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  1. #1
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    New question here. Pls. Contribute:Lefty 29er Specs and 26er conversion info thread

    From reading I'm not the only one looking for info here, there doesn't seem to be anyhow to resource forthe growing 29er movement.

    Also I think more people, not necessarily with a 'Dale frame, are looking to use a lefty so key geo info is very important, particularly for custom frames.

    Project321 have some great products and info.
    Blackcatbone bikes also.

    So this thread is for anyone looking to use a 29er lefty on a non 'Dale bike or convert a 26er Max to run as a 29er.

    Some of the info i'm looking to get on here is:
    A2C measurements
    Offset info
    Travel reduction info incl. How much it has to be reduced by on non 29er specific lefty's

    Hopefully this can be a resource that will result in some de-mystifying and wider use of this great fork.

    Be great to see examples of bikes that have been converted and their specs.

    Be great if this could be a? sticky
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  2. #2
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    When adding limiting spacers on a Lefty it does not change the A to C....

    When converting 26er to 29er 30mm spacing is advised, but others (including me) have used less - you need to check tire clearence after you add the spacers on the damper shaft.

    The air volume needs to be reduced, also using a conversion part. This allows the air pressure to ramp up properly with the shorter travel.

    As for axle to crown, this was posted by Mendon CycleSmith:

    A to C for all Leftys (vintage not relevant), 100mm fork- 480, 110 fork- 490, 120 fork- 500, 130 fork- 510, 140 fork- 520. 137 mm space between the clamps, be sure to consider stack height of headset when planning HT length

    This is a good thread of converted bikes: Leftified NON-Cannondale bikes - post your pic's!
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  3. #3
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    Thanks for that very helpful for conversion.

    Let's also hope some of the 29er fork specs come along if any different , or just factory travel adjusted?

    I'm especially interested in any 2012 xlr specs.

    Also are offsets the same on all lefty's 29ers And 26 forks.

    26ers are 45mm aren't they? In comparison g2 geometry is 51mm to reduce the trail on 29ers.

    In some ways it's a shame the clamps are bonded now or it would be possible to produce increased offset clamps for 29ers?
    Aka chainline...

  4. #4
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    29er lefty in 26er frame?

    What about the other way around: Can I use a 29er 90mm Lefty PBR in a 26er frame? Would it keep being 90mm travel in that case?

  5. #5
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    I have the same question about converting a 29er lefty to a 26er.

  6. #6
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    Quote Originally Posted by CactusJackSlade View Post

    A to C for all Leftys (vintage not relevant), 100mm fork- 480, 110 fork- 490, 120 fork- 500, 130 fork- 510, 140 fork- 520.
    My two 100mm PBR Leftys measure 470mm a-to-c. They both measured 480mm a-to-c when they were 110mm DLRs. Basically I think your measurements are 10mm off..

    I can add this:

    For 2012 and earlier Leftys there are no internal differences between 29er and 26er versions aside from 30mm of clip-on "spacers" that cause the Lefty to bottom out earlier. For 2012 and earlier Leftys, any 29er labeled Lefty can be used on a 26er by removing those spacers to get more travel. Likewise any 26er labeled Lefty can be used on a 29er by adding those spacers.

    Some examples:
    • a 100mm 26er Lefty (470mm A-to-C) can be used on a 29er by adding 30mm of spacers to make a 70mm Lefty (470mm A-to-C)
    • a 120mm 26er Lefty (490mm A-to-C) can be used on a 29er by adding 30mm of spacers to make a 90mm Lefty (490mm A-to-C)
    • a 90mm 29er Lefty (490mm A-to-C) can be used on a 26er by removing 30mm of spacers to make a 120mm Lefty (490mm A-to-C)
    • a 140mm 26er Lefty (510mm A-to-C) can be used on a 29er by adding 30mm of spacers to make a 110mm Lefty (510mm A-to-C)


    When using a Lefty on a non-Cannondale frame, the important number to consider is Axle-to-Crown. The A-to-C your frame's geometry requires determines which Lefty (100m, 120mm, 140mm) you'll need to get.

    My friend recently got a Lefty to use on his Jabberwocky singlespeed. The bike originally came with a Reba set to 80mm. He wants to maintain the same handling and feel with the Lefty so he first looked up the A-to-C of the Reba@80mm, which is 486mm. Knowing that he needs to stay at or around 486mm showed him that he needed to get a 120mm Lefty (490mm A-to-C) and install 3 spacers to limit the travel to 90mm. The 4mm extra A-to-C shouldn't be too noticeable.


    Now for the big word of warning: None of this is true for 2013+ "Hybrid" Leftys.

