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  1. #1
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    Mojo HD with a 650b front wheel

    Has anyone tried the Mojo HD with a front 650b or even both ?
    Does it have too much travel to be mucking with a bigger wheel ?
    I love a front 650b on my standard Mojo and will be getting an HD later this year.

  2. #2
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    Has anyone tried the pacenti neo moto 2.1 on the Mojo Sl? Will this tire work without the need to shim the shock to avoid seat tube/tire rub issue as with the 2.3 model?

  3. #3
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    Search the Ibis forum and the 650b forum and you'll find a lot of posts on the subject, many of which are by Derby.

  4. #4
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    Quote Originally Posted by doismellbacon
    Search the Ibis forum and the 650b forum and you'll find a lot of posts on the subject, many of which are by Derby.
    B-man, some have reported seat tube rub issues bottoming the Mojo C or SL with a 2.3 Neo-moto 650b tire. With this tire there is 4 - 5 mm clearance at the stays, enough. Shimming the bottom travel with home made split plastic washers is very easy, without removing the shock from the bike. The HD I tried my rear 650b 2.3 Neo-moto had plenty of clearance in every way. Most 6+ inch travel bikes clear any 650b tire.

    My overly wordy how-to might make shimming the shock sound more complicated than it is... http://forums.mtbr.com/showthread.php?t=623853

    Front-only 650b slacks the bike, lowering the handlebars the same 1/2 inch difference the axle is raised by 650b brings the ride weight balance back to familiar, with increased traction, smoother and easier rolling, although it feels like 1 degree slacker angled steering overall. Rear 650b raises the BB 1/2 inch, to 13.65 (Mojo C and SL), very nice for rocky or eroded trail climbing pedal clearance, and no frame angle change so very little steering feel change. Only 6+ inch bikes with DH tires feel as smooth riding.

    Edit added: I did a pretty comprehensive 20 mile demo ride on the HD on familiar rocky rooted trail. I'm a little concerned that raising the BB 1/2" on the HD using 650b may be getting into an awkward BB height, from 13.75 with 26 inch wheels to 14.25 inch with 650b. Using deeper recommended sag would reduce the weighted BB height more than 650b on the Mojo so it should be OK. If still to tall feeling, then using 5mm longer cranks could lower seat height, and help compensate for the reduced torque and higher gearing of bigger wheels.
    Last edited by derby; 09-06-2010 at 07:30 PM.

  5. #5
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    Quote Originally Posted by derby
    I'm a little concerned that raising the BB 1/2" on the HD using 650b may be getting into an awkward BB height, from 13.75 with 26 inch wheels to 14.25 inch with 650b. Using deeper recommended sag would reduce the weighted BB height more than 650b on the Mojo so it should be OK. If still to tall feeling, then using 5mm longer cranks could lower seat height, and help compensate for the reduced torque and higher gearing of bigger wheels.

    Derby,

    I am not sure this is the case... According to the frame drawing / geometry chart on the Ibis web site, both the Mojo and HD are designed with 0mm of BB drop. That means the static BB height will always be equal to the wheel radius.

    The HD was obviously designed for large (2.4"+???) 26" tires. If the drawing is accurate, the wheel radius is almost exactly the same as a 2.3" 650b tire, resulting in a 352mm BB height. There should be very little if any rise in the BB.

    This is the very reason I am so excited to pick up an HD frame. It seems perfectly suited for a "Plus 1" type 650b conversion

    Cheers,

    KP
    Attached Thumbnails Attached Thumbnails Mojo HD with a 650b front wheel-mojohd_geo1.jpg  

    Last edited by Kirk Pacenti; 09-07-2010 at 06:41 PM.

  6. #6
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    Quote Originally Posted by Kirk Pacenti
    Derby,

    I am not sure this is the case... According to the frame drawing / geometry chart on the Ibis web site, both the Mojo and HD are designed with 0mm of BB drop. That means the static BB height will always be equal to the wheel radius.

    The HD was obviously designed for large (2.4"+???) 26" tires. If the drawing is accurate, the wheel radius is almost exactly the same as a 2.3" 650b tire, resulting in a 352mm BB height. There should be very little if any rise in the BB.

    This is the very reason I am so excited to pick up an HD frame. It seems perfectly suited for a "Plus 1" type 650b conversion

    Cheers,

    KP
    The WTB Mutanoraptors are unusually tall for their width, the Race version I used on California trails measured only 3/8 inch less in diameter compared to your excellent 650b x 2.3 Pacenti neo-moto tires. The UST AM Mutanoraptors appear even taller, but the thicker AM tread may be deceiving.

