Cycling UK Forum

I have an annoying issue with my gears. It is very intermittent and I’m not absolutely sure whether it occurs after changing up or down (because it is so intermittent), though I suspect it is probably after I have changed from a larger to a smaller rear sprocket (of my 9 speed cassette).
Let me first say that the chain and cassette are not worn, and are well-lubed. What happens is that I change gear pretty frequently and most of the time there is no issue. But a few times during the course of say a 30 mile ride, the pedalling will be fine but I can suddenly experience a sort of “snap”, as if the chain had not been located properly and has suddenly dropped onto the cog, and the pedals briefly slip. Then pedalling will be fine.

I fitted a new gear cable inner at the same time as my new chain and cassette, but not a new outer. I suspect that the problem may be cable friction, but would like confirmation before replacing, and if it is cable friction, I wonder why it is so intermittent. Most of the time shifting is perfectly OK.

your symptoms sound weird, and not clearly associated with any one simple thing like the gear cable.

One thing I am suspicious of is that the rear derailleur is sticky, and doesn't tension the chain fully for a second or two after an upshift. An untensioned chain is more susceptible to skipping, eg from a stiff link or something (BTW how did you join the new chain?).

cheers

Brucey wrote:your symptoms sound weird, and not clearly associated with any one simple thing like the gear cable.

One thing I am suspicious of is that the rear derailleur is sticky, and doesn't tension the chain fully for a second or two after an upshift. An untensioned chain is more susceptible to skipping, eg from a stiff link or something (BTW how did you join the new chain?).

cheers

Thanks. The chain (PC971) is joined with the supplied powerlink. There doesn’t seem to be any stiffness evident when I manually “backpedal” it to apply lube. In fact, I am alternating 2 chains and the issue seems to occur with both.
WRT the derailleur, it certainly feels fine when I move it manually when the cable is not connected, though it has over 40,000 miles under its belt.

What about worn or damaged jockey wheels

TimDoran wrote:What about worn or damaged jockey wheels

They were replaced along with the other components

Thornyone wrote:WRT the derailleur, it certainly feels fine when I move it manually when the cable is not connected, though it has over 40,000 miles under its belt.

My RDs are invariably worn out or pranged well before then. If the RD is worn, it won't be dictating the path of the chain so much as making oblique hints as to the direction it ought to be going.

I'd try a different RD and see how that goes; if it turns out you don't need it now, you soon will do....?

cheers

Hi
I'd go simple to complex...
Replace the outer, especially the loop at the rear axle, because this is the weak point IME. Lube to choice
While the cable is disconnected spray WD40/GT85 or similar on the derailleur pivot points to blast the muck out, followed by a spray grease lube. Don't forget that there are twice as many pivots in the parallelogram Removing the whole derailleur and cleaning it thoroughly isn't too much more effort, will make a better job and saves cleaning the rear brake afterwards
Test ride
Regards
tim-b

Thanks Brucey and tim-b for your suggestions. Whilst the rear derailleur may well be due for replacement as Brucey advises, it certainly doesn’t feel sloppy, so I’ll try tim-b’s approach first. I’ve got some spare outer lying around somewhere, and new inner cable. If that doesn’t sort it then I’ll certainly replace the RD.

When you take that outer cable off remove the end caps and see what condition the ends of the outers are in. I suspect that may be contributory.

Brucey wrote:One thing I am suspicious of is that the rear derailleur is sticky, and doesn't tension the chain fully for a second or two after an upshift.

I had similar symptoms to the OP when the grease in the B pivot dried out. It felt ok when articulated by hand, but was less reliable under it's own spring tension. Stripped and re-greased, and no problems since...

peetee wrote:When you take that outer cable off remove the end caps and see what condition the ends of the outers are in. I suspect that may be contributory.

Thanks. I noticed that there was a bit of rusting at either end of the chainstay to RD section.

iow wrote:

Brucey wrote:One thing I am suspicious of is that the rear derailleur is sticky, and doesn't tension the chain fully for a second or two after an upshift.

I had similar symptoms to the OP when the grease in the B pivot dried out. It felt ok when articulated by hand, but was less reliable under it's own spring tension. Stripped and re-greased, and no problems since...

Thanks. I’ll bear this in mind if there is no improvement when I get to test ride, probably tomorrow.

Are you sure it is the gears ?
Is it an old freehub ?
Could be worn or sticky pawls suddenly jumping.

cycleruk wrote:Are you sure it is the gears ?
Is it an old freehub ?
Could be worn or sticky pawls suddenly jumping.

That was my thought too.

I think have the exact same issue as the original poster. It usually occurs a little while after shifting from 6 to 5 on a 9 speed cassette.
Initially thought it was the cassette as it started happening at about 2500 miles and 5 and 6 were the most used sprockets. It isn't the chainset because it happens with an octalink M430 and Hollowtech 2 M590. It isn't the chain KMC 9.93 or Shimano HG93. It isn't the shifters M390 or M430. It isn't the cassette HG200-9 (11/13/15/17/19/21/24/28/32) or HG50 (11/12/14/16/18/20/23/26/30). It isn't the front mech M390/M581/M590/M591.
It isn't the rear mech or cables M591 and M772. So I think its the freehub FH-RM66.