2019 Fox 36 Factory harshing my ride after air spring change- Mtbr.com
Results 1 to 18 of 18
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,212

    2019 Fox 36 Factory harshing my ride after air spring change

    I got a new bike and moved my 2019 Fox Factory fork over --my LBS swapped out the 160mm air spring for a 170. The fork now feels like the HSC is stuck shut. With everything set as before, I was getting only about 3 inches of travel and that was mostly from pumping the fork through bumps. I tried letting out about 15psi and got some improvement. Backed the HSC and LSC all the way out and got some improvement.

    I decided i would let all the air out test the damper but found even with 0 air it was difficult to get the last 2.5 inches of travel just by pushing on the fork. Put 50 PSI in the fork and continued experimenting

    Added 2 tokens in addition to the two that had always been there and that made it worse. Took all tokens out and got some relief but still not getting more than 4 inches of travel.

    Last tuning option was to play with LSR and HSR. Adding rebound damping helped some.

    The shop took it apart and cleaned out any grease that may have been obstructing the dimple that allows from pressure equalization between the positive and negative chambers

    What's the issue? I was convinced it was the damper but we didn't touch the damper and the air spring is acting funning even without air in it.

  2. #2
    Keep on Rockin...
    Reputation: Miker J's Avatar
    Join Date
    Nov 2003
    Posts
    6,151
    Doesn't sound like a damper issue. Sounds like too much air trapped where it shouldn't be. Something likely happened with the air spring install.

    Even with a damper set full on, with no air in the system you should be able to fully compress most forks.

    All that said, its been years since I've worked on a Fox fork.

    Good luck and let us know how it turns out.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    944
    Iím betting too much oil, probably in the lowers air spring side or maybe in the spring itself

    Undo the footnut and tap it loose, then try to compress. You will probably need to loosen it again once compressed as far as you can. Donít have the brake or wheel installed though in case of oil spray!

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    1,236
    Taking the spacers out is good as the longer fork will be more progressive. Let all the air out and cycle the fork. Make sure it feels smooth. If no one touched the dampener side then there shouldn't be any issue there.

    Sonetimes they poor a bit of fox gold ontop of the oil spring. Make sure there isn't too much. This will act like spacers.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Sep 2017
    Posts
    120
    I'm experiencing the same issue. At 160mm fork 29er was working great, bumped it up to 170mm and I've had nothing but problems. Airshaft has been replaced, new bushings, new CSU, still the same problem! The local suspension shop states, that from their experience it seems the 170mm have a hard time getting full travel, even with guys heavier than me. I've contacted Fox, and they seem baffled at the problem. They've said they've heard of this problem when everything being replaced.....it's a brand new fork.

    The local suspension shop is recommending that I go back to 160mm

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,212
    Quote Originally Posted by Graveltattoo View Post
    I'm experiencing the same issue. At 160mm fork 29er was working great, bumped it up to 170mm and I've had nothing but problems.
    Well that's bad news ...just dropped big money on a new fork for one of my other bikes

    I can honestly live without the other 10mm of travel but the bike was designed around a 170 fork so I guess I would run a spacer.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    95
    Hi glazedham, not sure if this helps, but this is a reply I got from a well know suspension company when I had the same issue a few years back..

    "As compared to the air spring side the compression ratio
    of the 180 system is enormous, it adds around 400 lbs to the air side at the
    last 1/2 inch of travel at 65 psi starting. This is about 20% more than the
    160 set-up for the same fork. This is why the coil forks work so much
    better with 180-200 mm set-ups."

    Cheers.

  8. #8
    Underskilled
    Reputation: CaveGiant's Avatar
    Join Date
    Aug 2007
    Posts
    4,271
    Well it's a bit of a strange offer, but here goes.

    I've designed a calculator for mapping air springs (specifically the 3 chamber dorado).

    If you give me a few details I can see what the curves come out like.

    Before I mapped mine it was linear until sag, softened then ramped up hard. I now know that if I set my fork from 200 to 180 and up the third air pressure I'm linear until 90% in to travel, then ramps up.

    I've not mapped any other forks yet, so if you are willing to strip the air spring and take some measurements we might both learn something!

  9. #9
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,212
    Quote Originally Posted by CaveGiant View Post
    Well it's a bit of a strange offer, but here goes.

    I've designed a calculator for mapping air springs (specifically the 3 chamber dorado).

    If you give me a few details I can see what the curves come out like.

    Before I mapped mine it was linear until sag, softened then ramped up hard. I now know that if I set my fork from 200 to 180 and up the third air pressure I'm linear until 90% in to travel, then ramps up.

    I've not mapped any other forks yet, so if you are willing to strip the air spring and take some measurements we might both learn something!
    Sure. I've got the stock Fox 160 air spring sitting here and can measure that easy. The 170 is in the fork which is at the shop but that's not too much of a challenge to access.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Sep 2017
    Posts
    120
    Just an update on my fork problem. I dropped my fork off at Fox, they agreed that it was not functioning properly. When he took it apart, apparently there was too much oil on the air side. They inspected everything else (which was fine), put the proper amount of oil back in. He says it working way better and they can get it through its travel now. Once I go for a ride, I'll confirm that it's functioning properly.
    So you might want to confirm your using the correct amount of oil in your lowers.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Dec 2007
    Posts
    6,793
    The shop added too much oil?

