I thought I'd take a moment to offer some useful information - a rarity!

Yes, yes, I KNOW I'm a couple of ride reports behind, but with a memory like mine it's gonna be a real chew to get those finished, and time seems to be against me every time I try a catch-up.

Anyway. Chains stretch. They do this unannounced. The harder you press on your pedals, the bigger your calves, the more gear shifting you do, the more gear "slams" you make (banging it down a cog or more in the middle of a climb while you've got full power applied), the more cross-gearing you use (titchy front "granny" ring paired with "top gear" - your smallest rear sprocket or vice-versa) and the less maintenance care you take of your chain produces sometimes meteoric deterioration to your whole power train prime mover.

Funds permitting, I try to change my chain three times a year. This way, your rear cassette and two of your front rings will last a season. I say two rings because most of us flog our middle ring to death, while the other two are used much less and can last maybe two years.

See this: it's a pic of two SRAM chains, new one on the right, old one on the left from my Trek. Got the bike in August or something, done maybe three or four hundred miles. Note how the left one is longer!

Now take a look at the next few pics. By the time you reach link 50 on the new one, the old one has it's 49th link level, meaning it's a whole link longer over about two feet. When you reach the bottom, link 98 on the new one lines up with 96 on the old! The whole chain is almost an inch and a half longer than it was when it was new. And we wonder why it misses the odd gear change and skips a bit!

bit longer     bit longer      bit longer      and...

Get a new chain then. Also:

1. DON'T use granny ring with smallest 3 sprockets

2. DON'T use big ring with largest 3 sprockets

3. DON'T change down with maximum pressure applied to the pedals - lift off just a touch as you press the shifter - it won't bang, you won't break it and you won't make your pals whince with dismay as your gears cry out for help. Look ahead and see that hill coming instead of letting it take you by surprise.

4. DO ignore the Gollum and use oil on your chain after cleaning it first. BUT NOTE! WD40 is great at chasing lubrication away! Use it to free stuff off and clean it, then apply some proper lube oil.