Crankycrank

Oh boy, you lucked out finding that just in time. As long as the outers are not gunked up or rusted and the ends have a clean, square cut on them they could be used again but seeing how old they are you would be best replacing them.

Drew Eckhardt 

It's not risky as in you'll be stuck with one cog for the last 100 miles of your ride, although you will probably need to deal with housing replacement before your cable wears out again.

Depending on shifter (whether there's a 90 degree guide inside and how tight that is), cable (Campagnolo double die drawn cables don't saw through housing lining as fast), and environmental conditions (the rear loop gunks up) rear shift housing lasts about 1-2X as long as its cable (Except old unlined housing, which was good until sunlight caused the plastic coating to crack).

I save myself hassle by keeping a bulk roll of housing and bunch of inner cables on hand. When a rear shift cable is going to wear out (like clockwork, because it depends on number of shifts) I unwrap my right handlebar just past the lever, replace housing plus cable, rewrap the bar tape, and finish off the end with electrical tape.

Shimano SP41 housing is about $1.70 per meter for a 10 meter roll, and it takes less than a meter when you don't have full length housing. Just replace it.

Coated inner cables can be found for less than $10 each. Just buy them individually.

Brake cables last indefinitely because the levers pull them in a straight line instead of around a tight curve which causes fatigue, unlined brake housing lasts almost indefinitely until the plastic cracks, and front shift cable plus housing lasts a multiple of rear because you shift it much less. Replacing them all at the same time is a waste of money and effort.

Johno59

I don't know if you had both jockey wheels off but they are not interchangeable and neither are their respective bearings. Some have upper and lower embossed on them but many don't.

jgwilliams

I've not used that tool but I do have an X-Tools torque wrench set and it appears to be a very solidly built piece of kit for the money.

dja1

Sorted. New inner & out cable fitted and the bike now indexes right. Only concern was I feel like an STI might've gotten jammed; but I think it was my own fault, after index I left it in the 28 and shifted all the way up just as I started pedalling. the cable must've ended up with a load of slack around the shifter because it only ended up in about half way in the 18t but the ratchet was in the position for the 11.

Probably me, but may need de/regreasing. All seems good now though.

2_i 

What sort of bike is that? I occasionally loaned a department store level bike, ran into indexed gears skipping and found that tuning the bike was impossible as a matter of principle. No matter what I did, how many hours I spent, I was left with the choice of either losing a gear on the way up or down. I decided that trying to tune such bikes was not worth my life.

dja1

I can't imagine a basic bike rented form a large department store having much of a maintenance schedule at all... bit oil and a wipe down how any then.
New cable sheathings & an inner gear wire fixed this, I have just been on a 5 mile ride to verify my repairs and the bike feels good.
All gears are usable, and there is no dangerous chain skip almost making me crash as I move off.

dja1

I can't imagine a basic bike rented form a large department store having much of a maintenance schedule at all... bit oil and a wipe down how and then.
New cable sheathings & an inner gear wire fixed this, I have just been on a 5 mile ride to verify my repairs and the bike feels good.
All gears are usable, and there is no dangerous chain skip almost making me crash as I move off.

2_i 

Sounds good. If the bike worked fine in the past, you are presumably done. At the more general level, for lower-level components, you may find at times a temporary balance, that lasts a few days, with the setup turning back to its regular out-of-tune afterwards.