New chain now I can't index gears properly

DasBike

Bought a 2nd hand bike few months ago - cube peloton race with 10 speed shimano 105 gears. Gear changes were working fine but not 100% smooth. I changed the chain after checking the old one with a wear tool.
I started playing around with the rear derailleur barrel adjuster to try get crisp changes and I've totally messed it up and can't seem to get back to even remotely smooth changes. I followed some YouTube videos on indexing gears but when I get the tension right to shift up to larger cog it then won't shift down to smaller cog with 1 click. As a result I've had a few instances where I've gone to push down the pedal hard and the chain has finally slipped down a cog or 2 to the correct gear.
I'm at a bit of a loss where to go next. I think the rear cassette is fine - no visible signs of wear and I can pedal hard when in the right gear. Possibly the cable needs replaced - the bike is a 2013 model so has a couple years of riding in it.
Otherwise I can take it to LBS for a service and hope they can sort.
Any guidance much appreciated!

dj58

Most likely the inner cable has started to brake down/fray and is snagging on the outer. Check the loop that leads to the RD and the STI shifter, where the cable enters the unit along the front of the handle bar.
viewtopic.php?f=40004&t=13039045

keef66

Two possibilities: as suggested above, a fraying inner cable. With my 105 the most likely spot is inside the shifter; it seems to eat the cable there every 2 or 3 years.

Easy way to check without undoing anything, as long as you have external cable routing:

Shift all the way into your lowest gear (biggest sprocket)
Now without turning the pedals, and while maintaining tension on the inner wire somewhere, click the shifter all the way up to the other end. (you'd now be in your hardest gear if you'd been turning the pedals)
You should now have enough slack in the inner cable to unseat the loop of outer cable from the frame stop on the chainstay. Then you can push the inner wire back through the shifter unseating the nipple, and inspect the first 2 cm of wire which is where it usually breaks.

Possibility 2 is a bent mech hanger. Next to impossible to check by eye, but an alignment tool is cheap enough and makes it easy to straighten if slightly bent. Or have the LBS check it

rs6mra1

I'll firstly say my knowledge is limited but one question comes to mind - how did you go about checking the new chain length before installing? I changed my chain thinking it would be a case of remove the old and put on the new. That was not the case and IIRC I had to remove 2 or 3 links and then index the whole thing again which was something i had never done before.
For those that are experienced what would the effects be if the chain was too long?

keef66

rs6mra1 wrote:

I'll firstly say my knowledge is limited but one question comes to mind - how did you go about checking the new chain length before installing? I changed my chain thinking it would be a case of remove the old and put on the new. That was not the case and IIRC I had to remove 2 or 3 links and then index the whole thing again which was something i had never done before.
For those that are experienced what would the effects be if the chain was too long?

If your chain's too long the rear derailleur may not be able to take up all the chain slack when you're in the smallest chainring and smallest sprocket. The mech will be folded back on itself and the chain won't be running smoothly around the jockey wheels. Worst case it may actually be hitting the cassette. It will sound like a bag of spanners being kicked downstairs, gear shifting will be less than perfect, and lack of tension in the drivetrain could mean the chain drops off the chainring when you go over a rough patch.

Usually you assume the old chain was the correct length and size the new one to match it. But that assumption isn't always correct, so there are several ways to determine optimum chain length from scratch. Have a Google.

I usually wrap the chain round the biggest chainring and biggest sprocket - but not through the rear mech - then add a link (inner plus outer = 1 inch). Break the chain so there's an inner link at each end, thread through the derailleur, then join with a KMC Missing Link.

doug5_10

2nd all of the above points, another option to consider is a worn cassette, you'll never see wear by eye on a cassette. 20 quid for a replacement so not a massive outlay to check (if its not then you have a replacement ready when you do need it)

From your description, my money's on a frayed cable though, indexing is a 5 minute job if all components are playing ball.

DasBike

keef66 wrote:

I usually wrap the chain round the biggest chainring and biggest sprocket - but not through the rear mech - then add a link (inner plus outer = 1 inch). Break the chain so there's an inner link at each end, thread through the derailleur, then join with a KMC Missing Link.

