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  1. #1
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    Ibis mojo HD 26 to 650B?

    I want to convert my mojo hd to 650b, i read a lot and i didnt really understand what i need to do.is it even possible? I have 160mm travel, so do i need to change the limbos to 140? And what does it says? That i will have 140 travel at the back? And at the front i can keep with 160mm travel? I dont really understand. Do i need to change my shock and fork? Currently at the rear fox float kashima and at front fox rlc 160mm
    Thanks..

  2. #2
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    Alright, 650b'd HD owner here, it's certainly possible and could be sweet depending on what you're looking for. A couple things to keep in mind. You will change the bike's geometry or travel in one way or another, depending on what you do. You will limit your tire selection in the rear, so anything larger than a 2.3 will probably be off-limits. So it really helps to know what your goals are before you go into it. As in, what kind of bike do you want in the end, how do you want it to ride, why are you converting, etc.

    There are three ways to go about converting the rear end:

    1. Keep your 8.5"x2.5" shock and 160 limbo chips. If you do this, you must limit the travel of the shock by opening the air can and installing a few millimeters of "shim" on the shaft to limit the shock's stroke. If you do not do this, the tire will impact the frame at the seat tube during bottom-out. You'll end up with 152-155mm of rear travel. The bike's angles will all be the same, but your bottom bracket will rise to 14"-14.4".

    2. Switch to a 7.875"x2.0" shock and 140 limbo chips. You'd need to buy a shock, but in this case you don't have to open the shock and shim it. If a tire fits in the rear triangle, you can use it. 140 mode with the same fork will slacken the bike's front end and lower the bottom bracket (compared to 160 mode). You'd end up with 0.5deg to 1deg smaller head tube angle and a BB height of 13.7"-14" depending on fork and tires. Remember the 140mm HD is really closer to 133mm or 135mm of travel, less than 140mm.

    3. Switch to a 7.875"x2.25" shock and 140 limbo chips. This is similar to option 2, but gives you more travel in the rear, 147mm-150mm. With a small-volume tire (Neo-Moto 2.3 and similar), you do not need to open the shock and limit the stroke at all. With a larger tire, you can hit the seat tube at bottom-out and would need a spacer in there, but only 1mm-1.5mm. Otherwise same geometry as option 2.

    In fact, most 7.875"x2.0" shocks, are really 7.875"x2.25" shocks with a spacer in them anyway. Some shocks just don't come in a 7.875"x2.0" configuration but do come in a 7.875"x2.25", so it's nice to be able to use them.

    Personally, I run option 3. I like that it slacks out the bike, and the BB height is manageable. Probably the best compromise. Just remember, you have to make a trade-off between BB height, travel, and tire clearance - physics makes it impossible to have all 3 in this frame with 650b wheels.

    I don't know whether your fork will handle bigger wheels - you may have clearance or not. The older Fox forks fit 650b great, dunno about newer ones.

    If you run 140 in the back, you can still run a 160mm fork in the front (assuming it can fit 650b wheels). It gets you a ~66deg HTA, which makes for a sweet descender. Or you could use a 150mm or 140mm fork, whatever you like. Depends on your goal for the bike and how you want it to feel.

    As far as the tire hitting the seat tube, it could potentially catastrophically destroy your frame. I don't think that frame failure's ever happened to anyone, and the tire shouldn't be able to apply more pressure than the tire pressure anyway, but that area was not engineered for that force. That said, what it WILL do is lock up your rear wheel as if you grabbed a fist of brakes. That when landing a big hit can be very dangerous. So whatever you do, make sure you're clear at bottom-out.

  3. #3
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    I'm going to resurect this thread. I know it's been discussed extensively on Derby's excellent thread, but I'd like to hear some long-term input from riders concerning this conversion. How'd it work out? Any catastrophic failures? Did you move on, look back, and think it was worth it? I'm curious because my riding bros are getting HD3s now, and 650+. 3 years on the HD, I don't feel like spending 5-7K on a new bike, I still love the HD, but I'm considering a few upgrades. The 2 I will wind up doing is rear shock and wheels I think. Thanks.
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  4. #4
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    Hey there, me again. I'm in my 4th year with a 650b'd HD. I'm still running it with 140mm chips and a 200x57mm shock. I like the setup a lot, but I'd really rather be on an HD3 if given the choice.

    My biggest complaint with my setup is the limited tire selection. I had a really hard time finding a tire that had good volume, beefy cornering knobs, and wasn't so tall that it hit the seatpost at bottom-out. I've settled on the Specialized Slaughter/Minion SS, because the low-profile center knobs give me the extra clearance. Most "real" 2.3" tires don't work well with my setup. There would be more options if you used a 50mm stroke shock like Ibis would like you to, or if you put spacers in the shock to limit the stroke.

    I've had no catastrophic frame failures. Some occasional tire rub, like from cornering knobs when leaning into a berm, has worn into the rear triangle a little. Enough to feel with a finger but not enough to concern me. I've also bottomed hard with a too-big tire, which locked my rear and skidded me out, but it just rubbed off some of the seat tube paint. Frame's in great shape (other than cosmetically).

