stephr1

It's been a couple of weeks since I've had a chance to post back here (previous postings for informational purposes: https://www.bikeforums.net/showthread...edux-again-%29 and https://www.bikeforums.net/showthread...eur-adjustment NOTE: Moderator, please close these threads, thanks). I've been out of commission due to a virus and then as I got better I developed some back issues. So, it's only been the last day or so I could get back to this issue.

I previously posted that I would put back all the old parts and start replacing (as practical) one at a time. So I did. What I found was that the problem didn't seem to change much, if at all (This was a telling surprise since I didn't have any chain skip before trying to "fix" the bike). It now doesn't matter old or new parts. The problem must have been on the verge of appearing and my effort to upgrade some of the components brought it out. It would also seem to be related to a part that isn't one of the ones I replaced.

I also mentioned in my previous threads that I had borrowed a friend's bike while I work on mine. It has, maybe, 1K miles on it, so it's in good working condition. It has a Shimano Deore RD on it (nice shifting!!). This morning after my bike ride I decided to do a comparison. I checked the strength of the RD cage spring. It seems the one on my old, tired RD has more tension than the Deore. And the amount of right angle/perpendicular play in the cage to the parallel section is about the same.

One thing I did notice is that the tension of the spring associated with the B adjustment (torqued around the main mount) is weak on mine (as compared to the Deore). In fact, if I rotate the RD away from the cassette, it doesn't spring back all the way. There's about 1/2" of play at the untensioned end of the arc (when the RD guide pulley is supposed to be closest to the cassette). By contrast, the Deore RD springs back to its limit point.

So, this would make sense as a source of the skipping problem by not tensioning the chain enough around the 11T gear. Why it happened all of a sudden...hard to say.

My question is...could this be an (recently appearing) issue related to the mounting of the RD...meaning, is there any adjustment I can make in (re)mounting (mount is designed into the RD) the RD to the bike so it runs to the limit of the B adjust spring and provides much needed tension for the chain? Or, is this as I feared might be early on that the RD is finally gone? Or, maybe I can feel brave and take this section apart to see if it can be fixed (prob'ly not feasible

As usual...thanks much in advance for any help, suggestions or insight....

Cheers...Steph

Andrew R Stewart 

Steph- I would be surprised if the upper pivot spring tension was to blame. But if the pivot is sticky enough the spring won't overcome that and if the der is pulled back it might not swing forward to the normal postition. We see this often with winter bikes or those that live outdoors. Shimano pivot bolts have an "e" clip slid onto a groove on the bolt that if removed (watch out as the clip can fly) the bolt and it's plastic "seals" can be removed. Clean up with solvent and fine sand paper then lube all and reassemble (it helps to have a third hand here). I clamp a 5mm allen in a vice and have that hold the bolt while I slide and twist the der and remaining parts in place. I have done this repair MANY times and have a good record of getting the pivot to move freely. Whether this fixes your skip remains to be seen.


BTW you mention using the 11 tooth cog. Do you use this cog much of the time? With a suggested cadence of around 90rpm this would put you at a pretty high speed most all the time. I some how think this is not the case. The 11 tooth cog is the most likely one to have a skip issue even when not worn out. The fewest link/tooth in contact, cross chaining, der limit not fully set, possible cog on freehub body mis rotation. Skilled riders rearly need to use this cog unless they're going down hill or in a frenzied sprint. I see far more drivetrain issues with riders that don't have a smooth and rapid cadence. Andy.

stephr1

Andy,

Thanks for sharing your experience. I did remove the chain and twisted the RD on its mount. I noticed it didn't rotate without a good sense of binding or friction on it. Not sure if that's coming from the B adjust/cover or main body. I guess I'll know soon. It's never been taken apart and cleaned (has been oiled) in 19K miles/13 yrs., so it must be due for an overhaul.

I figure to chase the clip around the garage once or twice before I get the hang of it So, when putting it back together...do I have to get a full turn+ on the spring to get the spec'd tension, or do I only need to twist the spring enough to reinstall the B adjust assembly cover, and that would provide enough tension? Also, what do you recommend for lubing it? Tri-Flo? Light grease (like the Park blue stuff)?

What do you sandpaper inside? The inner walls? Spring?

