Can anyone help with giving advice on how to adjust my rear derailleur?

[SilentDeus]

Maybe it's because I've been I've been more agressive recently, but my shifting feels off. I did some research and did what I can, but I ended up making it worse Nothing is broken, but the adjustment is off and it's jumping gears.

Rear derailleur is the SRAM GX. I have no idea where the instructions are if any, and there isn't any labeling on the piece.

Here is a clip of the derailleur:

View: https://youtu.be/m4x8gFoQ8yU

 

[SilentDeus]

Maybe it's because I've been I've been more agressive recently, but my shifting feels off. I did some research and did what I can, but I ended up making it worse Nothing is broken, but the adjustment is off and it's jumping gears.

Rear derailleur is the SRAM GX. I have no idea where the instructions are if any, and there isn't any labeling on the piece.

Here is a clip of the derailleur:

View: https://youtu.be/m4x8gFoQ8yU

The 2 screws at 0:46 were the ones I was tinkering with.

 

[slowmotion]

Have a look at this clip about adjusting rear derailleurs. OK, it's Shimano, but the principles hold good, and it's widely regarded as one of the clearest explanations of what to do. Scales fell from my eyes having seen it a few years ago.

[media]

]View: https://www.youtube.com/watch?v=SkzvfCaIbyQ[/media]

 

[Colin_P]

You'll need to re-index them most probably, the way I do it is...

1, Shift to top gear (small rear cog, big front cog)
2, Undo clamp and release shifter cable, no need to take it off, just ensure any tension is off it
3, The two screws you were messing with are the high and low limit screws. Bit by bit turn the high limit screw until the chain is at the point where it is going to comes off to the frame side, it may even come off. Once at that point go back a half to a full turn until the chain is quietly settled on the small rear cog.
4, This bit is trial and error, it may take a few goes; pull any slack out of the cable and do up the pinch nut then check the the indexing of the gears obviouly by spinning the pedals. Don't go right up to the big cog as you still need to set the low limit screw. But go up and down the gears to see if everything is as it should be. There are two things to do if it isn't, either loosen the cable or apply more tension. Always adjust the cable when on the small rear cog. It should take you no more than a few goes but make sure when each gear is selected it runs smooth and quiet with the chain not trying to skip to the adjacent cog.
5, Once happy with the shifting on the smaller cogs, change the front cog to the small(est) one. Then carefully shift to the big rear cog , if it won't go, undo the low limit screw bit by bit until it does, if the chain falls off into the spokes turn the limit screw bit by bit until it doesn't.

Be logical and methodical and you should have it done in less than half an hour. If you think it has all gone wrong, go back to step one and work through again. It really isn't that difficult once you get a feel of what is going on when you turn the limit screws. The base cable tension is the tricky trial and error bit. Don't graunch the cable clamp bolt up each time you need to adjust, just a nip sufficient to secure the cable and then a 1/4 turn as you don't want to crush and ruin the cable.

You can do it !

 

[Salty seadog]

The video that slowmotion linked to is about the best you will find. Watch it and then do the work with the vid nearby so you can stop rewind, do a bit etc.

 

[screenman]

Start with alignment, most are slightly off.

 

[bonsaibilly]

You'll need to re-index them most probably, the way I do it is...

1, Shift to top gear (small rear cog, big front cog)
2, Undo clamp and release shifter cable, no need to take it off, just ensure any tension is off it
3, The two screws you were messing with are the high and low limit screws. Bit by bit turn the high limit screw until the chain is at the point where it is going to comes off to the frame side, it may even come off. Once at that point go back a half to a full turn until the chain is quietly settled on the small rear cog.
4, This bit is trial and error, it may take a few goes; pull any slack out of the cable and do up the pinch nut then check the the indexing of the gears obviouly by spinning the pedals. Don't go right up to the big cog as you still need to set the low limit screw. But go up and down the gears to see if everything is as it should be. There are two things to do if it isn't, either loosen the cable or apply more tension. Always adjust the cable when on the small rear cog. It should take you no more than a few goes but make sure when each gear is selected it runs smooth and quiet with the chain not trying to skip to the adjacent cog.
5, Once happy with the shifting on the smaller cogs, change the front cog to the small(est) one. Then carefully shift to the big rear cog , if it won't go, undo the low limit screw bit by bit until it does, if the chain falls off into the spokes turn the limit screw bit by bit until it doesn't.

Be logical and methodical and you should have it done in less than half an hour. If you think it has all gone wrong, go back to step one and work through again. It really isn't that difficult once you get a feel of what is going on when you turn the limit screws. The base cable tension is the tricky trial and error bit. Don't graunch the cable clamp bolt up each time you need to adjust, just a nip sufficient to secure the cable and then a 1/4 turn as you don't want to crush and ruin the cable.

You can do it !

I thought conventional wisdom was to start in the lowest possible gear, undo the cable, and build the tension from there. Because the derailleur's spring will default towards the central axis of the bike, so you should start by using the lower limit screw to line the derailleur up to the largest rear cog.

