Rear gear cable replacement

[doffcocker]

have ordered a new hanger (rather not invest in the alignment tool at the moment if possible), but a bit worried the derailleur cage might also be bent.

Not sure if it’s possible to judge from the pictures?

[Eyebrox]

Yes, it's bent and needs straightened. Put the chain onto the smallest ring at front and biggest cog at back. Look at the set-up from the rear. The likelihood, given what can be seen in the images, is that the bottom of the mech cage will be leaning in towards the spokes. Pull it back out using a very large shifting spanner. Lock the jaws of the spanner on the cage at the lower jockey wheel and gently pull towards you. If you have a new mech hanger, you won't need to worry about the misalignment being in that area. You have to be forceful and confident without overdoing the pulling. Keep testing the derailleur as you manoeuvre the cage out the way. Best of luck. Practice makes perfect and constant close inspection of the position of the cage in relation to the wheel will help.

[doffcocker]

Yes, it's bent and needs straightened. Put the chain onto the smallest ring at front and biggest cog at back. Look at the set-up from the rear. The likelihood, given what can be seen in the images, is that the bottom of the mech cage will be leaning in towards the spokes. Pull it back out using a very large shifting spanner. Lock the jaws of the spanner on the cage at the lower jockey wheel and gently pull towards you. If you have a new mech hanger, you won't need to worry about the misalignment being in that area. You have to be forceful and confident without overdoing the pulling. Keep testing the derailleur as you manoeuvre the cage out the way. Best of luck. Practice makes perfect and constant close inspection of the position of the cage in relation to the wheel will help.

Great thanks.

Just to be clear, once I have replaced the hanger which I plan to do in the morning, I might still have to manoeuvre the cage with the spanner?

[Eyebrox]

Yes. The likelihood is that both the hanger and the mech are bent, especially so from what I can see. A new hanger will correct that part of the positioning. That leaves the cage itself to be straightened. Take the chain off to make fitting the derailleur easier and make sure the B screw is sitting on top of the tab on the hanger. You might want to undo the screw anti-clockwise before you start then tighten it up once the new hanger and the attached derailleur are in place. This will ensure the screw hits the tab on the hanger and positions the derailleur at the desired place under the cogs (bigger distance at the smallest cog and ideally 5mm underneath the biggest one when the derailleur is fully tensioned).

[doffcocker]

Yes. The likelihood is that both the hanger and the mech are bent, especially so from what I can see. A new hanger will correct that part of the positioning. That leaves the cage itself to be straightened. Take the chain off to make fitting the derailleur easier and make sure the B screw is sitting on top of the tab on the hanger. You might want to undo the screw anti-clockwise before you start then tighten it up once the new hanger and the attached derailleur are in place. This will ensure the screw hits the tab on the hanger and positions the derailleur at the desired place under the cogs (bigger distance at the smallest cog and ideally 5mm underneath the biggest one when the derailleur is fully tensioned).

Cheers.

Is the chain removal crucial? I have a chain removal tool but always bit nervous about using it for fear of pushing the pin too far out so that it can't be put back in. My current chain is a quick release but don't have any experience of taking a chain off that way.

Generally speaking, when it comes to using a spanner on the derailleur cage, how easy is it to get that spectacularly wrong?
I have a 40 mile ride planned for Thursday, ideally I will feel comfortable by tomorrow night that it's running smoothly enough for me to go ahead with that, but is it the sort of thing where I could just take a spanner with me and if I'm having problems with my shifting on the road, adjust accordingly from the roadside?

[slowster]

I have a chain removal tool but always bit nervous about using it for fear of pushing the pin too far out so that it can't be put back in. My current chain is a quick release but don't have any experience of taking a chain off that way.

Experiencing problems breaking and re-joining a chain is probably *less* likely if a quick link is used rather than a chain tool.

Instructions here on how to do it without special quick link pliers: viewtopic.php?p=1510495#p1510495

NB Some quick links are not designed/intended to be repeatedly used to break and re-join chains. If it's a KMC quick link, the model number at one end of the link will have the letter R at the end if it is a reusable link.

[Eyebrox]

No need to remove the chain but screwing on the derailleur to the hanger can be difficult because of the tension on the chain. You can ease the tension by dropping the wheel out, attaching the hanger then the derailleur and finally putting the wheel and chain back in position. Using the shifter is only to give you grip and some purchase. You can do it by hand and bring the cage out in increments. Test the gearing every time you sense that the mech has moved into a straighter position. It should be straight, vertical and in line with the wheel. Over enthusiastically pulling on the derailleur might cause it to snap at the pins but they are fairly robust and you can generally tell when you are asking too much of it. Same with your hanger if you borrow an alignment tool. Push and pull it too severely and the hanger can snap. Some are better made and can take more bending. The whole procedure, like most other bike jobs, becomes easier when you've done it for the first time. If it does go belly up, all is not lost. A new mech costs little more than a hanger. And with everything replaced (by that stage) all should work faultlessly.

[doffcocker]

This is how it looks now with the new hanger and some manoeuvring of the cage.

To me it looks straight enough, I know it’s not possible really to say for sure, but it looks relatively well aligned and there’s still the marked jumping of the chain within the cage.

[slowster]

Have you measured the wear on your chain recently?

[doffcocker]

It’s interesting you mention that as I’ve literally just noticed that the jumping is consistently happening on the quick release link only.

Is that significant?

[doffcocker]

Sorry just to correct myself there, I've actually identified two very stiff consecutive links (that just happen to follow the quick release link) and it's when these enter the cage that it jolts.

I'm happy enough with how the gears are actually shifting now, it's just this jumping that is the issue. Is this likely the cause?

I do have a chain remover tool, is the chain serviceable or just better to be replaced?

[Eyebrox]

Stiff links and moreso very stiff links will indeed cause chain problems. Loosen the links with GT85 and nudge the pins into place using your chain tool . Go gently and test the chain's link by link movement as you tackle each pin. You can change the chain but this might present other difficulties if the new change with unworn rollers doesn't mesh with a worn cassette. I can't remember what you said about the condition of the cassette and chain at the start of the conversation. Your chain will flex properly if you follow the above. Better changing chain and cassette at the one time.

[Eyebrox]

Are you sure the cable is attached to the connector bolt as per Shimano instructions? The diagram here is of a Claris mech - but not necessarily the one you have.

[TheBomber]

Are you sure the cable is attached to the connector bolt as per Shimano instructions? The diagram here is of a Claris mech - but not necessarily the one you have.

When you're sorting that one out it would be worth flipping the plastic part of the barrel adjuster around so that the detents are held against the body of the mech by the little spring (part 5 in the picture below). It can go out of adjustment over time otherwise.

[doffcocker]

Thanks all.

Basically the gears are now shifting very nicely with the new hanger and my derailleur seemingly bent back straight enough.

The only issue I’m still having is this jolting of the chain in the lower gears. It’s only happening when I’m putting a lot of force on the pedal, so it’s very difficult to identify on the stand.

I have done a very thorough check now of each link in the chain and managed to force each one into moving without any restraint. The only thing that i have been able to identify from the stand is that although the area around the quick release is perfectly flexible, by moving the pedals slowly both forward and backward, it’s around that area that you can see the chain doesn’t connect quite as well with the cassette and the jockey wheels. It just doesn’t connect as naturally as the rest of the chain does - it kind of slides on to the sprockets rather than latches. I’m guessing that isn’t healthy and could be the main issue here.