Adjusting Derailleur / Cable Tension On Shimano Deore 10 speed RD-M4120

Catalyzt

Well-Known Member
Region
USA
Hi, folks,

Yesterday, I had my first ride over 10 miles for the season (15 miles, 1,100 feet of vertical) and I noticed that the chain was often not dropping into the right gear when I moved the shift lever a click-stop, made that rattling 'between gears' sound or didn't shift.

I also noticed that a few times when I was supposed to be in high gear, the crank was freewheeling-- no resistance while pedaling, no power being delivered to the rear wheel. What does this mean? Had the chain jumped past high gear? Or maybe didn't make it into high gear? I'll put it up on a cinderblock to check, but I'm guessing it jumped past 10th or was stuck between gears somehow. Never had this symptom on an acoustic bike.

Sometimes, it would pop out of gear and kinda freewheel, but with that rattling 'between gears' sound-- that's a symptom I am familiar with, the kind of problem I expect after owning any bike (or replacing the derailleur) after 18 to 24 months.

I'm going to prop the crank/motor on a cinderblock, leaving the front wheel in the rack, and try some adjustments, see if I can avoid a trip to the shop. I found a video tutorial for an acoustic Shimano Deore that seems pretty similar.

Any tips, links to relevant videos, warnings, etc. would be welcome. I just don't particularly want to lose the bike for four or five days, which is the typical turnaround for this time of year, or spend the money to adjust the cable tension if that's all it is.

What makes me a little suspicious -- the onset of the problem seemed very fast. Like, maybe it slipped a gear once or twice on the last ride or two, but it got much more pronounced during yesterday's ride.

Thanks so much!

Deiralleur:
SHIMANO RD-M4120, DEORE, SGS 10/11-SP, TOP NORMAL, SHADOW DESIGN

Cluster:
SHIMANO CS-M4100-10, DEORE, 10-SPEED, 11-13-15-18-21-24-28-32-37-42T
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
I agree there's some adjusting necessary. I would encourage you to go for it. See if you can adjust it yourself! Worst case, you're no worse off than you are now, facing a trip to the shop to let them do it for you!

Watch a couple of videos to familiarize yourself with the basics and give it a try. If it doesn't work out, go back to those videos and review with some first hand experience under your belt. Safe bet that new found/fresh experience will shed a new light on the videos, allowing you to identify the issues necessary to adjust as required.

The real beauty of learning this yourself, or at least have the basics in hand, is you can tweak your settings occasionally to maintain perfect shifting....
 

Catalyzt

Well-Known Member
Region
USA
Thanks, AH. I will give it a shot.

Okay, I jerry-rigged a stand using a microphone stand and a web belt-- I know, it sounds insane, but with the front wheel locked into it's stand, it's actually surprisingly stable, and I cannot duplicate the problem... exactly.

1) The bike seems to be shifting relatively smoothly... it's physically dropping into the gears correctly, and not failing to shift sometimes, as it does under load. Listening carefully, it's possible that there's a little more rattle / friction than usual in the drive train, but it's hard to tell. Is that unusual? I seem to remember with acoustic bikes, if it shifted badly on the road, it shifted badly upside down.

2) It is very hard to tell if the derailleur is aligned properly with each gear in the cassette. It doesn't look off. Gun to my head, the derailleur might be a little outside. Over time, does the derailleur tend to drift outside or inside? What typically happens, which way does it drift?

I'm fine for some trial and error, but just trying to figure out what's most likely to be wrong, decrease the number of trials. Thanks!

--Cat
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
The cables will sometimes wear/stretch a little, making them LONGER. A longer cable will have a tendency to carry the chain outside (towards a smaller gear) of where it should be. If this is the case, you would want to tighten/unscrew the adjuster to compensate. In my experience, a little goes a long way here. Maybe try unscrewing the adjuster, makes no difference which one, maybe 1/2 turn and give that a try.
 

Catalyzt

Well-Known Member
Region
USA
Ah, I missed your reply but I think that's what happened-- however, I think some of the other adjustments must have been off.

