Would you be prepared to put up with two cables for each Derailleur if it meant a quicker and more accurate gear change?

Currently we all run a single cable; pull and release (spring takes up the slack)

How about if we had two cables; pull in both directions (no spring taking up the slack)

Has it ever been offered on a bike? I’ve never seen it but it seems like an obvious solution.

No I wouldn’t. I’d go hydraulic, or more realistically electronic though.

If it we’re possible to combine the two into one housing I may be tempted

Has it ever been offered on a bike? I’ve never seen it but it seems like an obvious solution.

I’d imagine producing a system such that there was perfect tension in both cables at all times would be remarkably hard to pull off reliably.

Doesn’t a rohloff hub have that setup?

2 cables would lose tension against each other with no easy way of taking up the slack in the simple manner of a small adjuster that we currently have. It’s just doubling the complexity and not really solving the issue. Plus, a slow change is generally due to the time it takes to pull the cable. When it changes with the spring tension it’s far quicker. So going to 2 cables may actually slower.

The future is electronic… Takes away the whole slack issue.

Been done many times. Tricky to set-up up with no real advantage.

It works for Rohloff

If it ain’t broke… why not have two rims laced to each of your hubs to increase traction and provide security in the event of a puncture?

It’s simply not necessary to use two cables. Gear shifting is perfectly accurate enough as it is. In fact, I find XTR TOO accurate and prefer XT.

Has it ever been offered on a bike? I’ve never seen it but it seems like an obvious solution.

I had it on a cheap tourer in the early 80s. Don’t recall it being any better than a single cable

With two cables, you’ve got to have a bit of slack, there’s too much friction if they are both under tension.
Rohloff get round this by putting the indexing in the hub.

Nothing lacking at all in single cable IMO- as long as it’s set up right and in good condition, and a second cable wouldn’t help either of those.

The double cable doesn’t give an advantage over the single until you get crud in the cable…… which for MTB isn’t very long. So there is an advantage there.

I wonder if its possible to add indexing to a derailleur like they do in the Rohloff?

The sprung change is the better of the two. Come up with two springs and no cable and I’m in

It has been done recently. I can’t remember who it was though. Some boutique brand. Think the mechanism ran on two shafts rather than a parallellogram.

White Industries.

TBH OP it’s really a “non-problem” these days increasing the complexity and parts count would probably not improve the issue either, there are several answers to the problem already of course:

The current system with a single highly-tensioned cable is the nearest you’ll get to perfect. The only flaw is the loss of accuracy when poor maintenance allows cable friction to inhibit the pull of the spring.