Problem with STI shifter fails to downshift

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Banjowhacker
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Problem with STI shifter fails to downshift

Postby Banjowhacker » 15 Dec 2013, 6:23pm

My Shimano 105 L/H triple STI shifter has just started playing up. I can shift up but it fails to engage when I try to shift down. No clicks, so it sounds and feels to me like the ratchet mechanism has gone. Does anyone have any experience of this and/or a useful fix that doesn't involve buying a new shifter?
I'm a fairly handy mechanic (although, having said that, I ought to have my 'mechanics wings' ripped from me for a couple of howling errors I've made elsewhere on the bike recently - but that's another story, or two...) and know that the issue is in the shifter as I've detached the front derailleur to make sure the problem's not there.
Any help most gratefully received :)

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gaz
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Re: Problem with STI shifter fails to downshift

Postby gaz » 15 Dec 2013, 6:43pm

The phrase "no user serviceable parts inside" sums the situation up very well.

Squirt in a generous amount of WD40 / GT85, manipulate the levers a few times whilst praying to the deity of your choice; usually does the trick.

Attempt any other maintenance at your own peril.
Hand wash only. Do not iron.

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Banjowhacker
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Re: Problem with STI shifter fails to downshift

Postby Banjowhacker » 15 Dec 2013, 6:59pm

gaz wrote:The phrase "no user serviceable parts inside" sums the situation up very well.


Ugh... 'Tis what I feared. Have already soaked the thing in thin lubricant and will wait to see what happens.
Why are these things so expensive yet apparently so fragile? :evil:

Brucey
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Re: Problem with STI shifter fails to downshift

Postby Brucey » 15 Dec 2013, 7:07pm

if the shifter is the slightest bit sticky it will need the 'pull' of the mech for a downshift. So the mech needs to be free and the cable needs not to be draggy.

Gaz's pithy summary is pretty much spot on otherwise.

A further commonplace fault is that a frayed cable has left strands inside the shifter (maybe not recently even) and these are making the shifter stiff.

cheers
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coast 2 coast
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Re: Problem with STI shifter fails to downshift

Postby coast 2 coast » 15 Dec 2013, 7:44pm

Unwrap the bar tape and check the cable is not snagging or fowling, as it leaves the cable outer and enters the STI unit.

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Banjowhacker
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Re: Problem with STI shifter fails to downshift

Postby Banjowhacker » 15 Dec 2013, 8:37pm

No trouble with the cable. It's definitely the shifter...

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Re: Problem with STI shifter fails to downshift

Postby Banjowhacker » 15 Dec 2013, 9:18pm

Well. [slightly] Less pain than I feared. Have tracked down the same model (few years old) on Ebay and have ordered a brand-new shifter, which should be with me from Taiwan in a couple of weeks...
Including postage, it came to less than fifty quid, which is more palatable than over double this that I'd've had to pay if I'd bought it from a UK store.
Does mean my daily commute will be by full-bounce mtb until my package arrives. Weather's looking iffy too. Can't really fit 'guards to an Orange 5 so I guess I'll be showering at work for a while then...

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cycleruk
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Re: Problem with STI shifter fails to downshift

Postby cycleruk » 15 Dec 2013, 10:03pm

Can you not adjust the front derailleur low stop to set it on the middle ring for the time being ?
There's no such thing as a tailwind.
It's either a headwind, or you're going well.

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Re: Problem with STI shifter fails to downshift

Postby Banjowhacker » 16 Dec 2013, 10:08am

cycleruk wrote:Can you not adjust the front derailleur low stop to set it on the middle ring for the time being ?

I would do but I need the small ring to climb a steep hill each morning (Bear Rd, Brighton).

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Graham
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Re: Problem with STI shifter fails to downshift

Postby Graham » 16 Dec 2013, 10:36am

". . . . .No user maintainable parts inside . . . ."

Which I would personally modify to say is - if the soak & lube measures do not resolve the issue then there may still be some chance of recovery
IF . . . . . . . .
You can find some instructions & photos on interweb to show you how to dissemble / re-assemble the unit.

If there are one or more broken parts within then all you have is junk ( because there is no way to get replacement parts ** ) - but at least you know for sure now !!

However, many of the older units had a problem with fossilised grease which can be soaked and brushed off.

I have recently revived a pair of STI RSX 7-speed shifters that had a long-term problem on the LH shifter and developed a seemingly terminal problem on the RH side.

I found some good instructions&photos on the web --> pulled them apart --> soaked off the rubberised grease --> regreased --> reassembled --> now working perfectly !!

** You may be lucky to find an equivalent sick or dead STI on Ebay ( or elsewhere ) for spares.

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Re: Problem with STI shifter fails to downshift

Postby Brucey » 16 Dec 2013, 10:43am

if you want to soak the mechanism for days or weeks then ATF works quite well; it has some unusual additives in it which make it quite good at that sort of thing. However it attacks many types of rubber, so best remove the hood first.

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Graham
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Re: Problem with STI shifter fails to downshift

Postby Graham » 16 Dec 2013, 10:58am

What is ATF, Brucey ?

( I would have tried a Forum search, but it doesn't work with three letters or less. )

Brucey
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Re: Problem with STI shifter fails to downshift

Postby Brucey » 16 Dec 2013, 11:11am

ATF - Automatic Transmission Fluid.

It is a transmission oil which is a reasonable lubricant but also has a high detergent value. Not good for prolonged skin contact BTW; it contains nasty additives including alkyl thiazoles (IIRC) and has the distinction of being one of the few substances I have handled which gave me contact dermatitis.

Not that I can endorse this practice, but one ad-hoc use of it is as an engine flush; if an engine has gone too far on one fill of oil, a pint of ATF added for 100 miles or so seems to clean everything up. I worry about clogging the oil filter.... but others have used this scheme to good effect.

Anyway it cleans sticky deposits off pretty well; in a similar vein to the above, a couple of rides on an ATF-lubricated chain (when you have been using a different lube that has left a sticky deposit) usually makes the chain a lot easier to clean afterwards.

cheers
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Re: Problem with STI shifter fails to downshift

Postby Banjowhacker » 16 Dec 2013, 1:17pm

[UPDATE]
Madison (UK Shimano distributor) has now asked me to send in the broken lever and they'll consider it for a warranty replacement, FoC! They know it's a 2008 model and well beyond the usual warranty period but have suggested they might be able to have it fixed/replaced. If so, good on them! However, having now made my Ebay purchase, I'll then end up with two L/H levers...