Odd that they are so fixated on downtime shifters. I vividly recall a Schwinn "10-speed" I had c1969-70 that had shifters by the stem, and a touring bike I had in the late 70s - a Gemini World Randonneur - with bar-end shifters - both apparently would be deemed "unauthentic" for the purposes of a pre-1987 vintage ride.
Eroica Britannia has a slightly different set of rules than the Italian version, which
explicitly allows pre-1980 non indexed bar-end gear shifters and rod/hand manual operated front derailleurs.
In reality, no-one actually polices the Britannia other than the goodwill of the riders, and everyone makes an effort. To quote myself from a recent blog post,
Eroica Bike Guidelines and Why They're Important:
"A straw poll, conducted by yours truly, wandering around the fields and lanes of 3 separate Eroica events reveals that thankfully most folks are smart enough to do their research and tell the difference between an eligible bike and a non-eligible bike.
Don’t be that guy who does turn up on a bike like the one above. You’ll spoil the fancy dress party for everyone else, you’ll put the marshals, volunteers and your fellow riders in an awkward position and you’ll look a knob.
There are plenty of things you can do with a bike like the above (even excluding stripping the groupset and re-selling it to an Eroica-nut) It would make a smashing commuter or winter bike, I dare say it’s light, stiff, responds well to out-of-the-saddle efforts and all sorts of other Bikes Etc adjectives.
It’s just not very heroic."
The brake cable rule is exactly as described above - that by asking that cables pass up and over the handlebars, though they can be internally routed thereafter, it excludes aero brakes and anything that even looks like a brifter.
Similarly with rear derailleurs - anything that looks suitably vintage, irrespective of age, does nicely. New Campagnolo Veloce is very popular, and is used on the Bianchi l'Eroica so must be ok. Basically, if it's modern you can style it out with a silver mech, but not a thumping great black plastic long-cage mech.
Gear ratios are free-range and a matter between you and your knees.