I'm hoping this solves my problem. Apparently it's not the guide pulley nor the chain nor the cassette. Doesn't leave much else except the RD and the freehub.

You mentioned about "cadence". I mentioned in one or both of my previous threads, and I prob'ly should remention it here. I ride a mountain bike. And cadence is not something about which I ever think since I'm both on and off-road in the course of my rides. And in the 13 yrs. I've ridden the bike, I've never, ever had a skip problem (except when I put a new chain on an old cassette....changed out the cassette...skipping gone). This is a recent problem and it's beginning to seem like pure coincidence that it showed up when it did. It's been driving me nutso trying to eliminate the new parts as the source of the problem. I'm now convinced it's something else.

Re: 11T cog....for me, on my mountain bike, it works fine with the gearing. I'm primarily on the middle chainring and the 11T cog. I can get up to 20 or so MPH on flat road, which is fine for me. I understand the issues around an 11T cog. However, I had been riding without problems on an 11-28T cassette for ~5 years prior to the new one I've been trying to install. I just never saw anything until I tried to update components. Arrrgggggh!!!

Cheers....Steph

oldskoolwrench

Steph,

You turn the backing plate (with spring installed) just enough for the tab on the plate to engage
the tab on the derailleur body (½ turn counter-clockwise, as I recall), then install the e-clip.
As Andrew alluded to earlier, whether this cures the issue remains to be seen.

IMHO I would make the jump and purchase a new R DR; if you have that miles on the current Alivio
it's due to be replaced. It may feel tight, but there may be other unseen variables that warrant
replacement.

Keep in mind that even on the middle chain ring, when the chain is on the 11t cog in essence you
are still in a cross-chain layout; that lateral wear on the minimal surface area of an 11 tooth cog
can exacerbate wear, especially in this day and age when Shimano's lower end cassettes are made
in Indonesia, not in Japan as the earlier ones were. Lesser grade steel = less MTBF cycles... that
sort of thing.

jim p

It is 13 years old and has 19,000 miles on it. Your free hub maybe slipping. If you can try a different rear wheel, then you might be able to isolate the problem. I have never taken a free hub apart but if it has dried grease inside it may need to be cleaned and greased. If you can get some thin oil into the free hub it might dissolve the grease enough to free up the pawls and stop any potential slipping.

Andrew R Stewart 

Steph- The sandpapering is on the der's upper housing insides and or the bolt's shaft section. Really a method to remove corrosion or dried out grease then to remove metal. For the relubing i use grease, like which kind of soap you use to bath with the type of grease is less the issue (as compared to doing the maintanance).

Some of my answers are not soley for the OP but for those who are following the thread trying to gleem understanding. But to follow up you also just said that cadence isn't something you ever think about. So my comments might hold water for you too. If you never think about it how would you know whether you have a quick and smooth spin or not?

My gear/RPM/Speed calculator (from 1979) says your 20mph in the 11 cog and middle ring (32T?) is about 85 rpm. Not a slow slog RPM but no way would most call that a spinning RPM let alone a high speed or sprinting one. Of course slower MPH is less RPM. Some riders are not well trained or comfy pedalling at 90-110 rpm (let alone the 180+ trackies can get to). Some are not able to apply their power in a smooth circle (well even good spinners don't really do this) instead of "Up and Down" (usually called pedalling squares). Again I see far more worn out parts, shifting frustrations, bent chains/teeth as well as the inability to keep up with the group's accelerations when the rider's cadence is slow. Note I don't say the rider is slow or unskilled in the handling of the bike, just that the pedalling style adds to the challenge of the bike working well longer. Andy.

Al1943

The 11 cog requires the use of special special lockring. If the common lockring is used with an 11 it will cause chain skipping on the 11.

stephr1

OK, I took the RD apart (actually had to do it twice since I forgot to smooth where the upper pivot bolt goes thru and cleaned (wasn't all that gunked up), smoothed and lubed it. While it's not quite as "free-moving" as the borrowed bike's Deore RD is (that must have a better bushing/bearing setup and is much newer) my RD now moves much more freely and actually returns to the same "rest" point. No real sense of "stickiness". I'll test ride it tomorrow. Maybe this is that subtle problem I've been expecting to remedy...can only hope.....

@alan

Long time, no talk to

Thanks for the info about reassembling the RD. The suggestions, plus info I found on Park Tools' site, were a great help.

