Novice Maintenance- Gears Skipping - Do I need to replace my Chainring?

Aggerdoo

Hi

When I'm riding and pushing hard my gears seem to skip on their own, it can be a bit scary when trying to sprint up a short sharp climb and your gear just changes down one (usually on the rear cassette)

I've looked at various forums and the main causes for this and it all seems to be saying either Chain wear, or need to replace chain rings / cassette.

I had the bike serviced about a year ago and haven't ridden much since (maybe 300 miles) when the did it they replaced the chain and rear cassette. So I can't see it being that (I've bought a chain wear indicator to check it just in case but it's in the post)

But didn't know if anyone would be able to tell me if they can tell if you think the big chainring may need replacing to sort the issue or if there is another problem/solution you think may be causing it.



I've posted a few more pictures here : https://uk.pinterest.com/aggerdoo/does-this-need-replacing/

Thanks in advance for your help.

Chris (the bike maintenance novice)

964cup

Sadly, if you use Pinterest, we have to sign in to see your pics. Still, based on what you're saying, it's very unlikely to be your chainring. If the chain and cassette are 300 miles old, they shouldn't be worn - they are filthy though, so do clean them. It's much more likely to be adjustment - so either have a look at one of the innumerable videos on YouTube to learn how to index your rear derailleur, or pop in to your LBS and have them look at it.

Note that I am assuming you've never dropped the bike on the drive side; if you have, then you may need to get your hanger aligned, which is a job for your LBS unless you know someone with a hanger alignment tool.

[More technical: the cables that operate your gears stretch over time; that means that you need to retension them so that they pull the derailleur to the right position. There are lots of ways to do this - it becomes instinctive after a while - but one technique is to put the bike on a stand, shift to the fourth cog in from the smallest at the rear, with the front on the big ring; then using the cable adjuster on the rear derailleur, or the inline adjuster if one is fitted, add tension to the cable while pedalling until the chain is running noisily against the fifth cog inward; then slowly back the tension off until the chain is running quietly, but no further. Now test that you can run all the way up and down the cassette with no problems; if it's reluctant to go into the smallest cog, reduce the tension by a quarter turn at a time; if it won't go up onto the largest cog, add tension a quarter turn at a time. Your limit screws should still be set correctly, assuming the shop got that right to begin with.]

Aggerdoo

Hi

Thanks for your reply . That's good news if i don't have to replace it. I realise I need to give the chain and cassette a full deep clean to get the grime off.

I'll try giving some of what you have suggested a go before I take it to the LBS, I quite like to give it a go and see if I can sort it first.

I've (hopefully if this works) posted the other closer up pictures below.

964cup

The big ring looks fine to me. Here's a random picture of a new one the same as yours for you to compare to:

and here's a (really) worn (not Tiagra) chainring to give you an idea. You'd want to replace a long time before it looked like this, though...

AK_jnr

Rear hanger

Bobbinogs

Sounds like the OP just needs to turn the rear mech barrel adjuster by 1/4 or 1/2 turn anti-clockwise as this issue could be as simple as a little bit of 'bedding in' from the cables after the gears were last indexed.