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  1. #1
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    Bearing Migration

    I finally measured my lefty TPC (2005 model) last night and found it was short about +1". I never noticed any sounds or clunks or anything the only thing I noticed was the front tire seems to just "stick" into ground causing and endover situation. I called my friend who also has a lefty and his was 1.5-1.75" short. He took his apart and said it took considerable effort to bring it back into specification again. He hasn't ever check for bearing migration and has had the bike for about a year now. I have had mine for about 3 months. So my question, is there any chance of damage if you haven't realigned the bearing in a long time? He said that everything seems fine and smooth again but we aren't sure. Also, I am going to reset my left tonight, is there anything I should be aware of - you know the dos and don't of doing it? One more question my red rebound ajustment (the on the top of the lefty) got really hard to turn all of sudden and just seems to do nothing, is it broken or could this be part of the bearing migration realignment procedure.

  2. #2
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    Quote Originally Posted by mnbv1
    I finally measured my lefty TPC (2005 model) last night and found it was short about +1". I never noticed any sounds or clunks or anything the only thing I noticed was the front tire seems to just "stick" into ground causing and endover situation. I called my friend who also has a lefty and his was 1.5-1.75" short. He took his apart and said it took considerable effort to bring it back into specification again. He hasn't ever check for bearing migration and has had the bike for about a year now. I have had mine for about 3 months. So my question, is there any chance of damage if you haven't realigned the bearing in a long time? He said that everything seems fine and smooth again but we aren't sure. Also, I am going to reset my left tonight, is there anything I should be aware of - you know the dos and don't of doing it? One more question my red rebound ajustment (the on the top of the lefty) got really hard to turn all of sudden and just seems to do nothing, is it broken or could this be part of the bearing migration realignment procedure.
    You should turn the knob all the way clockwise (fully dampened) before reassembling the cap. This prevents damage to the plastic threads attached to the knob.

    I'd take the cap back off, grease the top of the assembly, and make sure the knob is turned all the way clockwise. Then place the cap on and make sure the knob is seated through the hole (not under the cap) before starting to engage the threads.

    Couple of other suggestions... make sure both the caps internal threads and forks external threads are clean and have a light coating of grease. If you get any resistance when tightening the cap, stop, don't force it. Back it off and reclean the threads and as stated above make sure the top of the knob is not hitting the bottom of the cap. The cap should screw down easily, if everything is aligned properly and your threads are gunked up.

    I had a few scares as the cap assembly stopped dead and felt like it was cross-threading only to find out it was hanging up on top of the knob. Now that I know this, I no longer have trouble reassembling the cap on the fork.

    Excessive bearing migration should not do anything to damage your fork...

    Ideally, C'dale (and Manitou) should figure out how to fix this design issue and retain the bearings in their seated positions.

    No matter how C'dale trys to put a spin on this as "normal", it's not normal. It design flaw in the Lefty.
    Last edited by MarkHL; 10-12-2005 at 06:39 PM.

  3. #3
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    Thanks for the help. I reset it last night, it was fairly simple to do. My red rebound knob is stuck and is still very hard to turn. It seems the threads on the red knob are screwed up as I can't unscrew it out of the nylon retainer. I guess this may be a job for my LBS or they may have to send it back to Cannondale to be fixed. I was quit surprised just how far my shock was really out. When I took the top cap off the spring came out about 1.5 inches. It seems to me that a shock that costs in the upper range of any shocks on the market shouldn't have a problem like this.

  4. #4
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    Some good suggestions above (they sound hard won). I will just back that up by saying that no damage will happen riding it that way, just reduced travel. If your rebound knob is hard to spin, it is most likely gunked up. Take the rebound knob off, small hole in the knobs' side, with a 2mm? allen in it, just crack it loose a turn or so, no need to remove the bolt. Gently pull the knob off, do this on a clean clutter free surface, as right underneath it, there are two little springs with ball bearings on top of them. They are not under tension, but may stick to the knob, and then hit the floor, unbeknowst to you. The balls create the notched feel by sitting in dimples on the underside of the cap. Clean the springs, ball, and cap, then regrease and reassemble. While you are at it, turn the silver shaft you just exposed, if it turns well, you will be fine, if it feels bad, you need a dealers attention, but this scenario is unlikely. As to migration reset, just follow the instructions found in your manual, or in the tech section of Cannondales website. They have made it very easy to do, with a minimum of tools and time. Do it twice, and you will be able to perform the whole procedure in about the same time as airing up both tires. As for a design "flaw", this is patently untrue, and a poor characterization. It is an inherent part of the design, and cannot be designed out, ever. They continue to improve the reset procedure,( no special Cannondale tools now, no trip to the shop, 3 minutes to complete) and do everything they can to minimize it, but it will never go away. Do you think a company would make 4 generations of a design(speaking Lefty only here, several more generations if you go back through the Headshock years), and continue to allow something that is a true flaw by definition? I think not. Statements such as this only serve to back up the irrational reservations some people have for the Lefty, and Cannondale in general. Reset, and ride on!

