SpongeDad

It actually goes away or at least becomes less pronounced as the day warms up.
No problem when riding indoors on trainer.
No problem when riding in the fall (same cables - no changes to bike).
No problem downshifting.

Thoughts?

skol

had the same issue on my bike which had a old 105 on the rear - sold bike and solved problem. Probably a warning sign that cables and housings need to be replaced like a old battery taking longer to turn over in the cold.

simplify

To be clear, are we talking about the STI shifter lever moving but not doing anything? The lever moves with no resistance, and nothing happens? If this is what you mean, it's the shifter, not the cables, and the cause (at least in my personal experience) is that there is factory-applied grease inside the shift mechanism and when it's cold, that grease firms up. That prevents the mechanism from catching properly when you move the inside lever to shift to a smaller cog. It was happening to me following long descents in cold weather. The solution has been to flush those shifters internally with WD-40 to dilute and redistribute that excess factory grease. I routinely flush them every couple weeks, and never have problems now.

Velo Dog

Assuming you aren't confusing upshifting and downshifting (no insult intended--my buddy the shop owner says about half the people who complain about shifting problems mix them up), your problem is going from the larger cogs to the smaller ones. That's driven by a spring, so if something's interfering, you can't overpower it. I wouldn't think 40 degrees was cold enough to make the minimal lube in those moving parts so stiff it would impede the shifting, but it's a place to start. Clean and relube everything, maybe with a lighter lubricant, and see if that helps. Depending on what you use on the chain, I suppose that could be a factor, too. Way back in the day when we soaked chains in paraffin (for you Brits, that's household wax, not what we call kerosene), they'd get so stiff in cold weather the wax would just flake up and fall off.
One place I've often found grit is where the cables go under the bottom bracket. Generally they just slide across the paint down there, and it's right in the path of crud off the front wheel. Be sure to clean that up. I've heard two opinions about putting lube there--either it helps, or it just holds dirt and makes the problems worse.

Mr. Beanz

Works fine for me. One of my bikes, mtb takes on this symptom after non use for several months

Wow, sold a bike over a $5 cable replacement issue?

skol

^^^^ ha I wa just looking for any excuse for a new bike - justification is a beautiful thing

thompsonpost

There's also the possibility that a spring in the mech may be fatiguing and ready to snap. It's happened to me before, once.

Sixty Fiver

If it not freezing it is a mechanical issue that could be in the cable, shifter, or derailer.

Shifting problems in sub zero temps are often because of moisture in the cable housings or iced up derailers and i would also make sure there is no debris in the derailer as this can cause things to stop working properly.

Mr. Beanz

I was thinking that might be your response!

joejack951

I pulled an early 90's Trek road bike out of a friend's trash pile. He was going to toss it because the rear shift cable broke and he didn't feel like fixing it. I gave him a lot of crap about it at first then overhauled the bike completely and gave it back to him.

Wanderer

It could just be a gummy RD. Clean the derailleur by flushing it really well with something like WD-40, and wipe really well. Thoroughly exercise the RD while doing this.

Now is the time to use some bicycle specific oil for lubrication, and oil it really well, exercising it thoroughly again.

Wipe it as dry as you can, and oil it one more time, wiping it with a less than dry oily rag.

Make sure you oil every moving part.

SpongeDad

cleaning and relube are probably in order.

What it feels like at the brifter is that it's not catching the shift mechanism - no "click"

and yes, we're talking about going from larger cog to smaller cog (i.e., to more gear inches)

availpunk9

I'm guessing you have Shimano STIs. When you hold the larger "blade" and click the smaller one, does it click then?

Machka 

The only time I have had trouble shifting because of cold, it was down below -20C .... not +5C.

nitropowered

Old sticky cables and housing. Change them and you should be fine. Also clean out the bottom bracket guide

SpongeDad

The cables and housings are practically brand new (Jagwire). If it turns out to be the cables, I'll be a bit ticked. It really is temp sensitive - no problems when the bike is at room temp. I will clean the guide.

Allan Pollock

Exactly describes the problem I'm having...flushing with WD40 doesn't seem to solve it. Is it toast?

Allan

availpunk9

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