Rockrider e-st900 skipping chain on 10th gear.

[RonnieX]

My bike chain has started jumping/skipping on the smallest 11t cog of the cassette. It doesn't happen in any other gear and only happens under load! The derailleur has been adjusted every which way to no avail.

The bike is 6 months old and covered 1000 miles.

My local Decathlon store, 20 miles away, is currently closed indefinitely due to Covid.

As an interim measure, I’m going to replace the 11t cog for a new one as I suspect it’s worn!

anyone any views?

 

[routrax]

Your cassette needs replacing, along with your chain and possibly chainring too.

 

[steve_sordy]

Your cassette needs replacing, along with your chain and possibly chainring too.

@RonnieX You might get away with just replacing the 11t, but what @routrax is saying is that your transmission is worn. Check your chain length. There are a variety of ways to do it, but the simplest and most accurate way is the remove the chain and measure it with a metal tape measure. Lay it out on a flat surface, pull the chain to ensure all the links are touching and in a straight line and then measure pin to pin over 100 links. A new chain should measure 50". A worn out chain for immediate disposal (and probably the rest of your transmission) will measure 50.5" ie 1% "stretch". The most you should take it to if you want to get more than one chain per cassette is 0.75% ie 50-3/8". Some recommend 0.5% (50.25") for emtbs.

If you put a new chain onto a worn cassette, you may find the chain skipping under load in the gears you use the most. The front ring usually takes longer to wear out then the cassette, but not always and some riders change the front and rear gears at the same time. I only change when they are worn.

You can buy a chain gauge that has Go/NoGo marks at 0.75% and 1% and maybe also 0.5% depending upon the make. I don't have one because I use a Vernier calliper.

 

[RonnieX]

Thanks fellas I’ll see the winter out with the new 11t cog then replace the cassette and chain in Spring. If Decathlon ever get them back in stock!

 

[chamaruco]

have you tried any adjustment?
btw decathlon on line under the voice" est900 spare parts" could help

 

[Worthy]

Hi have you tried adjusting the B screw ?

 

[RonnieX]

@Worthy :- Yes, I’ve adjusted the B screw.

@chamaruco :- not sure what you mean, but not in stock on line.

obviously, I know I can buy the original equipment, (Shimano Deore HG500 11- 42t cassette and a KMC x10e chain), elsewhere. But to be fair, not as cheap as Decathlon, hence the wait until Spring!

 

[chamaruco]

I mean this https://www.decathlon.co.uk/p-a/mtb...ta-e-st-900-grigia-27-5-plus/_/N-0?mc=8487240
check it daily..then buy it when available.

 

[RonnieX]

Thanks @chamaruco I’ve set up an email notification when back in stock.

 

[BeBiker]

I start to have the same issue. (1200 km)

As a lot of us, I E-drive often in 11t and 13t.
What makes it worse, is that the cadence is highest when we use those gears.
On top of that, every tooth on the 11t get used al lot more often than the 42t, per pedal rotation.

I ordered the separate 11t and 13t on aliexpress "original shimano"
We'll see what it's worth.

 

[chamaruco]

I have two of these bikes. Mine has 1300km the wife’s one 200km. Repalcing my chain with her one everything works better. So I’ve decided to replace my chain with a new one. Misusing the consumption with the dedicated tool I wasn’t at 0,75..

 

[RonnieX]

I replaced the 11t cog and the problem was resolved.

I bought a cheap chain wear indicator tool and it shows my chain is good.

 

[RonnieX]

Here’s a weird update......

checked the chain again the other day with the measuring tool and the 0.75 ‘hammer’ dropped straight into the chain. So I replaced the chain and the new one now skips/jumps on gears 9 & 10.

I’ve put the old chain back on and everything is sweet again!

my bike is now 7 months old and 1200 miles.

Am I being sucked into, perhaps, a marketing gimmick to buy more stuff? (I’ve ordered a new cassette by the way! )

 

[BeBiker]

After 1200km, I started to sometimes have the problem.
After greasing the chain, cleaning the cogs 100%, it went away.

But came back faster and faster. So I replaced the 11t cog.

SHIMANO CS-HG500-10 HG81 CS-M4100-10 10-speed Cassette Cog Sprocket Wheel - AliExpress 18

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www.aliexpress.com

The problem it totally solved now.