Also, in your item 3 above, what do you mean by "comes off to the frame side"? As far as I can tell there is frame on both sides of a rear wheel cassette so perhaps be 100% clear when giving instructions?

*

All that aside, a chain jumping on the cassette can usually be sorted out by adjusting the barrel tuner if there is one, can't it? The limit screws set the upper and lower extent of the derailleur spring but the barrel adjuster can tune out a slight off-line in the middle of the gear range..?

bb

 

[bonsaibilly]

Start with alignment, most are slightly off.

That's *really* helpful. Not.

 

[screenman]

That's *really* helpful. Not.

How do you make that out? most out of synch indexing I come across that has not been fiddled with is cured by realigning the rear mech.

Also it is the very first and most obvious place to start.

 

[Nigelnaturist]

@screenman I think that what @bonsaibilly meant is a bit more of an explanation might be warranted, I knew what you meant others might not though.

 

[Dogtrousers]

How do you make that out? most out of synch indexing I come across that has not been fiddled with is cured by realigning the rear mech.

Also it is the very first and most obvious place to start.

By "alignment" do you mean checking whether the hanger is bent? Isn't that a specialist job requiring expensive tooling?

I'm curious because all my bikes have steel frames, so I've never dealt with Alu hangers. The concept of "alignment" isn't one I've ever dealt with.

Just get the limit screws right and the minimum necessary amount of tension in the cable.

 

[bonsaibilly]

He means using the barrel adjuster I think. Bb

 

[screenman]

Yes I mean checking to see if the rear mech is out if alignment, the tool is about £20 and worth investing in. If it is out indexing will never be as smooth as it could be.

 

[Colin_P]

I thought conventional wisdom was to start in the lowest possible gear, undo the cable, and build the tension from there. Because the derailleur's spring will default towards the central axis of the bike, so you should start by using the lower limit screw to line the derailleur up to the largest rear cog.

That is what I said but it is not the lowest gear, the lowest gear at the back is the biggest cog. You need to start with aligning the small cog which is the highest gear. The default position which is governed by the spring in the rear derailleur will be to move the chain to the highest gear which is the small cog.

Also, in your item 3 above, what do you mean by "comes off to the frame side"? As far as I can tell there is frame on both sides of a rear wheel cassette so perhaps be 100% clear when giving instructions?

I was clear. I'll ask you this; when looking at the cassette / freewheel / cogset or what ever you wish to call it, what is each side of it? The answer is the frame on one side and the spokes on the other. As far as I'm aware bikes chains are not ghosts and cannot pass through solid matter which it would have to do to contact the frame on the non drive side.

I'd suggest you go out and have a look at your bike.

All that aside, a chain jumping on the cassette can usually be sorted out by adjusting the barrel tuner if there is one, can't it? The limit screws set the upper and lower extent of the derailleur spring but the barrel adjuster can tune out a slight off-line in the middle of the gear range..?

No, a chain jumping as opposed to not indexing properly is caused by a worn chain and or sprocket or the forward and aft derailleur tension not being sufficient, for that there is another adjustment screw or new chain and cassette. The bike may of course have a worn chain and that may be the cause of the problem. The chances are and if it is a new'ish bike that the gear cable outer sheathing has compressed (usually at any cut ends) and that has thrown the indexing out a tad.

Indexing is all about getting the base position and correct cable tension as that most excellent video talks about.

My post was aimed to try and help the OP further undertand how to get the base setting / alignment back on the small cog (highest gear) and then to the big cog (lowest gear) with mimimum fuss.

 

[bonsaibilly]

That is what I said but it is not the lowest gear, the lowest gear at the back is the biggest cog. You need to start with aligning the small cog which is the highest gear. The default position which is governed by the spring in the rear derailleur will be to move the chain to the highest gear which is the small cog.



I was clear. I'll ask you this; when looking at the cassette / freewheel / cogset or what ever you wish to call it, what is each side of it? The answer is the frame on one side and the spokes on the other. As far as I'm aware bikes chains are not ghosts and cannot pass through solid matter which it would have to do to contact the frame on the non drive side.

I'd suggest you go out and have a look at your bike.



No, a chain jumping as opposed to not indexing properly is caused by a worn chain and or sprocket or the forward and aft derailleur tension not being sufficient, for that there is another adjustment screw or new chain and cassette. The bike may of course have a worn chain and that may be the cause of the problem. The chances are and if it is a new'ish bike that the gear cable outer sheathing has compressed (usually at any cut ends) and that has thrown the indexing out a tad.

Indexing is all about getting the base position and correct cable tension as that most excellent video talks about.

My post was aimed to try and help the OP further undertand how to get the base setting / alignment back on the small cog (highest gear) and then to the big cog (lowest gear) with mimimum fuss.

You're quite right of course, I had my small and large cogs mixed up, thanks for explaining.

I have had a look at my bike though and there is definitely frame to be found on both sides of the cassette.

bb