What is a "Birdy 3 standard" ?

Is it a Riese & Müller Birdy 3 or a Pacific Cycles Birdy 3 ? What model, what transmission ?

The current Riese & Müller Birdy 3 all have Shimano Deore hydraulic disc brakes. Moving to Shimano XT only bring a small weight reduction, no change in braking performances.

The R&M City Birdy has a bad transmission : Shimano Nexus 8 is not efficient, heavy and has a too small gear inch range.

The two other R&M model, Birdy Rohloff and Birdy Touring are pretty good with their factory components. The only drawback of the Touring are the Sunrace rear hub and cassette that are heavy and proprietary (you cannot mount anything else than a Sunrace cassette on it). But the gear inch range with the 9-32t cassette is excellent.

The Pacific Cycles Birdy come with different transmission that are all short due to their cassettes that all have a 11t smallest cog. The Birdy R20 11SP has a ridiculous 11-28t cassette, too short and too small gear inch range.

Its possible to improve a lot both the wheels and transmission and have huge weight saving with a 11s or 12s transmission.

I changed the wheels for custom build wheels with Kinlin wide rims, Sapim CX-ray spokes, Hubsmith front hub and Tune rear hub and a transmission with a Ethirtheen 9-34 cassette, Shimano Ultegra M8000 derailleur, Shimano SL-RS700 shifter and KMC X11SL Gold chain.