Chain ring question!

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robrichards
Posts: 23
Joined: 17 Sep 2016, 8:12am

Chain ring question!

Postby robrichards » 6 Mar 2018, 6:15pm

Currently have a GT Grade with FSA Vero Compact 50/34t alloy on front & Sun Race 9spd 11-28 on back with Sora derailleurs.

Noticed today when I'm pedalling that it's skipping and I think I may have damaged the teeth on the front chain ring somehow.

I don't know if I can replace just the chain ring or it needs a whole crankset? Also sometime I could with a lower gear for hills and a higher gear for downhill than I currently have could I change it to help?

Cost is an issue (quite a big issue!) but as I use my bike daily to commute it needs doing so any advice appreciated!

rotavator
Posts: 576
Joined: 6 Jun 2016, 9:50pm
Location: North Wales

Re: Chain ring question!

Postby rotavator » 6 Mar 2018, 7:04pm

1. In my experience chain skipping generally occurs because the cassette is worn not the chainrings so I would check them both carefully before buying anything new. Look for teeth that are pointed or asymmetric like a shark's fin.

2. The cheapest way to get a lower bottom gear is to buy a new cassette (and chain) with a bigger low sprocket, e.g. 11-32T, but you will also need to check that your rear derailer can handle the bigger range.

3. If you need to change a chainring because it is worn or damaged, you need first to check the bolt circle diameter (BCD) of your current set-up and obviously order one with the correct number of bolt holes. There may also be some variation in the shape of the "shoulders" around the bolt holes so check that also unless you are happy to file them down. Spa have a good range of chainrings.

robrichards
Posts: 23
Joined: 17 Sep 2016, 8:12am

Re: Chain ring question!

Postby robrichards » 6 Mar 2018, 7:39pm

Rotavator that's very helpful, thank you!

drossall
Posts: 5113
Joined: 5 Jan 2007, 10:01pm
Location: North Hertfordshire

Re: Chain ring question!

Postby drossall » 6 Mar 2018, 8:44pm

The introduction is a bit dramatic, but here's a guide to visual checks on chainring wear.

If you do need one or more new rings, this page says that you need 110BCD for your chain set. You don't have to buy the same brand, but consider how many speeds you have (10-speed chains are narrower than 7-speed, so a 7-speed ring might have teeth that are two thick). You might also want one that looks right.

rotavator
Posts: 576
Joined: 6 Jun 2016, 9:50pm
Location: North Wales

Re: Chain ring question!

Postby rotavator » 6 Mar 2018, 9:31pm

I guess that you have already checked 1. the indexing on the cassette, 2. the chain for wear (or "stretch") using a tool like this:
[url]
http://www.wiggle.co.uk/park-tool-chain ... ator-cc32/[/url]

Also, if you have fitted a new chain recently, did you use the correct sized magic link?