MTB Gears

[Audience/one]

My mtb's gears keep on slipping and changing at times.. There's no 'teeth' missing on rear cok that I can see of. I did put on a new chain recently and had bike serviced, also recently. Any ideas on what's wrong??

[Griffin]

Had bike serviced ? At a LBS or dealer..or a back yard mech ? Did this happen before you had it serviced..and did you mentioned it to them ?

[Audience/one]

At dealer. No, bought bike second hand. New in mtb'ing. deore lx front and deore xt back der. Sometimes the gears just tend to jump without me pushing any levers. specially when im pushing hard. happens like 3 or 4 times in 3hr ride.. The geras still work great, just now and again has a mind of their own..

[Cheryl J]

Cassette and / or chain could be worn or could be new chain on old cassette etc ?

Also check if your derailleur hanger is bent - doesn't need to be out a lot

 

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Cheryl J2009-12-14 01:06:57

[Johan Bornman]

The problem is you put a new chain onto a worn cassette. That skipping is the indicator that you should fit a new cassette.

[kosmonooit]

hmm I had the same problem even after new chain and cassette, LBS could never sort it out  drove me nuts eventually replaced cables and RD with SRAM, no more problems.

[evolve]

Assuming that the chain and cassette are fine and in good shape, more than likely there is some dirt in the cable housing thats keeping the cable from shifting on time and hence you get the delayed shift.

[Johan Bornman]

hmm I had the same problem even after new chain and cassette' date=' LBS could never sort it out  drove me nuts eventually replaced cables and RD with SRAM, no more problems.[/quote']

 

Your equipment was replaced for all the wrong reasons.  Neither cable nor RD cause a chain to skip.

 

 

Nevertheless, the end result is what you wanted. I do suggest you try another bike shop though.

 

 

 

[kosmonooit]

Thanks JB but given that the chain and cassette has just been replaced, gears were still jumping which no adjustments (by lbs or myself) could help, I went through process of elimination and solved the problem.  So how does my reasoning fail with that logic?

 

As for lbs, might buy a tube or lube there, thats about it. Skills here in SA are few and far between,  bad service and workmanship and lack of ethics have become the norm.  Sadly.

[Johan Bornman]

Thanks JB but given that the chain and cassette has just been replaced' date=' gears were still jumping which no adjustments (by lbs or myself) could help, I went through process of elimination and solved the problem.  So how does my reasoning fail with that logic?

 

As for lbs, might buy a tube or lube there, thats about it. Skills here in SA are few and far between,  bad service and workmanship and lack of ethics have become the norm.  Sadly.

[/quote']

 

I find it difficult to figure out what was changed when. However, with a new cassette and chain on there, it is not difficult to find out what makes the chain jump. But lets define jump first.

 

1) Does the RD remain completely stable Left-Right but the chain rides on top of the teeth of the cassette?

2) Does the RD move left or right and then just partially engage the chain onto the next gear?

 

Those are the only two options I can think of, but they could happen under different conditions:

 

1) When pedalling hard in certain gears.

2) When just pedalling along with very little pressure on the pedals.

3) In the workstand right there in front of your eyes.

 

Some obvious questions.

 

1) Are the speeds on the cassette and chain and shifter matched?

2) Does the shifter move the cable smootly in even incriments when the cable is removed from the RD and tensioned in one hand whilst shifting with the other?

3) Is the jockey hanger properly fixed onto the frame?

 

Problems like these are difficult to diagnose via e-mail with scant information and without the exact sequence of what was changed when.  When an experienced mechanic approaches a problem, he or she looks at a dozen things with several permutations thereof. I bet you an experienced mechanic can make the old jockey work.

 

 

 

 

 

[INDABUSCHE]

Something that one often overlooks is the knarled cable adustment nut on either the shifter end or in some cases at the RD. This nut is made of plastic and the small knarled indentations wear off with use thereby allowing the adjuster nut to slip, hence releasing cable tension and ultimately gear adjustment. Blame is always placed on a so called "worn derailer" as probably was the case with Kosmonooit

[MadScientist]

Sorry for cjipping in but have a similar problem 3rd time this is happening to me normally it is fixed after a service but then 2 or 3 rides later it starts again, symptoms are as follows:

 

Only happens when in largest sprocket on the cassette (granny) and only when paddeling hard (steep hill)

 

1) Does the RD remain completely stable Left-Right but the chain rides on top of the teeth of the cassette? Can't say haven't had time to check it yet started happening yesterday

2) Does the RD move left or right and then just partially engage the chain onto the next gear? Can't say haven't had time to check it yet started happening yesterday

3) When pedalling hard in certain gears. Yes

4) When just pedalling along with very little pressure on the pedals. No

5) In the workstand right there in front of your eyes. Not checked yet

6) Are the speeds on the cassette and chain and shifter matched? Yes

7) Does the shifter move the cable smootly in even incriments when the cable is removed from the RD and tensioned in one hand whilst shifting with the other? Will check tonight

8) Is the jockey hanger properly fixed onto the frame? Yes

 

Thanks JB now I have some point of referance to start trouble shooting from. will report back tomorrow