WRT a new RD...yeah, that has crossed my mind more than a few times in this challenge to figure out what's going on. I've even thought of checking my LBS for a good-priced, better quality RD that someone left behind when they had the LBS upgrade them to an even better RD. I may end up taking this approach, but I'm not quite there yet.

Point well-taken about the issues of running an 11T cog. I know I've said this before. If I hadn't had nearly 5 years of solid operation using an 11-28T cassette, I would be much more concerned on this. However......for now, I believe I can still use an 11T cog as my high gear. Always subject to change, of course

@jim p

My educated guess, and I could be wrong, is the freehub, while showing some signs of wear and tear, seems to function well (enough?). I would expect that a freehub issue would show up in more than just the high gear, which is not what I'm seeing. I've performed some static testing and the freehub seems to be working as expected.

@andy

Thanks, as well, for your continued help.

I had to take the RD apart twice 'cause I forgot to smooth where the pivot bolt goes...it seemed much easier to reassemble the 1st time....go figure...

My sense is the stickiness I found was due more to corrosion/oxidation than dirt, etc. The sandpapering seems to have smoothed it out reasonably well. Apparently the stickiness showed up only under stress, as in reassembled. When I had it apart, the bolt moved around freely in both the pivot hole and thru the B/backing plate.

The cadence issue is interesting. My only response is to say that I'm sure that my "cadence" has been the same (with improvements in rotational speed) since I've owned the bike. And only when I attempted these recent repairs has any kind of problem like this shown up. However, as I'm always looking to improve my biking experience, I'll certainly give more thought to the cadence aspect of things. Thanks.

@Al1943

Thanks for the suggestion. This is one of those thing I checked early on. The lockring specifically states it's for a hyper-C setup, which is what I have.


Well, here's hoping that I'm finally finished with repairs and can get back to riding (on my bike, that is)

Thanks again for all the help and support. I'll let you know if the recent repairs had any effect.

Cheers...Steph

stephr1

Interim update.....

I have done some minor on-road testing and the results look promising. The test was for a little over a mile and on a paved road with a very slight incline. I did try shifting up fairly quickly to stress the drive train (7th gear at a slower speed). This was using the old chain and cassette with the new guide pulley (I reinstalled the new guide pulley because I decided the old one was prob'ly past its prime). Shifting certainly seemed better with the new pulley installed.

The first test ride was after I cleaned and reassembled the upper pivot section, but before I smoothed the pivot bolt hole (since I forgot this second part Results were pretty consistent. No skip in 1-6 gear. OK for ~1/2 mile then the skipping began in 7th and continued to occur occasionally. This is what I have pretty much been experiencing.

I then tested it after I sanded the pivot bolt hole. Same road, same distance. This time no skipping. I even tried to stress test it a bit more than on the 1st ride test. No obvious or apparent problems.

Granted, these tests were not my normal riding conditions. Tomorrow early AM I'll go do a 10 mile ride with a few bridges, etc. and the results from that will tell me if I've improved anything. I am optimistic.

For those of you who said smooth pivot hole issues are prob'ly not the cause of skipping, I hope I prove you wrong (otherwise, it's a new RD I think I mentioned previously that my sense this was something subtle, and this seems a good possibility.

I'll post back results of my ride tomorrow.

Thanks again to all for the help and suggestions. Maybe now I can finally get back to focusing on my riding (and less on maintenance and fixing for a while).

Cheers....Steph

Kimmo

You have that back to front - your spring has more tension the the Deore one, in the upper pivot at least. Both pivot springs serve to tension the chain, pulling the bottom of the upper knuckle back and up, and the bottom of the cage back and up. When you wind on the B screw, it effectively adds tension to the upper pivot spring, changing the relative tension between the two springs, which has the effect of lowering the upper jockey wheel away from the cassette. When you disassemble the pivots, sometimes you'll see a pair of holes for the end of the spring, to allow another tension setting.

However, I'd be surprised if the issue is insufficient chain tension. Ensure you have the correct 11t lockring by removing the wheel and putting some chain on the cog; the chain shouldn't touch the lockring.

stephr1

Thanks for the info on the pivot points. I kind of figured that but hadn't really thought it thru. However, I do now understand that both pivot points must be free (as in non-sticky) for this tensioning to work correctly. And my sense is that the upper pivot may be more sensitive to this than the cage pivot, at least, in my situation.

