Adjusting Barrel and wire tension

smd13

Hi all, new to the forum so bear with me...

I've a quick question about the basic working of changing the tension to the rear derailleur via the barrel adjuster. I know roughly how to do it etc, but is there one tension for the whole cassette, or each time I change gear and adjust the tension is that maintained for that specific gear? Hope that question makes some sort of sense, I'm just trying to smooth up the gears on a road bike I have.

sungod

you set the tension (aka indexing) once, it will be correct for all gears

there are four other adjustments...

i) the rear hanger, if this isn't aligned correctly, shifting will be poor in some or all gears
ii, iii) the high and low limit adjustment screws, these set the maximum outer and inner limits of the rear mech movement, these are important limits, especially the inner one as going too far could cause the rear mech and/or chain to foul the spokes
iv) the b screw, it sets how close the jockey wheel gets to the cassette teeth, too far can give poor shifting, too close can result in a jam

the rear hanger needs a tool to adjust, there are workarounds, but unless it's been bent or there are obvious shifting problems just assume it's ok

the other adjustments are documented in the manufacturer's instructions (on their websites), but for generic instructions this is an excellent source of how-to info...

http://www.parktool.com/blog/repair-hel ... derailleur

...in general, you do not need all the tools park suggest!

arlowood

Have a look at this YouTube video.

http://www.youtube.com/watch?v=SkzvfCaIbyQ

Gives the simplest explanation i have seen on how to index your gears properly

smd13

hey guys, thanks for the replies. To explain where I'm coming from I have a cannondale bike from about 7-8 years ago and have started to use it again. I've replaced the original ultegra block with a new one (still 9 speed), and also replaced the chain (as both of these were fucked to be honest). Since then just trying to smooth out the gears, the front chainrings probably a little too worn but trying still!
So far loosened all tension and set the H limit, then added cable tension and set the L limit fine. I've tried adjusting the barrel tension to fine tune the changes but on some gears it works better than others. So, I was wondering how else to help smooth things out? (also, I've adjusted the b screw almost fully each way and seen little difference, is that just me?)

keef66

Have you fitted new gear cables? Last time my bike was shifting poorly in some gears I discovered the cable was fraying inside the shifter and on the point of breaking.

The other possibility is the cable snagging at some point in the outer.

Either way a new cable would eliminate these possibilities.

With a smooth running, properly tensioned cable, once it's indexed for one sprocket it should be spot on for the rest.

smidsy

Indexed gears essentially means that once you get the first jump to happen correctly (so the cable tension is correct) all other jumps are the same.

So you only need to get it to work once and the rest should follow (without any further cable tension adjusting). To check this shift all the way up and down the cassette after you have set the cable tension to get a nice clean single jump.

If yours is not doing this then something else is wrong. e.g if you have trouble with either of the extremes it could be that the H and L screws are not quite right (this only applies to the biggest and smallest sprockets). Do not adjust H or L screws unless you have travel issues. All other adjustments should be with the barrell adjuster or cable clamp/routing only. The H and L screws should not be adjusted if the mech has enough travel. Again once it is set, it is set.

Issue in the middle of the cassette mean another issue will be the cause.

smd13

did the usual commute on it today, and again there's an issue in shift between the fifth and sixth cassette... Seems to be unhappy shifting between these cleanly and occasionally I will have a partial rotation of the cranks with no resistance like the chain in popping out from the teeth and then settling back into them. Would that point more to the front chainring being worn? Granted I've never replaced them because of the cost :S

smidsy

Are the 5th and 6th sprockets worn more than the others?

keef66

I've never been able to spot a worn cassette / sprocket just by looking at it, just that it skips when a new chain is fitted.

Worn chainrings are more obvious / measurable, as is a worn chain.

smd13

Nope the cassette and chain are virtually new (~200miles) which is why I'm surprised there isn't a smooth transition between certain gears. Any chance the spring in the mech isn't responding like it should?

sungod

it may be that the hanger is slightly bent, inability to get good shifting across the whole range can be a symptom

the easiest way to check/align it is with an alignment tool, for instance...

http://www.wiggle.co.uk/lifeline-derail ... ment-tool/

...there may be cheaper equivalents

another thing to check is that the hanger is secure, they often are fitted to the frame with small screws, if these have loosened then the hanger will be held in place by the qr instead, which is not so good