Results 1 to 23 of 23
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jul 2009
    Posts
    86

    20" hotrock 2X9 ???

    I want to build a two-front chain ring by 9 speed rear cassette upgrade to my daughter's Hotrock 6 speed.
    I have seen several posts of 1X8's and 1X9's with pictures, but no double chain-ring conversions. A 22/32 front setup is what I want, but can't find a website that offers crank shortening and drilling for pedals. Anyone know a URL for such services? I checked Sinz and other BMX cranks options and can't find 130mm cranks with a compact drive bolt pattern.
    All help is welcomed.

  2. #2
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,012
    Don't bother. Here's a test to prove my point. Hold her on your bike and see if she has enough strength to actually shift a FD.

    I found my son didn't and getting a Marin 20 inch with a double up front was a waste for him. Just throw the 9 speed on the back, and the Sinz 135-140 cranks. Seems like 20 inch bikes are still coming with too long a crank.

    If you insist on doing it- Truvativ IsoFlow 175mm MTB crankarms Shortened to 153mm
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jul 2009
    Posts
    86

    Grip shift for front

    I thought about the finger strength issue for shifting a front derr and it's still worth the effort to have the two range choice on the cranks because of the long climbs we do in our area....push come to shove I will shift the front for her and she can spend 30 minutes climbing with 9 low range choices.

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,012
    Quote Originally Posted by yetipop View Post
    I thought about the finger strength issue for shifting a front derr and it's still worth the effort to have the two range choice on the cranks because of the long climbs we do in our area....push come to shove I will shift the front for her and she can spend 30 minutes climbing with 9 low range choices.
    Then you should be fine, my son could drop the front down to the granny, just couldn't shift it back up.
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jul 2007
    Posts
    36
    You can use a "triplizer" chainring to add a granny to a standard 110 bmx crank.

    IRD Compact Road Triplizer Chainring

    Origin 8 makes a triple Crank set in 145,155 & 165 lengths for a 130/74 set up too.

    Hope it is of some help to you!

  6. #6
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,442
    My son runs 2x8 on his Hotrock 20, 22/32 in front, sram pg-850 in rear. Shifting the front back up is not totally easy, but doable. Shifting down is easy. The downshift is the important part. When it's on the climb, it's more important to be able to drop down than it is to go back up.

    I used bikesmith design for a 145mm triple crank, running 2 rings + bash.

    It's useful for these, which we ride. Steady, with pitches over 10% and sprints. 7/8yo rider.






  7. #7
    mtbr member
    Reputation:
    Join Date
    Apr 2005
    Posts
    1,142
    How about a 11/36 rear with 1X front? Its pretty darn low?
    Enjoy every ride!

  8. #8
    Inspector Gadget
    Reputation: abeckstead's Avatar
    Join Date
    Feb 2012
    Posts
    497
    Yeti did you ever do anything?

    I just sent the guy an email that does the shortened truvativ cranks. Want to do this for my son's 20" Hotrock so he can climb some real hills. This bike will eventually be handed down to my daughter so I am ok with the $ spent. A 36 front is just too tall and even a big rear casette doesn't get it low enough IMO. My thought was a grip shifter for the front too... keeping it simple as possible.

  9. #9
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,442
    Quote Originally Posted by abeckstead View Post
    My thought was a grip shifter for the front too... keeping it simple as possible.
    I use grips. I don't think a trigger is manageable, as I have difficulty shifting the front trigger from 1-2. There's too much throw needed with my SRAM attack trigger. I think my x.7 and x.9 shifters are a bit better in that regard, but I would want an indicator for the kid's bike.

    I use the bikesmith designs cut down crank. It's fine.

    m-dub, 32T front and 36T rear isn't low enough.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,012
    Good rings with a good shifter can help.

    It's been since last spring since we tried, but today he was able to up shift the FD on my new Specialized that has a X9 shifter and X7 FD 2x10 and still can't on his Marin.
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  11. #11
    Inspector Gadget
    Reputation: abeckstead's Avatar
    Join Date
    Feb 2012
    Posts
    497
    Alright ordered the crankset and told my son... he was so excited I think he danced for 5 min's! lol

    So which gripshift and FD would you recommend? This bike has been upgraded to an stx RD and looks like another freewheel hub.

  12. #12
    mtbr member
    Reputation:
    Join Date
    Mar 2011
    Posts
    669
    My kid had a problem on the 24" 3x7 Hotrocks going from middle to the large chain ring using the SRAM X3 grip shifter, I got them some X3 Trigger shifters and she is fine with that. The X3 and x5 also have indicator windows on the triggers
    My youngest kid has a a 20" MT60 and I reckon it would be a big hassle to do any thing to that - any bigger in the back and the chain is going to up around the rear brake - and the 6 speed freewheel is considerably narrower than a the 7 speed megarange on the 24" hotrocks - so there would be a lot to do with changing the wheel dish if it was to fit in the 130mm dropouts with a 7 or more speed. Wouldn't mind getting a second crank with a 24T Ring that she can use off road trail riding

  13. #13
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,012
    Quote Originally Posted by abeckstead View Post
    Alright ordered the crankset and told my son... he was so excited I think he danced for 5 min's! lol

    So which gripshift and FD would you recommend? This bike has been upgraded to an stx RD and looks like another freewheel hub.
    Sorry can't help you there since my son hated grip shift, first thing I did on his 20inch was switch to triggers.

