Bicycle Mechanics - Chronic poor shifting - hanger alignment question w/ pic

I have 2 bikes, one shifts great the other has never shifted well. The one that shifts poorly tends to friction shift "Okay" for maybe 3-4 rides, then eventually will "pop" while riding along on some random gear, and by process of elimination seems to be related to derailleur hanger alignment, which was pretty bent when I got the bike. It has NEVER indexed well.

Okay, so I have the park hanger tool and have tried it about 6 times on this bike that won't shift right, and though I think I got it to mess up *less after using the tool the 1st time, it still will not index and does the same "pop" after a few rides wihch drives me ****ing nuts.

On the flip side, this crappy mountain bike shifts great....so I figure "well, I'll put the hanger tool on there and see what it reads". I put the tool on, and it actually is telling me that the hanger is slightly bent, such that the tool is too far from the rim at the bottom of the rim (near the pavement) and is too close at the top of the rim.

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What the hell am I doing incorrectly? I make sure to rotate the wheel so that I'm measuring at the tube valve each time and I use the little stick and the rubber o-rings to try to get an accurate measurement each time.

Anyone else had this much trouble figuring out how to bend the hanger? Should I not be measuring this with the bike upside down like the picture or something? (can't see why this would matter)

To me, it doesn't make any sense that the bike with the bent hanger shifts great, whereas the one I've "adjusted" multiple times won't index properly. To boot, I "adjusted" a 3rd bike and its shifting went from average to worse.....so it must be my technique or something. I just can't see how though..

Thanks,

First off leave the bike that shifts well alone before you bullox it up too LOL.

Tell us a bit about the poorly shifting bike? what brand model drive? tons of miles? how is the chain? if the hanger was bent when you picked it up it is posssible that the derailleur is bent too, but not enough that you can see it.

you can change the shifter from friction to index? so it has thumbshifters? I somewhat suspect a shifter or cable binding issue.

BTW working upsidedown should not have bearing on this measurement but is hard on the knees

First, what shifters and derailleurs do you have?
Second, are you measuring and correcting the alignment of the derailleur hanger in both the horizontal and vertical planes per the instructions that come with the tool?

Third, what condition are the cables and cable housings in?
Fourth, how many miles are on the chain and how many miles are on the rear gears?
Fifth, what is the condition of the pulleys on the rear derailleur? are the teeth in good condition?
sixth, is the chain the correct length?
Seventh, you should not have a problem with friction shifting if the chain and gears are not worn excessively...is the shifter slipping? if not then go back and check for wear and tear of the chain and rear gears.
Eight, is the derailleur itself bent? If so then adjusting the derailleur hanger will be of little use as this will not correct a bent component.

Report back with info and more pictures.

Also sometimes when working on a bike upside down you can get shifting dialed in and then it will not work as precisely when right side up. Better to suspend the bike from some rope/chord around the seat post than put it upside down if you do not have access to a repair stand.

-j

Poor shifting is most often due to worn/bent/crimped cables and housings, or improperly installed housings. Housings need to have cleanly cut and square ends and be seated tightly in the shifters, cable stops, and DRs.

I don't think that you are using the hanger alignment gauge properly. Rotate the hanger gauge to multiple places on the rim. When the distance is the same regardless of where you measure, you've got it straight.

I am glad to see the logic of my 11-year-old self is alive and well: any time something is wrong with the bike it is because something is bent, and the answer is to go about bending things.

What you're (the OP) describing isn't characteristic of a derailleur problem, but more typically an indicator of a chain or sprocket issue. It could be as simple as a stiff link or series of links (very common) or a worn chain and/or sprockets.

Before going further, shift to a neutral combination, say outer chainring with 2nd or 3rd high in the rear. Back pedal slowly while pushing the lower RD pulley forward enough so the chain sags very slightly. Watch the chain coming off the pulley for any links that don't straighten right away, and also be attentive to any tugs or pulses you feel in the RD cage. if you're lucky you'll spot an easy to fix problem this way.