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  1. #1
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    Building a 650B HD: 140 or 160?

    Greetings folks,

    I'm preparing to build a 650B Mojo HD to replace my (stolen) SL, and I'm having trouble deciding whether initially I should run the frame as an HD140 or HD160. I understand that I could always change my mind later, but I'd prefer to get it right the first time. So, I have some questions:

    1) I understand to run it as a 160 with 650B wheels, I'll need to shim the shock to keep the rear wheel from impacting the seat tube at bottom-out, which will result in something like 153ish mm of usable travel. So, given the reduced usable travel, is the difference between that and a 140 really noticeable?

    2) I've heard mixed things with respect to how the 140's geometry is different from the 160. Some sources say that the shorter eye-to-eye brings the swingarm in, lowers the BB, and steepens the HTA. Others have said the limbo chips compensate for this and that the measured geometry differences are only because a 150mm fork is used rather than a 160/180. Which is accurate? Forks being equal, is the geometry the same?

    3) Should I go 140, would the bike feel unbalanced with 170mm or 160mm in the front? I'm looking at the XF Vengeance specifically. Would 140mm in the rear limit the bike to the point where a 35/36mm platform would be excessive?

    4) I understand that Ibis has only sanctioned the 140 for 650B use due to the bottom-out issue, and theoretically running a 160 with 650B wheels voids any warranty. Given Ibis' spectacular customer service, though, a responsibly-shimmed shock, and assuming any issues are unrelated to the bigger wheels, would I really be out in the cold should the worst happen? Not that I expect problems, these bikes are damn durable, but no one ever "expects" to crack a chainstay or the like. Does anyone have relevant experience, or will Hans just say "Please don't do that."?

    For context, I spent the last year on a Mojo SL, built a bit AMish and 27.0-28.0lbs depending on tire choice. I expect this one to come in around 27-29lbs depending on fork/shock/wheels/dropper/tires. My local and daytrip rides are twisty, rooty, rocky Northeast singletrack (like Ellicotville, Rothrock, etc), and honestly I think I'd be happy with most any DW-link bike under 30lbs for that stuff. I love rocks (slow and fast, up and down), I don't really hit stuff bigger than 4' but I'm working on being more comfortable in the air, and I plan on doing maybe three lift-assisted weekends a year. I don't know where in the country I'll be living in a year, I intend to travel with the bike (Whiteface/Lake Placid, Seattle/BC area, CO Front Range, Fruita, Moab, Flagstaff, etc). I would also like to get into Enduro racing this coming year. This will be the only bike in my quiver for a while.

    Thanks in advance for any advice you can give me. And sorry for writing a bit of a book here.

  2. #2
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    Check out the 650b forum. There are a lot of HD riders that have converted their rides to 650b's using both fork options, some have tried both the 140 and 160mm. It may be nice to have 20mm extra in some conditions but a 140mm fork covers a broad spectrum, may feel more balanced overall, and keeps your warranty intact.

    I would start with the 140 + 650b. Have fun with the build.

  3. #3
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    Just run a 26" with a big tyre, it's exactly the same outer circumference and you get the bonus of better overall grip and comfort.

  4. #4
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    Quote Originally Posted by The Bike Chain View Post
    Just run a 26" with a big tyre, it's exactly the same outer circumference and you get the bonus of better overall grip and comfort.
    A 26x2.7 is nearly 27.5" wheel diameter. Every 26" wheel and tire 2.6" wide and smaller is less in circumference than a 27.5" diameter wheel and tire with 650b rims. The largest 2.5 tires that can clear an HD are 27.175 inch in wheel diameter and have more rolling resistance with a similar tread design than 650b. The rough rocky rooty trail rolling resistance is noticeably better with 650b.

    Regarding the OP's question, using 650b with HD160 or HD140:

    The HD140 is plug and play with 650b, and is the only bike option sanctioned by Ibis for 650b use. The HD160 requires careful custom modifications of shock travel to avoid dangerous seat tube contact with a 650b rear wheel.

    All years of HD140's clear 650b wheels with up to 2.3 tires, but get too tight in leaf and mud clearance with larger volume than 2.3.

    And the HD140 works fine with longer travel forks, I think many HD140 riders like a 150mm travel fork with the HD140, your bar height and seated fit can be adjusted forward for using a longer travel fork with 140mm rear travel to keep climbing well balanced without lifting the front end easily.

    The HD160 will not clear any 650b wheel and tire, unless bottom travel is custom limited to 140mm to 150mm travel, 1st or 2nd generation HD frames respectively.

