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3x9 - 1x9. which chainring

DanieljephcottDanieljephcott Posts: 334
edited February 2017 in MTB workshop & tech
Hi all,

I have been looking at swapping my 3x9 to a 1x9 on my wifes bike. Seems fairly simple but before ordering the bits I wanted to double check what chainring to have and what gear would be equivalent to my 1x11 setup on my bike

So both myself and the wife aren’t the fittest so I want the best 1x9 setup for hills rather than top speed as this will likely be better. The cassette is a 11-34t and I’m thinking of having a 30t chainring. So if I was in first gear what would be the equivalent in my 1x11 setup which is a 10-42t cassette with a 32t chainring. Atleast then I can have a go in the relevant gear on my 1x11 so I know what first would likely be like in my 1x9.

Im thinking that 30t is probably the best.

Posts

  • First gear on 32/11-34 is 25.4" which is between 2nd and 3rd gear on your set up. 2nd gear is 24" and 3rd gear is 27" assuming your cassette is 42/36/32...

    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".
  • First gear on 32/11-34 is 25.4" which is between 2nd and 3rd gear on your set up. 2nd gear is 24" and 3rd gear is 27" assuming your cassette is 42/36/32...

    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".

    wow my brain just cant work this out haha.

    Ok so if I had a 32t chainring on my 11-34 cassette first gear would be the same as my second gear on my 1x11 setup which is a 32t chainring with a 10-42t cassette?

    ideally it would be great to keep the current 11-34 cassette on the bike so I only have to replace the chainring
  • First gear on 32/11-34 is 25.4" which is between 2nd and 3rd gear on your set up. 2nd gear is 24" and 3rd gear is 27" assuming your cassette is 42/36/32...

    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".

    wow my brain just cant work this out haha.

    Ok so if I had a 32t chainring on my 11-34 cassette first gear would be the same as my second gear on my 1x11 setup which is a 32t chainring with a 10-42t cassette?

    ideally it would be great to keep the current 11-34 cassette on the bike so I only have to replace the chainring

    Not quite. The calculation to use is front/rear * 27. This gives you the gear inches (27 is a nominal wheel size but is used by everyone when discussing general gear lengths). Crank length also alters the feel of a gear due to the change in leverage but that does not alter the length and most data seems to show it makes no difference with normal length cranks. They will vary slightly based on tyres etc. too. You need to remember that cassette spacings are different too. the 9 speed is 11-13-15-17-20-23-26-30-34 and the 11 speed is 10-12-14-16-18-21-24-28-32-36-42.

    So for your examples:

    32/34 * 27 = 25.4"

    32/36 * 27 = 24"

    Your 2nd gear is a bit easier than the lowest gear on the 9 speed.
  • The RookieThe Rookie Posts: 27,756
    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".
    The trouble is that cassette weighs the same as a small house.

    If a wider range is wanted then a wide range 11-40 Sunrace would be a better bet in my opinion, lighter and wider range.

    Only Dan knows the terrain they will ride but as climbing rather than top speed seems the priority a 30T seems a no brainer.
  • First gear on 32/11-34 is 25.4" which is between 2nd and 3rd gear on your set up. 2nd gear is 24" and 3rd gear is 27" assuming your cassette is 42/36/32...

    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".

    wow my brain just cant work this out haha.

    Ok so if I had a 32t chainring on my 11-34 cassette first gear would be the same as my second gear on my 1x11 setup which is a 32t chainring with a 10-42t cassette?

    ideally it would be great to keep the current 11-34 cassette on the bike so I only have to replace the chainring

    Not quite. The calculation to use is front/rear * 27. This gives you the gear inches (27 is a nominal wheel size but is used by everyone when discussing general gear lengths). Crank length also alters the feel of a gear due to the change in leverage but that does not alter the length and most data seems to show it makes no difference with normal length cranks. They will vary slightly based on tyres etc. too. You need to remember that cassette spacings are different too. the 9 speed is 11-13-15-17-20-23-26-30-34 and the 11 speed is 10-12-14-16-18-21-24-28-32-36-42.

    So for your examples:

    32/34 * 27 = 25.4"

    32/36 * 27 = 24"

    Your 2nd gear is a bit easier than the lowest gear on the 9 speed.

    I suppose the bit in red is what I was wanting, I think I get the calculations. so with fitting a 30t chain ring I will be getting 23.8" which is identical to my second gear on my 1x11.

    fingers are crossed that I'm finally getting it :)
  • Yep, that's right. You'll obviously lose some top end speed, 30/11 at 80rpm is about 17.5mph, whereas your gear, 32/10, will do 20.5mph, but I'm guessing that's not much of a worry.
  • The Rookie wrote:
    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".
    The trouble is that cassette weighs the same as a small house.

    If a wider range is wanted then a wide range 11-40 Sunrace would be a better bet in my opinion, lighter and wider range.

