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  1. #1
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    Magura Thor FCR troubleshooting help

    All,

    the Thor worked well when new, but recently it's been uncooperative. I'm trying to understand if that is just the way these forks are after some use. The main problem is that small bump compliance is abysmal when the fork is in the 140mm setting. If I shorten the travel it works much better, even if I just compress the fork about an inch and cycle the FCR lever. The travel adjust doesn't really work anymore either, it kinda reduces travel somewhat but inconsistent and it appears to be creeping back up when riding.

    Hence I wonder if there's something wrong with the FCR mechanism, but I haven't found a description of the internal workings. There is a picture in this thread here: http://forums.mtbr.com/showthread.ph...25#post5377025

    but it doesn't tell me how/where the valve mechanism works. I assume there is some magic happening inside the cartridge ? And how does the rod operate ? Can't tell from the picture of it is hollow and drilled like in the TALAS or does it physically turn/push something ?

    Basically I'm wondering if there should be some amount of negative spring in the longer setting to make the fork more supple, and that is somehow not working any longer.

    Thanks for any hints,

    C>

  2. #2
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    I am yet to install my Thor, but when you added air to it did you switch the FCR a few times while pumping it up? This will add air to the negative and positive chambers.

    Also it may be worth checking out Maguras forum for some other tips:

    http://www.support-english.magura.co...p?showforum=48

  3. #3
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    The Thor travel adjust works by transfering air from the positive to the negative spring when reducing travel. Hence it is plusher when lowered.
    As shiny said, when adding air, hold the travel lever down, cycle the fork a few times, add some more air, cycle the fork with the lever open again...and so on. Do this about every 20psi.
    Also, when adjusting the travel while riding, some lubrication oil gets past some seal or something and ends up near the bottom of the fork. This could be why you've lost some small bump performance. The trick here is to activate the travel lever and strap or tape it so it stays open. Then turn your bike upside down for a few hours or over night. This will allow the lube to get back to the top of the fork. A good idea, if you have hydraulic brakes, is to strap the levers to the bars (so the brakes are on) so air doesn't travel up the lines to the calipers when the bike is upside down.
    That Magura forum is quite good.

  4. #4
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    I found some info in the german language section of Magura's website that points in a similar direction as chrisem's suggestion. There's also some indication that Magura reduced the initial oil volume. In the end I opened the left stanchion cap, pulled it up about an inch so the "skewer" stays in the cartridge and added some 5ml of fork oil. Problem solved.

  5. #5
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    Interesting about the oil volume.
    Which problem did it fix? Small bump compliance or the travel problem, or both?

  6. #6
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    Both. I assume the oil creates a seal between the skewer and a tube inside the FCR cartridge. Without having seen the innards I guess there are strategically placed holes in the skewer that limit the function of the valve to a range of say 10mm to 40mm. So there is some negative air pressure at the long travel setting for small bump response, and higher pressure to reduce the travel up to 40mm. When that mechanism runs dry air seeps in between the chambers making the travel adjust iffy and there is no negative air spring function in the long travel setting.

    As for the oil volume, apparently there were too many complaints about the amount of oil coming out of the fork during the break-in phase. I have to say it looked pretty bad but it's fine now. It didn't reoccur after adding oil either.
    Last edited by csuder99; 06-06-2010 at 10:44 PM.

  7. #7
    Clyde
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    I love how linear the thor (2009) is through the full travel but I'm thinking that I would like a little ramp up progression at the end. Got pitched on a sketchy grade last week. I got into my front brake a little too much and paid the price. Does adding a little 3-5mm of 3 or 5 wt fluid to the air side take care of it. Any how-to links out there. There was a mountain bike action article on how to relube the seals but I can find it any longer. It showed you how to pull the lowers. Do you need to pull the lowers or can you add fluid to the top or bottom without going in that deep?

    I'm a 230 lbs clyde. Any recommendations on tuning the fork. Did what has Magura done to the fork for 2010 to better tune the fork. Did they go from a 5wt to a heavier weight fluid on the damper side. I read of tuning a Wotan by changing the fluild on the albert select from 5wt to 10wt. Sounds like that would slow the compression and rebound a bit which might be a nice adjustment for my weight since there is no other rebound control.

