Shimano 105 shifting issues
 

Awhile back, I went to clean my chain and cassette and found that the cassette chain rings had dug into the aluminum freehub of my Swiss hub. It is somewhat common. Why it is not stainless, I do not know. Anyway, I replaced the freehub and the bike wasn't shifting too well. I checked the hanger alignment and it was good.

The chain had a couple of years on it as did the cassette so I picked up a new cassette, chain, guide and tension pulleys.. It ended up that the chain was pretty worn and the cassette had quite a few miles on it.

It had been a few years since I'd restrung it, so I replaced all of the housings and shift cables. Pretty cheap maintenance really. When checking hanger alignment, I found a hairline crack in it and it broke apart fairly easily. So a new hanger was ordered.

Today, I installed the new hanger and aligned it. Installed the wheel with new cassette which is mounted properly and installed the chain. It shifts like crap, especially on the lower end. Mind you the hanger alignment is spot on. The low end screw is adjusted to give it plenty of bottom end (near the small sprocket) and there is slack in the shifter cable but it doesn't want to always drop to the lowest chainring. I have adjusted the rear tension screw in and out with no effect.

I am now thinking that the derailleur might just have too much friction or a weak return spring. Like I said, the cable and housings are all new from the shifters to the back and the back loop isn't too tight.

Thoughts? Suggestions?

ETA.. standard compact crankset with 11-28 10 speed cassette.

Are you sure the cable is routed through the correct side of the derailleur clamp bolt?

I went and double checked because I have missed simple things before. It is routed through the correct side of the clamp bolt.
Fiddling with it a bit, I got it where it will shift up to the 2nd smallest gear properly and on up and down the sequence, but it doesn't want to drop into the low gear again. If I manually aid the return spring with my hand it will drop into the smallest gear. I have gone in and lubricated all of the moving parts of the derailleur but to no avail.

The last time that I got my backside kicked by a shifting problem was with a bent hanger. I went and got the alignment tool and have never gotten beat again until now.

Since you mentioned the B-Tension screw had no effect are you sure the chain is the correct length?

The chain is the same length that I've been running for years. I can check to see if I can take an inch out of it but I've always kept it the same since I got the bike.

FWIW. I have built a handful of bikepacking bikes with 11-36 10 speed rear derailleurs and 22/36, 24/38 and even a 24/40 chainring combinations and have gotten pretty good at getting combinations that work and shift great. This is just really kicking my backside.

I gather you mean it won't shift to the smallest cassette cog/sprocket."Chainring" is generally used for the rings on the crank/chainset. You didn't mention if the new chain is directional.

Typically I use Sram PC-1051 chains. Unless it's for our tandems and the I believe that they are KMC. Non directional as far as I know.
Yes, cog is a more appropriate term.

...at this point, the most common cause of your symptom I know of is some sort of cable tension issue, with the rear derailleur cable either adjusted just a skosh too tight so it won't allow the rear to drop all the way to small, or possibly some sort of burr or other friction increasing impediment on one of your recently cut and installed cable housings at an end jooint. Try pulling the cable with your hand some place where it runs bare, like along the chainstay, and work it back and fort to see if it's running free.

You already lubricated all the pivot points on the rear derailleur (which is the other common cause). Did you work the rear derailleur back and forth a bunch of times by hand to make sure it's running freely ? If not, you might want to try that too.... also cursing. Cursing is appropriate in certain situations like this one.

Finicky adjustment on stuff like this is why I don't run much over 8 in the rear. More than that and I quickly lose patience with the setup.

...oops,I missed this. Forget I said anything. :)

The easiest way to diagnose the issue is to isolate each component individually. The most common issues with the symptom you've described is most likely 1 of 3 problems.

First thing, double check and make sure your small cog is correctly clocked into the splines on the free hub body. If it's not engaged into the correct splines, the cog will sit out a little far making it difficult to drop down to the small cog with everything else shifting fine.


The second thing to check is if the derailleur, with the cable unhooked can manually drop into the small cog. With the bike in the repair stand, rotate the cranks and manually push the derailleur up the cassette into the larger cogs. When you let go of the derailleur and continue to rotate the cranks, does the derailleur return spring easily pull the derailleur down into the small cog? If not, I suspect the high/low limit screws need to be reset. If the derailleur was adjusted to work on a damaged hanger, the limit screws will be off when paired with a new straight hanger.


If all of the above is good, it's probably a cable friction issue. Cables cut straight? No kinks in the inner cable? Under BB cable guide clean with cable routed correctly? You can check if there's any friction by pulling the disconnected end of the inner cable while shifting through the indexes on the shifter. It should have no/very minimal resistance.


It could be an issue with the shifter, but that's pretty rare.

RESOLVED....

This morning, I went back out and double checked the cable resistance coming from the shifter. It was crisp and clean.
I checked the derailleur without the cable attached. Manually, I was able to get it to climb the cassette and return properly.
I pulled the adjustment knob and inspected it. When I reinstalled it, I removed the plastic housing and spring and tightened it up. As I did this, it knocked out a small bushing that sits where the cable comes out of the housing arm. Upon inspection, I noticed that a groove had worn its way into this hardened bushing where the cable rubs across it. I flipped the bushing over, rotated it 90 degrees and reinstalled it.
Once I did this, it shifts exactly as I expect it to shift.

I knew that I wasn't going nuts. I wonder how many derailleurs have been replaced due this issue.

Good job!:thumb:

Greetings

Quite fascinating, and congrats on diagnosing the problem. Can you post a pic of the bushing and its location?

Good job. I'll have to add this to my "potential causes of shifting issues" list.

You mean this part?
https://cimg6.ibsrv.net/gimg/bikefor...de01581a94.jpg
Huh, I never noticed that before. Is the housing not going into the barrel adjuster straight then?