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  1. #1
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    2011 leftys: How to lengthen a 120 to 140?

    I heard this involved some internal parts. Anyone know what's involved, and how much it would cost? Is this a DIY job?

    Akin to the question. If you had a 2011 stock lefty 29 fork, could you increase the travel to 110mm, from 90mm?

    Thanks

  2. #2
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    It all depends on the setup. If it started off as a 140 and was reduced to a 120 it's pretty simple to remove the spacers. Same goes for 110 from 90. If it's a 120 and hasn't been reduced I think it'll be a PITA if it's possible at all.

    The air volume spacer will require tools. It's not hard, short of waiting for the LBS to order the tools for you. I'm in the Bay Area as well, so I can loan you tools and or give you a hand with it some night.

    Finally, when changing the air volume spacer it's a good time to change out the negative spring if needed. No one stocks them locally (sometimes I wish I still lived in Rochester), but they can order them for you.
    My bicycle gets more dirt than your 4x4.

  3. #3
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    Craig mentioned that the 2011 120 and 140 were very similar and a few parts inside changes them back and forth. I just don't know what, and how to do it.

  4. #4
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    Can't help with that, sorry.
    My bicycle gets more dirt than your 4x4.

  5. #5
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    Dug into it further, and it looks like if you're starting out with a 2011 PBR/XLR 29er fork, you need a shorter upper air seal. Seems like the difference between a 140 and a 120/29er is -19mm in seal length.
    A 29er fork also has a 60mm volume reducer that the 140 max does not. I then wonder if you increase the travel on the 29er fork from 90mm to 110mm, you'll need to reduce the length of the volume reducer as well, say down to ~40mm or less.

  6. #6
    mnt bike laws of physics
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    You're on to something rensho

    Yes, you are correct. The two tools you will need are the Castle Tool to remove the cartridge and the 0.500" shaft clamps (which Cdale sells) to remove the Solo Air assembly. You will not have to buy a new smaller Upper Air seal buy you can if you want. I ordered the Lefty Max, buy Cdale sent the 29er Lefty instead. I didn't feel like waiting so I used a pipe cutting tool that plumbers use to cut copper tubing to cut the Upper Air seal down to 45mm. Now this is 4mm shorter than the Lefty Max so I get about 124mm of travel on my Tallboy ( I use (2)10mm C-clip spacers to reduce the travel by 20mm). No worries as I have been riding the hell out of it and raced it this past weekend for 26 miles in El rocky Paso Texas and finished 10 minutes behind the top pros.
    I recommend using a CC Thudbuster elastomer for an air volume reducer. It has worked perfectly and it also fits perfectly inside the chamber. I could measure one for you if you want or even send you one as I have an extra. If you weigh as much as me or more (I am 185#) I also recommend changing out the oil from 5 to 7.5 weight while you have the cart out as that makes a huge difference. The stock oil was definitely too thin and the compression was way too fast in stock from. I used Golden Spectro which Cdale also uses.

  7. #7
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    That's really great info Yogi, thanks!

    I was wondering if that upper seal could simply be cut.

    On the volume reducers, are you just cutting donuts from the elastomers and dropping them in there?

    I'm 155lbs.

  8. #8
    All Lefty's, all the time Moderator
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    Quote Originally Posted by rensho
    I was wondering if that upper seal could simply be cut.

    On the volume reducers, are you just cutting donuts from the elastomers and dropping them in there?.
    Yep, you can cut it down, works just fine. The 120 fork contains the same damper as the 140.

    You can do the elastomer trick, but Cannondale now offers tuning "pucks" that drop into the bottom of the fork.

    Yes, volume compensation must be commensurate with travel changes, if that makes sense....
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  9. #9
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    Quote Originally Posted by yogiprophet
    Mendon, I've heard something about an adjustable air volume reducer from Cannondale. Could you elaborate on that? What sizes are they and part # etc.
    Haven't heard of anything like that. Could they be referring to the Solo Air's ability to self adjust?
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  10. #10
    mnt bike laws of physics
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    Quote Originally Posted by MendonCycleSmith
    Yep, you can cut it down, works just fine. The 120 fork contains the same damper as the 140.