    With the HD160 and 650b, shock shaft bottom out shims must be added to mechanically limit travel to avoid seat tube damage when approaching bottom-out travel. Shimming the shock is easy to do. The 1st generation HD160 frame with 8.5x2.5" shock requires 1/2 inch reduction in bottom travel using custom made shims (thin plastic split washers stacked to this thickness on the main damper shaft, coil or air), the 2nd generation (after August 2011 availability) requires 1/4 inch shaft bottom travel reduction.

    The only advantage using an HD160 for 650b requiring custom limited bottom travel, is swapping to a 26" rear wheel and removing the custom shock bottom travel shims to obtain full 160mm rear travel.

    I do this 650b/26" HD160 combo for DH park days with a 170mm travel fork to gain full rear travel, slack the frame geometry, and keep the frame low. For trail riding I shim my HD160 shock to limit travel for 650b because the larger rear wheel is an advantage when pedaling for reduced rolling resistance, but is a minor factor for rear wheels while descending.

    With the 2n'd generation HD140 frame I have fit a 2.25x7.875 Fox shock that cleared the seat tube with no custom travel limit shims with a 650bx2.3 rear tire. The 1st generation HD140 must us a 2.0x7.875 shock with 650b.

    With the same fork and wheel set, an HD160 has a 1/4 inch higher BB (unweighted) than an HD140.

  5. #5
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    I've had those exact questions too. Thanks for posting the question, and thanks for the great answers so far. Esp. derby, who's been a one-man 650b HD information clearinghouse for years now. +rep.

  6. #6
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    I would start with 140. And an Angleset personally.
    The issue in my mind of running 650 on a 26" bike is the high BB. The 140 w/ the Angleset helps offset this.

    I have a 26" HD140 and I haven't felt the bottom of the travel yet. And I've been riding it VERY aggressively.

  7. #7
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    Thanks for the input folks. I'm starting to consider this a sort of false dichotomy. I'm considering purchasing a 140 frame set, keeping the rp23, and also grabbing a more substantial 8.5x2.5 shock (vector air or monarch plus), and switching as the spirit moves me.

    Quote Originally Posted by buildyourown View Post
    I would start with 140. And an Angleset personally.
    The issue in my mind of running 650 on a 26" bike is the high BB. The 140 w/ the Angleset helps offset this.

    I like to run higher-than-average sag and play with the rocks. I'm actually looking forward to the higher BB, coming from an SL. Having options though wouldn't be a bad plan, though.

    Quick question on the angleset, can it be run as 0deg? Or would I need a second headset and have to swap cups?

  8. #8
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    Started on a 26 160 hd..changed to a 650b 160 hd.. Changed to a 140 650b hd.. And went back to the 160 hd 650b...i don't know how they do it, but the160 actually rides better then the 140.. I liked the extra rear travel which allowed me a bit more sag, and allows the shock to work better.. The 160 650b just felt right..

    Thinking about trying a angleset to take 1 degree out of the front.. Then it would be perfect..
    Last edited by SB Trails; 11-07-2012 at 04:25 AM.

  9. #9
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    Quote Originally Posted by SB Trails View Post
    Started on a 26 160 hd..changed to a 650b 160 hd.. Changed to a 140 650b hd.. And went back to the 160 hd 650b...i don't know how they do it, but the160 actually rides better then the 140.. I liked the extra rear travel which allowed me a bit more sag, and allows the shock to work better.. The 160 650b just felt right..

    Thinking about trying a angleset to take 1 degree out of the front.. Then it would be perfect..

    What have you been running up front during these changes?

  10. #10
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    Ran a talas 36/160... Which during all the changes to the bike,i also converted the talas to a float.. And from 160 to 150 while i was running the frame @140.. Pretty much tried every configuration i could to find what worked best..

  11. #11
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    Quote Originally Posted by derby View Post
    A 26x2.7 is nearly 27.5" wheel diameter. Every 26" wheel and tire 2.6" wide and smaller is less in circumference than a 27.5" diameter wheel and tire with 650b rims. The largest 2.5 tires that can clear an HD are 27.175 inch in wheel diameter and have more rolling resistance with a similar tread design than 650b. The rough rocky rooty trail rolling resistance is noticeably better with 650b.

    Regarding the OP's question, using 650b with HD160 or HD140:

    The HD140 is plug and play with 650b, and is the only bike option sanctioned by Ibis for 650b use. The HD160 requires careful custom modifications of shock travel to avoid dangerous seat tube contact with a 650b rear wheel.

    All years of HD140's clear 650b wheels with up to 2.3 tires, but get too tight in leaf and mud clearance with larger volume than 2.3.

    And the HD140 works fine with longer travel forks, I think many HD140 riders like a 150mm travel fork with the HD140, your bar height and seated fit can be adjusted forward for using a longer travel fork with 140mm rear travel to keep climbing well balanced without lifting the front end easily.