    I'd think any decent front derailleur would be good.

    I could be wrong, but I honestly think it's more the rings, I looked at the rings on his bike and they have nothing, no ramps just 4 pins to help up shifts. No wonder it's so hard to up shift.
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  14. #14
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,442
    Quote Originally Posted by abeckstead View Post
    Alright ordered the crankset and told my son... he was so excited I think he danced for 5 min's! lol

    So which gripshift and FD would you recommend? This bike has been upgraded to an stx RD and looks like another freewheel hub.
    I would look at the lower end of Shimano. My wife has Alivio stuff on her bike, and it's pretty easy to shift. I changed the shfiters for SLX and they remain easy.

    My bikes have "higher" end Deore, SLX, and XT parts and the shifting requires more force. The firmer springs in the derailleurs is what makes it harder.

    That said, my son's X.5 derailleur and my X.7 and X.9 derailleurs seem fairly easy to move too. It is not as easy as Alivio though. You can go around and flip the derailleurs by hand instead of cable to get a feel for it.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Jul 2009
    Posts
    86

    Half finished with the 2X9 hotrock upgrade

    Thanks for the info on bikesmith (crankshortening services).

    I used an old XT hub and re-laced the 20" rear wheel and added a Sram 34-11 cassette. I switched out the grip-shift for a Sram X9 trigger shifter and my six year old daughter has little problems down-shifting. Trigger shifters are the way to go....because it's easier to hit one cog at a time. With the grip shift she would shift from the 28 right to the 12 and back again while missing all the cogs in the middle.
    The Sram X9 medium cage derailleur works well and I hope it will suck up enough chain when I add a small 22 or 24 tooth front chain ring.

    The upgrades are working well for now and we are logging road miles and technical single track. For now, the single-track my daughter is learning on is flat enough to be handled by the 34-11 cassette with the stock 36 front chain ring.

  16. #16
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,442
    Quote Originally Posted by yetipop View Post
    The Sram X9 medium cage derailleur works well and I hope it will suck up enough chain when I add a small 22 or 24 tooth front chain ring.
    It'll be fine. I run a SRAM X.5 medium cage on my son's 2x8.

  17. #17
    Inspector Gadget
    Reputation: abeckstead's Avatar
    Join Date
    Feb 2012
    Posts
    497
    I found a shimano tourney twist shifter set last night. They are inexpensive and appear to be what it came with. He does great with it so I think I'll just keep them for now. Instead of changing too many things at once on him. Also was going to keep the 6 spd cassette long as that works.

    I'm also doing some upgrades to my wife's bike and mine. So I will have some parts to experiment with and figure out what he likes without wasting money.

  18. #18
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,442
    Quote Originally Posted by abeckstead View Post
    I found a shimano tourney twist shifter set last night. They are inexpensive and appear to be what it came with. He does great with it so I think I'll just keep them for now. Instead of changing too many things at once on him. Also was going to keep the 6 spd cassette long as that works.

    I'm also doing some upgrades to my wife's bike and mine. So I will have some parts to experiment with and figure out what he likes without wasting money.
    The Tourney is hard to shift, it's hard to get through the click tension. The SRAM MRX is easier to shift. SRAM twist shifters are better.

  19. #19
    Inspector Gadget
    Reputation: abeckstead's Avatar
    Join Date
    Feb 2012
    Posts
    497
    Ok cool thanks for the heads up on shifters!

  20. #20
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    257
    Great thread. Just bought my daughter a Trek Mt 240 and she is having troubles upshifting from granny back to middle. I'll look at replacing the middle ring with something with ramps. I was planning to replace the big ring with a bash guard anyway.

    I am also considering changing her over to trigger shifters, at least for the front derailleur. I have a SRAM X3 or X5 at home that should work with the front derailleur.

    Her upgrades are cutting into my upgrades budget :-)

  21. #21
    I Tried Them ALL... Moderator
    Reputation: Zachariah's Avatar
    Join Date
    Dec 2007
    Posts
    3,930
    What needs to be done to make Grip Shift 2x9 work on the two largest front gears(no granny)? Can a 10-speed front derailleur work? I'm trying to find a solution for my 2001 Cannondale Bad Boy Urban commuter.
    "The mind will quit....well before the body does"

  22. #22
    Mantis, Paramount, Campy
    Reputation: Shayne's Avatar
    Join Date
    Jan 2004
    Posts
    4,291

    Nothing

    Quote Originally Posted by Zachariah View Post
    What needs to be done to make Grip Shift 2x9 work on the two largest front gears(no granny)? Can a 10-speed front derailleur work? I'm trying to find a solution for my 2001 Cannondale Bad Boy Urban commuter.
    It should work fine as it
    *** --- *** --- ***

  23. #23
    banned
    Reputation:
    Join Date
    Dec 2012
    Posts
    13
    yeah,i think so, You can use a "triplizer" chainring to add a granny to a standard 110 bmx crank.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •