Papa Tom

Some of you may have read my rants about the problem I've had with my drive-train for over a year now.

You know when your derailleur is slightly out of adjustment and you feel like your chain isn't sitting quite right in the chain ring or cassette? This is annoying, but it can usually be fixed with a simple tweaking of the shifter cable tension, right?

OK, so I use a 1996 GT Outpost mountain bike as a commuter, a touring bike, and as a recreation vehicle. Don't judge me...just listen. This thing has been kept in top form for twenty years and its gears have always shifted like a steak knife slicing through room-temperature butter. However, for at least the past year, any time I shift onto the 4th cog (sometimes the 5th), my chain starts mashing around like it just doesn't want to sit on the teeth for some reason. After replacing the chain (which was nowhere near the end of its life) I started with a succession of adjustments, at first doing it on my own, then finally calling on more than one local mechanic. Nothing made a difference.

Then, on one mechanic's suggestion, I swapped out both pulleys on my rear derailleur. Nothing. So I replaced the whole rear derailleur. Same problem. Then I replaced the Shimano HG cassette with the exact same one -- and I replaced the Shimano HG chain again, too. No difference at all. Naturally, I figured "It's gotta be the chain rings on the crankset, then!" and I proceeded to replace the entire crankset with an exact match. It should be noted that I have literally not shifted out of the middle chain ring (I have a triple) for what seems like years, which is why I was so confident the ring must be worn so badly it can't even line up with the 4th cog anymore. Idiot.

Once I installed the new crankset, I couldn't wait to get on the bike, certain that the problem HAD to be solved. Bottom line? A few hundred dollars later, that damned chain is still dancing all over the 4th cog, although it sits beautifully on every other one (except, as mentioned, the 5th, which is sometimes smooth and sometimes borderline).

This problem pre-dates a new bottom bracket and a new set of platform pedals, so I can also rule out those components as possible culprits. The only drive train component that has not been replaced is the front derailleur, but that seems like a stretch, as the problem is with the rear gears. If anything, I thought the new set of chain rings on my new crankset might deliver a straighter chainline, but apparently, I'm a dreamer.

I have ridden the bike enough hours and certainly enough miles to satisfy myself that this is not a life-threatening issue. I don't seem to be breaking chains or slipping gears. But the mystery of this sound and this frustrating crunching-feeling every time I pedal has really dampened my enjoyment of riding. The last bike mechanic I brought this to recommended that I get a loud radio. I laughed, but this isn't funny anymore, and it has gotten expensive. So here I am, pleading with anyone who might have an answer to share it with me. I don't want to give up the bike that has carried me so many miles through so many cities over so many years, but I am only willing to invest another $50-100 in a solution before I have to start cutting my losses.

Anybody got anything????

darkhorse75

Derailleur hanger alignment?

bradtx

Papa Tom, Well, you're down to cable housing, cable, or the indexed shifter.

A glob of hardened grease maybe blocking proper engagement of the detent in the shifter, perhaps large enough to also effect the 5th cog. Clean and exercise the shifter with WD40 and relube with a medium weight spray lubricant of your choice.

A frayed section of cable within the cable housing may have damaged the housing and when the two meet, there's trouble.

Does the problem occur on both downshifting and upshifting into the 4th cog?

Brad

well biked

+1.... When mid-section of gear cluster is the only problem, bent hanger is a likely cause.

_ForceD_

When I read the OP, I began to think it must be in the index shifter. Then bradtx alluded to it. I'm thinking that the shifter (when new) has to machined to precise tollerence so that the shifting is accurate. Like anything else with friction, over time...it has to wear down. And it probably is noticed first on the gears that are used...or shifted to...most often. So it might actually be a problem with the shifter.

Dan

FBinNY 

As mentioned it might be a worn cam on the index shifter which allows it so slip back out of the correct trim position.

This would be confirmed if the trim were a bit outboard on those sprockets, because this cause can't cause the trim to err inward. You might look at the chain to see of it's climbing outward as if planning to upshift.

However, if the wear is slight you might not see anything so can test this theory by leaning on the lever slightly as if getting ready to upshift. Or you can adjust the overall trim inboard a hair and see if all the other sprockets are off and 4th is spot on. Or you can stick a pencil between the cable and frame in 4th and see if the trim improves.

