I ran into this issue when changing out a crankset, on one of our bikes..
Yeah, I've seen this issue too. Some modern triple FDs have cages that are too deep if there's not a huge tooth difference between middle and large ring. You can usually "solve" it by raising the FD, but obviously that can potentially create chain retention issues, and depending on the derailleur in question and how much height you need to add, it might be too high for the small ring.
With a friction-shifted setup, the "safe" option is a simple straight cage, like on vintage triples. But those don't necessarily provide as snappy shifts.