Huggable

Over here, we have 5 Birdy models (excluding the P40), they are the new classic (with tubular frame), the City, GT, R20 and the Rohloff (all having the same monocoque frame). All the above models only have single front chainring.

Jipe

The Birdy with internal gear hub like the Birdy Rohloff and the R&M Birdy City have a different value of chainline and it might be more difficult to fit a front derailleur on hem than on Birdy with a rear derailleur like the GT, Standard, Touring...

Huggable

Thanks for attaching the screenshot! Looks like there are some extensive modifications needed to install a dual chainring.

I will be sending my Birdy for Rohloff conversion by next month, will ask more about the amount of modifications required.

Jipe

On the Birdy Rohloff, the dropout is different and the chainline too to accommodate the wider chainline of the Rohloff hub (+ of course the rotating grip and dual cables furnished with the Rohloff hub).

2_i 

I wonder about absorbing the chain slack on a Birdy with a double ring in the front. The somewhat unusual tensioner on Brompton absorbs plenty of slack and I was able to get away with a triple ring in the front without essentially any modifications regarding the slack - I can actually fold the bike with the chain on the smallest ring in the front. However, when I replaced the rear Brompton derailleur with a regular one, like on a Birdy, I ran into problems with the slack for a folded bike. I made a chain catcher, such as one I saw in photos of some Birdys, but it only helped with one ring in the front. Two or more rings were turning into disasters. You could always fold, of course, exclusively with the chain on the largest ring, but it is a hassle.

Huggable

Just curious, do you guys do a lot of climbs? I find the stock 10-speed with single chainring more than sufficient for my commute. The only mod so far is to upgrade from 52T to 56T Oval.

Jipe

The titanium Birdy is factory equipped with a 52-36 front and Shimano 105 front and rear derailleur (rear is a RD-5800-GS, front FD-R7000, the frame has a front derailleur mount for a braze-on front derailleur).

It has the current Birdy chain tensioner around the crankset chainring.

Folding is OK whatever the chainring with, as always for BIrdy with a rear derailleur and cassette, the chain on the smallest cog.

Now, the frame geometry of the TI Birdy is different from the Birdy 3 and I do not know if it will also work with a Birdy 3 with double chainring?

About the choice of the front 52-36, with the small wheels of the Birdy, 36t front gives really short gears, I never need the 36t front + 32t rear I have. A 53-39 combination is probably better.

The original gearing of the Ti Birdy (and R20 SP 11) with only a 11-28 cassette is not a good choice (gearing too long for hills on the 28t, too short on flats with the 11t). Its probably the reason why Pacific Cycles mounted a front compact crankset and front derailleur on the Birdy Ti. The 9-32t cassette range of the R&M Birdy touring is a much better choice.

Winfried

Thanks much for the link. Looks like a wider bottom bracket is indeed required, as a replacement for the original TH BB-7420ST 113mm square taper.

Good call, although I personally don't mind since the smaller ring is only used on very steep hills, and i'm always back on the bigger ring when I need to fold to catch a train, etc.

It depends where you live, and/or if you use the folder for touring (= heavy bike) like I do.

JRat

15% hills need a good gearing range. I can just get up a 15% hill in 3rd gear on my Birdy Rohloff and like to have a couple of gears in reserve for headwind / extra load / tired legs.

Jipe

Indeed, it depends where you live.

Even in cities, there are places with short but very steep streets where the 52x32 2.21m, the lowest gear of the Birdy Touring, is too long

For those places, the Birdy Rohloff with 1.55 - 8.27m goes everywhere while the Birdy Touring with 2.21 - 7.86m can have problems on steep hills.

For me, the Birdy City with its cheap and limited Nexus 8 is a very bad choice. I wonder why at his price, R&M doesn't install an Alfine 11 hub on the Birdy City instead of the low end Nexus 8 ?

Huggable

I see. Come think of it, there's hardly any hills here in Singapore, hence generally 7-speeds onwards is sufficient for most of our commuting needs.

I'll be swapping out my SRAM X5 10 speed to the Rohloff hub next month, looking forward to the modification!

Jipe

One benefit you will also have when swapping to a Rohloff is longer gears because with a 11-32t cassette and a 52t chainring, 52x11 is quite short, the R&M Touring Birdy has a 9-32t cassette with the same 52t chainring which provides a much longer 52x9 gear.

JRat

I agree. While the Alfine 11 is more than double the cost of the Nexus 8 this difference is a relatively small proportion of the total bike cost. I briefly considered putting an Alfine 11 onto a Birdy City but quickly crossed off that option because I knew that it wouldn't have the gearing range I wanted (I've got another bike with the Alfine 11 which is waiting to be re-homed).

The standard Birdy Rohloff uses a 52T chainring and 13T sprocket (the smallest available). I'm planning to fit a 14T sprocket to get slightly lower gearing for my hills but if you don't have steep hills then you may want to investigate fitting a bigger (56T but even bigger if feasible) chain ring. Otherwise you'll never be using the bottom gears and be wanting another gear at the top end.

Note also that Rohloff hub gears improve with use but are very low maiintenance except for the oil change every year or 5000km, whichever comes first.

Huggable

Most of the Birdy owners I know use the bike for leisure speed rides. Hence they focus on weight savings (eg lightweight cranks) and highest gear ratio available.

I'm likely to retain my existing 56T oval chainring with the Rodloff hub before deciding if I need a smaller chainring.

​​​​​​​I also read that the Rudloff hub can be noisy at gear 7, did you observe that?

Huggable

My current setup.
Birdy GT. With 18" Schwalbe Kojak.
​​​​​

JRat

I agree that if you've already got a 56T chainring and no very steep hills then it would be best to keep that chainring.

Any of gears 1 to 7 of a Rohloff hub are noisier than gears 8 to 14 as an extra set of gears is used to create the low range. However, 7 tends to be the noisiest as it is effectively overdrive low range and involves both the low range gears and a freewheel mechanism. The sound difference between 7 and 8 provides a useful way of knowing which gear you are in without looking at the shifter. The gear noise reduces with use. My No. 1 Rohloff bike is approaching 10,000km and the gears have become much quieter which is very noticeable when compared with the much newer Birdy Rohloff.

Probably the best English discussion about Rohloff hubs is at Rohloff Internal Hub Gears .

Jipe

Current Rohloff are less noisy on their 7 lowest gear than older ones. I have two bikes with a Rohloff, he first one of 2021 even if it now has a lot of km remain noisier than the second one of mid 2016.

The break-in time of current Rohloff is also much shorter that it was with the first models.

If somebody will build the wheel for you, it is strongly advised to add the flange support rings

Huggable

Thanks for sharing! I'll slowly read up the discussion threads.