Help me understand what to do next, bicycle shifter woes

[WobblyHand]

Sounds like a plan. Just realize, bike shops are in the business to make money, and selling you new shifters makes them more money than spraying the guts down with WD-40 does.

If you decide to get new shifters, please collect the old ones back and ship them to me. I'll pay. I'd love a new project, and I have never taken one apart...but it's time for me to learn. My similar Dura Ace shifters are low mileage, but sticky, so it would be great to know how to take apart those 10 speed vintage STIs for servicing.

The more I think about this, the less I want to go to a shop. No shop has much incentive to fix this by actually attacking the problem. It's too labor intensive and risky for them to make money.

It appears to be the up shifter that is the issue. It should lengthen the cable so the derailleur moves outward towards the smaller gear. Sometimes it actually does this. Other times, it moves the other way! The down shifter seems to work correctly.

To replace the cable, I need to do something to get inside the unit. Not quite sure how that's done at the moment. I'll have to search for a video on that. I think the unit needs to be in the highest gear (loosest cable). I'm struggling to see the big picture at the moment, takes me a while. Once I understand that it's easier for me to proceed.

 

[WobblyHand]

Shifter is a ST-6600. So the corresponding datasheet can be found at https://si.shimano.com/en/pdfs/si/6K20A/SI-6K20A-001-ENG.pdf
That helps a little. Now to inspect the sheet, it is rather full.

 

[Nesse1]

I'd start, by removing the shift cables. Keep track of what goes where. When you get down to just the inner wire sticking out of the shifters, then you need to slow down and start diagnosing the problem.

Is it the front or rear derailleur shifter which is messing up? RH grip or LH?

Assuming it's the rear/RH, you should test it by grabbing the cable right where it exits the shifter and pulling, then jab the small downshift lever. See if the shifter will downshift. Then, try upshifting. Keep pulling on the cable to provide tension. If you get inconsistent action, then it's WD-40 time...and give it some time to work. Then try again.

 

[mksj]

Worth reviewing, it your problem is that they no longer shift then it can be that the grease has hardened and flushing it out and re-lubricating them seems to work. If it is sticking in the cable, I clean the cable and replace the cable tubing/set.

Shimano ST-6600 fix? Rescuable? - The Paceline Forum

Shimano ST-6600 fix? Rescuable? General Discussion

forums.thepaceline.net

Ebay item is another option

Shimano Tiagra ST-4600 ST-4603 3x10 Set Black Gear Shifter/Brake Lever - New | eBay

Find many great new & used options and get the best deals for Shimano Tiagra ST-4600 ST-4603 3x10 Set Black Gear Shifter/Brake Lever - New at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[WobblyHand]

I'd start, by removing the shift cables. Keep track of what goes where. When you get down to just the inner wire sticking out of the shifters, then you need to slow down and start diagnosing the problem.

Is it the front or rear derailleur shifter which is messing up? RH grip or LH?

Both RH and LH have an issue. Since I use the RH more, I'll start there.

Assuming it's the rear/RH, you should test it by grabbing the cable right where it exits the shifter and pulling, then jab the small downshift lever. See if the shifter will downshift. Then, try upshifting. Keep pulling on the cable to provide tension. If you get inconsistent action, then it's WD-40 time...and give it some time to work. Then try again.

On a ST6600, where do you actually spray? It's not clear to me where the ratcheting mechanism resides. The pdf I posted uses such tiny pictures its unclear where the mechanism is.

 

[WobblyHand]

Worth reviewing, it your problem is that they no longer shift then it can be that the grease has hardened and flushing it out and re-lubricating them seems to work. If it is sticking in the cable, I clean the cable and replace the cable tubing/set.

Shimano ST-6600 fix? Rescuable? - The Paceline Forum

Shimano ST-6600 fix? Rescuable? General Discussion

forums.thepaceline.net

Ebay item is another option

Shimano Tiagra ST-4600 ST-4603 3x10 Set Black Gear Shifter/Brake Lever - New | eBay

Find many great new & used options and get the best deals for Shimano Tiagra ST-4600 ST-4603 3x10 Set Black Gear Shifter/Brake Lever - New at the best online prices at eBay! Free shipping for many products!

www.ebay.com

If I were to remove the whole thing, I'd stick it in an ultrasonic bath and get it over with. Not there yet. Will try squirting lube in there - where ever "there" is. A bit fuzzy on that at the moment. The ratchet mechanism isn't visible so it's not apparent to me where to attempt to lube/clean.

 

[mksj]

I would put it in an ultrasonic bath, try to clean out the old grease which has probably solidified and then try to spry it with some wd40 or penetrating oil. If I recall you may be able to get lubrication into the mechanism either through the cable hole and also around the pivot mechanism. I had these types of shifter on my Kestrel road bike many years ago and that is what I did. The problem when they sit for very long periods was the grease wold hardened. I have taken apart the MTB shifters to clean and replace the cables but not the road bike ones.

 

[Nesse1]

Both RH and LH have an issue. Since I use the RH more, I'll start there.

On a ST6600, where do you actually spray? It's not clear to me where the ratcheting mechanism resides. The pdf I posted uses such tiny pictures its unclear where the mechanism is.

Pull the brake lever against the bars, and look in through the front. The shift mechanism is literally in the head. Put a rag under the unit, and spray in every opening you can find...

 

[WobblyHand]

My shifter has evidence of some light grit on the grease which has wept out. I will try the spray lube stuff first, but I may end up dunking it in a tank. Of course I don't have an ultrasonic cleaner, but hey, that's how we collect/justify new gear?

I did get to the point where the cable freed up enough to replace it. The cable was a bit stiff in the sleeve at first, it took a bit of effort to move it. It now moves quite a bit more smoothly (by hand). I need to bring the bike outdoors for this next spraying operation, it will be too messy for living space areas.

I found somewhat accidentally that if the upshift lever is pushed away, it tends to shift better then if it is slightly pulled forward towards the operator. This might be wear, but I'm going to try a blast of lube everywhere first to see if anything gets better.



Does anyone know what the bottom black screw does?

 

[Nesse1]

I'm not sure what's under the plastic cover. If you can remove the screw and remove the cover, do it. Just don't force anything and break the cover.

I'd leave just the wire cable attached to the lever. Put the housing aside. The shifter works best when there is tension in the cable, which you can supply by pulling the cable.

Spray the heck out of it, then pull the cable and shift up the range, then right back down. Up, up, up, down, down, down. Work the shifter, while pulling the cable. And with lots of lube spray. It shouldn't take very long to figure out if the shifters can be saved.