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Shimano Sora Thumb Shifter

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Shimano Sora Thumb Shifter

Old 08-18-21, 08:10 AM
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SethL
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Shimano Sora Thumb Shifter

I have a 2012 Specialized Dolce with Shimano Sora. Bike has not been ridden in awhile but my wife wants to start using it again.

Its a 9 speed with two chain rings on the drive side. For that year bike shimano designed the shifters with a big lever and a thumb shifter. The thumb shifter does the same thing the smaller shifter would do. On the left side the big lever pulls the chain up to the bigger ring. It takes 2 shifts to do this and I imagine this is because it was also designed to work with a a 3 ring chain.

When I use the thumb shifter to get it back on the smaller ring, you have to press really hard to get it to release and then its two clicks

Any suggestions on how to unfreeze it so you don't have to press so hard? Is it possible to adjust the system from 1 to 2 clicks?
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Old 08-18-21, 08:21 AM
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It may be set such that the derailleur hits the stop before the shifter has pulled enough cable to hit the final click. This means you have to reach super high cable tension to compress the housing enough to get to the click, and then that tension is pulling against the shift mechanism which makes it difficult to actuate the lever.

A couple thoughts -

1. If you shift to lowest gear (shifter lets out all cable), is the cable completely slack, or is it close to being under tension? In my experience, if using a triple shifter on a double crank, it is best to use the click between the shifter's gear 1 and 2 - the first click rather than between the shifter's click between 2 and 3. If you let all the cable out of the shifter, set the L endpoint screw so the F derailleur is barely touching the chain when the rear derailleur is on the smallest cog, then undo the F derailleur cable bolt and pull all the slack through. Adjusting the point on the cable that is anchored to the derailleur may be the solution to all your problems.

2. Are you sure you have the F derailleur cable routed through the front derailleur properly? A lot of F derailleurs require a specific angle of approach for the cable and it is not necessarily intuitive when putting it together.

3. Is it possible there are 'trim' clicks in your shifter - clicks half way between the gears intended to allow you to move the derailleur slightly to keep the derailleur from rubbing when the chain is at more of an angle? Most indexed road shifters have this feature, but possibly not Sora.
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Old 08-18-21, 08:24 AM
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The firmness of the thumb clicker release button has to do with how hard the shifter mechanism is jammed against the derailleur limit screw. Try backing off the inline tension adjuster. Or, if you don't have one or if it is as short as it can be made, back off the front derailleur H-screw, but not so much the derailleur overshifts over the big ring. If this helps, but overshifts, reset the cable tension at the fixing bolt.

Sora came in both double & triple versions. Don't confuse the trim position of a double version with the 2nd chain ring position of the 3 ring version. The model number embossed in the shifter under the hood will tell you which one you have. IIRC triple versions of most Shimano things end in "03"
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Old 08-18-21, 09:57 AM
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I recently found the chart below online, although I think it has been around for a while. I posted it in another thread but so far no one has said it is wrong. I find invaluable for knowing where the trim points are, and what each click is supposed to do for different STI shifters.

The first thing you need to do is figure out what each click does. I've never had an issue with an STI shifter freezing if I used the inner-middle positions, but I understand others have.

It is my understanding that the one thing about the Shimano thumb downshift lever is that is has no trim function. When you press it, it will drop down to the next chainring position. Inner chainring trim to inner, outer chainring to first, outer trim to outer.

I would remove the chain, disconnect the cable go to the inner shifter position, reconnect the cable and see how the derailleur moves each direction for each click (Added: The ST-3400 has an optical display that will move more for a complete shift and less for trim). Cable tension, how slack in the inner chainring, and the high limit stop play a part in forcing the shifter and wedging/freezing against the pawl in the shifter.

John

Last edited by 70sSanO; 08-18-21 at 11:03 AM.
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Old 08-18-21, 11:24 AM
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These responses are so helpful. I will take a look at the cable tension and limit screws on the front derailleur. Do the shifters need any kind of lubrication?
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Old 08-18-21, 12:52 PM
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When I set up a triple shifter to shift a double, I set it up so that the unused position lets the cable go slack when the derailleur is on the small ring, rather than using the high limit to lock out the third shift. This avoids jamming (and potentially damaging) the mechanism against the high limit while accidentally attempting to shift past the big ring.
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Old 08-18-21, 02:13 PM
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The only way I can see it getting jammed, using the inner and middle shift positions, is if you set the high limit screw to stop the FD; which you don’t need to do. There is no middle limit screw stop to set on a triple and it doesn’t overshift. Of course you have to set it to prevent another shift.

It can become a bit of an art form getting the right low limit, cable slack, or lack thereof, so that the shift works correctly. Actually, I set the high limit after I’ve got everything setup correctly with an STI. That way there is no pressure or forcing against a hard stop. I just try to get barely backed off.

Running a triple STI shifter with a double crank requires a high limit to stop from shifting to a non-existent 3rd chainring. A double STI shifter with a double crank makes a high limit a bit redundant; but we all set it. Same with a low limit setting on an RD with an STI shifter. And it is just as possible to force a RD shifter pawl with a bad low limit setting.

John
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Old 08-18-21, 09:02 PM
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Originally Posted by SethL View Post
These responses are so helpful. I will take a look at the cable tension and limit screws on the front derailleur. Do the shifters need any kind of lubrication?
Oh boy! do a quick search for lubing STI shifters and see how many hits you get. Yes, the shifters do want periodic lubing. That almost no one does this level of routine maintenance is why there are so many gummed up shifters to write forum threads and make vids about At one time early on in the move friction shifters Shimano offered guidelines on the lubing schedule. Suffice to say it's like keeping hydrated. If you don't drink before you get thirsty you are already behind the curve. I suggest adding medium weight oil to the shifter pods annually. Not much is needed to keep the factory lube soft and slippery. Too much and you get drainage that wants wiping off. Andy
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Old 08-18-21, 09:50 PM
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Originally Posted by 70sSanO View Post

It is my understanding that the one thing about the Shimano thumb downshift lever is that is has no trim function. When you press it, it will drop down to the next chainring position.

John
I have ST3300 brifters and they definitely have a trim position with the thumb switch. You can press the thumb switch down half way and itíll move the FD slightly to the left.
Anyways, to the OP: you should definitely take the brifters apart, flush out the old grease and lube with new grease. They all get gunked up with age.
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Old 08-18-21, 10:24 PM
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Originally Posted by icemilkcoffee View Post
I have ST3300 brifters and they definitely have a trim position with the thumb switch. You can press the thumb switch down half way and it’ll move the FD slightly to the left.
Thanks, that’s good to know.

John

Edit Added: It appears that there is also a thumb (B lever) trim on the ST-2300 double; not the ST-2303.

Last edited by 70sSanO; 08-19-21 at 09:15 AM.
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