How to make a "Birdy" to "Your Birdy"

Bar ends

The straight MTB-like handlebar I have completed with bar ends (see photograph on the page before). They would stick out when the Birdy is folded.
I solved this problem supplying a quick release lever at the stem. So it is possible to revolve the handlebar to get the bar ends in a parallel position to the frame.
I took a quick release lever from a saddle post. I cut a longer thread and shortened the bolt. then I needed another nut. The original one was too big. Even a M6 nut was too big. I had to take a M5 nut and cut a M6 thread in it. Additional I had to file off one side to fit the nut to the stem.

Now I have a new, height-adjustable stem. I drilled a 4 mm whole through one hole and cut a 5 mm thread. Then I could use the same quick release lever. The clamp force can be adjusted with the other screw.

The quick release lever fixes the handlebar in a reliable way.

Fixing the saddle against theft

I am used to leave my Birdy for some hours to go shopping or something like that. I have mounted a U-lock. Because of fixing the saddle with a quick release, it can be stolen.
Replacing the QR by a bolt is not very useful. So I took a shifter cable and lead it beetween the tube and the bracket fixing the saddle through the post tube. The nipple is too large to slip through the crack. The end of the cable is fixed with a screw of the folding hinge (red arrow in the photograph).
In addition I have mounted a spring at the cable. This will pull the cable in the post when the Birdy is folded.
The cable has an additional effect: When I unfold my Birdy, I pull out the saddle until the cable is straight. After letting it a few cm in again, the saddle has the right height!

Changing to a chain drive

Changing the belt drive with the chain drive kit as it is offered by riese und müller, is the expensive way. I bought the following components at my local dealer:
Dotek cranks inluding chainwheel (52 T) and aluminium guides on each side (80 DM), a used rear shifter Shimano Exage 300 LX to strain the chain (10 DM), a bottom bracket (118 mm, the original one had 126 mm)(30 DM), one cog (18 T)(5 DM) and a chain (20 DM) all together about 145 DM. If I had bought the chain drive kit from riese und müller I'd had to pay about double the price.
With this changes the Birdy had a gear ratio from 1.83 to 4.46. It was not enough for me, so I mounted a 16 T cog. The gear ratio is now from 2.50 to 6.10. So the Birdy still is not a racing bike. But should it? No. The Birdy makes me ride quite speedy, fast enough. Besides that, mounting a smaller cog is not possible, because the screw, which holds the shifting cable, would scratch at the chain.
Changing from belt drive to chain drive was a good decision!

Mounting a bicycle computer

I mounted a Sigma computer to my Birdy. The sensor is fixed at the fork with a rubber ring. The cable you can wind around the brake cable to the handlebar. Attend to give enough reserve at the hinge! The Handlebar holder is fixed with a rubber ring, too. Setting of the circumference is 1370 mm (1295 mm with the Schwalbe Stelvio tyre).

I have mounted a Cateye-Computer to another Birdy. The plasic clip is very elastic. So you can fix it at the angular fork.

Some cableless computers won't work reliable. Between sensor and computer is a distance of about 75 cm (with a comfort stem). You can get a distance of about 65 cm, if you mount the sensor at another position. On a non foldable bike there is a distance between sensor and computer of about 45 to 50 cm. This 20 cm difference can be decisive, because the radius of action must not be too great. Imagine two bikes with the same computer riding next to each other. The computers would affect each other.
Also take a look at Mike Hessey's hints.

Internal hubs and broken spokes

The internal hubs of the Birdy green and Birdy blue have a great diameter. So the angle between spoke and rim is not very good. Some spokes have a kink just at the beginning of the thread (photo, right hand side: this spoke is one of my "original" Birdy spoke). This is the position where they broke usually (not at the elbow).
The early Birdy green models had the spokes two times crossed. So the angle between rim and spoke was even more stressy. Newer models have single crossed spokes (by the way: 136 and 138 mm).
You can minimize the problem when you build the wheel properly and by checking the rear wheel periodically.

riese und müller try to solve the problem this way (information from June 1999):
First, they use stronger spokes now: single-butted spokes 13 gauge (2.34 mm) at the head end and 14 gauge (2 mm) at the thread end. In addition there will be used washers, because the flanges of the Sachs hubs are very thin. This will reduce the problems with broken spokes at the elbow.
Nipples are usually formed conical (photo, middle). riese und müller will use ball-ended "poly-ax" nipples from the belgian manufacturer Sapim (photo, left hand side). They will be able to turn in the hole of the rim, so that the nipple and the spoke are in a straight line. So the spokes won't be stressed at the beginning of the thread. In addition, since October 1999 they use 36-hole-rims (instead of 24-hole) to build the rear wheels.
Another possible step is a modified spoke pattern. Usually head-in and head-out mounted spokes alternate each other. In opposite to this you can mount all spokes on the drive side head-out and all spokes on the left side head-in. This reduces the disparity in tension between the drive side and non-drive side spokes. The wheel will become more stable.

I rebuilt my rear wheel with 14 gauge (2 mm) spokes from Sapim and the poly-ax nipples from Sapim. I used the pattern described above but I did not use washers at the elbow of the spokes (photos). My dealer could not offer single-butted spokes (I didn't purchase them from riese und müller), so I decided to take usual 14 gauge (2 mm) spokes. I didn't use washers because the spokes are fitting quite good at the flange and I did not had any problems at this position (spokes broke at the thread, not at the head) In addition, I took my old 24-hole-rim. On this occasion I exchanged the 4-speed hub for the 7-speed hub from Shimano. By the way: it was not necessary to change the rapidfire shift lever. It is compatible to the 7-speed hub.

The Front Brake

was originally a simple side pull brake from the "Simano Exage" group. The brake cable was layed in a great bow down the fork an up again to the brake. A straight layed cable would have affected folding the bike. But so the efficiency of the brake was not very good.
Newer Birdy models come with a V-brake, which is more effective. The exchange of the side pull brake with a V-brake was not possible, because the V-brake needs special bases. So I took a brake from the "Shimano 105" group. This brake is constructed in another way: While a simple side pull brake has only one centered pivot, the "Shimano 105" brake has another, not centered pivot ("dual pivot"). This makes the brake more efficient. As an alternative you can choose the brake from the "Shimano RX 100" group. This brake is constructed in the same way, is as efficient as the "105", but has another surface and is therefore cheaper.
A slight reconstruction was necessary because the brake cable of the Birdy has to be layed to the brake from the bottom and not, as usually from the top. All spare parts I took from the originally "Exage" model. In addition I could retain the quick release lever which was not present at the original brake.

Now I mounted hydro stop brakes from Magura. It is the very old model "Hydro-Stop-Mountain", I took it from a crashed bike from 1994. Though the front fork does not have braze ons for cantilever or V-brakes (remember: my Birdy is from 1996, the Birdy comes with V-brakes since 1997) I had to take an adapter to mount the brakes. In former times this adapter was sold by Magura, now you have to built it yourself or you find it as a remainders. My adapter was too big, so I had to take off the middle. The shanks I mounted with hose clamps to the fork. The tube I fixes with cable mounters.

The photos show:

• mounting of the brake and fixing of the tube to the fork.
• the adapter and it's mounting with hose clamps, viewed from the front.
• the adapter, viewed from the side.