BCDrums

Hello all,

I am running a Shimano 9-speed setup, and it has worked without trouble for 20 years. Back in April, I started noticing that occasionally, maybe 1 in 10 times, the shift from smallest cog to second cog would hesitate, or not shift at all, accompanied by some chain chatter. I would move the STI lever back to position one and try again, and the shift would execute crisply. Hmm...

Since then I have replaced the chain, cassette, shift cables and housing (all as part of routine maintenance) and the problem persists. I have checked the RD limit screws and b-screw, and adjusted the indexing as best I can. If I adjust for a perfect shift every time from 1 to 2, it messes up shifts further up the cassette, so I have been tolerating the occasional bad shift from 1 to 2.

I haven't had the derailler hanger alignment checked, but the RD has not been bashed and it looks straight. Photo below.

I am wondering if the Ultegra 6700 RD has worn out. It has served for at least 10 years. I replaced the pulleys a couple of years ago. Or is it possible that the STI DA 7700 lever has worn and doesn't pull correctly for that first shift?

Gory detail: The cassette is a HG-something 13-28 9sp, from which I removed the 14T to add the 28T at the back. This means a 2-tooth jump from 13T to 15T. For a moment I suspected this combo, but I have used it for years across a couple of cassettes and it shifted fine, so I have ruled that out.

Photos below. What might I have overlooked? Thanks.

Crankycrank

I would say the shifters would be most suspect due to their age. I had a pair of 6600 shifters that started getting sloppy after about 27k miles before finally breaking. Try flushing them out and re-lubing to see if that helps. Has the B-tension screw on the derailleur been checked recently?

BCDrums

CC,

I wouldn't be surprised if the DA 7700 is failing. Bought it used a couple of years back. Will try a flush 'n' lube. I believe the b-tension screw to be correctly adjusted, checked it yesterday.

Thanks.

Iride01 

Are you calling the small cog the 1st gear? 1st gear is the lowest ratio gear on your bike, that will be the biggest cog on the rear.

If you are in fact talking about the smallest cog going to the next bigger, then are you certain you just don't need to turn the barrel adjuster a tad to shorten the cable? (counter clockwise)

BCDrums

Understood. I'm calling the first cog/smallest cog position one, not first gear.

Yes, I tried that, it was my first instinct. It did improve the shift from cog 1 to cog 2, but it made the chain chatter against the larger cogs as I went to the larger cogs/lower gears. It also made shifting to higher gears unreliable; the chain didn't want to drop onto the smaller cogs.

andrewclaus

Have you checked for play in the axle bearings and freehub?

BCDrums

AC, have not checked, didn’t think of it. Will do. Thanks.

SoSmellyAir

When did you remove the 14T cog to add the 28T cog? Have you tried a normal cassette rather than one you spliced together from multiple cassettes? Shimano cogs are designed with their adjacent neighbor(s) in mind so that the Hyperglide ("HG") ramps line up for smoother shifts. Maybe as your cassette wore with use the misalignment became more pronounced, thus precluding consistently making that shift. What you describe is similar to my experience building a custom cassette from two donor cassettes:
Bike Forums - View Single Post - Custom 12-28 cassette

KCT1986

Another possible cause is the placement of the wheel in the dropout. Shimano frame specs call for the center of the wheel axle to be forward of the center of the RD mounting bolt. The axle should be 4-10mm in front per Shimano.

Moving the hub forward in the dropout and readjusting the b screw may help.

The removal of the 14T cog may also cause some problems as the shift gate built into the system is affected. Usually the shift from the smallest cog to the 2nd is a little for forgiving as the shifter pulls a little more cable on this first shift. Shimano shifters usually has this to enable taking up any slack in the cable system.

base2 

How tight is the cassette lock ring?

If it loosens up a bit, it's not uncommon for the cassette to migrate a bit towards the drop out. The derailleur can't shift that far to the right because of either mechanical construction reasons or limit screw setting & the big cogs can get sloppy because they can start to float. A fact helped by their larger diameter magnifying the deviation from nominal.

Rolla

It takes five to ten minutes to check with an alignment tool. I'd do it, if only to rule it out; you can't really eyeball it accurately.

