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Discussion Starter · #1 ·
my DH bike sat about 2 weeks when i went out for a ride in the Park, same Park as always. On my first ride that day i felt that my fork is using only about 70% of travel and felt really harsh and hard. Absoulety NOTHING has been made on the fork, pressure is 76psi as always, not even changed brake pads or removed the front wheel that could have affected the allignment of the fork. Neither did i something on the shock od anything else on the bike. the fork does NOT feel harsh when i sit on the bike and push it to its travel though

at home i was performing a lower leg service and equalized the pressure on the spring side though the bike has only about 20 hours of use.

this weekend i was riding again in the same park and the fork still feels waaay too stiff.

Whats the problem?

its a 2020 Fox 40 with a GRIP2 Cartridge
 

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Did lower oil migrate to the air chamber? That will cause the fork to ramp up and lose travel. Make sure there is not grease plugging the transfer notch, that can cause the negative spring to not equalize.
 

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Discussion Starter · #3 ·
Did lower oil migrate to the air chamber? That will cause the fork to ramp up and lose travel. Make sure there is not grease plugging the transfer notch, that can cause the negative spring to not equalize.
i also removed the air piston and you are right, there was a ton of grease. i cleaned everything including the transfer notch but fork still has that ramp up feel.
 

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Wonder if your damper sucked in some extra oil and now is overfilled. Try compressing the fork without air and see if the big ramp up is still there at the end.
 

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Discussion Starter · #5 ·
Wonder if your damper sucked in some extra oil and now is overfilled. Try compressing the fork without air and see if the big ramp up is still there at the end.
i also did this, when i had the lower leg removed i could move the damper shaft all the way in and out several times without the feel of progression or harshness.
 

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This is a head scratcher. Perhaps try a rebleed. When you compress the fork with no air do you feel a big ramp-up at the end?
 

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no ramp up or progression at the end with the air chamber empty and the Schrader valve removed, did the rebleed several times in 20 psi steps.
Try with the valve in and see if you get a hug ramp up at the end. It seems like these are the possibilities:
  • Contaminated Damper Cartridge- The Grip 2 is designed to purge and bring new oil into the cartridge and uses a 5 weight oil for the damper and lowers on that leg. It is possible that it ingested grease at some point or the oil got contaminated. An oil change on that side might help.
  • Damper Cartridge- It is possible something got damaged inside. I would consider just doing a rebuild on it while apart. The Grip cartridges are much easier to service than the FIT.
  • Fork Settings- Assuming you did, but did you baseline the fork settings to your original ones? Sometimes they get bumped.
  • Pump Change- I am assuming the fork feels the same in the first 70% of travel, if not, it is possible your pump gauge went haywire and is now reading off.
  • Changed Conditions- This one will sneak up on you. As the season progresses, the same runs at the DH park can massively change from being smooth at the beginning of the season to rutted out messes with braking bumps all through them. This will change your speed and how the entire run feels.
  • Tire Pressure- Same as your shock pump, make sure your tire pump gauge hasn't come out of calibration and you are now running 35psi where you were running 25 psi before.
 

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Discussion Starter · #9 ·
Try with the valve in and see if you get a hug ramp up at the end. It seems like these are the possibilities:
  • Contaminated Damper Cartridge- The Grip 2 is designed to purge and bring new oil into the cartridge and uses a 5 weight oil for the damper and lowers on that leg. It is possible that it ingested grease at some point or the oil got contaminated. An oil change on that side might help.
  • Damper Cartridge- It is possible something got damaged inside. I would consider just doing a rebuild on it while apart. The Grip cartridges are much easier to service than the FIT.
  • Fork Settings- Assuming you did, but did you baseline the fork settings to your original ones? Sometimes they get bumped.
  • Pump Change- I am assuming the fork feels the same in the first 70% of travel, if not, it is possible your pump gauge went haywire and is now reading off.
  • Changed Conditions- This one will sneak up on you. As the season progresses, the same runs at the DH park can massively change from being smooth at the beginning of the season to rutted out messes with braking bumps all through them. This will change your speed and how the entire run feels.
  • Tire Pressure- Same as your shock pump, make sure your tire pump gauge hasn't come out of calibration and you are now running 35psi where you were running 25 psi before.
  • regarding the pump, i have 2 of them, digital ones.
  • tire pressure the same as always, checked with the the pump and checker
  • i have run the bike 2 times since this weird harshness and its always the same no matter what i do
  • the next step really would be to tear apart the GRIP2 cartridge, but it feels smooth when i bench test it and the comp/reb adjusters work fine
 

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it could be a few things:
1) you need to do a lower leg service
2) positive/negative air chambers aren't equalized
3) you're trying to run any significant amount of HSC on the adjusters
4) you changed other clickers when doing the lower leg and forgot
 

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Discussion Starter · #12 ·
it could be a few things:
1) you need to do a lower leg service
2) positive/negative air chambers aren't equalized
3) you're trying to run any significant amount of HSC on the adjusters
4) you changed other clickers when doing the lower leg and forgot
as i wrote in my first post i did a lower leg service

air chambers are equalized

no change in clickers

the real question is here: how can a fork get so much stiffer in 2 weeks with absolutely NOTHING done on it???
 

