This page provides lots of technical information about the Birdy. Its most suited for people who need to know a specific technical detail about the bike. Its also handy for people who might want to upgrade some componentry on their bike.

What are the OLDs on the front and rear drop outs?
What kind of hubs could I use on the Birdy ?
What are the crank and Bottom Bracket details ?
What are the details of the cassettes you use ?
Can I convert my existing Birdy to a double chainring?
Tell me about the headset ?
What about pedals ?

The Birdy uses standard MTB dropout widths. The OLD for the front is 100mm and for the rear it is 135mm

Any front or rear hub that uses the above OLD dimensions should be OK to use.

For the front we recommend 24 hole hubs spoked radially to the rims. Since 24 hole hubs are not as common, its no problem to use a 36 hole front hub and miss out a hole every two spokes. This allows you to spoke a 36 hole hub to a 24 hole rim. Since small wheels are strong, its no problem to use this arrangement.

For the rear you can also spoke a 36 hole hub to a 24 hole rim. This is fine on 8 and 9 speed models and saves a bit of weight. But on DualDrive, Intego, Nexus or Rohloff rear hubs (these all have wide flanges) you should certainly spoke the 32H or 36H hub to an equivalent 32H or 36H rim. We have 24H, 32H and 36H rims all available. If you are a heavy rider and think you will be doing demanding riding on your Birdy, you should consider getting a 32H or 36H rear wheel built by your retailer.

The standard Bottom Bracket (BB) we use has a 68mm shell with 113mm axle. On top of this there is a 1.5mm BB spacer used on the drive side (although this can be optional). This BB uses a JIS spline for attaching the crank arms. Any BB that matches these specs should be able to used.

For cranks we use 170mm crank lengths on all Birdys. The BCD is 130mm which allows a variety of chainrings to be attached. Standard chainring is 56 tooth, but smaller ones can be fitted (as long as they support BCD = 130mm ). We have 54T and 52T in stock. 49T and 47T are also available from other suppliers.

It is also possible to replace the entire crank and BB combination to alternatives such as ISIS drive or Shimano Octalink type systems. But you will have to consider the chainline carefully when using alternatives. There is a tight trade-off between a good chain-line and good folding performance.

Generally any 8 or 9 speed cassette can be fitted onto the spline of the freehub of most Birdys. We generally use either a 11-32T cassette or 11-30T depending on the derailleur compatability.

Switching to 11-34T is also possible but when in the 34T sprocket there is likely to be more noise whiloe riding. There is also a greater chance of the chain occasionally tapping against the underside of the rear swingarm if an 11-34T cassette is used.

In short, probably not. It is possible to have double chainrings and front derailleur systems on the Birdy (see Racing Birdy) but these bikes have the following adaptations made to them:

* Ideally Birdys would need a brazed on mount near the bottom bracket for the front deraileur to attach to. Clamp type f/derailleurs won't work because the tubing diameter is not standard.

* The rear swing arm and main frame need machining to make room for double chainring.

* The axle on the rear swing arm needs to be slightly shorter

* A cable stop for f/derailleur cable needs to be brazed on the frame.

The racing Birdy has all these features integrated into its design. But our standard Birdy line-up does not.

Here we also use standard cycling industry componentry. The headset details are :
1-1/8" with top cap and 22.2mm star nut. Its also important to use a 2mm headset spacer before the front fork is slid onto the steerer tube.

The pedals on the Birdy use industry standard threads so you can change the pedals to anything you like.

We don't use folding pedals on the Birdy for two reasons (a) if you look at a folded Birdy from side-on you'd see that folding pedals won't really make any difference to the folded size (b) its hard to find good quality folding pedals that match the rest of the high quality componentry we use on our bikes.