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  1. #1
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    Need sort drivetrain - shorter cranks and considering going from 3x8 to 1x

    Hello all!

    Trying to sort out the better half's bike - the main problems are that it's a bit on the heavy side, the gears don't work half the time (front derailler mainly, other changes on the 8sp are generally ok, but I do need to try and adjust them) and I think the fit of the bike could be refined a bit - which combined means that she struggles on hills - although her fitness is not bad so I don't think it's just that. Bike iwll be used for XC/trails so nothing too taxing.

    I'm looking at the drivetrain thinking that it could help on all these fronts (wheels have been sorted and will look at the fork in due course)!

    Bike is a 2009 carrera vulcan but very lightly used. Currently it's SRAMX4 rear derailler, the cassette is 8sp and goes 18-21-26-32 which I don't think is the best spacing for climbing. It's a Suntour XCT v2 22-32-42t chain ring with 175cm crank.

    So several options swimming around my head here.

    - I'll be getting a new rear cassette regardless as its cheap and going on a replacement wheelset which currently has no cassette.
    - I also want to sort the cranks out - in terms of getting shorter ones at 160mm/165mm, also to help with bike fit and ease the toll on her knees (which have some issues).
    - but question is do drop the front derailler and go 1x8, or start changing the derailler/shifter and go 1x10etc....

    My present thinking is to go to 1x8 but with a more capable cassette. I saw a Claris 11-34T 8sp with good spacing - but this is listed as road. Is this going to be a problem on a MTB? And then what are the options on the crank?

    Any help to demystify would be appreciated.

  2. #2
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    Why not spend a bit more and go 11-42 1x10spd? The new Shimano Deore M6000 is at an affordable price, imho.


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  3. #3
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    Economically, doing a derailleur swap and crankset swap don't seem especially practical. I think for the money you'd be better off buying a more suitable bike used. You didn't mention the frame size but if she needs 160 cranks and the bike came with 175s it's possible that the frame is too big for her anyway as most bikes come with relatively size cranks.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  4. #4
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    I had a quick look at that , but most options in that deore range seem to offer cranks in 170 or 175. Saw the m8000 but thats quick a bit for the cranks alone.

  5. #5
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    Quote Originally Posted by Forster View Post
    Economically, doing a derailleur swap and crankset swap don't seem especially practical. I think for the money you'd be better off buying a more suitable bike used. You didn't mention the frame size but if she needs 160 cranks and the bike came with 175s it's possible that the frame is too big for her anyway as most bikes come with relatively size cranks.
    Thanks for the replies Forster and Shadow4eva.

    I have thought about a new bike - she does fit the bike ok, just. But as we have got out of the habit of riding, I really want to make sure we get going again, with a relatively low expenditure, before we splash out on a new bike.

    I've just seen a suntour XCT 414 JR which is 160mm crank - around £25. Wondering if I could swap that straight on. Maybe even lose the two outer rings?

  6. #6
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    Dropping the triple in the front will not help her on the climbs, if she is already struggling.

    Most knee pain comes from improper saddle height or fore and aft of the saddle, not crank length.

    Need to post a picture of the bike, will help a lot.

  7. #7
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    Bike is same as Carrera Vulcan Disc Spec Ladies 2009 review - The Bike List

    I'm pretty comfortable that the saddle height is right. She has knee pains for various reasons and I would like her to be able to cycle without aggravating it. From doing some reading, shorter cranks can help with that. Most reference material (bike dynamics, highpath engineering etc) that I have seen on this suggests that 160mm is right for it so thought it would be worth trying.

  8. #8
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    Quote Originally Posted by MrBigglesworth View Post
    Bike is same as Carrera Vulcan Disc Spec Ladies 2009 review - The Bike List

    I'm pretty comfortable that the saddle height is right. She has knee pains for various reasons and I would like her to be able to cycle without aggravating it. From doing some reading, shorter cranks can help with that. Most reference material (bike dynamics, highpath engineering etc) that I have seen on this suggests that 160mm is right for it so thought it would be worth trying.
    160mm might help if she spinning high cadence, but with a 1x8, climbing will not be high cadence.

    Need a pic of the actual bike you are working on, not a catalog pic.