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as i wrote in my first post i did a lower leg service

air chambers are equalized

no change in clickers

the real question is here: how can a fork get so much stiffer in 2 weeks with absolutely NOTHING done on it???
I saw the note about the lower leg service in your OP. You didn't make the sequence clear of where the lower leg service fit into the entire sequence. That matters significantly here, because if the fork was fine but needing service, you did a lower leg and then it felt different... then you had an issue with your lower leg service. Which then could dictate a different list of potential issues, for example:

1) hair trapped between the main air spring seal head, meaning that the negative chamber is equal to the positive all of the time and they are basically 1 chamber. This will cause the air spring to be intensely pre-loaded
2) you put slightly too much bath oil in either the damper or the spring side, causing hydraulic lock or excessive ramp up of the air trapped in the lowers
3) you created a +/- chamber imbalance by inserting the air spring into the CSU and trapping air in the negative chamber, which can then be very hard to equalize back out completely

Separate from the sequencing of lower leg vs issue/occurance onset, other issues could be:
1) off brand dust wipers causing excessive drag prior or dust wipers that have been on the shelf for a bit too long (supply chain) and then breaking in fast enough
2) using 20wt oil in the damper side, while also having a worn grip 2, cartridge bottom 1 way seal that is worn out, and the damper injesting 20wt and mixing it with the 5wt oil. Using 20wt oil in the damper side on a grip fork isn't a problem... unless your grip 2 is one that is wanting to injest and cycle oil constantly. which can be cause by a worn seal head, over filled lowers and or, pressure build up in the lowers which I assume isn't the issue because it's a 40 with bleeders.
3) letting the bike sit for long periods of time, upright, which causes the bath oil to leave the foam rings and the top bushings to be dry. this is something that should be remedied by just riding the bike, over time. However, it's good practice to flip the bike over, let the oil get to the top bushings and then cycle the suspension a few times right after. Seriously, this has more of an impact then you think, and if your bike is sitting, not being ridden for weeks/months, then this is something that will need to be done.
 

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Discussion Starter · #15 ·
I saw the note about the lower leg service in your OP. You didn't make the sequence clear of where the lower leg service fit into the entire sequence. That matters significantly here, because if the fork was fine but needing service, you did a lower leg and then it felt different... then you had an issue with your lower leg service. Which then could dictate a different list of potential issues, for example:

1) hair trapped between the main air spring seal head, meaning that the negative chamber is equal to the positive all of the time and they are basically 1 chamber. This will cause the air spring to be intensely pre-loaded
2) you put slightly too much bath oil in either the damper or the spring side, causing hydraulic lock or excessive ramp up of the air trapped in the lowers
3) you created a +/- chamber imbalance by inserting the air spring into the CSU and trapping air in the negative chamber, which can then be very hard to equalize back out completely

Separate from the sequencing of lower leg vs issue/occurance onset, other issues could be:
1) off brand dust wipers causing excessive drag prior or dust wipers that have been on the shelf for a bit too long (supply chain) and then breaking in fast enough
2) using 20wt oil in the damper side, while also having a worn grip 2, cartridge bottom 1 way seal that is worn out, and the damper injesting 20wt and mixing it with the 5wt oil. Using 20wt oil in the damper side on a grip fork isn't a problem... unless your grip 2 is one that is wanting to injest and cycle oil constantly. which can be cause by a worn seal head, over filled lowers and or, pressure build up in the lowers which I assume isn't the issue because it's a 40 with bleeders.
3) letting the bike sit for long periods of time, upright, which causes the bath oil to leave the foam rings and the top bushings to be dry. this is something that should be remedied by just riding the bike, over time. However, it's good practice to flip the bike over, let the oil get to the top bushings and then cycle the suspension a few times right after. Seriously, this has more of an impact then you think, and if your bike is sitting, not being ridden for weeks/months, then this is something that will need to be done.
the lower leg service was performed after the first time the fork was feeling so incredibly stiff and it changed nothing. to me that means it has nothing to do with that area.
remember the fork was new this spring and had only about 20h on it when it felt stiff.
 

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the lower leg service was performed after the first time the fork was feeling so incredibly stiff and it changed nothing. to me that means it has nothing to do with that area.
remember the fork was new this spring and had only about 20h on it when it felt stiff.
So what are your settings then? Have you validated them, that you didnt' change one on accident? Are you running any more then 10 out (from closed) on HSC?
 

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thanks for your advises guys, but still....

how can a fork get so much stiffer buy just sitting for 2 weeks with absolutely NOTHING done on it???
Correlation != causation. Check your settings, pull the lowers and see if there is bushing drag when no air spring or damper is installed. check your triples, make sure one side isn't loose and it's binding, check the wipers. I once was struggling to get a f34 to equalize +/- and tore the lowers off 5 times to look for issues. Sometimes, that's what it takes.
 
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