noglider 

Here is my 1971 Raleigh Super Course. I recently rebuilt it with new wheels and drivetrain. It's a Claris 2x8. I installed the rear derailleur on a hanger. I have aligned the dropouts with the Park tools and the derailleur hanger with a Park alignment gauge. When I ride in the big chainring and in the 3rd cog (3rd biggest), it jumps into the 4th cog (next smaller) and then quickly back again. To help me troubleshoot this problem, should I provide any further pictures? Chainline looks to be decent though I know the chainrings are a bit far out towards the right. Even knowing that, I would expect the problem to be worse in the two biggest cogs, but the problem doesn't occur there.

Thanks.

pdlamb

My first two guesses are a worn cassette or rear derailer adjustment needs fine tuning.

dsaul

Start with a 1/4 turn counterclockwise on the adjuster at the derailleur and see if that works. It also could need a bit more B-tension, as that 3rd largest cog may be a larger jump that some of the previous cogs and the top pulley may be too close to the cog. Its best to watch it carefully in the stand, to see if the chain is centered on the cog and if the upper pulley is too close or maybe even contacting the cog. In rare cases, I have found a bent tooth on the cog from some previous bad shift under load.

noglider 

Thank you for the responses so far. The cassette and chain are brand new. I will check out the ideas you suggested, @dsaul. Unfortunately, the problem does not happen on the stand. It happens only under moderate load.

For what it's worth, the cassette is 32-28-24-21-18-15-13-11. I especially like your theory about the B screw. Easier to fix than a bent tooth.

Iride01 

Seems like my Raleigh Comp GS used to do this when it had friction shifters and Campy group on it. Don't quite remember what solved it, but don't overlook typical things like a frayed cable or your shifter tension screw getting loose. One of mine was always loosening itself on almost every ride toward the end.

If yours isn't friction shift anymore, then are you certain all the cog center to center spacings are correct for the DR's and shifter pull?

70sSanO

What I will typically do when setting up index shifting is place the chain in the middle cog and turn the derailleur adjuster until I get it to rattle or jump to the next cog. I then turn it in the opposite direction to get it to do the same. From there I can set it in a neutral position or shade it slightly in one direction. This seems to work for 7/8 speed drivetrains to fine tune for any poor cog spacer tolerances. I've measured the plastic spacers and sometimes they are not very consistent is thickness. There is also some debate over the consistency of cable pull.

The one thing I have noticed is a very slight tingle sound of the chain lightly rubbing against the next cog when there is a spacer that is too narrow.

John

icemilkcoffee 

OK- correct me if I am wrong, but the 7 and 8 speed Sora shifters have the stubby thumb switch. The 9 speed Sora shifter has the lever paddle. Yours look like the 9 speed ones. Can you check what part number your shifters are? Are they ST3500? If so they are for 9 speed.

trailangel

11-32 and what on the front? 34-50... you are exceeding the limits on that short cage rearDR for chain wrap.

jimincalif

It's a cassette, not a freewheel, right? Is the cassette lock ring good and tight? It's a longshot but I was chasing ghosts a few years ago and this turned out to be the problem.

Iride01 

Oh, when I expand the pic, I see you've put sti's on it and gotten rid of the downtube shifters. If you haven't done it yet, then shift to the small cog. Remove the cable from the DR hold fast and then pull up or down the hood covers which ever direction lets you get to where the cable end is and extend it out a two or so inches to ensure there isn't a frayed strand. You usually can just push up on the bare cable running along the downtube.

Frayed cables probably account for most weird issues IMO.

I am a little concerned about that big loop your housing makes from the chainstay stop to the DR. That angle right at the chainstay stop can't be good. You might need both to shorten the housing and get a stepped down cable end to fit that cable stop.

edit....
now that I look even closer at the pic, is that a wire tie holding the cable end and no cable stop? I'm sort of getting afraid to zoom in any more for fear of other stuff I might find. <grin>

andrewclaus

I agree, the rear housing loop does look suspect.

And excellent point above about the old Sora 8-speed shifters. If you can get eight clicks out of those shifters with a loose cable, they're 9-speed shifters.

alcjphil

OP specified that the brifters are Claris, so 8 speed. That rear loop looks too big to me and the ferrule is probably the wrong type. A close up of that area would show this

70sSanO

Claris is not the same as the old thumb shift Sora. It has dual levers. And it is only 8 speed.

John

noglider 

Right, it's Claris from about 2017. It's a 2x8 drivetrain, as I said earlier.

@Iride01, I don't know if there is a modern ferrule of the right size that fits the cable stop on this old frame, so I used what I found and secure it with a zip tie. And I used a cross of zip ties at the seat stay to keep the cable there, too. The idea is to maintain the compression on the cable. I suspect this work is good but I will try to remember that it's not as it was designed. Remember, the problem occurs only on one cog, and only when the chain is on the big ring.

@trailangel, I doubt I'm exceeding the limit. The cassette, derailleurs, shifters, and cranks came off a new bike, so I bet they worked properly there. The buyer of the new bike sold me these components.

@70sSanO, that's a good technique. I'll try it.

@jimincalif, I will definitely check the lockring's tightness. A loose lockring could make the spacing bad, especially if a spacer is plastic.

