Chainring/cassette woes...

[Dan_K]

Just replaced my cassette (gone from 12-27 to 11-28) and chain but am getting a lot of noise in the 11 and 12 cogs.
50T chain ring on the front is really worn so need to get a new one. Any ideas where I can get a good price? I run Shimano 105 50/34 compact in silver.
Noise is when on either of the front rings and in 11 and 12 on the back but only when the bike's weighted. It runs fine in the stand.
Bottom bracket gone? Just seems strange that this only has happened since fitting the new cassette and chain.
I'm baffled....

[Iliya]

What a coincidence, seems like I am not the only one having trouble with cassettes. Just submitted another post about it.

Clearly I am not an expert on the subject, but if you’ve gone from 12-27 to 11-28, do you also need to adjust the chain length?

[George]

check to make sure your using an 11 lock-ring!

[Dan_K]

I'm pretty naive with maintenance stuff - is the 11 lockring effectively the screw on nut that came with the cassette?

[Andrew G]

[quote="George"]check to make sure your using an 11 lock-ring!

[Dan_K]

I used the new one that came with the cassette and tightened it with the tool. Chain length i left the same as the old chain.
Shifts and runs perfectly on the stand but starts to make a horrible grinding noise under stress/load.

[Iliya]

Whilst we are on the subject of chain length, is there a rule for how long chain should be for different ratios of cassettes?

[Phil H]

For chain length, if it's too short for large-large and you accidentally try to change into that, things will be bad. So size the chain so it fits large-large, add an extra 2 links and all should be well.

Might be slack in small-small but that is a devil's own combination.

(Shamelessly nicked from Sheldon)

[George]

I always select large chainring and smallest cassette cog and cut chain so jockey wheels are pointing straight down

[kieran]

isn't that the only combination you use anyway??

[kieran]

Grinding might be to do with the rear deraillleur not set up correctly so that the chain is not going onto the teeth nice and smoothly, check the exact line up of pulley wheels to cassette teeth. Also check if the chain on the top pulley wheel is touching the cassette teeth.

[Elliot M]

What exact model rear derailleur do you have? if it's an RD-5600-SS (previous generation 105, short/standard cage) it's only supposed to take a 27t max sprocket, and has a total capacity (difference between front gears + difference between rear gears) of 29t, i.e with your chainring combination, only a 12-25 cassette. You have 33t total capacity.

http://cycle.shimano-eu.com/publish/con ... type-.html

Not to say these are necessarily hard limits, but I think you're definitely pushing it with that gear range.

Latest 105 equivalent will take a 28t sprocket and has a 33t capacity.

Disclaimer - this isn't necessarily what's causing the specific grinding issue you're describing, but worth checking out.

[Dan_K]

Cheers for the information/ideas guys but what I’m struggling with is how it all runs perfectly in every gear combination (bar the usual crossed chain rubbing on big to big) but the issue manifests itself only under load when being ridden?
If it was a chain length or jockey wheel rubbing, would this not become apparent in the bike stand?

I’ve ordered a new BB today and front chainring as these could do with replacing anyway as both have done 4-5,000 miles so will see if I still get the issue after I replace them.

The cassette and chain are the first bits I’ve replaced since owning the bike from new so could it be a case that everything’s loosened up and worn in together? By replacing just 2 parts of the drivetrain, the rest of the sloppy bits have shown themselves?

[Phil H]

Dan, when I changed my cassette to a 11-25, I managed to leave out a small spacer which put the alignment slightly out. I'd fiddled the mech so the changing was fine, but the limit screw was wrong so it was noisy on the 11. It took me a while to notice because I only used the 11 when going pretty fast so wind noise/distressed panting meant I didn't hear it at first. When I swapped back for the 12-27 for the ToBM I found the spacer and used it when I switched again (for TTs).

It might be that the spacing of the SRAM cassette is a bit different to the Shimano one so you need more/fewer or to fix the mech adjustment.

Also, [url=http://www.sheldonbrown.com/derailer-adjustment.html]Sheldon on gear adjustment[/url]

[Dan_K]

Phil, was everything working fine in the stand and then just making this noise when you were actually out?