Or that's my story, anyway, because I adjusted... all of them.

Very frustrating, sweating, the terrier was trying to help, I'm trying to keep his tail out of the spokes, the bike is banging around on the microphone stand, bad light, weird screwdriver.... kept rewinding the YouTube video repeatedly and being forced to watch ads because I'm too cheap to subscribe... some bad moments.

I was constantly forgetting which direction I was supposed to be turning the cable adjustment... my brain was never great for short-term recall of that kind of detail, (and it didn't get any better in the '70s and '80s) -- I can forget where I put down a cup of coffee (or anything else) and spend 5 minutes looking for it, and I'm terrible with tools. I always tell people, if you see me with a power tool in my hands, don't even try reasoning with me, just call the fire department.

I got it to sound as good as I could in each gear, but it still seemed kind of noisy, too much friction somewhere. Worked on it off and on about two hours.

Imagine my shock when I wheeled it outside, rode up and down the street rowing through the gears, and it shifted... perfectly.

The lower limit screw is just a little too tight, needs another half turn or so, and my "B" screw adjustment was a total hail Mary-- I screwed around with it a LOT, can't even remember what I did... I may have eventually moved it to a completely different position, or wound up setting it back to where it was originally.

I think I'll tweak the lower limit and try a SHORT ride tomorrow. Thanks again for your encouragement!
 

Catalyzt

Well-Known Member
Region
USA
Definitely better-- no freewheeling, or complete gear misses, 95% of shifts were okay.

Chain is still slipping out of gear on rare occasions when under load-- less frequently, I can go miles without it happening, but I suspect chain wear, ordered Park Tool to measure. Thx.
 

Davey Do

Member
Region
USA
City
Goofy, Illinois
Chain is still slipping out of gear on rare occasions when under load-- less frequently, I can go miles without it happening, but I suspect chain wear, ordered Park Tool to measure. Thx.
Mine was doing the same thing, Catalyzt, even after adjusting the derailleur. I found the derailleur mounting screw was not tight and the rear set screw was adjusted out too far. Problem solved.
 

Catalyzt

Well-Known Member
Region
USA
Mine was doing the same thing, Catalyzt, even after adjusting the derailleur. I found the derailleur mounting screw was not tight and the rear set screw was adjusted out too far. Problem solved.
Thanks-- I think the mounting screw (sort of a bolt) is okay, but will recheck.

Also, what do you mean by the rear set screw? Do you mean the "B" screw-- the third screw that is neither the Upper Limit screw or Lower Limit screw?

I really guessed on the that particular screw, not confident of my adjustment. Do you mean that you adjusted that screw so the derailleur "closed" more-- moved the pulleys closer to the axle? Thanks!

It could be chain wear, but might be a little soon for that-- had the bike 900 miles, though I've been riding more dirt for the last 200-300.
 

rich c

Well-Known Member
Plan out your adjustment, and make fine adjustments each time. Like 2-3 clicks one way with the tensioner by the shifter. Doesn't improve, then go back the same number of clicks, and THEN go 2-3 more. Spin the pedals and shift gears. If no skipping, then go to the limit screws and get them aligned. It's pretty easy if you just don't make wild swings in the adjustment without taking notes. A work stand will be a great investment.
 

Catalyzt

Well-Known Member
Region
USA
Mine was doing the same thing, Catalyzt, even after adjusting the derailleur. I found the derailleur mounting screw was not tight and the rear set screw was adjusted out too far. Problem solved.
And good thing I checked. The derailleur mounting bolts were fine... but the quick release was open, and the bolt on the other side was loose enough to spin with only the slightest amount of pressure. Don't know how I missed that.

There was nothing holding the wheel to my bike but gravity and-- apparently-- a bit of good luck. You, sir, have done your very good deed of the week-- and may have saved me from serious injury or damage.

If the wheel was moving around in the bracket, that could totally explain the occasional chain slip-- and the sudden onset of the problem.