    You can do the elastomer trick, but Cannondale now offers tuning "pucks" that drop into the bottom of the fork.

    Yes, volume compensation must be commensurate with travel changes, if that makes sense....
    Mendon, I've heard something about an adjustable air volume reducer from Cannondale. Could you elaborate on that? What sizes are they and part # etc.

  11. #11
    mnt bike laws of physics
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    I was talking about the "tuning pucks" you mentioned about. Isn't that a way to fine tune the air volume of the main air chamber?

  12. #12
    All Lefty's, all the time Moderator
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    Quote Originally Posted by yogiprophet
    I was talking about the "tuning pucks" you mentioned about. Isn't that a way to fine tune the air volume of the main air chamber?
    Yep, exactly, and they come in a few thicknesses to mix and match...
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  13. #13
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    Is this conversion only possible for the 2011 Lefty, or can I do the same for my 2010 Lefty PBR?

  14. #14
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    Quote Originally Posted by tmg49
    Is this conversion only possible for the 2011 Lefty, or can I do the same for my 2010 Lefty PBR?
    Yep, the top air seal's throat needs to be shortened, or swapped out to the 140 version.
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  15. #15
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    Quote Originally Posted by MendonCycleSmith
    Yep, you can cut it down, works just fine. The 120 fork contains the same damper as the 140.

    You can do the elastomer trick, but Cannondale now offers tuning "pucks" that drop into the bottom of the fork.

    Yes, volume compensation must be commensurate with travel changes, if that makes sense....
    Thank you for jumping in with all your invaluable Lefty knowledge.

    I'm going to undertake this Lefty mod at the end of the week.

    Seems like I need to do 2 things.

    Reduce the top seal length by ~20mm.

    Remove or replace the volume reducers by xx? What are the thicknesses of those tuning pucks you're referring to? Do I remove the reducer that is stock in the 29er, and put in these pucks?
    Is there a way to shorten the current reducer? If so, what range?

  16. #16
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    I'm VERY interested in this, I've got a 2010 Lefty Ultra 120 PBR & would be very interested if the same could be applied to this also.

    I'm also working on the logistics of turning my RZ120 into a 140, from what i can see all I'd need is a new linkage off the 140 plus a 200x50 shock instead of the 185x45 currently since teh swingarms are identical as to are the frame fittings, etc.

    Anyone done this or got any reason why it's doomed to failure??

  17. #17
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    And people told me that you cannot change the fork length (and travel) of a Lefty fork. Thanks for the info. One question remains, what happens when you don't change the air volume reducers when you go from 120 to 140mm?

  18. #18
    mnt bike laws of physics
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    info

    You cannot cut the 60mm air reducer that comes in the 29er. That would render it useless. The Air Tune Kit comes with a 25mm, a 10mm and (2) 5mm sizes. I think the part # is KH076 but I will check to make sure tomorrow.

    When you increase the travel, you increasing the air chamber by the same amount. If you were to keep the 60mm air chamber reducer in there it would work but now you are compressing more air (since the chamber is bigger) so it would be more difficult to attain full travel although you will still have more travel than before. If you are lighter and therefore use less air pressure, you may try and keep the 60mm spacer in there and give it a go.

    Edit: Part number confirmed - so the tune kit comes with a total of 45mm of spacers. They are just plastic pieces which slide in and have a hole through the middle to let air through.
    Last edited by yogiprophet; 03-29-2011 at 08:11 AM.

  19. #19
    All Lefty's, all the time Moderator
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    Quote Originally Posted by yogiprophet
    You cannot cut the 60mm air reducer that comes in the 29er. That would render it useless. The Air Tune Kit comes with a 25mm, a 10mm and a 5mm size so I am told. I think the part # is KH076 but I will check to make sure tomorrow.