  9. #9
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    Quote Originally Posted by Forster View Post
    Economically, doing a derailleur swap and crankset swap don't seem especially practical. I think for the money you'd be better off buying a more suitable bike used. You didn't mention the frame size but if she needs 160 cranks and the bike came with 175s it's possible that the frame is too big for her anyway as most bikes come with relatively size cranks.
    Used with short cranks is tricky.

    To not dump too much money in this bike, I'd go for the same cranks on ebay in 160mm length -- see item 112811582843 -- and use the limit screws to adjust the front derailleur to skip the big chainring. This way it will be a simple two gears up front and the limit screws set the adjustment. If you want, you could throw a bash ring on for the big chainring. IMHO, a 22T up front is a nice thing for a rider struggling for enough torque.
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  10. #10
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    Quote Originally Posted by J_Westy View Post
    Used with short cranks is tricky.

    To not dump too much money in this bike, I'd go for the same cranks on ebay in 160mm length -- see item 112811582843 -- and use the limit screws to adjust the front derailleur to skip the big chainring. This way it will be a simple two gears up front and the limit screws set the adjustment. If you want, you could throw a bash ring on for the big chainring. IMHO, a 22T up front is a nice thing for a rider struggling for enough torque.
    I just thought that I should try it in stages, with the first stage much as you suggest. I'll get that set of Suntour cranks and a better spaced cassette, put the replacement wheelset and tyres on (that should knock off >1.5kg) and see how she goes still on a 3x8 (or 2x8 and lose the bigger chainring). If she still only keeps using the 32T chainring, then I can see further


    So questions for now:

    - Will the Suntour XCT JR go on the same BB as the Suntour XCT V2 that is currently on there/anyone know how to find out (looked on Suntour website to no avail)?
    - In terms of 8sp cassette - main options appear to be a HG41/HG51 11-32T (11-34 seems worse jump in gearing), or a Claris HG50 11-34T that is well spaced. Will the Claris be ok as it seems to appear under "road" on the shimano website rather than MTB?

  11. #11
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    Quote Originally Posted by MrBigglesworth View Post
    - Will the Suntour XCT JR go on the same BB as the Suntour XCT V2 that is currently on there/anyone know how to find out (looked on Suntour website to no avail)?
    Hard to tell, but since they're both square taper, probably. Worst case you have to get a little longer or shorter BB....

    Quote Originally Posted by MrBigglesworth View Post
    - In terms of 8sp cassette - main options appear to be a HG41/HG51 11-32T (11-34 seems worse jump in gearing), or a Claris HG50 11-34T that is well spaced. Will the Claris be ok as it seems to appear under "road" on the shimano website rather than MTB?
    8 speed is 8 speed

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  12. #12
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    Quote Originally Posted by J_Westy View Post
    Hard to tell, but since they're both square taper, probably. Worst case you have to get a little longer or shorter BB....



    8 speed is 8 speed

    https://www.sheldonbrown.com/speeds.html
    Thanks again, and for the useful link!

  13. #13
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    I don't see the 1x8 as a viable option given the range of gearing for the terrain that you're presenting. Couple that with a shorter crank and the results might not be as anticipated.
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  14. #14
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    Quote Originally Posted by Cleared2land View Post
    I don't see the 1x8 as a viable option given the range of gearing for the terrain that you're presenting. Couple that with a shorter crank and the results might not be as anticipated.

    I'm there now! Thanks to all the posters on this thread.

    I will retain the existing gearing system - tune it up so it works properly, possibly drop to 2x8 with a bash guard for aesthectics, and get a better rear cassette whilst I am changing wheels. No weight saved, but should have the right range of gears and right cranks without much expenditure.

  15. #15
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    Quote Originally Posted by MrBigglesworth View Post
    I'm there now! Thanks to all the posters on this thread.

    I will retain the existing gearing system - tune it up so it works properly, possibly drop to 2x8 with a bash guard for aesthectics, and get a better rear cassette whilst I am changing wheels. No weight saved, but should have the right range of gears and right cranks without much expenditure.
    Wise route, I think - good luck.

    Quote Originally Posted by MrBigglesworth View Post
    If she still only keeps using the 32T chainring, then I can see further
    It's ok if she rides only in the 22T too

    Any ride with your wife is a good ride!
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