    The HD160 will not clear any 650b wheel and tire, unless bottom travel is custom limited to 140mm to 150mm travel, 1st or 2nd generation HD frames respectively.

    With the HD160 and 650b, shock shaft bottom out shims must be added to mechanically limit travel to avoid seat tube damage when approaching bottom-out travel. Shimming the shock is easy to do. The 1st generation HD160 frame with 8.5x2.5" shock requires 1/2 inch reduction in bottom travel using custom made shims (thin plastic split washers stacked to this thickness on the main damper shaft, coil or air), the 2nd generation (after August 2011 availability) requires 1/4 inch shaft bottom travel reduction.

    The only advantage using an HD160 for 650b requiring custom limited bottom travel, is swapping to a 26" rear wheel and removing the custom shock bottom travel shims to obtain full 160mm rear travel.

    I do this 650b/26" HD160 combo for DH park days with a 170mm travel fork to gain full rear travel, slack the frame geometry, and keep the frame low. For trail riding I shim my HD160 shock to limit travel for 650b because the larger rear wheel is an advantage when pedaling for reduced rolling resistance, but is a minor factor for rear wheels while descending.

    With the 2n'd generation HD140 frame I have fit a 2.25x7.875 Fox shock that cleared the seat tube with no custom travel limit shims with a 650bx2.3 rear tire. The 1st generation HD140 must us a 2.0x7.875 shock with 650b.

    With the same fork and wheel set, an HD160 has a 1/4 inch higher BB (unweighted) than an HD140.
    Wow, great write up. I'm playing with the idea of 160mm and 650b also. I like the travel and run my Monarch soft and plush. Is there any benefit to run 140 vs 160 besides lower BB height and not having to shim the shock?

    I'm pretty new to Ibis and the HD. Mine is a 2012 frame so is this 2nd gen? Is there a write up with pics on the shock shimming procedure? Anyone happen to have pics of the rear tire clearance with 160 and 140 set ups? This would be helpful. Big mahalos bruddahs.
    We Ride In God's Country!

  12. #12
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  13. #13
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    Go 160, the mods are really easy and it gives you more options, you can always go with offset bushings if needed. Derby is the best pay really close attention to whatever he writes he really knows his sh!t.

    Heres mine
    http://forums.mtbr.com/650b/mojo-hd-...ld-815365.html

  14. #14
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    If you want to go 160 then have a look at the new X-Fusion 34mm Slant fork. I think it has about the lowest A/C height for a 160mm fork @ 545mm (this link lists it at 170mm but it's really a 160 fork). It can also be lowered internally to 140mm. Me thinks this fork would be ideal for the Mojo HD

    X Fusion Shox - RL2R
    2013 Banshee Spitfire V2 650b

  15. #15
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    Quote Originally Posted by skidad View Post
    If you want to go 160 then have a look at the new X-Fusion 34mm Slant fork. I think it has about the lowest A/C height for a 160mm fork @ 545mm (this link lists it at 170mm but it's really a 160 fork). It can also be lowered internally to 140mm. Me thinks this fork would be ideal for the Mojo HD

    X Fusion Shox - RL2R
    I've been thinking the same thing.

  16. #16
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    So 545 is at what amount of travel? 170? So at 160 it would be 535- or 10mm less than fox 36 on my 160.

    I was just planning on reducing travel on my fork because I would not gain much by going to a 150 32. New fox 34 26" not enough clearance, and27.5 too high

    Most of the bellow info taken from another thread- I lost the link. Please feel free to complete chart

    2013 Fox 36/160 26": A2C=545.3mm, A2-Crown-Bottom=514mm
    2013 Fox 34/160 26": A2C=537.9mm, A2-Crown-Bottom=506.9mm
    2013 Fox 34/160 27.5": A2C=554.4mm, A2-Crown-Bottom=523.4mm
    2013 Fox 32/150 26": A2C=520.9, A2-Crown-Bottom=497.7mm
    2013 Fox 32/160 26" (hypothetical): A2C=530.9, A2-Crown_Bottom=507.7mm.
    RS revelation 32/150 27.5" a2c 539
    RS revelation 32/150 26" a2c 528

  17. #17
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    Quote Originally Posted by Bones2 View Post
    So 545 is at what amount of travel? 170? So at 160 it would be 535- or 10mm less than fox 36 on my 160.