    P.S. People that are much more familiar with Lefty internals have made some non-standard travel/A-to-C options, i.e. 100mm / 500mm A-to-C Lefty for a 29er. Though this is definitely doable, it isn't easy and a botched attempt could quickly ruin your expensive Lefty.
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  7. #7
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    Quote Originally Posted by egoncalves View Post
    What about the other way around: Can I use a 29er 90mm Lefty PBR in a 26er frame? Would it keep being 90mm travel in that case?
    As long as the fork is a 2012 or older, you have the ability to remove the 30mm spacer stack, and gain 30mm of travel without changing the axle to crown. I don't think this is possible with the 2013 forks. For sure though, you could install the 29er Lefty on your bike and use it as-is - there will be no change in the axle to crown or in the travel; instead, the fork will just be longer axle-to-crown than the equivalent travel 26" version of the fork.

  8. #8
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    Quote Originally Posted by ohpossum View Post
    My two 100mm PBR Leftys measure 470mm a-to-c. They both measured 480mm a-to-c when they were 110mm DLRs. Basically I think your measurements are 10mm off.
    I'm curious as to how you measure these numbers. I tried measuring the AtoC of my Lefty Max 140 using a measuring tape (definitely not the most accurate way). Since the fork is installed on my bike, I measured from the center of the axle bolt to the bottom of the head tube, trying to keep measuring tape parallel with the fork. The measurement I got there was 20.375", which is about 517mm. The kicker here is that I haven't performed a bearing reset all season - there's probably more than 1000 pretty hard miles on that fork, so I would guess that it isn't fully extended anymore. Am I not measuring this correctly?

    Incidentally, while I believe it shouldn't matter, my Lefty was converted to a 29er with 30mm of spacers.

  9. #9
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    Quote Originally Posted by TurnerConvert View Post
    I'm curious as to how you measure these numbers. I tried measuring the AtoC of my Lefty Max 140 using a measuring tape (definitely not the most accurate way). Since the fork is installed on my bike, I measured from the center of the axle bolt to the bottom of the head tube, trying to keep measuring tape parallel with the fork. The measurement I got there was 20.375", which is about 517mm. The kicker here is that I haven't performed a bearing reset all season - there's probably more than 1000 pretty hard miles on that fork, so I would guess that it isn't fully extended anymore. Am I not measuring this correctly?

    Incidentally, while I believe it shouldn't matter, my Lefty was converted to a 29er with 30mm of spacers.
    Measure from the center of the axle to the top of the lower clamp. Without knowing what frame you have I can't say if you've accidentally added the hight of your lower headset to your AtoC measurement.
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  10. #10
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    Quote Originally Posted by ohpossum View Post
    Now for the big word of warning: None of this is true for 2013+ "Hybrid" Leftys.
    I thought the same would hold true for the 2013 Hybrid Lefty's. I know the a-c on the Hybrid Lefty's are slightly different but the basic spacer theory should be the same...right?

  11. #11
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    Quote Originally Posted by KtKona View Post
    I thought the same would hold true for the 2013 Hybrid Lefty's. I know the a-c on the Hybrid Lefty's are slightly different but the basic spacer theory should be the same...right?
    Not quite. In 2012 and older Lefties, the amount of travel is solely determined by the amount the damper can move. There is a rubber bottom out bumper below the damper's top cap that contacts the top of the damper cartridge at full compression. The Lefty won't compress any more once the bumper hits the top of the cart. Those spacers that are added to 29er versions make the bumper hit the top of the cart sooner in its travel. That makes sure the tire won't hit the lower crown and cause you to have a bad day.

    If you were to take the damper out of a 2012 or older 26er Ultra, and measured the distance between the top of the damper and the bottom out bumper, you'd get 120mm. If you added three 10mm spacers to the damper shaft, moving the bumper closer to the cartridge, you'd have a 90mm Lefty for 29ers.

    Now, with the new Hybrid Lefty's, the amount of travel is determined by two things: 1) the amount the damper can move, and 2) the length of the needle bearings. The needle bearings on a 2013 29er Lefty are longer than the 26er Lefty. At full compression (possibly at maximum, big-time "oh sh!t" full compression), not only has the damper's bottom out bumper contacted the top of the cart, but the bearings themselves have hit an internal stop inside the upper part of the Lefty. In fact, each time that happens, it resets the bearings to their proper location, hopefully solving the issue of bearing migration and losing travel/A-to-C.

    There's absolutely nothing to keep you from using whatever flavor of Lefty on whatever wheel size as long as you're happy with the A-to-C, but the concept of easily increasing or decreasing travel is gone...especially if you're looking to increase the travel.. The different needle bearing lengths means that to go from a 29er Lefty to a 26er Lefty will require taking the whole damn thing apart to install the shorter bearings.

    But wait! There's more! It should be possible to use a 26er Lefty on a 650b or 29er bike by snapping on the normal 1, 2 or 3 spacers but realizing that the "automatic bearing reset" stuff isn't going to work. You'd have to routinely remove the spacers and the wheel and compress the fork to reset the bearings. Wouldn't be any harder than what we have to do to reset the bearings on the 2012 and older Lefty's..well, except for having to take the wheel off.

    This pic shows one of each of the types of bearings installed. Green is a 29er bearing and white is a 26er.
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