Plan out your adjustment, and make fine adjustments each time. Like 2-3 clicks one way with the tensioner by the shifter. Doesn't improve, then go back the same number of clicks, and THEN go 2-3 more. Spin the pedals and shift gears. If no skipping, then go to the limit screws and get them aligned. It's pretty easy if you just don't make wild swings in the adjustment without taking notes. A work stand will be a great investment.

All good advice. I'm adding a pad and pen to my tool kit, my short term memory is just too bad.

There is no longer any gear/chain slipping on the stand, it's only under load, but I could have gotten this done much faster if I'd taken your advice.

And yes, I will get a stand. Though knowing myself, I will try several other stupid ideas first-- suspending the bike between two mic stands, setting up some kind of sling from the banister on the stairs or the upstairs balcony, etc.

This is gonna be great. Wife will be thrilled.
 

Catalyzt

Well-Known Member
Region
USA
And tightening the quick release eliminated the last of the chain slip. 7 mile shakedown ride last night over pretty bad pavement, steep hills, lots of shifting, not a single episode of chain slip.

My theory: At some point, maybe when crashing through brush, maybe just when backing it out of the living room, the quick release got flipped. The wheel loosened, and movement of the wheel yanked the derailleur slightly out of position and/or changed the cable tension.

It's possible that the flipped quick release was the only problem, but I think the fact that part of the problem resolved with derailleur adjustment suggests that the loose wheel screwed up the derailleur adjustment. Hard to be sure.

Okay, that took a few hours, but saved me at least $150, as well as being without the bike for 5 days or so... and having to do the 2.5 mile walk first from, and later to, the bike shop in the hot sun. And I wound up with a chain measuring tool, which I should have anyway. Thanks everyone for their help!
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Awesome. Congrats on the persistence to track down the issue and get 'er done - yourself.
 

PDoz

Well-Known Member
Check your wheel bearings are ok - that's another explaination for the axle starting to come loose. It usually takes me 3 adjustments before I remember this....
 

Davey Do

Member
Region
USA
City
Goofy, Illinois
There was nothing holding the wheel to my bike but gravity and-- apparently-- a bit of good luck. You, sir, have done your very good deed of the week-- and may have saved me from serious injury or damage.
Whew! Lord love a duck!

Thank you for your kind words, Catalyzt. I usually don't think about going over my bike to make sure everything's tight until I'm heading down a hill at a breakneck speed. Then, by the time I get home, it's usually forgotten.

But I've told my wife and everybody else that if I die while bicycling, I died happy.
 

rich c

Well-Known Member
Whew! Lord love a duck!

Thank you for your kind words, Catalyzt. I usually don't think about going over my bike to make sure everything's tight until I'm heading down a hill at a breakneck speed. Then, by the time I get home, it's usually forgotten.

But I've told my wife and everybody else that if I die while bicycling, I died happy.
That's fine for you, not so much for your family and friends! When my Dad died in a combine driving to the field, I heard that from everyone. But to suddenly loose your father or close friend because he didn't tighten a bolt on his bicycle would be a devastating blow for the family and friends.
 

Catalyzt

Well-Known Member
Region
USA
Check your wheel bearings are ok - that's another explaination for the axle starting to come loose. It usually takes me 3 adjustments before I remember this....
Whoa... let me see if I understand... you mean that a bad bearing inside the axle could cause the wheel to come loose?! I believe you, just curious how this works, I'll remember better if I understand the mechanics of it. What, so... the bad bearing causes extra vibration when the wheel is spinning, and that extra vibration, over time, would cause the axle to become loose in the dropout, maybe even popping open the quick release? Sorry if I'm a bit dense. My short term solution: Take the bike in if this happens a second time, at least within the next few months.
Whew! Lord love a duck!

Thank you for your kind words, Catalyzt. I usually don't think about going over my bike to make sure everything's tight until I'm heading down a hill at a breakneck speed. Then, by the time I get home, it's usually forgotten.