Notice that these are all FREE diagnostics you can do before spending a cent (except for the pencil), and are the kinds of things that should have been done all along rather that simply spending dough without a theory.


One other possibility is a poorly adjusted B-screw. Shimano derailleurs use a design where the upper pulley rises and falls as the cage rotates to take up chain slack. Most mechanics adjust the B-screw based on the largest sprocket, and disregard Shimano's instruction to confirm the setting for every combination. Sometimes the combination of chain length and sprocket mix cause the upper pulley to end up too close to middle sprockets despite a "correct" B-screw adjustment, and it needs to be brought in to correct that.

bulldog1935

do you have the proper torque on your cassette ?

AlexCyclistRoch

It's the shifter. There are plastic pieces that wear. A $50 upgrade to new shifters should've been done after chain and cog replacement, and BEFORE replacing the derailleur. A replacement crankset will do nothing to fix a rear cog problem.

Papa Tom

Y'know, I've got to check my maintenance record, but I'm pretty sure I replaced the rear shifter about two years ago. Before that, it would have been the original one, about 18 years old!

Anyway, is everyone clear that this only happens on the 4th cog?

FBinNY 

Yes, from reading, it seems that most got that point.

Since it's limited to a single or two spockets, that eliminates things that would be across the board, such as the chain, worn chainrings, the derailleur, etc.

So you're looking at something very specific to that sprocket. It could be a slight variance is cassette spacing, but that could be measured, and anyway you replaced the cassette, so the odds are against that. So, after checking down the list, we come to a worn detent on the shifter, which would only affect it's own coresponding sprocket position.

That is logical, but I don't diagnose by logic alone, and after forming a theory, I test it as I described in my prior post.

IMO you were ill served by mechanics who either didn't diagnose, or did so poorly and never tested their theory and simply replaced parts trial and error, mostly error.

So, while there's consensus that it's the lever, you should still test before spending more dough chasing unicorns.

fietsbob

I have morning coffee in my hand ..

nitroRoo

Since you've replaced the chain and cassette, my vote would be the shifter as well. I went through something very similar with my gary fisher mountain bike (sram x7). Chain would slip (dangerously) on steep climbs in lower gears. Getting that shifter to index properly is what fixed the problem (after a new chain, and then new cassette).. finally addressing the shifter is what fixed my problem.

AnkleWork

You could continue on the same course for another year and replace the whole bike, piece by piece. But really, if you've replaced the entire drivetrain then maybe you are just imagining the problem.

masi61

+2,
Can you verify alignment of the derailleur hanger? If that side of the rear triangle got bumped, or it fell over it is very easy for the rear derailleur to mistrack. This is consistent with some cogs shifting fine & others not.
I would say get a derailleur alignment tool & follow the directions to verify that the rear derailleur pulleys run parallel to the crank chainrings.
You might look to YouTube for demonstrations. You could also pay your LBS mechanic (~15$?) to do it for you.
I would say this is your next task. So check this out & then report back with a status report...

ExpertTools

+3

FBinNY 

The OP has already spent a lot of dough, much of which was probably wasted replacing parts that were OK, and is still plagued with the same very specific problem.

Before he spends another nickle exploring possibilities, he should confirm any theory by testing it thoroughly. The OP was given some possibilities here, like those a bent hanger is only another possibility.

There's no great harm in buying a tool if he'll get good use out of over the years, but that's still a decent outlay, and there's a good, even very good chance that it won't get him any closer to a solution, unless you count eliminating another possibility.

Repair by process elimination eventually works, but it also eventually adds up to serious wasted dough.

The tools the OP needs most are on either side of his nose, and between his ears.

Observe and think before going any further.

AnkleWork

FB, with respect, when sound advice is ignored, repeating it does no good but gentle ridicule sometimes does a little good.

FBinNY 

I don't have a dog in the fight. I offer advice in good faith, but am not invested in whether it's taken.

The OP is a stranger, he has advice from me and others, but in the end it's his own problem, his own bike and his own money, so he'll have to make his own decision.

