Bike data logger project.

I want to use arduino as a data logger for my bike which happens to be electronic. The problem is getting the data. I don't want to use any external sensors except cheap ones. I tried opening my bike and found that speedometer did not have wires but instead there was some kind of metal pipe like a break wire. I don't know what to do. Does any body know how speed value is passed to the analog speedometer.

It's passed by twisting. The cable inside the metal spring sheath will spin making the speedo move.

I opened up the speedometer wire and it turns out to be mechanical. I don't think there is a way to read it. However the battery meter seems to run with current. Maybe analog dial. I'm posting some pictures.
The one wires is the battery meter which seems to be an analog dial.

So I guess the only way to read speed is with a hall effect and magnet setup.

You can view them here and can someone tell me how to post pics to arduino directly.
Imgur