I do get that both the upper pivot and cage pivot points both help keep the chain tensioned (1 from the chain rings, the other relative to the cassette/cogs). My understanding is that an appropriate adjustment for the B-screw is to put the RD in the lowest/inner/1st gear and adjust the B-screw so there is just enough clearance between the upper pulley and the cog. I couldn't do that before I overhauled it.

While I didn't do my 10-mile ride this morning, I did get out for 5 miles, but no bridge tests (prob'ly tomorrow). It seems I may have, indeed, solved the problem. No skips, not even the hint of one, on this morning's ride. My next regular ride should confirm or deny this.

Curious about your comment wrt the upper pivot tension. Is that a design function due to the Deore being a better RD?

BTW1 - only 1 spring mount hole in the upper pivot assembly. Have not opened up the cage pivot assembly, tho (at least, not yet).

BTW2 - wrt lock ring. Already been checked and verified.

Thanks again for the help. I think I may have proven those of you wrong wrt upper pivot issues not causing chain skip. In my case, that seems to be exactly the situation

Cheers....Steph

Kimmo

Not likely; just a logical conclusion from your description. Likely just down to chance, or maybe different largest cog spec.

Andrew R Stewart 

A comment about chain tension and rear der spring tensions. Bikes without a tension arm acting on the chain's lower path have a very high resistence for the chain to be able to climb up and over the teeth (the classic worn chain/cog skipping). This resistence is equal to the adjustment of "free play" in the chain (or chain tension as it's usually called). Chains don't have much elasticity so if the free play is less then the amount needed to let the chain ride up and over the cog teeth (if the RH axle nut is tight enough to keep the axle in place within the drop out slot) it won't skip. Not so with a tension arm. There is no way that the spring tension will be greater then the pressure your legs can generate. If it was then the chain would stay seatted in the cog's valleys and not ride up the slope of the teeth. So to half the spring tension or double it won't have the result lay people might think it should. I do agree that the number of teeth and links that are in contact will come into play (and this is why, the only reason why, that the upper pivot being sticky might contribute to the skipping). But don't confuse this chain/cog amount of connection with chain tension.

The proof of this is seen when using a chain whip to work on a cog. The chain (that's attacheed to the lever arm) and wraps around the cog only needs enough teeth/links connection and no spring acting on the free end, of the chain, to hold tight. A very high force can be placed on the lever arm with out the chain 'skipping" (letting loose) UNLESS there is not enough chain/cog overlap. In fact if you were to set up a chain whip and place a load on the arm then feel the tension on the small bit of the tool's chain that is dangling off the cog you'd see there is no tension on this tail of the chain.

We see this misconception all the time in the shop. "MY chain's skipping, Can you shorten it?" Well, as long as there's still the der cage acting with a spring tension on the chain taking a link or two (and increasing the tension) won't fix the problem. In reality this will worsen the problem as the shorter chain will also have the guide pulley further away fron the cog's underside (reducing the number of teeth/links connecting).

This is why we have said that the der's ability to tension the chain is less likely the cause of skipping. Andy

stephr1

Andy,

Thanks for the great explanation. To clarify, I never thought that chain tension was "the key" issue in and of itself (apologies if some of my comments inferred that). I understand the operation of the pivots in keeping the chain from going slack as shifting moves it from larger (low end) to smaller (high end) gears. But I also believed (after much investigation and experimentation that the binding and stickiness in the upper pivot might prevent the chain from wrapping around enough teeth on the 7th cog (where the no. of teeth are most critical). This was the only explanation I could find as to why this problem would be limited to the 7th gear (maybe if I had 12T on the 7th cog, this may not have been as much a problem)

Having said all that, I rode the bike a couple of days ago (still using old chain/old cassette) and, while the problem hadn't completely gone away, it was greatly reduced. Yesterday, I again disassembled the upper pivot section because I wanted to make sure I had smoothed the pivot bolt hole enough. Took a 12 mile ride this morning....no skipping (Because 1 of the bridges I normally take is under construction this week, I couldn't do the ultimate stress test. Should be able to do so on Sunday).