    Only Dan knows the terrain they will ride but as climbing rather than top speed seems the priority a 30T seems a no brainer.

    basically she will come with me to Cannock and ill be doing coed y brenin in a few weeks. she wont ride fast so top end isn't a worry. being unfit I want to simplify as much as I can so she enjoys it as much as possible.

    changing to a 1x9 will stop the gearing confusion and I think a 30t front will allow her to peddle up most things. for instance I would use my second gear on my 1x11 setup for cardiac hill so her 1st gear should be the same if I use a 30t... I think.
  • The RookieThe Rookie Posts: 27,756
    I can do Cannock on a 32t with 11-34 quite comfortably, but a 30T does seem the safer option.

    Just the Dog or the Monkey as well? Apart from Cardiac there isn't really anything on the Dog that I used to use lowest gear for and at least cardiac is walkable without getting anyone's way!
  • The Rookie wrote:
    I can do Cannock on a 32t with 11-34 quite comfortably, but a 30T does seem the safer option.

    Just the Dog or the Monkey as well? Apart from Cardiac there isn't really anything on the Dog that I used to use lowest gear for and at least cardiac is walkable without getting anyone's way!

    I only tend to do the dog however would like to try the full dog and monkey again now I'm fitter. the dog is no issues for me just cardiac which as said I'm in second on my 1x11. used to use 1st but realised that I'm putting more effort in rather than relying on leg power.

    my wife fitness wise is where I was 6 months ago so for her doing the dog will be hard going but as said making things as easy as possible will help her enjoy it more.

    even though ive got my biking life it would be good to get her into it for when we go away to wales which we do 3-4 times a year.

    Ive just notice that sunrace 11-40 comment... that would work out amazing with a 30t giving her the best of everything. seen one on ebay for £30.

    would that go straight on my hub? rear hub is a formula dc20
  • The Rookie wrote:
    12-36 9-speed cassettes are available, Shimano Alivio, that would put here lowest gear at 22.5, in between your 2nd gear of 24" and your 1st gear of 20.6".
    The trouble is that cassette weighs the same as a small house.

    If a wider range is wanted then a wide range 11-40 Sunrace would be a better bet in my opinion, lighter and wider range.

    Only Dan knows the terrain they will ride but as climbing rather than top speed seems the priority a 30T seems a no brainer.

    The Sunrace is heavier than the Alivio (500g vs 413g) and the those jumps at the low end are massive. Not sure I'd want to be shifting through them while climbing.
  • I will be making the 1x9 conversion first using a 30t chainring. will see how we get on.

    don't really want to spend much on this bike(voodoo hoodoo) so just some small changes. My spare reverb, a maxxis highroller II tyre on the front, changed the seat to a sdg allure (women) saddle and the 1x9 should make the world of difference.

    lets hope she likes it :)

    if not sod it ill go riding on my own haha
  • The RookieThe Rookie Posts: 27,756
    The Sunrace is heavier than the Alivio (500g vs 413g) and the those jumps at the low end are massive. Not sure I'd want to be shifting through them while climbing.
    Funny as the weights I've seen are pretty much the exact opposite.....
  • oxomanoxoman Posts: 10,455
    Dan, good idea not frightening your missus by doing dog and monkey together. Alot of people hate cardiac but if doing the double kitbag is a grueller and the start of the monkey is steepish to start with. Hope she likes it.
    Too many bikes according to Mrs O.
  • The Rookie wrote:
    The Sunrace is heavier than the Alivio (500g vs 413g) and the those jumps at the low end are massive. Not sure I'd want to be shifting through them while climbing.
    Funny as the weights I've seen are pretty much the exact opposite.....
    Links? I'm on my phone but the Sunrace weight came from the Sunrace website, Alivio from, I think, bike-discount.de. The Shimano site is bobbins.
  • The RookieThe Rookie Posts: 27,756
    Will have to find them, the Alivio weight was from a photo on a weighing scale on a forum from a reliable source.

    Will have to go search the Sunrace.
  • I might be wrong but I think there's several different makes of the 12-36 cassette with different weights. CS-HG400 being the lightest of them at 413g (on paper at least).
  • to be honest the bikes a voodoo hoodoo and were not the lightest people in the world so I don't think weight really matters :) haha.

    will try the standard cassette with the 30t front and see how we get on.

    the plan really is to get her into it and then buy her a full sus if she keeps it up.
  • supersonicsupersonic Posts: 82,708 Lives Here
    Another option is to fit a 28t N/W ring to the inside mount on your chainset. With an 11-34 cassette, you will get a lower bottom gear than a 30t ring and 12-36 cassette, and a higher top gear too - the cassette has more range (that 12t, rather than an 11t, cuts the overall gear range somewhat - and is why SRAM now have them down to 10t). Is also a lighter set up.

    You would need to use a 10spd chain though, and the chainline will be shorter (which would be better if using the lower gears more), but this could be tweaked with a longer bottom bracket axle.
  • ade555ade555 Posts: 216
    Just a idea, there is few bargins on pink bike for 1x10 setup now everyone wants the next best thing, also have a look in this link you can play with setups and will give you a bit of idea what gears would look like. There is Sunrace 9 speed 11-40 but only from HK on ebay I can't found one in UK

    http://gears.mtbcrosscountry.com/#26I1I1
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