    I was just planning on reducing travel on my fork because I would not gain much by going to a 150 32. New fox 34 26" not enough clearance, and27.5 too high

    Most of the bellow info taken from another thread- I lost the link. Please feel free to complete chart

    2013 Fox 36/160 26": A2C=545.3mm, A2-Crown-Bottom=514mm
    2013 Fox 34/160 26": A2C=537.9mm, A2-Crown-Bottom=506.9mm
    2013 Fox 34/160 27.5": A2C=554.4mm, A2-Crown-Bottom=523.4mm
    2013 Fox 32/150 26": A2C=520.9, A2-Crown-Bottom=497.7mm
    2013 Fox 32/160 26" (hypothetical): A2C=530.9, A2-Crown_Bottom=507.7mm.
    RS revelation 32/150 27.5" a2c 539
    RS revelation 32/150 26" a2c 528
    2013 X-Fusion Slant 34/160 26"/27.5" A/C 545
    The Slant is a 160mm fork NOT a 170. X-Fusion was supposed to fix that on their site. What is also kinda neat is they have a short travel version with a max travel of 130mm (internallt adjustable to shorter lengths) to save some weight with shorter stanchions.
    2013 Banshee Spitfire V2 650b

  18. #18
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    Spits the same a2c as the fox 36 I already have.

  19. #19
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    Quick HD v.1 versus v.2 question:
    I know in the revision they increased clearance at the seat-tube at bottom out, but did they also increase tire clearance at the chainstay/BB? In other words, are the v1 & v2 rear triangles the same (other than the dropouts of course)?

  20. #20
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    Quote Originally Posted by doismellbacon View Post
    I've been thinking the same thing.

    It WOULD be ideal for the HD 160 except for this thread is for the 650b Conversions and the Slant has to be shimmed to 150 if you are running it with 37.5 wheels.

    So I am better off staying with my 150 mm DT EXC 150. I was really hoping that this was going to be the perfect fork too.

  21. #21
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    Quote Originally Posted by Bones2 View Post
    2013 Fox 36/160 26": A2C=545.3mm, A2-Crown-Bottom=514mm
    2013 Fox 34/160 26": A2C=537.9mm, A2-Crown-Bottom=506.9mm
    2013 Fox 34/160 27.5": A2C=554.4mm, A2-Crown-Bottom=523.4mm
    2013 Fox 32/150 26": A2C=520.9, A2-Crown-Bottom=497.7mm
    2013 Fox 32/160 26" (hypothetical): A2C=530.9, A2-Crown_Bottom=507.7mm.
    RS revelation 32/150 27.5" a2c 539
    RS revelation 32/150 26" a2c 528
    According to this:
    2012 RS Lyrik RC2 DH 26" A2C 545 (160 travel) or 555 (170 travel)

    This is my fork, and I'm encouraged to see that it has an A2C that's equal to the Slant and Revelation 650b and not far from the Fox 34. I'm confused, though, because I read in this thread that no way Lyrik will fit a 2.35 HD or NN. And I assumed all the 650b-specific works will fit those tires. So something's not adding up.

  22. #22
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    Quote Originally Posted by cmarshack View Post
    It WOULD be ideal for the HD 160 except for this thread is for the 650b Conversions and the Slant has to be shimmed to 150 if you are running it with 37.5 wheels.

    So I am better off staying with my 150 mm DT EXC 150. I was really hoping that this was going to be the perfect fork too.
    Don't necessarily believe it so we will wait and see. X-Fusion also says their 140 Velvet fork needs to be shimmed to 130mm for 650B. It doesn't.

    No mention of the Slant needing a spacer anywhere on their site (Velvet does mention this) AND the Slant has an additional 6mm of A/C vs the Velvet if you were to lower the Slant to 140. My hunch, 650B tires will fit no issue @160
    2013 Banshee Spitfire V2 650b

  23. #23
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    That would be great!

    I am just going off of every release I have read and they all say something to the effect of:

    " The Slant is aimed at both 26 and 650B riders (adding a 10-millimeter travel-limiting spacer enables you to run the larger wheel size) and comes in a crazy-wide range of travel options from 80 millimeters to 160 millimeters."

    We will have to wait and see...

  24. #24
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    Quote Originally Posted by skidad View Post
    Don't necessarily believe it so we will wait and see. X-Fusion also says their 140 Velvet fork needs to be shimmed to 130mm for 650B. It doesn't.

    No mention of the Slant needing a spacer anywhere on their site (Velvet does mention this) AND the Slant has an additional 6mm of A/C vs the Velvet if you were to lower the Slant to 140. My hunch, 650B tires will fit no issue @160
    Got this back from x-fusion today:

    "Hey xxxx,

    Actually the Slant will not be 650b compatible. We will actually have a 650b specific Slant available as well. Slant will become available by late Jan. and Slant 650b will become available in late Feb.

    Cheers,"

    Looks like there will be two versions of the Slant. 26 only and 650b specific.

  25. #25
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    Jeeeez, that's a freaking curve no one saw coming.

    Bet it's A/C goes up 10mm. Be nice if they offered it with a 20mm axle
    2013 Banshee Spitfire V2 650b

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