I have an old bike with Shimano 105 (5800). It has developed an issue where the inner lever won't "catch" when attempting to shift from the big to the small chainring. It'll just swing through with no resistance and not move the derailleur at all. I've attached a video to hopefully better explain what's going on.
I asked ChatGPT about this and it recommended spraying some lubricant into the mechanism. This did actually help, and it's working better now, but the issue still comes up intermittantly.
Does anyone know what's going on here and how to fix it?
Shimano 105 (5800) lever doesn't always "catch" when trying to shift to the small chainring.
byu/JoelJohnstone inbikewrench
by JoelJohnstone
9 Comments
Spray some speed degreaser in the mech. Does the shift feel like your pushing through stupor does it feel like alot of tension
Tension may indicate a cable/housing issue rather then gunk cleanup
Wonky shifting may be the result of a failing cable. The cable may be fraying inside the shifter, near the “stopper” where the cable is bent under pressure. No amount of lube will remedy that, and the cable will eventually snap totally. To examine the cable, release it at the derailleur, then pull the cable thru the shifter a few inches to inspect, and possibly replace if it appears damaged.
I think that grime builds up in there which messes with the mech
Spray it full of Clean Streak – like a whole bottle if you have to – it should clear it up. I did this with some badly gunked up 105 STIs and they both perform perfectly now.
Follow with compressed air (or just time for the degreaser to evaporate) then spray in a light lubricant to keep things moving smoothly. Good luck!
Have the same shifter and had the same problem. I sprayed a bit of degreaser into the shifting mechanism in the head of the shifter to free up the intricate mechanism that disengages the shifting when the brake lever is pulled as that was getting stuck in the old crusty grease. It happens worse when it’s cold because the grease solidifies.
Degreaser helped a lot and after than some light spray lube to keep it moving smooth. As it’s headed into fall, my shifter is acting up a bit again, so I’ll have to do another round.
I brought back some 105 5700 shifters I bought used on eBay for cheap with sticky mechanisms. I used brake cleaner and tri flow. Peel the hoods way back and use zip ties/tape to keep them out of the way. Spray the brake cleaner into the guts and work the shifters up and down through all the gears. Repeat as necessary. When you have all the old sticky grease flushed out lube them back up with light lubricant of choice, I used tri flow. I turned shifters that were sold broken/for parts into shifters that operated like new.
If the brake cleaner seems too aggressive, you can use hot tap water and citrus degreaser. If you use water, flush it all out with isopropyl alcohol before you lube them up.
It’s easier to diagnose with the cable freed from the derailleur and housing. Pull it apart and inspect the bare cable. Fire the shifter, and use whatever product you need on the internals. If it begins behaving consistently, you’re good. If it keeps skipping, then the shifter is dying, or there is debris in the cable path.
The grease in the mechanism dries and thickens over time, preventing the pawls from settling into place. Diluting the thick grease with a cleaner is the fix. WD40 is good because it leaves some lubrication in place.
Another scenario is that you’re slightly catching the big lever and that disengage the small lever.