Chain lengthened in a few hundred miles?

[PrettyboyTim]

In December I replaced the chain that had come with my bike. Using the ruler method, I determined that the chain had lengthened by about 1/16th of an inch (over a span of a foot), so I replaced the chain with a new SRAM one with a powerlink. Now, since then I've done probably around 500 miles but yesterday I noticed that everything did not look okay with the chain.

I noticed it first on the front cogs; the chain looks like the links are too long for the teeth seperation on them. When the chain first meets the cog, the teeth are resting against the front of the link as you would expect, but as you go around the cog, the teeth begin to move from the front of the link to the back of the link, as you would expect if the chain had lengthened. Looking at the cogs themselves, there's no visible bad wear (the teeth are still symmetrical and don't look worn down), so I'm wondering what's going on. I've been wiping down and re-oiling my chain fairly regularly, and I've given it a couple of soaks and scrubs in white spirit since it was put on, so it's not been neglected.

Unfortunately I couldn't find my tape measure to measure any stretch yesterday, but surely the chain can't have lengthened already? It's new! When I last took the powerlinks off, the pins in them didn't show any signs of wear, so I'm beginning to wonder if the pitch in the SRAM chain was a little bit different to the one my bike was supplied with...

Any ideas? I guess it might be worth getting one of those chain measuring tools...

 

[domtyler]

Did you replace the worn chainrings and/or cassette at the time you replaced the chain?

 

[PrettyboyTim]

No - but I didn't think they looked worn at the time. I bought the bike in June, and started doing around 70 miles a week on it. Granted, for the first three months I didn't clean the chain at all, but I did after that. I replaced the chain after (I guess) about 1,400 miles.

 

[PrettyboyTim]

Actually, you're right. When I think about it what I'm describing would happen when the chainset is worn, not the chain...

 

[domtyler]

What make/brand/model were the original chain/chainrings and cassette?

 

[PrettyboyTim]

They were the ones that came on my Claud Butler Urban 100

As far as I can tell, they are:

A Suntour XCC108 28/38/48 Chainset
Shimano MF-TZ07 Cassette
Not sure what chain it used to have, although I still have it in a box at home somewhere.

 

[domtyler]

The thing with low quality components [which, let's face it is what we are looking at here] is that their life expectancy is likely to be low. Or at least the amount of time at which they will perform optimally, as they start to wear quickly.

I would replace the front chainrings with decent quality ones and the rear cassette with a decent quality one. You will need another new chain too.

 

[PrettyboyTim]

But how do I determine the quality? With the cassette, Most of the ones I see online are at the cheap end, if only because the 7-speed cassettes seem to be cheaper than the 8, 9 and 10 speed ones. How would I choose?

Are the low quality ones made out of a different material than the high quality ones? Which material should I be looking for? (I'm not bothered by weight by the way - this bike is already heavy and a couple of hundred grams here or there won't bother me)