Chain jumping under pressure

[Matthew_T]

Recently my chain has been jumping when I have been going uphill/accellerating. It usually happens after I have just put some WD40 on the chain and gears after I have cleaned it.
I have inspected the gear cogs and they dont seem to be worn down or broken. Thre is no dirt (well not much) on either the chain or the gears as I gave the whole system a really good clean a fortnight ago.
The chain isnt too lose as it has been the same tightness since I got the bike and adjusted it.

Could the chain be wearing down and if so, how do I check this?


P.S. The jump is more of a slip and I feel like my pedal is snapping off (only with one revolution of the pedals).

 

[simon.r]

You can get special tools to measure chain wear, or use a good quality ruler.

From Sheldon's site:

Measuring Chain Wear:

The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark. [For accurate measurement, the chain should be held under some tension -- either on the bicycle, or hanging. -- John Allen]
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:

• If the rivet is less than 1/16" past the mark, all is well.
• If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
• If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
• If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones

From experince of working on old, unmaintained drivetrains, a good clean sometimes makes things worse. I think that the thick grease and grime sort of beds everything together and removing it causes the chain to slip! Not suggesting your drivetrain is that bad before you clean it, but it ties in with it happening after a clean.

It could also be that your freewheel is on the way out - this can result in a similar feel at the pedals.

 

[gaz]

WD40? Probably the worst thing you can do for your chain.. it will wash out the deep lubricant in the chain. That is unless you completely take apart your chain and re-lube from there.

Get some proper lube and see if it makes a difference, it may be jumping because the links are stiff.

It may be because your chain has stretched, you can measure your chain with a tape measure or better still, a chain wear tool

It may be because your re-derailure is out of alignment, check that.

 

[boydj]

Any idea how many miles your chain has done, Matthew? With daily commuting, I rarely get more than 1000 miles out of a chain and a worn chain will wear out your cogs too.If your mileage is much higher than that, then a new chain and cogs could be required.

Good quality lube will help the life of your chain - WD40 is a no-no.

 

[Rickshaw Phil]

The chain jumping when putting the power down is a classic sign of something in the drivetrain being worn out.

Unfortunately if you have been using WD40 as a lube you may well have worn out the chain and/or cogs and/or chainset prematurely as it is just too thin for this application and will also act as a solvent, washing out any existing oils.

There is really good advice given above. Follow it and replace parts as required.

 

[CopperCyclist]

GT 85 is much better than WD40 in the world of cycle maintenance. It's not a chain lube though - get a proper one and follow the Mickle Method for maintaining it!

I just tend to use GT85 to discourage rusting bolts etc. And as a disc brake cleaner.

(kidding about the brakes, just in case!)

 

[Matthew_T]

Any idea how many miles your chain has done, Matthew? With daily commuting, I rarely get more than 1000 miles out of a chain and a worn chain will wear out your cogs too.If your mileage is much higher than that, then a new chain and cogs could be required.

Good quality lube will help the life of your chain - WD40 is a no-no.

I have had the bike for about 4/5 years with the original chain and sprockets on. So I would say about 7,000 miles???????

 

[Matthew_T]

WD40? Probably the worst thing you can do for your chain.. it will wash out the deep lubricant in the chain. That is unless you completely take apart your chain and re-lube from there.

Get some proper lube and see if it makes a difference, it may be jumping because the links are stiff.

It may be because your chain has stretched, you can measure your chain with a tape measure or better still, a chain wear tool

It may be because your re-derailure is out of alignment, check that.

The links arent stiff as when I cleaned the chain, I made sure they were all flexing smoothly.

My rear deraileur is bent, but not out of alignment (that was the source of the chain skipping up a gear at christmas).

 

[Rickshaw Phil]

I have had the bike for about 4/5 years with the original chain and sprockets on. So I would say about 7,000 miles???????

And there was me saying it might have worn prematurely. After 7000 miles I reckon that chain has given you good service.

Time to treat your bike to some new parts.

 

[Matthew_T]

Just checked it and the pin is past the 12inch mark by .6 of an inch (6th dash along).

Is this bad? I think so. New chain ordered from CRC done.

 

[fossyant]

Just checked it and the pin is past the 12inch mark by .6 of an inch (6th dash along).

Is this bad? I think so. New chain ordered from CRC done.

You need a new cassette/freewheel as well. A new chain will jump all over the old cassette !

Chain and Cassette at that mileage !!!

 

[subaqua]

You need a new cassette/freewheel as well. A new chain will jump all over the old cassette !

Chain and Cassette at that mileage !!!

thats my thoughts too. go outdoors has a new store in Saltney. Shimano, SRAM KMC all lined up on the shelves. worth a trip on the train to shotton and then cycling over to there

 

[Matthew_T]

thats my thoughts too. go outdoors has a new store in Saltney. Shimano, SRAM KMC all lined up on the shelves. worth a trip on the train to shotton and then cycling over to there

I have ordered them onlie now. Chain from CRC and cassette and cassette tool from Amazon (not the best site but they are exactly the same as other places).

 

[boydj]

Check your chainrings too, Matthew. When I first started training for triathlons I knew very little about bikes and bike maintenance. I got to the stage of the chain jumping and got some stick (followed by good advice) from my LBS. A new chain and cogs were fitted immediately and it was pointed out that the chainrings - especially the 42 - would need to be replaced as soon as I could afford it - they had worn almost to sharp points.

Back then there was no internet to come to for advice so a good LBS was worth its weight in gold.

 

[Monsieur Remings]

I have ordered them onlie now. Chain from CRC and cassette and cassette tool from Amazon (not the best site but they are exactly the same as other places).

And keep your old chain mate, you need to cut down the new one to the same size as the old one, otherwise you'll end up with a similar symptom in the shape of a chain that's too long.

Get yourself a decent chain link extractor and it's a 5 minute job.