Been going back and forth adjusting limit screws and tension.
7 Speed. When in the largest cog, the Shimano gear shifter reads 2. The chain will not shift to the smallest cog. When in the 2nd smallest cog, the shifter reads 7. So, no clicks remaining to get to the smallest cog. Any suggestions to resolve the issue.
Undo the cable. Unclick the shifter all the way to the highest number. Dial the barrel adjuster for the derailleur all the way in (clockwise). Give a subtle tug on the cable to only remove the very most basic slack. Reattach the cable. Dial the high limit screw all the way out. Look over the cassette and the pulley. Dial the high limit screw in until you see the pulley align with the smallest cog. Turn the crank and begin to dial the barrel adjuster slightly out while you attempt to shift up. If it doesn't shift up, shift it back down, dial the adjuster out a little more and try again. Repeat this process until the shifting is smooth. If problems still persist, it means you likely need to replace the shifter or the derailleur.
Clicked the shifter to the highest number. Then aligned the derailleur to the smallest cog by rotating the high limit screw. I did not detach the cable. After that, worked just fine.
(10-31-2025, 03:46 PM)Michael Wills Wrote: Clicked the shifter to the highest number. Then aligned the derailleur to the smallest cog by rotating the high limit screw. I did not detach the cable. After that, worked just fine.
Thanks Michael !!
I do have a question about the initial problem. Did it just occur out of the blue (i.e. shifting was working just fine and then next ride or during a ride it became faulty)? Or, was this bike obtained with the fault pre-existing? Had you replaced any parts just prior to the problem?
It makes a difference since with your fix the latter easily makes sense, as I have found many shifting systems merely improperly adjusted upon receiving where it appeared replacement parts and/or owner/shop did not properly set up the bike. If the shifting was functioning fine and suddenly became faulty it is odd since limit screws are designed to not change their settings unless physically manipulated. That is usually by the owner, shop, and/or an accidental contact (accidents, transporting, etc.); or maybe by supernatural means (poltergeists, leprechauns, etc.).
I always blame the supernatural (called "PFM") to divert attention from my own defficiencies, as I'd like to think I am without fault.
I find it amazing when I see posts like this at the amount of bad advice given as if its the blind leading the blind. I think its great that someone wants to help and takes the time to do so and I mean no disrespect. But the only problem I see here is lack of knowledge and info/help of wrong or poor quality and procedure. The sad part is that this is the most common setup on any multi speed bicycle and yet bad advice abounds everywhere. So here is a novel Idea, How about taking a look at a Shimano tech document to see the basic starting point of a rear derailluer and index shifting setup. Even the Shimano Tech doc has bad info as you will see calling the h-limit screw the low, even the park tool video guy does not understand the importance of how cable tension is achieved or how to do steps 1,2,3, every time vs 1,3,2, half the time. Both Reap and park tool guys do not start with the h limit screw in the correct position to achieve proper cable tension, nor do they start with the most important step 1 of checking the derailluer alignment. Reap does not at all and the park guy mentions it but only as a course if what he tells you is not working very well, hence his steps end up being 1,3,2,. Nor does the Shimano tech doc. Reap must not start with the derailluer alignment check using a dag tool either, and his use of the h-limit screw and timing of cable attachment is also kinda wrong. he does however state start with the barrel adjuster screwed all the way in which would be correct and his attaching of the cable correct just at the wrong time.
I will try to simplify the steps in correct sequence to help understand how proper indexing should occur and how this relates to how proper cable tension becomes automatically achieved.
Step 1. using a dag tool check hanger alignment and adjust if needed. Make sure the wheel is true before this step.
Step 2. Set The h-limit screw. notice in the diagram how the pully is off center outwards of the highest cog. It is not directly centered under the highest cog
This is very critical for proper cable tension and smooth indexing.
Step 3. Pull cable by hand and click shifter several times to make sure it is in the highest gear and making sure all housing is properly seated in all cable stops.
Step 4. Attach cable by tugging tight enough to remove slack and secure cable.
Step 5. Pedal in stand and shift down one gear on the shifter. If it moves to the next cog great, if not but acts like it wants to and is noisy that is fine also. Now Turn barrel adjuster to tension cable until you start to hear chatter of the chain hitting the next cog, then back off barrel adjuster to the point the chatter has stopped. Work shifter up to first gear and set the L-limit so pully is directly under the cog. Indexing is now set. Check by moving up and down for smooth shifting.
It is now that your cable tension is set automatically. Because the pully starts off outboard of the smallest cog and setting the indexing in the above steps when you now are in the highest gear your pully will be directly centered below the high gear. So now you have zero slack and proper tension the second you start to push on your shifter it will move instantly at the proper ratio.
So all I can say is, if the poster thinks he has solved his problem, he did not. At least as far as having a finely tuned bicycle.
All of the above info will only work if all the components are in good working order, cogs, chain. shifter, cables/housing. etc.
I will also note that after the cable is attached and the first downshift is made it is best if it does at least grab the gear or at least be trying to. If it does not at all reattach cable with a bit more tension. This will avoid backing out the barrel adjuster excessively.
All this is really rather simple once you understand exactly how things work and doing it a few times. Hard to convey in a forum as opposed to seeing this happen on a video.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Bravo @Painkiller! I too make assumptions about what someone has or not checked when they request help online so I apologize. That is why I ask questions before giving answers.
