Chain jumping on smallest cog

[Russ34]

Hi , loving my new e bike conversion! Since doing a decent ride today I’ve noticed that my chain jumps on the smallest rear cog on the cassette, has anyone else experienced this at all ? Many thanks

 

[Andy-Mat]

Maybe the tension on the chain is slightly too little.
The smallest cog always has the least tension as the arm swings/tensions.
Try increasing it slightly.
A slightly overlong chain can make a similar problem.
If the bike is new, you should be getting it done on the guarantee anyway.....
regards
Andy

 

[Russ34]

Maybe the tension on the chain is slightly too little.
The smallest cog always has the least tension as the arm swings/tensions.
Try increasing it slightly.
A slightly overlong chain can make a similar problem.
If the bike is new, you should be getting it done on the guarantee anyway.....
regards
Andy

Thanks Andy , it’s a conversion I’ve done myself on a retro 1990’s MTB, it’s a 7 speed original cassette and chain maybe I’ll try and check the tension on the chain then ! Thanks for your reply

 

[Fordulike]

Also, check there is no muck collected around that cog. Mine tends to skip a bit, if there's crud on the cog.

You'll be surprised how much collects there

 

[Russ34]

Also, check there is no muck collected around that cog. Mine tends to skip a bit, if there's crud on the cog.

You'll be surprised how much collects there

Thanks I’ll take a look

 

[Andy-Mat]

Thanks Andy , it’s a conversion I’ve done myself on a retro 1990’s MTB, it’s a 7 speed original cassette and chain maybe I’ll try and check the tension on the chain then ! Thanks for your reply

We are all here to help each other as best we can. You would do the same on a problem that you better understand, but still thanks for your replay.
When you get it fixed, let us all know what it was please.
regards
Andy

 

[Nealh]

Is it jumping or trying to ride the cog , if the latter check that the L or adjustment isn't causing it.

 

[Russ34]

Thanks for all your replies , I’ve tried adjusting the derailleur etc and doesn’t appear to be making a difference, I think the chain is looking a bit sketchy so I’ve ordered a new one , I’ll give everything a good degrease and fit a new chain and see how it goes from there

 

[sjpt]

You haven't said if it is rear, min or front conversion. That could make quite a difference to the cause of the problem.

 

[Russ34]

You haven't said if it is rear, min or front conversion. That could make quite a difference to the cause of the problem.

Sorry it’s a mid bafang conversion

 

[sjpt]

Is the new chainring the same size as the old one? If not that could be a reason for changing the chain length (as mentioned by Andy-Mat above).

If the sprockets are worn it will be worth changing those at the same time as the chain.

 

[Russ34]

Is the new chainring the same size as the old one? If not that could be a reason for changing the chain length (as mentioned by Andy-Mat above).

If the sprockets are worn it will be worth changing those at the same time as the chain.

Yeah the front is a 44t which was the same size , I’m going to have a good look at the cassette when I change the chain

 

[Nealh]

If it is just the small sprocket worn then one can buy them separately.

 

[Russ34]

If it is just the small sprocket worn then one can buy them separately.

Thanks for that

 

[jokskot]

Nealh's reply "If it is just the small sprocket worn then one can buy them separately."

Does this apply to screw-on freewheel blocks as well as cassetttes? If so could you provide a link to a source, please?

 

[Russ34]

I’ve fitted a brand new chain and cassette all sorted , thanks for everyone’s advice

 

[Nealh]

Freewheels tend to be fixed and riveted, the cassette is more modular without internal bearings. With a cassette it is easier to build one up to have the gear jumps one prefers.

 

[esuark]

Screw on dnp freewheels are serviceable not sure about others, and have personally used zitto 11 12 and 13, 8 speed cogs for spares successfully on a 7 speed dnp freewheel.Both available on eBay and AliExpress.

 

[Sturmey]

Many freewheels have lockrings and most can be dismantled to get at the smaller gears. I have often used a chainsaw round file to dress the offending cogs after fitting a new chain and works ok. The shimano ones are difficult to open as the 14T acts as a lockring but there is a way to loosen the stack by slicing a bit of one of the plastic spacers with a junior hacksaw. The guy in link below explains how to file/grind the cogs.

Technical FAQ: Chain hops and grinding cogs

A reader is wondering why his chain comes off the biggest cog on a 1x mountain bike cog, and how to refurbish cassettes.

www.velonews.com