This is how I measured the chain and connected using KMC link.

I have internal cable routing but will have a look at cable as best I can tonight and check for signs of wear. Ordered a new anyway assuming that it will be the fault.

Thanks for the advice!

DasBike

Evening. Replaced inner gear cable for rear derailleur and managed to the gears indexed (still not 100% smooth but as close as I expect to get them).
Tool the bike out for a quick spin and changes were OK when pedalling easy but changing under harder pedalling was quite clunky/louftingshifting toto smaller sprocket. Any ideas what would cause that? Thanks

bbrap

DasBike wrote:

Evening. Replaced inner gear cable for rear derailleur and managed to the gears indexed (still not 100% smooth but as close as I expect to get them).
Tool the bike out for a quick spin and changes were OK when pedalling easy but changing under harder pedalling was quite clunky/louftingshifting toto smaller sprocket. Any ideas what would cause that? Thanks

Maybe a stupid idea but can you not put your old chain back on and see if the shifting is better. That would definitely point to worn cassette or rule it out.

keef66

I refer the honourable gentleman to my earlier reply, option 2, a bent rear mech hanger.

I bought an alignment tool; it's amazing how a hanger that looks OK turns out to be quite a long way out when you can check it properly...

Which reminds me, I must check the winter bike which almost certainly has a bent hanger. The cage is occasionally tickling the rear spokes when I shift into my lowest gear :shock:

DasBike

keef66 wrote:

I refer the honourable gentleman to my earlier reply, option 2, a bent rear mech hanger.

I bought an alignment tool; it's amazing how a hanger that looks OK turns out to be quite a long way out when you can check it properly...

Which reminds me, I must check the winter bike which almost certainly has a bent hanger. The cage is occasionally tickling the rear spokes when I shift into my lowest gear :shock:

I think I'll take it to the LBS to check the rear mech hanger as you suggest.

Can't put the old chain back on to check as the missus already threw it out. When I did put the chain wear indicator on the old chain it did sit flush both on the 0.75 and 1mm sides. So may also be a cassette issue in there.

svetty

DasBike wrote:

When I did put the chain wear indicator on the old chain it did sit flush both on the 0.75 and 1mm sides. So may also be a cassette issue in there.

Quite likely cassette is worn in that case. A 105 cassette isn't expensive so I'd replace this unless everything is settling down.

keef66

Svetty wrote:

DasBike wrote:

When I did put the chain wear indicator on the old chain it did sit flush both on the 0.75 and 1mm sides. So may also be a cassette issue in there.

Quite likely cassette is worn in that case. A 105 cassette isn't expensive so I'd replace this unless everything is settling down.

Or if you're wanting to do it cheaper, 10 speed Tiagra. Just remember the Tiagra cassette has the spacer built in.

DasBike

keef66 wrote:

Svetty wrote:

DasBike wrote:

When I did put the chain wear indicator on the old chain it did sit flush both on the 0.75 and 1mm sides. So may also be a cassette issue in there.

Quite likely cassette is worn in that case. A 105 cassette isn't expensive so I'd replace this unless everything is settling down.

Or if you're wanting to do it cheaper, 10 speed Tiagra. Just remember the Tiagra cassette has the spacer built in.

The 105 cassette is £20 on wiggle just now. £1 more than the Tiagra one.

Would a worn cassette cause clunky changes and difficulty with indexing gears?

How hard is it to replace the cassette? I've done chain and inner gear wire so far based on youtube videos!

svetty

Easy if you have the tools. TBH if you are going to be riding for the forseeable future the basic tools for cycle maintenance are a necessity unless you want to throw money at your LBS. You need a cassette tool (only a few pounds) and a chain-whip (about £15).

keef66

In that case get the 105! Need a chain whip or the Vise grip type alternative tool to hold the cassette still, and a cassette lockring tool to undo / tighten the lockring. Again Youtube will be awash with vids showing how easy it is. Or look at Park Tools.

Worn cassette usually results in a new chain skipping under load, ie jumping forward over the teeth. It doesn't usually affect the indexing / shifting.