I picked up a brand new looking 1984 bicycle. I seems almost unused and has shifting issues, it changes gear on the rear even though I am not shifting. Is this problem usually with the shifter being out of adjustment or the derailer? The teeth are all really nice looking and the chain looks new.

does it tend to upshift by itself, without you doing anything energetic at the time of the ghost shift? i can imagine that a very gunked up RD cable could cause that, and maybe running new cable and housing might fix?

Perhaps you just need to tighten the shift lever a smidge?

Yep, nothing energetic. I doubt this bike has 50 miles on it. I wonder if the problem is lack of use. The seller did oil the chain and derailers. Maybe lack of use affected the cables.

I just messed with it a bit. It it does seem to be the cable but does not seem to be gunked up. I think it is dried out. I will see if new cables fix this.

this too!

Thanks guys

New cable housing from Jagwire, for example, have a Teflon liner that is quite effective. They also recommend not lubing it because that can cause it to accumulate sludge. New cables and housing can make a huge difference.

Be aware that modern bikes with indexing shifter use different housing for brakes and derailleurs. The derailleur housing has multiple steel coils running more longitudinal than the traditional single coil. It makes the housing less compressible, necessary for accurate shifting, but it also makes it WAAAY too stiff if you aren't running index shifting. If you go to your LBS and ask for housing the person you speak to may try to give you derailleur housing, and possibly doesn't even know that friction shifting still exists. Also LBS youngsters tend to think all bikes have internal routing for rear brakes and aero levers, so they never give you enough for a complete cable overhaul.

Those youngsters!

Wait a minute. This makes no sense to me. I have been using modern Jagwire shift housing on my friction-shifting bikes for ages, and from my recollection the old shift housing was always the same. And I cannot understand why stiffer housing would screw up friction shifting. Seems to work perfectly to me.

Current cassette & now freewheel tooth patterns follow hyperglide designs and a side effect is ghost shifting.,

Modern shift housing is not the same as brake housing. It uses many (I don't know, a dozen?) wires wound into a very shallow coil so that the wires run more longitudinal along the housing line rather than one wire coiled mostly perpendicular. The purpose is to make it very much less compressible, a requirement for consistent index shifting.

I don't have any good pics to show at the moment, but the difference is obvious.

A side effect is that it is very much stiffer. Depending on your rear derailleur and how tight the bend has to be between the stop on the chainstay and the derailleur body, it may be too stiff to work well. For example on my Bianchi with 1st gen Cyclone GT the housing fits into a hole in a part of the derailleur that pivots with the parallelogram. This means the cable always emerges in a straight line out of the housing no matter what position the derailleur is in; it's one of the little features that makes the Cyclone so smooth. But when the chain is shifted to the small sprocket the housing has to enter the hole on an angle when viewed from above, entering from left to right. That requires the housing to bend from the housing stop inward around the DO and then swing back outward. With index derailleur housing the stiffness would literally prevent the derailleur from moving that far.

The added stiffness also tends to pull the derailleur body backwards by trying to straighten out the loop from stay to derailleur. Depending on the upper pivot arrangement that can affect how the derailleur takes up chain slack.

The thing is, with friction shifting all that incompressibility is unnecessary.

Thanks, Jim! Now I see what you are getting at. Indeed, I prefer the old spiral wound (and flexible) Suntour housing between the chainstay stop and the rear derailleur. I never have had a problem using modern cable housing for the rest of the run, though.

Excellent post.