Gears - yaaawn... « Singletrack Forum

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Gears - yaaawn...

31 posts & 16 voices | Started 1 year ago by Surf-Mat | Latest reply from boriselbrus

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Surf-Mat - Member

This is driving me slightly loopy.

Had an X0 medium cage rear mech fitted recently with "tight" indexing so the shifting is nice and snappy. My friendly bike mechanic (who does race stuff for SRAM) fitted it.

For some reason the 2nd and 3rd lowest sprockets (correct name?!) have started becoming a problem - totally skips the 2nd one, very unhappy in the third lowest but okay in the lowest/largest one. Smooth as silk in all other gears.

Followed the instructions and fiddled about with the "b adjustment" screw but to no avail. It's almost as if the mech has an issue? Not been crashed or anything recently.

Any ideas? I can get it looked at but it seems a bit minor for such an effort.

I use those two sprockets a lot though - riding "around" the issue is a PITA.

Cheers, Mr Gear Muppet.

Posted 1 year ago #
thebikechain - Member

On the face of it it sounds like hanger alignment problems.

p.s. can you explain what 'tight' indexing is please? Sounds interesting.

Posted 1 year ago #
Surf-Mat - Member

bikechain - checked hanger alignment - it looks bang on (had it straightened slightly when it was fitted too).

"Tight" may not be the right word but it's basically set up for very rapid shifting at the expense of some "extreme" gears - e.g. small ring, small rear sproket grinds a lot as does big ring, big rear sprocket. TBH I'm not sure about the details but it was shifting beautifully for a couple of weeks. Now "lost" two important gears.

Chain alignment in each gear looks fine.

Posted 1 year ago #
phil.w - Member

Moving the barrel adjuster to the wrong position can give the effect you are experiencing.

Could it have been wound in/out? (out i think but can't remember).

Posted 1 year ago #
Surf-Mat - Member

Phil - I had a fiddle with it both ways but no discernible effect or improvement.

Thanks for input so far - all very much appreciated.

Posted 1 year ago #
Luminous - Member

Sounds like cable stretch. If I've read it correctly.

Try adjusting the cable rather than the mech stops.

Were the cables replaced when the mech was fitted ?, if so, expect a bit of stretch.

Also, I tend to store my bike with the mechs in their relaxed position to reduce the static tension on the cables and to reduce mech spring stress, when not in use.

That means that I select the granny ring up front and 1st gear on the cassette (I use low normal rear mech with DCLs) just before I finish with the bike.

Posted 1 year ago #
thebikechain - Member

Is the cable baggy? Or is it got some grit in there - my Mojo has a tendency to gum up at the rear mech cable and SRAM mechs seem to be affected by it whereas Shimanos continue to work fine. Maybe a spring strength thingy.

Posted 1 year ago #
wwaswas - Member

it's basically set up for very rapid shifting at the expense of some "extreme" gears - e.g. small ring, small rear sproket grinds a lot as does big ring, big rear sprocket

for me, that's "how it should" and relates to front mech setup, not rear?

have a look on parktool.com for advice on how to adjust a rear mech - if you do what they say in the order they say to do it the result is spot on.

Posted 1 year ago #
stumpy01 - Member

Good tip!

Also, I tend to store my bike with the mechs in their relaxed position to reduce the static tension on the cables and to reduce mech spring stress, when not in use.

Might start trying to remember to do that.....sounds sensible.

It does sound like some kind of cable tension issue or you've got some muck in the cable somewhere - or perhaps a small kink?

Posted 1 year ago #
retro83 - Member

Skipping a gear in the middle of the block could be dirt in the cable, got the same problem on my bike at the moment due to the stupid cable routing.

Posted 1 year ago #
Luminous - Member

These little babies come in useful

EDIT: Also check the cassette, make sure you've nothing wedged deep between the gears themselves. I've had long grass wrap around the minor diameter of the cassette between two gears, which has prevented the chain sitting down fully on the gear.

Posted 1 year ago #
Surf-Mat - Member

Cable tension seems fine but I will double check.

Cables are XTRs and fairly recently fitted but again I will check.

Will check Parktool! I can adjust a rear mech more or less but this issue is foxing me - lowest gear sprocket fine, missing the next one completely and extremely "skippy" in the one after that but 100% fine in all other gears.

Posted 1 year ago #
thomthumb - Member

sounds like a hanger to me.

oh and buy a book.

"Tight" may not be the right word but it's basically set up for very rapid shifting at the expense of some "extreme" gears - e.g. small ring, small rear sproket grinds a lot as does big ring, big rear sprocket.

