If gear cables strech...

[Happiness Stan]

then why not make them thicker like brake cable?

And why don't you get fully enclosed gear/brake cables any more?

Save money maybe but then you have to weld on cable stops and fit more ferrules etc.

Whyohwhyohwhy?

 

[smokeysmoo]

Brake cables stretch too. I like having to tweak things from time to time as it makes you look at things that you might otherwise forget about.

 

[Svendo]

I read somewhere (Sheldon perhaps?) that the steel cables don't actually stretch like elastic (well they do but it's insignificant on a bike). What actually is happening when they lengthen in use is the twist of the cable is tightened up by the load.

 

[Flying Dodo]

And why don't you get fully enclosed gear/brake cables any more?

Save money maybe but then you have to weld on cable stops and fit more ferrules etc.

Whyohwhyohwhy?

More friction if they're fully enclosed.

 

[TheDoctor]

And gear cables need to be flexible to get round the bends in the bars, and the innards of STI levers.
IME, they stretch within the first few hundred miles of use, then they're OK for a good few thousand miles.

 

[Ian H]

More friction if they're fully enclosed.

And also more 'give', which makes for less precise changing.

In my experience, decent gear cables need virtually no adjustment, once setup properly, until they die.

 

[HovR]

Around October last year I snapped an old gear cable on the rear mech of my bike. I wanted to get the bike back on the road quickly, as it is one I use every day, so in a pinch I used some 1.5mm stainless cable designed for marine use, which just happened to fit in the outers.

The width of the original cable was 1.2mm - The 1.5mm marine cable is the same width as the brake cables. To this date it has been working fine, so I haven't bothered to replace it with actual gear cable. So I guess if your cable routing isn't too tight, (probably won't work on aero levers) and your outers allow, you can use thicker cable - although I haven't noticed any difference either positive or negative between the two thicknesses.