dougphoto

all last week when I'd shift it would take a couple taps to get my rear derailleur to shift, then today it stopped shifting completely so I turned around headed home ( I was very sad) spinning at like a million revs per minute to go very slow. Then suddenly about a mile or two from home it started working almost perfectly again. Shimano 105 with about 8000 miles on it.

dabac

I’d guess the cable is fraying and has started binding up somewhere.

Jack Tone 

I would turn the bike upside down and spray some WD40 or Triflow into the brifter.

dougphoto

wd40 fixes most stuff

Zaskar

When was the last time you re-cabled? Just replace the cable AND housing. Always a good place to start. When the shifter starts needing continual adjustment - MORE tension - that's a sign the cable is about to snap. The individual strands are snapping. This will leave you stranded. Worse - the final failure is typically in the shifter, making the repair a bigger pain in the ass.


Oh, and WD40 shouldn't be used on shifters... it's for bottom brackets and brake pads.

jadocs

Do you sweat a lot? I've seen sweat buildup and corrosion disable a rear derailleur.

noodle soup

+1

The OP didn't say which version 105 he has, but based on the low mileage, I'd guess it's 5800 or 7000 series 105. Fraying cables inside the shifter sounds like the cause of his issues.

Zaskar

So disappointed in you guys. No one got the "stranded" reference ;-)

TheDudeIsHere

YES this may explain the "weirdness" the OP mentions.

I had RSX shifters back in the mid 90's. Brifters were acting strange, shift but no shift at times. Read about the WD 40. Used it after the bike sat a while and wouldn't shift. Now I have and Ultegra bike that has this weirdness. All new cables. I believe it is a mechanism inside the shifter.

After the spray, the shifter worked perfectly fine. Once it works, it works. If it sits for a long period without riding, it will act this way.

But once it starts working, it works fine. I bet the OP just happened to get it working, luckily, then it was fine after that. WEIRD!

MidTNBrad

I had this happen on my old bike. The ratcheting mechanism in the shifter wouldn't catch. Follow

eduskator

It def. needs maintenance...or replacement of parts.

Tell us what was wrong.

Zaskar

Let me see if I have this right... "flood" or wash the shifter with WD40 then add lube. That's it? I see a couple issues with this...
- The WD40 is now in the cable housing and under the tape, etc.
- Adding the chainlube to the shifter either makes a diluted solvent or a diluted lube... with solvent

Wouldn't it be better to:
- Remove the shifters
- Clean the shifters - with WD40 or another solvent
- Flush out the cleaner/solvent
- Relube the shifter
- Reinstall the shifter

AndyK 

Maybe a small spray of dry-lube onto the brifter gears, instead of flooding them with WD40?

noodle soup

I spray clean streak into the shifter, and then use compressor to blow out the junk. Repeat this process until it shifts well, and then apply Tri-Flow and blow lightly with a compressor.

dougphoto

Turns out the cable at the shifter end was frayed, new cable and all better.