900 euro bike - very noisy gear changes - now I can make chain skip under pressure

worded

Bike was 900 euro - specialised Rockhopper.

I had its first service three weeks ago. It has been cleaned by me and Ive added silicone lub to the chain.

Concerns:
I can hear very noisy gear changes from the gears on the back wheel.
It just doesnt sound right at all.

If I cycle hard on the smallest cog on the back wheel I can make the chain
skip. Why oh why would it do this. I tested it on the flat and its the correct gear to be in, Im just cycling it hard. Ive had 200 euro bikes ok with that.

Two weeks after the service it was like someone took a screw driver to it a re adjusted the settings, the chain was coming off the biggest cog on the back wheel. It did that twice. I adjusted that myself.

Its in to be sorted again but I really dont trust the bike anymore.


Anyone any comments.

DirkVoodoo

worded wrote: »

Bike was 900 euro - specialised Rockhopper.

I had its first service three weeks ago. It has been cleaned by me and Ive added silicone lub to the chain.

Concerns:
I can hear very noisy gear changes from the gears on the back wheel.
It just doesnt sound right at all.

If I cycle hard on the smallest cog on the back wheel I can make the chain
skip. Why oh why would it do this. I tested it on the flat and its the correct gear to be in, Im just cycling it hard. Ive had 200 euro bikes ok with that.

Two weeks after the service it was like someone took a screw driver to it a re adjusted the settings, the chain was coming off the biggest cog on the back wheel. It did that twice. I adjusted that myself.

Its in to be sorted again but I really dont trust the bike anymore.


Anyone any comments.

When you say skipping and coming off, you mean the chain is trying to pop off the cog and into the spokes? Sounds like you may have messed up your limit settings. Put the bike in the smallest gear (litte ring/big sprocket) and adjust the limit screw. Normally Shimano put "H" and "L" next to each screw, You want to adjust the "L" screw while eyeballing the derailleur cage and have it line up with the large sprocket.

Sept Shamrocker

I'd check for a slightly bent rear derailleur hanger. Might have got hit out of alignment somehow?

chris85

If its slipping under pressure its most likely a worn cog. You should be able to change the particular cog rather than replace the whole block.

serendip

chris85 wrote: »

If its slipping under pressure its most likely a worn cog. You should be able to change the particular cog rather than replace the whole block.

It's probably not a worn cog on a new bike. It's probably a combination of incorrect limiter settings (the chain should not come off as described) and a bit of cable stretch.

kincsem

It is cable stretch imo. I bought a new bike and at the end of my first spin (70km) the chain started jumping on the back cassette. Nothing wrong, just needs to be adjusted.

chris85

serendip wrote: »

It's probably not a worn cog on a new bike. It's probably a combination of incorrect limiter settings (the chain should not come off as described) and a bit of cable stretch.

Not if its only skipping under pressure. skipping under pressure is usually a worn cog in my experience.

The other issues would cause poor shifting and noisy gears with the chain whipping of gear parts but not a skip under pressure.

worded

kincsem wrote: »

It is cable stretch imo. I bought a new bike and at the end of my first spin (70km) the chain started jumping on the back cassette. Nothing wrong, just needs to be adjusted.

Thanks, I hope you are right, I think you might be.