The other thing I noticed was the routing of the RD shift cable as it goes to the RD from the frame. I made sure it came off the frame (bare cable) in a much more straight line thru the cable housing that connects to the RD. I'm not sure, but it may have gone over the rear hub mounting nut before. Not sure if that helps with this problem (tho, it seems to put more pressure in keeping the upper pivot point in the right place), but it's got to be better routing for the cable.

If Sunday's ride goes as well as today's, I'll put on the new chain and cassette and see if my "luck" continues.

Again, thanks for all the expert help. It's provided me with much more insight into the physical dynamics of my bike.

Cheers...Steph

stephr1

I really wanted to prove the experts wrong....but then, that's why they're experts (and I'm not

Last Sunday (~a week ago) I finally got onto a ride that took me over a couple of bridges and provided a stress-test for the bike (Still w/old chain and cassette). The ride was better than it had been, but there was a couple of skips on flat ground and I couldn't go over a bridge in 7th gear (had been able to do so flawlessly before this problem). When I got home, I put on the new chain/cassette and rode again on Tuesday. This shorter ride has only 1 of the bridges (the "easier" one). Results? Pretty much the same as with the old parts.

So, here's my conclusion....given that I've done pretty much a rebuild of the RD (both pulleys, upper pivot...lower/cage pivot is still strong and moves well), I'm at the point where I can (temporarily) eliminate the RD as the main source. Chain rings are functional. Some wear and tear, but they've been in worse shape without causing problems.

I mentioned (earlier in this thread or in 1 of the other 2) that I saw a slight, but noticeable, side-to-side "wobble" in the cassette when I spin the wheel and hold the freehub fixed. I did do some DIY true-ing on the rear rim and have wondered for quite some time if this may be a source of the problem. Maybe I 1/2 dished it to put it out of whack. Or, I might have trued the hub off-center enough to cause the wobble. The freehub does have play in it, given the miles on the bike, but then that's prob'ly been there for some time before this current problem.

So, here's my approach....

1. Recheck the hub for centering and any possible dishing, and correct it
2. Re-examine the freehub to see if internal bearings are creating a problem (when I cleaned and re-oiled it, maybe some grease/dirt/gunk got caught in the bearings or on the race...tho I would expect a much more distinct symptom than what I'm seeing)
3. As a last resort, replace the rear wheel, and freehub, if necessary
4. Ultimately, replace the bike

Once again, thanks for all the insightful help. I certainly understand more than when I started.

I'll report back when I finally have this problem completely resolved.

Cheers....Steph

onespeedbiker

Perhaps I have missed this, but have you checked the parallelogram pivot bushings? This usually the first place that wears out if a derailleur does not succumb to corrosion. Try this; disconnect the cable from the rear derailleur. Place your right thumb over the front of the top pulley and 2 or three fingers on the back. Concentrate on the pivot bushings that hold the parallelogram (ie the front plate) to the cage housing on the right side. Now gently try and rock the cage side to side without moving the spring loaded cage pivot. If you can see the the pivot bushings moving like the pins are too small to hold the front plate securely in the cage housing yolk, then the bushing are shot and you need a new rear derailleur.

stephr1

Thanks for the suggestion. I don't know for sure that it's not the RD, but I haven't found anything that definitively says that it is.

I mentioned previously in this thread that I borrowed a friend's bike with a Deore set on it so I could still ride while I worked on my bike. That's given me the opportunity to compare parts on both bikes so I might be able to tell where problems might be on my bike (my friend's bike is 5+ yrs. old but it has less than 1K miles on it, so it's in fairly new-like condition).

I noticed higher spring tensions of the upper pivot and lower/cage pivots on my bike (Alivio) than on the Deore (which prob'ly explains why my friend's bike shifts so much "sweeter" than mine). I also looked at the play in the different pivot and rotational points on the RDs. As near as I can tell and for as new of a condition it's in, the Deore didn't seem that much "tighter" than my RD. I'm sure there was a difference, but it had to be very subtle.

Again, I appreciate the input. However, for now, my focus is on what I might have done to the rim to mess things up. It's the 1 variable at which I have not looked close enough. It's possible I may end up focused back on the RD. One of the things I am considering (with the permission of my friend, of course), is to temporarily mount the Deore RD onto my bike and see what happens. It certainly would be a definitive statement about where the problem isn't

Cheers...Steph