UKH

My chain snapped recently so replaced it with a new one, ever since when I pedal with force, in any of the mid rear gears, it feels like the chain is slipping or the pedal (my pedalling foot comes down a lot quicker than it should). After replacing the chain I replaced the front chainset as I noticed a chipped tooth and some worn teeth but its still doing it. Didn't change the rear cassette the teeth look fine. Bike is less than a year old with low milegae. Any advice on what the issue could be?

Thanks

How many miles have you done? Could well be that you need to replace the cassette. 

You could try adjusting the tension on the rear derailleur cable. You could be 'in between' gears. The very slight change in length / width / friction with the new chain could be the cause. Turn the barrel adjuster only a small amount at a time whilst shifting through the gears and see if it improves. It's unlikely to be a worn cassette with the usage it's had. 

Around 1000k. I did suspect that it could be that but couldn't see any signs of wear on the teeth and I took into a shop and they said the same, although it was Halfords I went too.

For the front gears there is a clear and obvious barrell adjuster on the shifter, not the case on the rear shifter though, could it be else where?

I would have thought it would look exactly the same on both shifters if it they both had them.

found it, at the rear of the bike. Will try that tomorrow and see what happens. Thnaks, hopefully that does the job.

You almost certainly need a new cassette of its only happening under load. 

Is the chain too long?

Sometimes there is one near the chain stay, or actually at the rear derailleur. Hopefully you'll be able to find it if you follow the cable.

Ah. Just seen your edit. Hope it works. 

No, measured it against old chain and counted links too and fitted and thats when the issue started. So removed one link from new chain after fitting when I noticed the issue as i thought it might have been too long, still same issue.

after a 1000k? its a cheap basic bike but would have expected a bit more use than that.

There’s a few variables at play but 1k wouldn’t be beyond the realms of a worn chain depending on terrain, how well lubed/clean it is, flat or hilly... 

My lad (5) has already worn his chain out according to a chain checker and he’s probably done 200k on it 

You can't see the wear, because it is measured in fractions of a percent, a decent bikeshop would use a tool to measure it.  For  6/7/8/9 speed between 0.5% and 0.75% worn you'll get away with changing just the chain but past 0.75% wear is enough to cause slippage and you have to change cassette and chainrings too.  10-12 speed chains have to be changed between 0.25% 0.5% to avoid slippage.

Is the new chain the correct match for the bike? bikes with more gears on the rear cassette use narrower chains (measured externally) so if you were using a 7 speed chain on a 10 speed cassette the chain may fail to fit between the adjacent cogs.

Otherwise 1000 miles is probably enough to wear out a cheap/poorly maintained drive train. A chain snapping at 1000 is a bad omen IMO.

Thanks. Didn't realise it would be so small, thought it would be something that was obvious to the eye.

Old chain was a KMC Z Narrow. Replaced it with a KMC X8 - was told this was a like for like replacement. It's an 8 speed cassette. I'm only at the 600 mile mark, i posted in KM's earlier.

If everything else looks ok slipping under load could be worn pawls inside of the freewheel cassette. 

Have you cleaned the chain? Mine got a bit jumpy over the summer when I started using a wax lube which then seemed to stiffen the links up after the first ride or two after application. A thorough clean and return to a more liquid lube sorted things out

Hi there.

its almost certainly the cassette. Your old chain will have been slightly stretched and worn the teeth so the gap in between the teeth is marginally increased. You can barely see any difference. When loading the chain when pedalling the links in the chain will ride up on top of the teeth on the cassette and after a short time clunk back in place but now one ‘step’ further on (the chain has jumped over a tooth).

it happens more on the small cogs as the chain is only in contact with a small number of teeth and rides up on them easier, but also because the smaller cogs get worn faster (used more, and much less material so faster wear rare).

you can watch it happen by putting the bike upside down, Getting a mate to hold the wheel but allow it to turn slowly, and peddling Hard and continuously with your arms.

new cassette, or like I usually do, avoid using the small cog till the new chain stretches to fit (not ideal!!)

does this require a new cassette?

no it was a brand new chain. Although the old one snapped on the first ride after cleaning it properly, not sure if that was a coincidence.

I repaired the old chain and put that back on and the slipping has stopped.