  5. #5
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    Quote Originally Posted by MendonCycleSmith
    Some good suggestions above (they sound hard won). I will just back that up by saying that no damage will happen riding it that way, just reduced travel. If your rebound knob is hard to spin, it is most likely gunked up. Take the rebound knob off, small hole in the knobs' side, with a 2mm? allen in it, just crack it loose a turn or so, no need to remove the bolt. Gently pull the knob off, do this on a clean clutter free surface, as right underneath it, there are two little springs with ball bearings on top of them. They are not under tension, but may stick to the knob, and then hit the floor, unbeknowst to you. The balls create the notched feel by sitting in dimples on the underside of the cap. Clean the springs, ball, and cap, then regrease and reassemble. While you are at it, turn the silver shaft you just exposed, if it turns well, you will be fine, if it feels bad, you need a dealers attention, but this scenario is unlikely. As to migration reset, just follow the instructions found in your manual, or in the tech section of Cannondales website. They have made it very easy to do, with a minimum of tools and time. Do it twice, and you will be able to perform the whole procedure in about the same time as airing up both tires. As for a design "flaw", this is patently untrue, and a poor characterization. It is an inherent part of the design, and cannot be designed out, ever. They continue to improve the reset procedure,( no special Cannondale tools now, no trip to the shop, 3 minutes to complete) and do everything they can to minimize it, but it will never go away. Do you think a company would make 4 generations of a design(speaking Lefty only here, several more generations if you go back through the Headshock years), and continue to allow something that is a true flaw by definition? I think not. Statements such as this only serve to back up the irrational reservations some people have for the Lefty, and Cannondale in general. Reset, and ride on!
    Bearing migration is a problem with the Lefty.
    No one decided to design a fork that gets shorter the harder you ride it.
    Last edited by MarkHL; 10-13-2005 at 05:58 AM.

  6. #6
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    Quote Originally Posted by MarkHL
    Bearing migration is a problem with the Lefty.
    Bearing migration is a problem with this bearing arangment no mater where it is used. Crossed roller and needle bearings have been used for close to 100yrs in industry and they have always and still do migrate. To this day it is still a phenomenon that can not be traced to any manufacturing defect or quality issue.

    However these bearings still have a number of features that make them desierable enough to use even if they need reset occasionally. And those are in no particular order, smotheness of travel, load capacity, economy, compact size and a few others i can't think of.

    This isn't much diffrent then saying that eveyone else in the fork industry makes forks that are defective because the bushings wear and need replaced. Can you belive that people would pay $2000 for a Durado MRD X-Works and the bushings still need replaces every season? It also takes a few hours to do and a few hundred dollars worth of special tools.

  7. #7
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    what huge difference to have that extra 1.5 inches back! My Prophet feels awesome again. Thanks for all of the help.

  8. #8
    All Lefty's, all the time Moderator
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    Quote Originally Posted by raelx
    Bearing migration is a problem with this bearing arangment no mater where it is used. Crossed roller and needle bearings have been used for close to 100yrs in industry and they have always and still do migrate. To this day it is still a phenomenon that can not be traced to any manufacturing defect or quality issue.

    However these bearings still have a number of features that make them desierable enough to use even if they need reset occasionally. And those are in no particular order, smotheness of travel, load capacity, economy, compact size and a few others i can't think of.

    This isn't much diffrent then saying that eveyone else in the fork industry makes forks that are defective because the bushings wear and need replaced. Can you belive that people would pay $2000 for a Durado MRD X-Works and the bushings still need replaces every season? It also takes a few hours to do and a few hundred dollars worth of special tools.
    Thank you! I am SO glad some else gets it! Lefty's rock!

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