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Discussion Starter · #1 · (Edited)
I am new to this so please bear with me. Why not just convert 29ers to 650Bs? Seems to solve tire rub issues. I have an older SC Blur "Classic", but just can't get it to work due to tire rub and that got me looking at my 29er hard tail and just wondering. I put the borrowed set of 650Bs and the 29er did just fine to me, obstacle rollover was better than the 26er and the tight, tech, single track was better than the 29er. (I did miss the full suspension.)

I know a 26" will be a lighter conversion and the bottom bracket will be lower, but what else am I failing to consider?
 

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BB clearance & wheelbase

pisgahrider said:
I am new to this so please bear with me. Why not just convert 29ers to 650Bs? Seems to solve tire rub issues. I have an older SC Blur "Classic", but just can't get it to work due to tire rub and that got me looking at my 29er hard tail and just wondering. I put the borrowed set of 650Bs and the 29er did just fine to me, obstacle rollover was better than the 26er and the tight, tech, single track was better than the 29er. (I did miss the full suspension.)

I know a 26" will be a lighter conversion and the bottom bracket will be lower, but what else am I failing to consider?
Putting b-wheels on a 29er will lower the bottom bracket by ~1". On most frames, this will result in lots of pedal strikes (pedals hitting obstacles), which are at minimum a power-robbing, flow-stopping PITA, and at worst will cause hard crashes. Also, 29ers tend to have a longer wheelbase, which to many riders isn't a good quality.
 

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If you have the frame and wheel set, there's no reason not to try it. The lower BB is the largest consideration. If your 29er has a high BB height, it would likely work fine.

I think that the reason that 29ers are converted less is because many people switch to 650b in order to get a larger wheel into the same space (on a 26er frame). If you have a 29er that already uses a big tire, what are you trying to accomplish with the smaller wheel: more standover, lower BB, etc.? On a 26er, or a frame specifically designed for 650b, there are more compelling reason to use the tire size.
 

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Discussion Starter · #4 ·
Second ride on a rockier, technical trail with the 29er with 650Bs.
The low bottom bracket is a big problem. But I do think it is a sweet spot of tire size for me.
This begs the question; what is the best choice of 26ers for a full suspension, light-ish XC 650B?
Any suggestions from you folks that have studied this?
 

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I wouldn't recommend it for 2 main reasons, lower bb height, and overly elongated wheelbase which directly affects handling and also compounds the lower bb height issue.

There are several good options in 26er FS frames that fit 650b, check out the 650b frame compatibility thread for some ideas there. Also consider running moto-x style with a 26" in back and a 650b up front, you get most of the benefits and still have all frame options open.
 

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My Mojo SL took a big step forward when I went 650b up front... I haven't gotten around to squeezing a 650b into the back yet, but it's been done with a minor shock mod. Derby has posted extensively on the subject.
While it's not really a "light XC bike", the Mojo HD 140 (which has a really low bb w/ 26" wheels) seems like the ultimate 650b trail / AM bike to me, and it's far from portly.... that's the top of my wish list anyway.
 

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pisgahrider said:
Second ride on a rockier, technical trail with the 29er with 650Bs.
The low bottom bracket is a big problem. But I do think it is a sweet spot of tire size for me.
This begs the question; what is the best choice of 26ers for a full suspension, light-ish XC 650B?
Any suggestions from you folks that have studied this?
Cannondale Rush, pre-2008, preferably. Or buy a genuine B'er from Ventana or Jamis!
 

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Go with a Scott Spark for 650b front/rear. Works fine and these days used full carbon Spark frames are not nearly as expensive as they used to be.
 

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Ventana

pisgahrider said:
Second ride on a rockier, technical trail with the 29er with 650Bs.
The low bottom bracket is a big problem. But I do think it is a sweet spot of tire size for me.
This begs the question; what is the best choice of 26ers for a full suspension, light-ish XC 650B?
Any suggestions from you folks that have studied this?
Try one of these:
http://www.ventanausa.com/frame_elchucho.html
 
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