Squeaking sound from cog 8
 

I noticed cassette cog 8 squeaks. As I pedal faster, it becomes higher in frequency, and as i pedal slower, it slows down. When I'm not pedaling, its gone. It doesn't matter if I am in chain ring 2 or 3, if I am in cog 8, it squeaks. why would 1 cog squeak? what should I do? inspect & rebuild the hub?

I doubt the cog it's self is making noise. More likely the moving parts around it are in just the right arrangement for a lack of lube/maintenance to show, by the noise. Squeaks make me first think of der pulleys and chain needing lube (and maybe cleaning). But you'll be told many other possibilities and you'll wander through the ones you can in some order. Andy.

What is "cog 8"? Smallest of an 8-speed cassette? Largest of an 8-speed? An interior cog of an 9 or 10-speed cassette? Where it's located can help with the diagnosis.

8 on the shifter, so next to smallest (9 speed cassette), SRAM PG-950 12-26T, 9-speed.

Drip a little oil into the interfaces on both sides of that (13T?) cog and be sure the lockring is torqued to spec. The recommended lockring torque is typically about 40N-m and a lot tighter than you would think without a torque wrench as guidance.

Sounds like you need some chain maintenance. Clean/lube the chain and clean/lube the derailleur pulleys.

I bought 1 of those chain cleaner contraptions, going to clean the driveline soon.

I cleaned the drive train really well and it seemed to quiet down the squeak. but there was an issue w/the chain rubbing against the derailer cage. I tried the hi/low adjustments. there's not enuff HI adjustments. I proceeded to play with the cable length and messed up shifting ;-) I took it to the shop and they corrected the cabling but he mentioned the chain might be a link short.... he got it close but it's still touching the derailer cage. he mentioned on some 3 cog CRs, it's almost impossible to set it up to not rub.... which is odd because my other bikes have 3 cog CRs and they don't rub....

he also mentioned my BB needs to be replaced, I agreed because it was gritty, will do it as soon as he gets the part in.

Is your front shifting indexed? If so then the wrench's comments about chain rub is partly true, sometimes. Without the ability to minutely position the ft der cage so to not rub on the chain (as an indexed system is when no trim feature is present in the lever) the manufacturer of the der instead depends on the cage's shape/contour and minimal tolerance of the system.


So if the rings are slightly bent, if the chain has any side ways waviness, if the spacing between the rings is not spot on, if the der's alignment isn't just right, if the limit screws aren't set right, if cable "tension" isn't right and if the rider insists in using cross chaining cog/ring combos then some rub is likely to be present some of the time. Even with a "perfectly" speced and set up system some rub can happen with the bike's flex.


When front indexing first came out Shimano printed a small instruction sheet pictorially describing the gear combos where rub was acceptable. That few ever got this slip of paper with their new bikes and that this is no longer published (or included with new bike packets) says a lot about both the buying public's and the industry's acceptance of some chain rub sometimes as being the norm. Andy

I'm not sure what you mean by "indexed"? he did mention I have the "trim" feature to reduce the rubbing. admittedly I have no clue what it's for / how to use it (it's new to me). will have to google later.

This is most likely the reason why you have "rubbing" issues on your front derailleur. If you don't know how to trim the derailleur (half shift) you WILL rub.

I've read and viewed that trimming applies to between gear changes, Since this is the highest cog, there is not outer edge trim, as far as I can tell.

BUT I found out I could manually bend the cage to give me enough clearance!!! DOH!!!