Ditto what @KCT1986 said. When I had similar shifting issues on my horizontal-dropout bike, I had to move the axle further forward and unscrew the B-tension almost all the way in order to get more chain wrap. Worked like a charm.

BCDrums

Smelly,

I liked your post on your custom cassette project. If I were on 11sp, I'd want that same cassette.

I have been using my homemade 13-28 for nine years, over a few cassettes and many chains, and it shifted flawlessly, so I don't think that the 13-15 jump is the problem. In fact, after the problem started, I put on a new cassette, and the problem persisted. So not likely the cassette.

Thanks!

70sSanO

1st position cog has always been the 1st cog from the dropout, which is the smallest.

An 11t is never the 8th position in one cassette, or 9th in another, or 10th, etc.

John

JohnDThompson 

If @Crankycrank's suggestion to flush and lube cables and pivot points doesn't help, consider checking hanger alignment.

BCDrums

Kansas City,

The manual for the Ultegra RD-6700 does not mention that. I checked my setup, and the axle is even with, or slightly behind, the RD mounting bolt. But that is interesting.
Maybe so. I removed the dropout screws in order to move the axle back in the dropout, to make it easier to remove a larger tire vs. the chainstay bridge.

Where does it say that??? I thought that the shifter cable pull was consistent at 1.7mm. Also, this 13-15 shift has worked well for many years, so I don't think it's that.

Thank you!

BCDrums

John,

I think the cables and housings aren't the problem, because they are new and post-date the problem. But the flush might help. and I should get the hanger checked but I'm...

lazy. But I'll do it if nothing else works!

BCDrums

Wicked tight!
This is a great note. I ran through the H & L limit settings last night, so I don't think that's it. And it shifts great from cog #2 (15T) to 28T.

BCDrums

True. I have been avoiding driving the bike to the shop, but I may have to do it.

Maybe that's the issue. At some point I removed the dropout screws to have a little more room for larger tires. I don't know whether it coincided with this problem.

SoSmellyAir

Thank you, even though my attempt ultimately failed. I may need some derailleur whisperer to tune my rear derailleur. Maybe I will do that if I ever upgrade to a short cage version.

70sSanO

How many ramps does the 15t cog have?

if it was made for a 1t change 14-15 and not a 13-15, it may have one ramp and there could be a shifting issue.

Been there with a 12-14 1st/2nd when the 14t designed for a 1t change. It shifted but there was usually a hesitation.

John

BCDrums

John,

The 15T in my cassettes were made for a 1-tooth change (one ramp), and I know that there is a Shimano 15T designed for a 2-tooth change (two ramps). But I have used this combo for 9 years, and the one-ramp 15T has never been an issue, so I don't suspect that. But it's a good point to think about.

KCT1986

See the attached from Shimano about recommended frame spec.

Regarding the shifter cable pull. It's not in the instructions. When you work on your bike next, notice the difference in the amount that the large (A lever) must move for the 1st shift (smallest to 2nd smallest) and compare to the same for the next shift. You'll notice a difference.

The cable pull is not 1.7mm. 1.7 is the estimated actuation ratio for this RD. The cable movement for Shimano 9 speed should be about 2.5mm for most shifts. The 1st and 8th shift is slightly different since the RD's H/L screw can limit the movement.

70sSanO

When all else fails, change the 1st/2nd cog spacing. But you need to eliminate an issue with the shifter first.

I can’t explain it, but every now and then a cassette will have a cog that doesn’t want to cooperate. If your shifter doesn’t quite get it there, take a little material off the 13t built in spacer to bring them closer.

You can also file the wider HG index spline narrower and see if you can clock it to work better with the 15t.

John

BCDrums

AC, I checked today, seems good. Wouldn't have thought of this, good suggestion.

BCDrums

Interesting! I had removed my dropout screws to slide the axle as far aft as possible to get a little more clearance between the chainstays for wider tires. Today I re-installed the dropout screws and set them to center the axle forward of the derailler bolt by 8mm, the middle of the range recommended by Shimano for a 26mm hanger.

I have good shifting in the stand, will see how it does under load tomorrow. Thanks for the tip, I wouldn't have thought of this.