Chainrings

by Richthornton   February 22, 2013  

Hello, I'm looking for some advice about chainrings. I replaced my chain and cassette the other day, thinking the chainrings look alright and would be more hardwearing I left them as they were, however I was getting a lot of chain slip under load, setting off in medium/high gear etc. which makes me think they need replacing too. First of all, after 3000 miles, is it likely that the chainrings need replacing or could I have set something up wrongly when I've made the changes? They don't look too bad, but then again you can tell they've been well-used.

If they do need replacing, here's my other questions:
(I have a 105 Compact 34/50.)
a) Can i increase the teeth on the large ring without having to change the deraileur, length of chain etc? and if so, by how much?
b) are all manufacturer's chainrings compatible with each other? I realise that Campag, SRam probably won't like Shimano, but what about FSA, stronglight, TA etc...?
c) Does the chainring I buy need to be compact-specific, many are labelled 'double'. Would that work?

Thanks in advance for any advice, as with buying many types of bike parts every seller seems to be a minefield of words with little explanation.

11 user comments

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Ah that's a lot of questions! First off 3000km isn't much for chainrings, I would have thought you would get more than that.

a) and c) If you currently have a 'compact' then you must replace with 'compact' as the so called BCD is different to a double. This is the diameter of the chainring bolts ring with respect to the axel.

As for manafactuer, most will work with each other although I have experience with Campagnolo. I have SRAM on my bike and replaced the worn chainrings to Stronglight and had no issues. Aesthetically it didn't look great though. Since then I moved to a ROTOR crankset.

One last advice, shop around. Chainrings can be expensive. I bought my Stronglight from Ribble at a reasonable price.

posted by boardmanrider [67 posts]
22nd February 2013 - 15:35

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Re changing the size of the chainrings - most rear mechs have a maximum number of teeth difference they can cope with. This depends on the spring in the mech, the cage length etc. So it would be worth finding the manufacturer's spec on the max capacity of the rear mech then see if it will cope.

If the chain is still slipping it's probably adjustment of the mechs or maybe the cassette is worn (if the chain was well worn the cassette could be shot as well) - it can be hard to tell if it's slipping at the front or the back.

Could be worth a trip to the LBS before you spend a lot on new chainrings etc

posted by jimmo62 [59 posts]
22nd February 2013 - 15:41

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Where is the chain slipping? Is it slipping at the front?!

No way have your chain rings gone at 3000 miles!

a) Yes you can increase teeth with deraileur, chain may become too short though.
b) Chainrings will say what chain they are compatible with
c) you do ride a double, but you ride with 34/50 the BCD will be 110 (double refers to the two chainrings compact doubles will have a BCD of 110 and standard doubles a BCD of 130)

But yeah, I doubt your chainrings have gone at 3000 miles, might be a rear derailleur setup issue.

posted by SammyG [295 posts]
22nd February 2013 - 15:42

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oops sorry just noticed that you said you replaced the cassette as well.

posted by jimmo62 [59 posts]
22nd February 2013 - 15:42

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Thanks for the advice, I will definitely be hoping to avoid a new chainring in that case, see if I can find the problem or get the LBS to find it before I splash out.
cheers.

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posted by Richthornton [99 posts]
22nd February 2013 - 17:28

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If your gears at jumping forward under load and you've replaced chain and cassette together in the correct way, the only 2 outcomes to this are 1) your chain rings are worn too although this is very unlikely. 2) the pawl springs inside your freehub have worn out and are failing to engage with the ratchet consistently. (Surprised nobody on here has considered this but as a mechanic this is a very common cause of gear slipping) the amount of people that have asked me for new cassette and chain when its the freehub causing the problem is simply staggering. Was it doing that before you changed everything? If so that's where I'm putting my money..

A) you can go up to 52 but will need to raise the derailleur a few mm and may need an extra 2 links on the chain. Nobody makes higher than a 52 for a compact chainset

B) providing BCD is the same compatibility shouldn't (in theory) be an issue although its best practice to match the brand of chainring to the brand of crank

C) compact just means that both rings run the same (smaller) BCD but any road groupset bar Campy will most likely run double. It doesn't need to be compact specific, just have the same BCD..

Hope that helps..

George

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posted by SpeshRider7287 [75 posts]
22nd February 2013 - 18:04

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Thanks George, This wasn't occurring before I changed the cassette and chain, plus the wheels and freehub are very new too (about 120 miles) so I'm really hoping it won't be caused by a worn freehub. Taking an overview of all the comments here so far I'm leaning towards it being my fault not setting the mechs quite right. I'm thinking it might be wise to disengage the cables and start from scratch, see if I can make any improvement before I start paying anyoe to look at it.

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posted by Richthornton [99 posts]
22nd February 2013 - 18:29

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My money is on rear mech alignment make sure that upper jockey wheel is perfectly in line with the sprocket !

posted by SammyG [295 posts]
22nd February 2013 - 18:36

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From what you have described yours chainrings are worn. Chainrings will last a long time unless they are run with a very stretched chain, it's worth getting them looked at by your lbs, and also getting a chain wear gauge so you can periodically check your chain.

posted by mrkeith119 [85 posts]
23rd February 2013 - 0:26

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If you need new chain rings, have a look at hese before you buy:
http://www.dotbike.com/p/5085

Relatively cheap and available in a good range of sizes

posted by Welsh boy [102 posts]
24th February 2013 - 8:58

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Contrary to a couple of posters above Stronglight make chainrings in non-compact sizes for compact bcd. Their CT2 rings are well regarded and go up to 53 tooth.

I've got them from dotbike (link above) and a french online shop i found, but can't remember the name of at the moment (they must have either been cheaper than dotbike or dotbike didn't have stock at the time), before.

posted by mustard [72 posts]
25th February 2013 - 18:30

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