How to replace chainrings (Advice needed please!)

Hey folks, noob here looking for advice.

I have acquired a new standard SRAM cassette (11-34T 9 speed) for my 2008 rockhopper and have decided its probably a good idea to refresh the chainrings too.

I’ve not replaced chainrings before and it doesn’t seem to be as obvious swapping cassettes.

I’m a student on a budget and it has occurred to me that I could potentially replace the current 3 with 2 intermediate rings, is this possible/advisable?

If replacing with like for like rings (22, 32, 44) is advisable, I’m unsure where to start as I can’t see sets of rings on sites, do I just have to locate separate correct size rings?

Any advice welcome,

Cheers

You need to know what crank you have, that will tell you the BCD value of the rings you need.

Easy enough to go for something like a 26/38 combo as a double

Yes, it’s doable and no need to buy a set, just the ones you need but if you want to convert to a double from a triple then there are a couple of ‘gotchas’  to consider:

– you might need shorter chainring bolts or spacer washers since you are bolting one ring on where there was 2

– your front shift lever may have a switch to operate on triple or double but given the age, probably not. In that case you need to set the limit screws on the front derailleur so it can’t shift onto a non existent large chainring AND be careful not to try to do that shift by accident since it can break the shift lever if you force it.

– you’ll want to get a new chain at the same time as replacing the rings and cassette.

Perfect response thank you!

Hadn’t considered bolts/washers but that shouldn’t be difficult to solve!

I did think I’d have to adjust limits; wouldn’t the middle shift just put the chain in between the rings and i just need to double shift each time?

Yep new chain sorted 🙂

26/38 sounds reasonable!

not sure I quite understand but you’re best off using the inner and middle ring positions and locking out the outer position, it won’t shift properly between inner and outer without a chainring there.

re the washers, you can get specific ones for this purpose

off using the inner and middle ring positions and locking out the outer position,

Definitely this, do not leave a “gap”

Are the chainrings removable on your crankset?  Some of the entry-level ranges had them attached with rivets rather than bolts.

As for rings, if they fit your cranks then individual bog standard shimano deore are cheap and last for aaage.  Don’t go for the bling until your happy with the ratios you’ve got.

Oh and make sure you’ve got the tools to get the cranks off your bike too.

I did think I’d have to adjust limits; wouldn’t the middle shift just put the chain in between the rings and i just need to double shift each time?

Not unless you leave a gap, see above re. leaving a gap.

Even using different specs of rings I’ve ended up with annoying chain sized gaps. Leaving out a ring will just totally bugger things up. Use middle/inner positions.

TBH 22/32 will do fine, 22/36 would be ideal for a 9s double for me. It will probably be easier to get rings in the three sizes you have, fitting an “outer” ring in the middle position will be an utter ball ache – I have done it on one bike to get suitable MTB cranks with a lowish road set of ratios on them. It involved washers, filing down rings, and still having bolts poking out and catching the chain in bigger gears (as the counterbore is on the wrong side). Given time to search/money to buy, I’ll put some other cranks on it, although the bodge kind of works if you want a 28/44 (or 26/42, 24/40) double.

You might find a new set of cranks is cheaper than getting 2 rings, so look at that too.

1/ you may not need to replace all the chainrings; if like most of us you spend 70% of your time in the middle ring then the others may not be as worn. Post up a pic if you can, worn chainrings are shaped like shark’s teeth and are usually diagnosable. And as you can replace them individually, you might try changing the middle only and having a go before committing to all three. Additionally, the inners are frequently steel (not as much weight to save on a small ring) and get used sparingly so there’s a good chance that even if middle and outer are worn out, inner will still be good.

2/ If going for a 2 ring set up, you need to ensure the BCD (bolt centre diameter) is correct. Wolf components have a handy table but it’s usually on the rings somewhere.

https://www.wolftoothcomponents.com/pages/how-to-measure-bolt-circle-diameter-bcd

3/ A standard triple chainset has the middle ring in the centre of the chainline and the inner and outer either side.  A specific double has the rings either side of the centre. If you convert a triple to run 2 rings you have to choose inner and middle or middle and outer, inner and outer won’t work as you’ll drop the chain between the rings when going between them. And if you choose middle and outer then you will only be able to go maybe down to 30T on the smaller of the two which will limit your climbing gears. You probably want to go inner and middle, TBH (say 22/36), and compromise on having a big gear.  Proper double chainsets are usually 24/38 teeth respectively but they also have 10 speed cassettes which go to 36 or nowadays, 40 or 42T at the back, which i think 9 speed won’t handle. So you need a smaller front chainring to compensate for the smaller 34T on your rear and keep the lowest ratio about the same (22/34 = 65%, 24/36 = 66.6%, 24/40 = 60%, etc.)

check the existing ones to make sure they arnt riveted to the crank

Sorry for the unnecessary bump, but I’d like to thank you all for your advice. Went to a 2×9 with a 36T big ring and a cheap aluminium bash plate which looks real clean. Didn’t need to replace the small ring as suggested so a nice cheap upgrade and the drive-train as a whole feels much tighter and there’s a lot less chain-slap, and less faff with gear changes 🙂