But I've told my wife and everybody else that if I die while bicycling, I died happy.
That's fine for you, not so much for your family and friends! When my Dad died in a combine driving to the field, I heard that from everyone. But to suddenly loose your father or close friend because he didn't tighten a bolt on his bicycle would be a devastating blow for the family and friends.
I'm with you, Rich! Davey, let's make a solemn pact here and now to give our bikes a careful going over at least every 30 to 50 miles, eh? And for me, that means don't just look at the bolts or twiddle at them with my finger, but get out the frickin' Allen wrench and test them. (One bolt on the suspension needed some attention as well, though not much.) Thanks again!

Rich, I had a terrible wipeout on my body board early last winter. It was due to a rogue wave, and as I realized I couldn't bail, that I was going to make a three or four foot drop through open air with a ton of water behind me, it was a great comfort to know: "I was not careless, I'm not tired, it's not too late, I trained well for these conditions, and this was not my fault. This was a stealth close-out. I have heard of this type of wave at this beach, and even surfers who've been at it three times as long as I have and who surf far bigger waves have told me that these are impossible to predict, that even two-footers can turn into neck-breakers."

That gave me a lot of peace-- and I needed that serenity to land correctly and survive the first two terrible impacts, and remember exactly what I had to do when the third ripped me off my board and held me under over 30 seconds with very little air in my lungs. Feeling guilty and careless would have been a distraction I really didn't need.

Yeah, I wouldn't mind dying on skis, on my board, or on a bike-- there are worse ways to go-- but only if I knew it was truly an act of God, that I'd done everything I could reasonably do to prevent it.
 

Davey Do

Member
Region
USA
City
Goofy, Illinois
C'mon, guys, lighten up!

I was a medical professional for over 40 years, dealt with my share of death many, many times, was hit head on by a drunk in a pickup while on my motorcycle at the age of 19, in a coma for three weeks, hospital for 3 months, had an NDE, have been stabbed in six places by a patient diagnosed with undifferentiated schizophrenia, rolled my pickup 4-5 times after careening 10-15 feet over a concrete guardrail and lots of other near misses!

I have been there, done that, bought the T-shirt, and paid my dues, so if I and my loved ones are okay with my demise, that's good enough for me!

Sheesh!
 
Last edited:

rich c

Well-Known Member
C'mon, guys, lighten up!

I was a medical professional for over 40 years, dealt with my share of death many, many times, was hit head on by a drunk in a pickup while on my motorcycle at the age of 19, in a coma for three weeks, hospital for 3 months, had an NDE, have been stabbed in six places by a patient diagnosed with undifferentiated schizophrenia, rolled my pickup 4-5 times after careening 10-15 feet over a concrete embankment and lots of other near misses!

I have been there, done that, bought the T-shirt, and paid my dues, so if I and my loved ones are okay with my demise, that's good enough for me!

Sheesh!
Death or near death is a personal thing Davey Do. I don't appreciate you telling me to lighten up. I don't know how old you are, but I'm turning 70 in September and it is definitely on my mind that I will not have 20 good years left. My Dad was gone in an instant, and my Mom died from complications of Alzheimer's. A 2 year experience of a day by day death. Both very hard shocks to the my psyche.
 

Davey Do

Member
Region
USA
City
Goofy, Illinois
Death is so personal to some that they bring up the sensitive subject on the internet during a discussion on derailleurs and honor the dead by trying to prove a point to a stranger.

A higher consciousness is gained through illuminating revelations due to dealing with trials and tribulations.
 

Davey Do

Member
Region
USA
City
Goofy, Illinois
Hey guys! Let's use derailleurs as a symbol to life's struggles!

A fella is pedaling in the highest cog when he comes to a hill, does not realize he is riding a multi-speed bicycle, so he stands up on the pedals and struggles up the hill.

Another bicyclist happens by while the first is struggling up the hill, and says, "You know, if you down-shifted that derailleur, you could take that hill with ease".

The first bicyclist says, "I don't appreciate your advice, and will continue bicycling as I always have!"

Some of us are more comfortable with pain & struggle.