Never is enough info provided when help is requested. To make things worse bike shops are becoming more and more casual in their "repairs"; more often trying for the quick fix as opposed to verifying the base elements and proceeding from there; but still charging for what should be done as opposed to what was actually done.
My most recent visit to a shop was due to not having a tool where I currently reside (though I do own one). I made sure by calling the shop first to see if they had the tool and would do the work. Affirmative to both, but upon giving the parts to the senior mechanic found he did not know how to do it correctly and out of 3 assemblies he only managed to complete one successfully with myself having to work in their service area to do the other 2; all the time being told how to do it! It was sad and funny at the same time.
When out riding with new biking partner who wanted to do some real cycling (high speed long distance) with me I found at the start thatvhis tide was all mucked up and not even set up for his size nor tires even close to proper pressures or drivetain clean and lubed; wheels were amazingly true so no issue there. I did what I could with my carry-on tools just to get him going (adjusted saddle and bar, some oil on the chain, pumped up tires, and tweaked the shifting). He could not believe what a difference it made, but I told him he needed to take it to a shop and have everything checked out since I could tell that the shifting was poor, hanger propably misaligned, derailleur cage misaligned, and noisy as heck. He apparently went and had it checked out, but they did not do a thorough job (seemed like nothing was done!) because it looked and sounded the same though he paid enough that it should have been done properly. They may have wiped down and lubed the chain, and adjusted shifting and brakes some (about 15 minutes work), but definitely did not clean the chain in a solvent bath or clean any of the cogs, nor any alignment check (derailleir visibly still misaligned). Now I am going to do it all for free to show him what should have been done for the money he spent (it was on a cheap generic bike with a low end Shimano "whatever" groupset). I know I'll have to align the hanger, straighten and align the cage (already recommended he buy a new mech), dip the chain (after checking its wear), and clean rhe cogs tooth by tooth before even testing if out. I want him to call that shop and ask them exactly whay they did so I can show the what they did not do. I do not want to work on another's bike anymore, but I hate riding along with someone that has a bike looking and sounding like it is going to fall apart.
I too had seen that Shimano instruction and at first scratched my head wondering why both adjustments were worded for the "low" limit screw.
It is so bad it seems anymore around my town that I just would not trust any of the shops to touch my bikes. These issues like this post are not even real issues, just owners messing with stuff they do not know about and getting bad advice when they get help that really isn't.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
(10-31-2025, 03:46 PM)Michael Wills Wrote: Clicked the shifter to the highest number. Then aligned the derailleur to the smallest cog by rotating the high limit screw. I did not detach the cable. After that, worked just fine.
Thanks Michael !!
I do have a question about the initial problem. Did it just occur out of the blue (i.e. shifting was working just fine and then next ride or during a ride it became faulty)? Or, was this bike obtained with the fault pre-existing? Had you replaced any parts just prior to the problem?
It makes a difference since with your fix the latter easily makes sense, as I have found many shifting systems merely improperly adjusted upon receiving where it appeared replacement parts and/or owner/shop did not properly set up the bike. If the shifting was functioning fine and suddenly became faulty it is odd since limit screws are designed to not change their settings unless physically manipulated. That is usually by the owner, shop, and/or an accidental contact (accidents, transporting, etc.); or maybe by supernatural means (poltergeists, leprechauns, etc.).
I always blame the supernatural (called "PFM") to divert attention from my own defficiencies, as I'd like to think I am without fault.
I had installed a new rear derailleur. Someone had set a Trek MT220 bike at the curb to be picked up by the trash folks. So, I took it on as a project. Never done maintenance before, so seemed like a good way to learn.
(11-03-2025, 08:43 AM)Michael Wills Wrote: I had installed a new rear derailleur. Someone had set a Trek MT220 bike at the curb to be picked up by the trash folks. So, I took it on as a project. Never done maintenance before, so seemed like a good way to learn.
Thanks again Michael.
I suggest you read Painkiller's comment about derailleur hanger alignment and derailleur adjustment. Many frames new out of the box are misaligned so on a used bike that needed a rear mech it makes really good sense to get the alignment checked. The rear wheel needs to be true so if it is not and you take it to a shop for alignment make sure you have it trued beforehand or have the shop do it prior to the alignment check. Hub needs to be mounted properly also.
Note: a truing wrench is cheap and you can true the wheel on the rim without using a truing stand but you need to know what you are doing so I recommend you let a shop do it for you. The DAG tool is not cheap: good ones about $75 and up; cheap ones can be had for around $30, but they are not really that accurate without modification. Since you are only dealing with your bike it is again something I'd have the shop do (hoping that they are using a quality tool).
BTW The "B" screw is NOT a tension screw, It adjusts the distance from the jockey sprocket to the largest sprocket on the cluster. On my SCRAM derailer, the distance should be 7mm.
My $0.02 cents. The hanger bracket can come loose. Easy quick check and fix. 2mm of wobble could cause lots of issues. Don't assume it's always a big problem.
(01-24-2026, 08:47 AM)rydabent Wrote: BTW The "B" screw is NOT a tension screw, It adjusts the distance from the jockey sprocket to the largest sprocket on the cluster. On my SCRAM derailer, the distance should be 7mm.
The "B" screw is not for adjusting chain tension per se, but it does affect chain tension and that should be talen into consideration when mak8ng adjustments.
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