    When you increase the travel, you increasing the air chamber by the same amount. If you were to keep the 60mm air chamber reducer in there it would work but now you are compressing more air (since the chamber is bigger) so it would be more difficult to attain full travel although you will still have more travel than before. If you are lighter and therefore use less air pressure, you may try and keep the 60mm spacer in there and give it a go.
    I think there's several things being talked about here. The 60mm volume reducer is a dog bone shaped thing, which no, you do not and should not cut.

    The Air tune kit you refer to, (the pucks) has nothing to do with the other volume reducer, it's a further reduction on top of what's already been reduced, should a rider want a more progressive spring rate.

    The cutting that I am referring to is the air piston, which is on the damper shaft, at the top of the stack of guts, on the lower end of the damper.

    If you were addressing something else, all good, but I can see this turning into a frenzy of folks cutting the wrong thing, part of why Cannondale doesn't allow this info out of the barn really, too many cut happy people, too little true understanding of the consequences
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  20. #20
    All Lefty's, all the time Moderator
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    Quote Originally Posted by zonoskar
    And people told me that you cannot change the fork length (and travel) of a Lefty fork. Thanks for the info. One question remains, what happens when you don't change the air volume reducers when you go from 120 to 140mm?
    You can't. This is the first and only fork that present this option. No other forks can this be done to.

    If you don't correct the volume reduction, you'll find the fork to be too squishy, it will wallow in the travel.

    Also know that if you attempt this, you'll need some proper tools, and, do some research on getting into the damper, know it can be a delicate thing, and that one slip of a wrench will cost you around $260.....
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



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  21. #21
    All Lefty's, all the time Moderator
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    Quote Originally Posted by rensho
    Remove or replace the volume reducers by xx? What are the thicknesses of those tuning pucks you're referring to? Do I remove the reducer that is stock in the 29er, and put in these pucks?
    Is there a way to shorten the current reducer? If so, what range?
    If the fork was already set up for 29, it should have the properly resized volume reducers installed, but by taking it to 140 from 120, it will be too long by 20mm.

    The issue if you want to call it one, is that the volume reducers are not available on their own, the tuning pucks are, but not the VR's. So, you need to buy a $40 kit, and not use most of it's contents. Just kind of along way 'round the barn, that's all.
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



    www.mendoncyclesmith.com

  22. #22
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    watch out on that 29er fork!

    If you increase the travel simply by removing spacers that taller 29 in. wheel will contact the crown at full compression and send you on an unplanned trip into the dirt.
    for the 29er it may not ever be (safely) possible to increase travel.

  23. #23
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    Does above mentioned 140 Max Conversion trick work for both Alloy and Carbon 120's? They have the same internals, right?

    Thanks in advance.

  24. #24
    All Lefty's, all the time Moderator
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    Quote Originally Posted by Kosmonooit
    Does above mentioned 140 Max Conversion trick work for both Alloy and Carbon 120's? They have the same internals, right?

    Thanks in advance.
    Assuming they are 2010 or 2011, and both started life as 120's, yes, they are the same internally.
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



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  25. #25
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    New question here.

    Quote Originally Posted by MendonCycleSmith
    Assuming they are 2010 or 2011, and both started life as 120's, yes, they are the same internally.
    Just got my new Lefty Ultra to replace damaged Speed DLR2. I've been looking at these Owners Manual Supplements & with the 2010 120 it shows the same upper air seal 35mm! See here:
    2010 Lefty Max page 33

    2010 Lefty Ultra page 16

    but in the 2011 it has the 49mm on the 140 & 68mm on the 120
    2011 Lefty OMS page 28/29.

    So if that's correct you how can you shorten the upper air seal on the 120 to make it a 140?? Or is the 2010 OMS showing the wrong diagram on the 120 damper?

    Bit confused, don't want to go to the expense of buying the castle tool, shaft clamps, etc. if it can't be done.

    Cheers guys.

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