ChuckD6421 

Still no confirmation the hanger alignment has been checked?
Last year I spent a good amount of time (some documented here) t-shooting Ultegra shifting problems. I spent 20 minutes in the nearest Authorized Trek Dealer, Blue Sky in Saratoga NY, having my intelligence insulted by a kid who insisted the B screw must be adjusted with the chain on the smallest cog and big chainring, after he whined about the general cleanliness of my Domane and my choice of Jagwire cabling. I'm sure there are good mechanics out there, I like to think I was one of the good ones many years ago, but far too many with poor analytical skills, bad attitudes and poor people skills.
You really owe it to yourself as an avid rider to invest in some bike-specific tools so you can do the basic checks yourself (and maybe help your friends and neighbors). I really recommend the Park DAG-2 tool (US$66 on Amazon now) and learning how to use it. It's very easy. You may not use it once a year, but when these shifting issues pop up, hanger alignment should be one of the first things you check. They're very easy to get bent.

Papa Tom

From the OP: Hey, I'm not ignoring anyone! I only posted this thread this morning and I've been at work all day!

Yeah, I guess I've been trusting some bad mechanics for too long. Next, I will have the most expensive wrench in town check the hanger alignment, which, truthfully, is above my scope of knowledge. If it's misaligned, do I have it realigned, or does it need to be replaced AGAIN? The problem pre-dates AND post-dates the installation of my new rear derailleur, so is it possible that the NEW one is out of alignment, too? In other words, does the new derailleur sit in some kind of space that can be out of alignment whether or not there is a derailleur attached to it?

The shifter solution also sounds feasible, IF it was the FRONT shifter (and not the rear) I changed a couple of years ago.

Yes, I am definitely taking everyone's input 100% seriously -- even the post that told me I'm imagining the whole thing! I just need a day or two to do something about it - and I won't have time today. I WILL get back to you all, though.

ChuckD6421 

I think once you see how it's checked and fixed (if needed) you'll kick yourself for paying him (or her).
Look at where your derailleur connects to the frame. It screws into either a part of the frame or a piece called a hanger attached to the frame. The alignment tool simply screws in place of the derailleur and has an arm that you adjust to the size of the rim and swings around allowing you to see that it's equidistant all around, thereby assuring your hanger is perfectly perpendicular (lots of online vids showing it). If you find the hanger out of line you use the tool to very gently bend it into line. 40 bucks please!

Also, I'm not discounting what others have said about the shifter. Just saying hanger alignment is fragile and should be known before other things that are more complicated.

Papa Tom

I know you are all on the edges of your saddles waiting for me to report back about my derailleur hanger, but I just haven't had the time to find and consult a mechanic that seems trustworthy. This is high on my To-Do List, though, so keep your eyes open for the nail-biting conclusion of this episode very soon.

Steve B.

Take it to Doug at the Bike Junkie in Bethpage. Doug and/or Ray Diaz at Brands are the best wrenchs I've dealt with. They know everything.

Papa Tom

I just got back from bringing it to Brand's. Of course, it wouldn't act up while I had an audience with the mechanic, and he only spoke four words of English, so it was nearly impossible to explain what the problem is. I think he confirmed that the derailleur is not bent and he did say "shiftsee goodee," so now I'm pretty much out of ideas to throw at the next mechanic.

The only good thing that came out of this schlep to Wantagh was that I got a good look at how freaking filthy the new lube I'm using has made my whole drivetrain. The chain, derailleur, and cassette all look like they were collecting burger gristle at the bottom of my barbecue all summer long. The problem pre-dates the switch from White Lightning, so changing back won't be the solution, but it will save a lot of laundry detergent trying to degrease my Fruit-Of-The-Loom white socks.

I'll check out Bike Junkie, but they never seem to be open when I go by there. They've probably read my posts and are avoiding me.

bikeman715

+4 about the derailleur's hanger . Have it check again . If it is out of alignment then any and all derailleurs mount to it will have the same problem . If it a replaceable one then have it replace . Here a thought had the hub been overhaul during any of this time ? maybe a spacer on the axle been remove or replace or move to the other side ? if so it could affect the placement of the derailleur .