    After looking closely at the published BB height numbers the BB height at sag is within .35 inch across all models of Mojo C, SL HD 140, and HD 160. (See "Numbers" for calculations, below)

    The Ibis geometry graphic is just a reference map, not to scale. The C/SL frame has no BB drop at top-out, the HD 160 has .5 inch negative BB drop, the HD 140 .25 in negative drop.

    Conclusion...

    650b will bring the sagged BB height up 1/2 inch with same width tires to about 12.5 on any Mojo model. Very little difference in BB height when sagged.

    I'm very happy to see the BB height HD when sagged is no higher than the Mojo C/SL, and ideal for 650b. My plan is to swap my 650b x 2.3 wheels over for most uses, and also build some much heavier 26 inch DH wheels using 2.5 Minions for ski park use.


    Numbers....

    BB height w/o sag::

    HD 160mm BB height at top travel front and rear is listed at 352mm (13.8″) I presume with 2.4 WTB tires as demoed.

    HD 140mm BB height at top travel front and rear was announced at 343mm (13.5″)

    C and SL 140mm is listed as BB height unsagged: 336 (13.23") with 2.1 Kendas as sold.

    But sagged is what really matters for CG and pedal clearance.

    BB height sagged:


    HD 160/160mm posted BB height at sag: 304mm (12″) @30%

    (HD 150/140mm BB height at 25% sag: 308 mm (12.12")

    C/SL 140mm BB height at sag: 314 (12.36") Presuming @25% (and 2.1 tires)

    http://www.ibiscycles.com/mountain/mojohd/geometry/
    http://www.ibiscycles.com/mountain/mojo/geometry/

    Your sag may vary. I use at least 25%/30% front/rear sag on my C.

    Edit: corrected mistake in Numbers
    Last edited by derby; 09-08-2010 at 07:36 AM.

  7. #7
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    OK guys great job with the numbers. Just let us know how the 650b works on the front and rear with the new 140 HD.

    Mojo

  8. #8
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    Hi Ray

    I am not following your numbers. You have multiplied the BB height (352mm) by 0.7 ( which is assume is for 30% sag) to give 246.4.
    Instead, shouldn't you multiply the suspension travel by the sag percentage i.e. 160mm X 0.3 = 48mm and subtract this value from the BB height to give 304mm. This assumes that the travel is vertical wheras for the front shock with a 67 deg head angle, the sag will be closer to 44mm. I donít know what the axle path is like for the rear.

    Cheers
    Roger

  9. #9
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    Yeah..what he said.....

  10. #10
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    Quote Originally Posted by doismellbacon
    Yeah..what he said.....
    Thanks Roger. Duh! (Fixed)
    Last edited by derby; 09-08-2010 at 07:37 AM.

  11. #11
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    I'm currently running 2.4 mutano raptors on my Mojo and have been considering trying a 650b wheelset. From Derby's comments, there is only about 3/8" of a difference in diameter between the two setups (based on a 2.3 Neo-moto 650b tire) . Is 3/8" difference in diameter really going to feel that much different and be worth the change?

  12. #12
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    I can't speak to those tires, but I went from a 26" Nevegal 2.35 to 650B Nevegal 2.35, and the difference was quite noticeable.

  13. #13
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    Quote Originally Posted by doismellbacon
    I can't speak to those tires, but I went from a 26" Nevegal 2.35 to 650B Nevegal 2.35, and the difference was quite noticeable.
    It's been over 2.5 years since I went to 650b and measured my old mutanoraptor 2.4 against the 650b neomoto 2.3. It may have been 5/8 inch difference, either way not a lot of difference. The ride feel is different, less side wall flex and wallow with lower pressure slower trail conditions, and the neo-moto 2.3 rolls very easily with a big step up in corner grip.

    I tried going back to my 26 inch mutanoraptors for a ride and it just felt harsh and slow rolling in comparison. When demoing bikes I always must remember the 26 wheeled rolling feel is not as smooth as I've become used to.

  14. #14
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    HD 160/160 W/650b/650b

    a. I don't know what "plus 1" 650b conversion means.

    b. I just posted a question about HD 650b before I saw this thread.

    --So it sounds like 650b on the rear of HD 160 does NOT require a modification to RP23 shock?

    I was thinking of HD 160/160 with 650b front and 26 rear, but it sounds like now I can go with 650b front AND rear?