@pdlamb, there is no wear, as the components were removed from a new bike before they were used. I am the first user.

70sSanO

You need to go on eBay, or elsewhere, and get a clamp on chainstay cable stop.

I realize that it is only one cog/chainring, but if there is any give in that zip tie, whatever fix one place might just pop up elsewhere. The issue is that you need a full length housing or cable will move the cable housing as the derailleur goes through the gears.

John

dsaul

Step down ferrules are available for that rear cable loop. https://www.universalcycles.com/shop...s.php?id=62560

djb

I set up an old bike as a commuter for my wife and it has a "only at one gear ghost shifting" also.
I figured it was either the used 7 spd trigger shifters I bought for it or some housing issue somewhere, but just got tired of figuring it out and left it like that....I know I didnt put new housings on when I overhauled stuff, but cant be bothered to redo it all.

hope you find the issue.
my money would be on a housing slash cable friction thing, but who knows. good luck

Iride01 

I took my bike to the oldest bike shop in the area and they searched through a box of old cable endcaps and came up with one that fit like a glove. It lets the housing come out of the chainstay cable stop in a more straighter orientation and the recurve is more gentle.

The cable housing looks a little long though. But maybe just the pic. My housing going to the DR is only about 11".

I can maybe sorta imagine (feel free to add more iffy terms) that the sharp angle of the housing coming out of the cable stop might be flopping around a little letting the cable length change as it flops and causing your shifting issue.

I did zoom in a little more on your pic, it does look like you do have the little ball shaped cable stop on the chainstay that is on my two old bikes.

noglider 

Update

I took the bike out for a test and was unable to reproduce the problem. Who knows, maybe my test was too short.

I tightened the cassette lockring as @jimincalif suggested. Yup, there was room to do so, so maybe it was a bit too loose.

I did some things I had been meaning to do which are unrelated. Since the frame has a bolt-on derailleur hanger, the axle overhang should be longer on the drive side than on the non-drive side. Since it was symmetrical, I had to turn the skewer to remove or replace the wheel. So I removed the rear axle and moved the cones towards the drive side to create the required asymmetry. I think this was only the second or third cassette hub I ever overhauled, so I wasn't sure how to remove the freehub, but that wasn't hard to figure out. It required a 10mm allen key and a lot of torque. I also bound the brake cable to the seat post because my leg tends to rub annoyingly against it.




After overhauling the hub, I put the cassette back on and made sure the lockring was good and tight. Sorry, I don't use a torque wrench.

I also tightened the B screw. It was almost all the way out. This can't hurt and could help.

I took a look at my jury-rigged cable housing setup. I still think it's OK. I do have a clamp-on cable stop if I need it, and I could drill it for a step-down ferrule or maybe I could just use a normal ferrule in it. As you can see, I use a cross of two zip ties to keep it where it is on the seat stay. I am reasonably certain it doesn't jiggle around when I shift, and I know jiggling is bad for shifting precision.

I used the barrel adjuster on the derailleur to tighten the shifter cable with the chain on one of the middle cogs. I was not able to make it make the scraping sound that @70sSanO recommended, but noticing that the shifting was the same or better with the cable, I decided this is an improvement.

I took the bike for a test ride and was unable to reproduce the problem. So maybe it is solved.

Thanks. I'll post updates.

The cables are all new, fresh, and unfrayed, and the chain and cassette are new, so are the derailleurs, shifters, and crankset.

noglider 

So far, I 1. made sure the cassette lock ring was tight. 2. I slightly re-tweaked the derailleur hanger alignment. 3. I screwed in the B screw. 4. I tightened the cable while the chain was on a middle cog. I don't know which of these changes did the trick, and it's probably a combination thereof. Thanks to all of you for the suggestions.

I have not changed the rear-most cable housing and feel I have confirmed that it's not causing a problem.

There was one tiny incident when I think I felt the chain jump in that critical gear, but only once and only briefly, and I might have imagined it. That's why I feel 95% certain that I've solved the problem.

I don't know about durability of Shimano Claris equipment, but I can say that when it is new, it works very well. In fact, this is now the most precise-shifting bike I have, and I have lots of bikes. I'm attributing this to two things: 1. the equipment is new (not worn), and 2. I adjusted it more carefully since it started out working badly. My feelings are confirmed that expensive derailleurs are generally not worth the money. When I'm spending money on bike equipment, I'd rather pour it into hubs than derailleurs. Hubs spin all the time. Derailleurs shift only every few minutes. A good hub really does last longer than a cheap hub.

Kapusta

I have nothing to add here other than to say... cool bike!

alcjphil

Looking at the last pictures I still say that the rear loop is much too large and the loop should be not that high on the seat stay. Also, and this may be a trick of perspective but it almost looks as if the barrel adjuster on the rear derailleur has been broken off where it goes into the derailleur body

djb

ya, the rd barrel adjuster does look a little weird, like its missing the little plastic sticking out bits that fit into the recessed bits on the rd to hold its position in place. You can see this because it is askew a bit, and not set against the rd like I believe they usually are (but come to think of it, being slightly askew is probably something Ive seen before. Main thing is that the little ridges keep it from turning on its own)