    There there any minor changes to the internals that make the 2010 better than previous years. thanks for you insight
    Last edited by LuckySomer; 06-12-2010 at 04:20 PM.
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  8. #8
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    i just picked up a lightly used 09 magura thor. i had the opportunity to buy one, and did as much research as i could before doing so - so i knew that setup would be bit finicky. spent some time on it yesterday morning and got out for a maiden ride in the afternoon. everything's great, but i can't seem to get the travel adjust to work at all.

    as per recommendations on this forum, i made sure to equalize pressure in both the negative and positive air chambers, which apparently is key to getting the fcr operating properly. but i couldn't get more than hint of reduction in travel.

    next i tried locking the fcr in the open position and inverting the fork, so that the necessary lubricating oil that had escaped would return to the upper seals/mechanism. still nothing.

    next step i supposed will be to open the fork up and check/add oil volume. if that doesn't help, it's off to our resident suspension expert.

    is there something i'm missing or haven't tried?

  9. #9
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    Quote Originally Posted by boomforeal
    i just picked up a lightly used 09 magura thor. i had the opportunity to buy one, and did as..........
    To confirm, turn the travel adjust, push down on the fork and then let go of the travel adjust, does the fork stay in the lowered position or not?

    If it doesn't or goes back to it's normal height I'd say it needs to be serviced.

    If you scroll down in the following link, there is a good video showing the travel adjust in action:

    http://www.gramslightbikes.com/2009/...or-review.html

  10. #10
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    Quote Originally Posted by shiny
    To confirm, turn the travel adjust, push down on the fork and then let go of the travel adjust, does the fork stay in the lowered position or not?
    correct - when i follow the procedure try to reduce travel, the fork just returns to full height.

    any idea what servicing the shock to repair this feature would entail?

  11. #11
    Clyde
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    my guess is it is low on oil if inverting with the FCR open over night doesn't address it.
    09 Ibis Mojo - All Mountain Moab Edition

  12. #12
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    yeah, pulling it apart to check and up the oil levels is the next step. i don't have anything heavy enough for the air chamber on hand, though - 20w is what i've been advised to use

  13. #13
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    Quote Originally Posted by boomforeal
    yeah, pulling it apart to check and up the oil levels is the next step. i don't have anything heavy enough for the air chamber on hand, though - 20w is what i've been advised to use
    You can use gear oil... it will be more difficult to make it return from the neg chamber though as it's more viscous.
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  14. #14
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    so i bought some 20w suspension oil from the moto store and finally got around to trying the fix suggested above. removed the top cap, unreaded the fcr unit and poured 5 cc's of oil in. replaced everything pumped it back up (making sure to equalize the pos and neg air pressures), tried to engage the fcr and... nothing. wtf!

  15. #15
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    i finally got my thor's travel adjust issues sorted out this evening thanks to some good advice - which having trolled the internet i can't find posted anywhere. so i figured i'd write it up for others who find themselves in a similar situation.

    so, to recap - fork was working fine but travel adjust was totally non-functional. i made sure that positive and negative air chambers were equally pressurized, tried to get the oil back into the top of the fork/fcr chamber to help, and finally opened the fcr chamber and added some oil: nothing worked

    what did work: i removed all of the air i could from the fork, positive and negative air chambers. then very carefully, with the fork held horizontal, loosed and removed the bolt from the bottom of the leg on the air-spring side. as soon as i removed the bolt a bunch of air was released - i reinstalled the bolt, inflated the shock and the fcr travel adjust works just fine!

    no idea why this worked but it did - would love to understand what the issue was, but i'm happy to have the fork back to full function

  16. #16
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    Quote Originally Posted by boomforeal
    what did work: i removed all of the air i could from the fork, positive and negative air chambers. then very carefully, with the fork held horizontal, loosed and removed the bolt from the bottom of the leg on the air-spring side. as soon as i removed the bolt a bunch of air was released - i reinstalled the bolt, inflated the shock and the fcr travel adjust works just fine!

    no idea why this worked but it did - would love to understand what the issue was, but i'm happy to have the fork back to full function
    Sounds like your air unit is leaking air into the lowers, though. Keep an eye on it.
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  17. #17
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    Quote Originally Posted by Warp
    Sounds like your air unit is leaking air into the lowers, though. Keep an eye on it.
    Good point. But man, way to piss in my cereal - I literally read that while having breakfast!

  18. #18
    "El Whatever"
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    Quote Originally Posted by boomforeal
    Good point. But man, way to piss in my cereal - I literally read that while having breakfast!
    In my defense I can only say that I posted 8hrs ago.

    Sorry, bro. I know how much it sucks.
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