12 speed and chainring size?

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This topic has 14 replies, 10 voices, and was last updated 6 years ago by charliemort.

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12 speed and chainring size?
bluearsedfly
Free Member

I’m moving from a 32t chainring and 10-42 cassette on an 11 speed setup, to a 10-50 cassette on a 12 speed setup and I’m unsure what size chainring to go for?

My new crank came with a 34t chainring by default, new bike build is from a frame only and it will take a 34t chainring but the complete bike comes as standard with a 30t chainring.

I have a feeling 34t will be too high but 30t too low? Am I best to stick to a 32t?

Posted 6 years ago

mcnultycop
Full Member

Same wheel size as the old bike on the new build?

Posted 6 years ago

martinhutch
Full Member

http://www.gear-calculator.com/?GR=DERS&KB=24

Put your numbers into the compare function on this and it will tell you the difference between your current and new setups.

50×34 will give you a significantly easier bottom gear than 42×32, all other things being equal, I would have thought.

Posted 6 years ago

mikewsmith
Free Member

I have a feeling 34t will be too high but 30t too low? Am I best to stick to a 32t?

Build it and ride it, the new setup will have a lower easy gear and a harder top end so more range either side of your current setup.

Posted 6 years ago

bluearsedfly
Free Member

Going from 27.5 to a gnarpoon 29er.

Top end was fine on 42×32, sometimes span out. Will give it go on 34t then. £70 for a chainring!

Posted 6 years ago

tdog
Free Member

Blimey, I had a look at that calculator gearing link on a moby and well f me that is tricky to use and tge display is simply aweful.

I at the same time too am unfamiliar. It looked as though I’ll have 458% gear ratio running a 34T ring with 11-50T on a 29er.

but unsure tbh and well I think I know what to expect but feel too that I should be on a 32T for the 29er.

but yeah don’t feel the need to stomach £50 on a new ring

Posted 6 years ago

Onzadog
Free Member

Full suspension? It might be that the linkage is optimised around a particular ring size, or that you can tune to your preference slightly by tweaking ring size.

Posted 6 years ago

mikewsmith
Free Member

but yeah don’t feel the need to stomach £50 on a new ring

Any 11sp ring will be fine

Posted 6 years ago

whitestone
Free Member

On a 1x system you’ll get the same gear range for any given cassette no matter what size chainring you are using.

Are you running out of gears at either end of your current setup? If you need more at the bottom end then stick with 32T, if at both ends then 34T. 30T will give you lots more at the bottom end but lose you some range at the top end – roughly making the new top equivalent to the 11T cog on your current cassette.

Posted 6 years ago

tdog
Free Member

Any 11sp ring will be fine

Yeah shoulda said circa £50 on another Renthal.

or a cheapy SS tatt that wouldn’t suffice on my build muwhahaha

Posted 6 years ago

vincienup
Free Member

Just took a look and that’s pretty much the standard gear calc although someone seems to have hacked the drop downs a bit since I last saw it. It turns up with many different names in different places. I just hope the guy that originally front it is happy with this!

Anyhoo. Plugging a 32T 10-42 in and comparing to a 34T 10-50, the 10-50 has more bottom (20 gear inches vs around 22) and more top too. If you already found 10-42 hard work then maybe moving down for a bigger bailout would make sense but as it is, you’ll not be losing out at all. Frame pending, you could probably just about squeeze a 36T in there without climbing getting any harder than 11sp SRAM.

Posted 6 years ago

bluearsedfly
Free Member

So going up to a 34t with 10-50 I’d be less likely to spin out on the top end and have a bit more lower down.

Sounds better all round then. Thanks everyone, I’ll give the 34t a go then.

Posted 6 years ago

nickfrog
Free Member

Have you entered both configurations in the gear calc? It’s the only way to eliminate guess work, it’s a great tool.

Posted 6 years ago

RamseyNeil
Free Member

Myself and one of my pretty fit cycling pals have both swapped from 32 tooth front rings to 30 with a 10-50 casette on the back , both on 29ers . I managed with the 32 but felt like I was in the 50 more often than I wanted to be . The 30 oval feels much better to me and I don’t find myself spinning out either . I live in the Isle of Man and it’s pretty hilly .

Posted 6 years ago

charliemort
Full Member

I don’t really get on with gear inches and personally prefer basic maffs

32:10 – 1 turn of the front ring turns back wheel 3.2 times

32:42 – 1 turn of front ring turns back wheel 0.76 times

34:10 – 1 turn of the front ring turns back wheel 3.4 times (ie a bit faster)

34:50 – 1 turn of front ring turns back wheel 0.68 times (ie a fair bit lower / easier)

personally i use 32 on a 29’er and works fine, never spin out and a nice bail out gear

Posted 6 years ago