    Ummm, measuring the correct amount of oil is pretty elementary, esp when the specs are listed on the Fox website.

    This ^ is why I do my own stunt work.
    Guerilla Gravity Shred Dogg
    Fezzari Signal Peak (For Sale)
    Pivot Shuttle (wife's)

  12. #12
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    944
    It can be easy to overfill the lowers, it only takes a couple of extra cc's plus not cleaning out all the old oil to make a significant change to the progression created by the lowers

    It's amazing how often major fork problems are caused by elementary things
    www.thesuspensionlab.nz
    Servicing in Rotorua, NZ/Vorsprung Elite Tuning Centre/DVO service centre/Insta @thesuspensionlab

  13. #13
    Underskilled
    Reputation: CaveGiant's Avatar
    Join Date
    Aug 2007
    Posts
    4,271
    Cool.
    I'd need to the OD of the spring piston (probably about 32mm).
    The OD of the shaft (probably about 10 mm).
    The length of the spring chamber primary spring and secondary spring.
    Any spacers.
    How far in to the spring the equalisation point is.
    Finally anything weird (E.g. I think RS make the spring shaft hollow and add to the negative spring).

  14. #14
    Underskilled
    Reputation: CaveGiant's Avatar
    Join Date
    Aug 2007
    Posts
    4,271
    2019 Fox 36 Factory harshing my ride after air spring change-screenshot_20191130-190444_excel.jpg
    If I've uploaded the pictures in the right order, this is stuff for the calcs.

    2019 Fox 36 Factory harshing my ride after air spring change-screenshot_20191130-190424_excel.jpg

    This is with an undersized negative spring.

    2019 Fox 36 Factory harshing my ride after air spring change-screenshot_20191130-190317_excel.jpg

    This is with only a 2 chamber, not 3 chamber spring.

    2019 Fox 36 Factory harshing my ride after air spring change-screenshot_20191130-190008_excel.jpg

    This is Dorado 3 chamber spring. I've reduced travel from 200 to 180 (changes POS/neg spring ratio) and upped Tertiary spring pressure.

    P.s. This is a quick calculator, it should be reasonably accurate, but not perfect.

    P. P. S. The blue line is a 44lb/" coil spring with zero preload.
    Why would I care about 150g of bike weight, I just ate 400g of cookies while reading this?

  15. #15
    mtbr member
    Reputation:
    Join Date
    Sep 2017
    Posts
    120
    Quote Originally Posted by Nurse Ben View Post
    The shop added too much oil?

    Ummm, measuring the correct amount of oil is pretty elementary, esp when the specs are listed on the Fox website.

    This ^ is why I do my own stunt work.
    Another suspension shop apparently add too much oil.

    We'll see when I take it for a ride, I'm not super optimistic because I've been dealing with this for 8 months now! But if that was the problem, obviously I'll be happy, but disappointed that I had to endure 8 months of frustration.

  16. #16
    hispanic mechanic
    Reputation: sslos's Avatar
    Join Date
    Jan 2004
    Posts
    2,524
    Having too much oil will definitely reduce travel. Air can be compressed, oil canít.

    While this isnít a great thing to have happen, it might have been a simple mistake- perhaps the tech filled it, had to take a call or help a walk in, and when they got back to it they forgot they had already filled it.

    25 years as a mechanic, I admit Iíve done this. But they should have cycled it to check travel and damping, so thatís not so great...
    Whiskey is my yoga.

    dongerparty.com

  17. #17
    mtbr member
    Reputation:
    Join Date
    Sep 2017
    Posts
    120
    Quote Originally Posted by sslos View Post
    Having too much oil will definitely reduce travel. Air can be compressed, oil canít.

    While this isnít a great thing to have happen, it might have been a simple mistake- perhaps the tech filled it, had to take a call or help a walk in, and when they got back to it they forgot they had already filled it.

    25 years as a mechanic, I admit Iíve done this. But they should have cycled it to check travel and damping, so thatís not so great...
    I wish I could give them the benefit of doubt, but they've had the fork apart 7-8 times trying to fix the problem since March. They're a very experienced suspension shop, so I'd be surprised if they made that error. But once I get out for a ride, I'll confirm in fact that was the issue

  18. #18
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,212
    LBS quoted Fox as saying something about a self-leveling bleed valve in the Grip(e)2 damper got messed up with the air spring change. They need some special tool to reset/rebuild it. We shall see.

Similar Threads

  1. 2019 Fox 36 oil change
    By kenwood72 in forum Shocks and Suspension
    Replies: 3
    Last Post: 09-18-2019, 09:43 AM
  2. 2018 vs 2019 fox 36 air spring - 2019 smaller neg chamber?
    By paddy73 in forum Shocks and Suspension
    Replies: 8
    Last Post: 01-31-2019, 05:10 PM
  3. 2019 SJ29 Factory Rx Tune vs. Factory DPS
    By furball in forum Specialized
    Replies: 2
    Last Post: 07-11-2018, 09:33 PM
  4. PCMR, harshing my mellow!
    By MSU Alum in forum Utah
    Replies: 19
    Last Post: 06-25-2014, 05:17 PM

Members who have read this thread: 147

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.