    For me, it has been worth it, but only because the HD3 wasn't out in 2012. My next upgrade will be an HD3 frame with the boost/plus size swingarm, wide rims, and 2.5" Minion WTs. More tire clearence, longer top tube and shorter chainstays, lower bottom bracket, updated dw-link kinematics, etc

    For you, you might consider getting an HD3 frame and wheelset for 3-5k instead of a whole new bike for 5-7k. All your parts will move over, except wheels, headset lower cup, and possibly fork (can it clear 650b wheel/tires? Have you checked?).

    If you're sticking with your HD frame for a while, a shock upgrade is one of the biggest you can make, up there with wide carbon rims. I'm really happy with the Vector Air HLR, though the DBAir (not inline) and Float X2 are good choices too. If you convert your HD but think you might eventually be on an HD3, consider a 200mmx57mm shock, which is the correct size for the HD3. You could swap it over and keep from buying the same shock twice.

  5. #5
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    Thanks Lazarus,
    Great info. Really appreciate the advice. One of my longtime friends just upgraded to an HD3 sort of based on my love of my HD and all that's been written about it (which is extensive and mostly glowingly positive as I'm sure you know). It really is a great bike. He was strong before, and now it's amazing to see what he can do on that (he was coming off a 2006 Yeti ASX!! I think he droped 8-9 lbs with the new bike). As I said, I'm looking at wheels and rear shock. I do some pretty technical riding here in New England that can involve 5-6 ft drops to flat so I'd like to keep the 160 mm of travel. I have the Special Blend version, so I think upgrades would really make a big difference. If I were to do fork, rear shock, and wheels, I'd be in this bike for another 1600 - 2000, which could be worth it, but obviously a new HD3 would be ideal. I do tend to like bigger tires (ardent front, minion rear currently) so maybe I'l go with a rear shock first and see what that does for me. I'd like to try wide carbon rims too. New fork would also be nice. I'd most likely use the washer system in 160 mode if I pick up some 650s, but it's good to know about that shock size compatibility too.
    Did you try different rear shocks?
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  6. #6
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    Your profile says you're in Gloucester. That makes things easier.

    I upgraded my shock from the stock Float CTD because I was living in northern MA and riding Lowell-Dracut, Harold Parker, Lynn Woods, etc. The Float wouldn't stay composed on repeated ledgey rock hit, like rock waterfalls and stairs and such. It also didn't have a great deal of bottom-out support, so those drops to flat were... eh. I was looking for something more aggressive, with a piggyback and more compression adjustment.

    I switched to an X-Fusion Vector Air HLR, and was blown away by the improvement. Very good control, supple over small chatter, and easy to dial in the support you need. I went with the Vector based off several reviews here and elsewhere that were fantastic. This was right about the time the DBAir came out, and I considered it as well, but it was a bit untested at the time.

    As I understand it, the Special Blend came with an X-Fusion O2. To be clear, I didn't go with the Vector as a budget option - it was what I thought would be the best shock I could buy at the time. I didn't get the opportunity to try any other shocks before I bought, though. Nowadays you would look at the Float X2 and DBAir (not Inline), for sure.

  7. #7
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    Again, great info. I now live in Danvers, and my go to spots are Greenwood, Lynn Woods, and Willowdale when I want to get some miles in. I travel around NE with riding buddies and frequently hit other spots like Foxboro, Lincoln Woods, Borderland, and also ride with another group of friends down on the Cape, which tends to be multi-hour cross country hammerfests.

    After I posted yesterday I rode Greenwood and was just reminded how much I love the bike. I definitely need to have the shock and fork serviced. I actually like the X-Fusion 02, but I think the DBAir in particular might be a sweet upgrade. Based on resale value, or lack thereof, I'd keep the X-Fusion as a back up.
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  8. #8
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    Defintely avoid the Inline?
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  9. #9
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    I'll preface this by saying that I haven't owned either the DB Air or Inline. Demo'd and briefly played with both, but nothing long-term. Others might be better able to chime in, but this is what I know:

    The Inline doesn't have a reservoir, so it displaces less oil during compression. That on paper can make it more difficult to tune the damping circuits. In practice, from what I've heard from riders who have been on both the Inline and the DBAir, you get less consistency and the rear can feel less composed on the Inline. The smaller oil volume can also heat up more easily, so again less consistent damping from the beginning of a descent to the end (though I wouldn't consider that a problem in NE except for bike park days)

    The Inline had a lot of reliability issues the first year it was out, which may or may not be completely solved. I don't want to spread too much FUD here, so check out some other threads on the topic. In general, though, the miniaturization of the valving, and using a diaphragm to compensate for oil displacement rather than an IFP, don't do good things for reliability or service intervals.

    IMO the only downside to the DBAir over the Inline is weight, on the order of 150g. For a bike like the HD, I don't consider that to be significant, especially for sprung, non-rotating mass near the CG.

  10. #10
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    Found a Vector RC Air for a decent price. It looks to be vey simlar to the HLR without as many adjustments. I probably wouldn't need new mounting hardware either.
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  11. #11
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    Before you go piggyback - what is your frame's size?

    Both Vector coil and air won't fit into small frame, hardly clear medium (needs testing) and Ok in large.

  12. #12
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    Found a Vector RC Air for a decent price. It looks to be vey simlar to the HLR without as many adjustments. I probably wouldn't need new mounting hardware either.
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  13. #13
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    Anyone still riding this set up?
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  14. #14
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    Ia still on one but thinking of upgrading to hd3.

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