Followed the instructions and fiddled about with the "b adjustment" screw but to no avail. It's almost as if the mech has an issue? Not been crashed or anything recently

I had a fiddle with it both ways but no discernible effect or improvement.

you really have no idea about gears.

Posted 1 year ago #
cynic-al - Member

Blimey tomthumb that's harsh!

Mat it sounds like an odd one but I would echo the above, check:

Cable for grit/rust/grease/contamination and KINKS!
Everything bolted up tight inc. jockey wheels.
Nothing wrong with sprocket teeth?
Hanger alignment.

Can you take some pics or even better a video?

(when I was a wrench we had a guy phone up to say his transmission was noisey...held his mobile to it so we could diagnose! )

Posted 1 year ago #
ski - Member

Surf-Mat, its worth double checking you have not kinked the gear cable in the shifter, I did this with my setup, kinked the cable when fitting it into the shifter & had the same scratching head problem.

Posted 1 year ago #
BikePawl - Member

That sounds odd, which direction of changing does it happen? if it is always when you are changing into the higher gears then it would probably indicate a problem with the cable as the Bike Chain says, if it is when you change into lower gears then it could be cable stretch. Good luck sorting it out.

Posted 1 year ago #
iainc - Member

also check that all your cables are properly seated in their end caps and the lugs and nothing obstructing the cable runs

Posted 1 year ago #
Surf-Mat - Member

Iain - checked end caps (that was my first thought) but all fine.
BP - both directions! It totally missed the 2nd lowest sprocket.

Thom - nice, helpful comment- you really have no friends don't you?

Posted 1 year ago #
thomthumb - Member

sorry. genuinely trying to be helpful. you sounded like you were fiddling with different things hoping it might fix the problem.

apologies if that's not the case.

and i still think it is the hanger.

Posted 1 year ago #
Surf-Mat - Member

Thom - in the lowest gear, the mech/jockey wheel is 100% in line with with smallest sproket. It was lined up (with the correct tool) three weeks ago and not crashed since.

But yes, not the Worlds best on gears...

Posted 1 year ago #
cynic-al - Member

Either put the bike in a stand or (shudders) upside down.

"Pedalling" in the gears and having a good close look at what's happening should help a lot.

Posted 1 year ago #
thomthumb - Member

the park big blue book is really good if you want to learn. the trick with gears is to be systematic. the difficulty is where to start and how to progress through adjustments.

Posted 1 year ago #
dufresneorama - Member

+1 Put bike in a stand
Makes sorting gears easy peasy

Posted 1 year ago #
Surf-Mat - Member

Can you get any that just have the clamp bit?

My garage has a well fixed pole (like a scaffold pole) that is perfect for fitting the top bit of a stand to.

Otherwise I might do a DIY job with some clamps from a tool store. Often need one - time to bite the bullet and get one.

Posted 1 year ago #
cynic-al - Member

IIRC Park's (overpriced, as ever) stand is available in a "bolt to the wall" format - there may be others worth looking at.

Posted 1 year ago #
Surf-Mat - Member

Cheers al - Park may be a bit OTT for my humble needs but will check them out.

Posted 1 year ago #
TheBrick - Member

"bikechain - checked hanger alignment" With a hanger alignment tool? I've seen many hanger that look fine but when you put the tool on them they are a little off and it can make all the difference.

Posted 1 year ago #
spooky_b329 - Member

Are the numbers on the shifter corresponding with the cassette at the back? I've had problems before where the chain is sitting in high gear (the smallest cog) but it turned out the shifter was in position 8, with position 9 redundant. Shifts fine as you go up through the cassette until the 3rd lowest gear, with the shifter in position 2. Then when you shift to 1, the shifter appears to have a bigger throw to get the chain onto the last cog, so it skips gear 2 and goes straight to lowest gear.

An easy way to check is shift to the highest gear, then pull the gear inner gently and see if you can click the shifter again. It usually happens when someone has fiddled around with the barrel adjusters, after a whole turn of the barrel you should see a noticeable change in shifting performance.

Posted 1 year ago #
Surf-Mat - Member

Spooky - that could be part of the issue. Strange it's suddenly happened. Shifters are X-9s.

The Brick - it was checked properly when it was fitted three-ish weeks ago (with the a proper tool). Not dinged it since then but I guess it's a possibility.

Posted 1 year ago #
thebikechain - Member

It doesn't need much effort to knock one off line. give it a double check to rule it out.

Posted 1 year ago #
boriselbrus - Member

Bent tooth on the cassette sprocket?

Posted 1 year ago #