    I'll be building a Small HD 160 with a Talas 160/32; I ride mostly XC/AM technical singletrack, from the roots and rocks of NH, to National on South Mountain in Phoenix, to Mr. Toad's in Tahoe, etc.; I travel a lot and cannot bring another wheelset.... I've been riding my classic Mojo for 4.3 years, and the past 8 months I've loved the 650b front/26 rear with 150/32 Talas fork. I ride Nevegal 2.35's.

    Which would be the best for me:

    1. 26 f / 26 r

    2. 650b f / 26 r

    3. 650b f / 650b r

    ? I know this is a difficult question, but I'm struggling here as I prepare to build my HD 160, but thanks in advance!

  15. #15
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    You guys make things so complicated with this 650b thing....but all the more power to ya!

  16. #16
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    maybe .. but once it's on the trail the complication stops and it's pure joy... I guess someone has to break new ground. I can't wait 10 or 20 years for this to be figured out!

  17. #17
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    Quote Originally Posted by rshalit
    a. I don't know what "plus 1" 650b conversion means.

    b. I just posted a question about HD 650b before I saw this thread.

    --So it sounds like 650b on the rear of HD 160 does NOT require a modification to RP23 shock?

    I was thinking of HD 160/160 with 650b front and 26 rear, but it sounds like now I can go with 650b front AND rear?

    I'll be building a Small HD 160 with a Talas 160/32; I ride mostly XC/AM technical singletrack, from the roots and rocks of NH, to National on South Mountain in Phoenix, to Mr. Toad's in Tahoe, etc.; I travel a lot and cannot bring another wheelset.... I've been riding my classic Mojo for 4.3 years, and the past 8 months I've loved the 650b front/26 rear with 150/32 Talas fork. I ride Nevegal 2.35's.

    Which would be the best for me:

    1. 26 f / 26 r

    2. 650b f / 26 r

    3. 650b f / 650b r

    ? I know this is a difficult question, but I'm struggling here as I prepare to build my HD 160, but thanks in advance!
    It's a no brainer! For wet NH roots 650-b front 26 rear.You need some mud clearance for the rear.You'll love your HD it's an amazing bike.Are you going tubeless so you can run low pressure? Nothing like floating up a slick rooty trail on 17 psi.

  18. #18
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    17psi? Really??? I don't think I could pull that off in Austin... I bet it is smooth and grippy on the climbs though. What tires are you running at those pressures?

    For what it's worth (I have not ridden the HD yet... local Ibis dealer isn't stocking them ) I'd vote for 140 mode, 650b front and rear for your main rocky singletrack riding.

  19. #19
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    Quote Originally Posted by doismellbacon
    17psi? Really??? I don't think I could pull that off in Austin... I bet it is smooth and grippy on the climbs though. What tires are you running at those pressures?

    For what it's worth (I have not ridden the HD yet... local Ibis dealer isn't stocking them ) I'd vote for 140 mode, 650b front and rear for your main rocky singletrack riding.
    Nevegal single ply 2.5. That was when I lived on Maui.The Redwoods trail was
    steep & very eroded, all roots.I'm in Norcal now so no need for extreme low pressure.The sandy mud has more grip.
    I still think 650-b with 2.3 wouldn't have enough mud clearance on the rear.

  20. #20
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    Yeah, maybe... not much mud riding around here... our trails are highly susceptible to damage when it's wet, so everybody who's not a ****** stays off when it's really muddy...thankfully, that's not very often.

  21. #21
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    So what is the difference in BB height of the Mojo HD 160 vs. 140? I am thinking that the Mojo HD in the 140 configuration and 650b front/650b rear and a 140 fork should yield similar angles and bb height to the stock 26' version of the Mojo SL/140 fork , right?

  22. #22
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    Quote Originally Posted by buggymancan
    So what is the difference in BB height of the Mojo HD 160 vs. 140? I am thinking that the Mojo HD in the 140 configuration and 650b front/650b rear and a 140 fork should yield similar angles and bb height to the stock 26' version of the Mojo SL/140 fork , right?
    Yeah, that's what it looks like based on early reports, but with a 1 degree slacker head angle and better clearance.... BOMBER.... Seems like the ultimate do anything setup. I can't believe nobody's tried it yet. I've been trying to save some $ for this purpose, but I broke my standard Mojo and took Ibis up on an awesome crash replacement deal, so my HD140/650b nest egg went for a new SL frame that I'll run 650f/26r....still gonna be sweet!

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