derailleur cable -- why does it have to go in the back?
 

Cleaning the bike last night I started thinking about this...with all the shifter-cable issues (length, weight, hanging out a loop back there that could snag) has anyone ever tried to design a derailleur with the cable coming in the other side, near the front of the bike? Is it possible?

It needs to go in where the derailleur pivots. The derailluer body moves back and forth as it goes up and down the cluster. If the cable entered in the front, opposite the side of the pivot, it would impinge on the movement of the cable, and change the length of the cable run.

IT would be a PITA to engineer around that.

I think the derailleur on my hybrid is closer to what you are thinking about. (it changes incredibly smoothly)

http://i49.photobucket.com/albums/f2...c/DSC_0125.jpg

Yeah. SRAM mtb RDs are all like that now. Routing the shifter cables under the bar tape doesn't help. The old style brifters where the cables come out the sides and makes a single smooth large radius 90 degree bend to the stops on the downtube work much better in this regard.

Of course Di solves that problem completely.

Yup. I like that a lot, and it would work well with internal routing...

I've never seen polka dot rims on anything other than a fixie...
Full pics please.

Curious. What are all those red dots about?

I have been staring at the picture for like 10 minutes. I've finally decided that they're not photoshopped on there, but I can't figure out what they are.

optical illusion? - chain looks bent where it intersects the non-driveside seatstay.

You're not crazy. I see that too.

It probably has something to do with those red spots. That's not really a factory-bought polka-dot rim, is it? It seems that someone missed a spot at about 5:00 on that rim. :o

For what its worth, my experience with the SRAM mtb stuff pictured is that they work decently when the cable comes down the seat stay (like on an mtb frame), but not as well when it comes along the chain stay (like a road bike). There is enough of a difference in the angle that you have to have the short piece of cable perfect or you have trouble reaching the full gear spectrum. A tad too long, and you can't spring return to the smallest cogs, too short and you have no tension on the housing to allow relative movement (nothing happens when you index, if I recall correctly).

Edit: not saying that it doesn't work spectacularly once figured out. My primary bike has SRAM X9, and it works smoother and more consistently than 105, IMO.

Exactly what I was thinking. If the cable came down the chainstay, I dont think you would be able to bend it right for that derailleur.

dude, you are talking about the future! Its not here yet..