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Rockshox Pike: Really low PSI to hit correct Sag

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Discussion starter · #21 ·
fredcook said:
Mick-e, I was chasing this same issue last year. Stiff until travel got tarted, took a fair amount of weight to get it to start moving. While at OuterBike, had the SRAM guys look at it. They took the lowers off and said it was pretty dry, and needed more oil. I had, on more than one occasion, added exactly what the spec calls for. They said, "we hear that a lot, add a little more". Right or wrong, it resolved the issue.

Some differences, though. My fork is a 2018 140mm. But, I also run at 30% sag, and weight 175-180 loaded. It takes 50-60 lbs of air in my case.
Click to expand...
How interesting.
I've always cheated the oil a little on the lower side.
Now I'll have to cheat the other way!
 
Discussion starter · #22 ·
Miker J said:
Unless I missed something in this thread, something is up with the air spring.

Check if air leaked into the lowers. Push a pin past the dust seal to see if air spits out.

Let all the air out of the fork. Take off the air cap. Cycle the fork. If its smooth and all is good, then you can be fairly sure its not anything on the damper side or the bushings.

Empty the air, then try airing up again, cycling the suspension every 25 psi or so.

30% might be a bit much but that's not causing the issue. Unless there is something very different about a 2016 that 45 psi sounds way low, and yes something is not right.
Click to expand...
I did a lot of this today, read through this whole thread about air in the lowers
https://forums.mtbr.com/shocks-suspension/air-pike-lowers-psa-929695.html
I am highly suspicious this is the issue.

I did some riding over the weekend, and by the EOD Sunday my hands were trashed, my shoulders were sore, and the front of the bike felt like a rigid.

Today I started in again. First thing was to check PSI. It was in the 60s
Now this is an analog gauge, and the numbers are tiny so being really accurate is hard. I can say I started at 70 the last time I assembled it. I have checked it a couple of times and everytime you put the gauge on you lose a couple PSI pressuring the gauge, and I didn't pump a pump or 2 to put that back so it's possible that going down to just above 60 is correct.
The below picture is at the 60ish PSI before starting anything. At last assembly I was 70 psi for 30%
Note this is a 160 so we're looking at the inside number. Not 30%

The below pic is after doing the ziptie gag on both forks.
I shot some video, but you can't hear anything, but it definitely let some air out. Much closer to that 30%
The mistake I made right here was not riding it. I have this little circle I do in front of my house riding up and down some curbs as a test course. Outside of the small difference in Sag would this have brought back the plushness as theorized in the other thread?

Here is what the uppers look like after cleaning and checking things. Air cap is off. I did pull the seals off the lowers, and slide them onto the uppers to check for any binding. They slide smoothly with no notches or binding.

Here is a test I decided to do before final assembly to make sure no air was escaping the air shaft side. I flipped the whole thing upside down (had to get a step ladder) I filled the underside of the air seal with fork oil, put the air cap on, and pumped it up to 100 psi. No visible bubbles. I had to let some air out to actually be able to push the plunger. I moved it up and down and again no visible bubbles. I believe the air shaft is safe, and not pressuring the lower.

A pic of everything assembled prior to adding air.
when I started adding I put in a little at a time and cycling the forks as much as possible before settling on the chosen PSI 70

And here is the final setting after full assembly, riding it around etc ..
70 PSI 28% SAG right in the money just like it was after I put it back together last time.

One notable difference. I was only putting 5cc of oil in each leg as recommended in some SRAM service video, except the 2.1 damper says 10cc. Is 5cc of oil the deal breaker? Only time will tell.
Right now it feels super plush. Oh so nice. How long will that last?
Do I need to put ziptie, and piece of paper towel in my porkchop bag so I Psst before every major decent?
Is this why new forks like Fox's 36, 38, and 40, or MRP's have relief valves built in?
If it is pressure in the lowers why did this only start happening when I put in the Debonair air spring, and note that I had this issues with the B1 Debonair which is why I thought something was wrong with it so bought the new C1 Debonair
Thanks for playing along with me.
 
Discussion starter · #23 ·
Update after my lat post.
Took the bike for a short 10 mile ride that had plenty of techy bits.
Fork felt terrible after a short amount of time.
By the time I got back to my truck it was like riding a rigid again.
Today I bled the seals and definitely had some air come out, but fork still feels like ass.

Below is the sag picture after burping the seals
1 ride and my SAG has gone from 28% to 20%.
I checked the PSI and it's reading just above 60.
Even though you lose a little putting the pump on I don't think you'd lose 8 PSI
My next move is to ditch the C1 debonair air spring, and go back to the original.
 
Discussion starter · #24 ·
#26 ·
Looks like the entire C1 air spring should be compatible, just not the seal head/foot nut only upgrade. That said, what you're describing is def a leak and most likely the negative into the lowers (it's a double whammy - loss of negative pressure and increase in lower pressure, which acts as a second air spring). I would expect a loss of positive pressure to lowers would result in either no effect, or it getting slightly softer, by comparison. I have the same problem with my fork (not a Pike), but it's in the shop to figure out which seal is leaking.

If you have the old air spring handy I would start there to isolate it. You could be burping the seal head at the shaft, or the seal head rocking in the stanction under load. Could even be the foot nut itself (I believe RS uses a hollow air shaft as part of their negative volume, so a torn o-ring on the footnut could be a leak point).
 
Discussion starter · #27 ·
CCS86 said:
Talk directly to SRAM support?
Click to expand...
No, I didn't know that was an option

InVeloVeritas said:
Looks like the entire C1 air spring should be compatible, just not the seal head/foot nut only upgrade. That said, what you're describing is def a leak and most likely the negative into the lowers (it's a double whammy - loss of negative pressure and increase in lower pressure, which acts as a second air spring). I would expect a loss of positive pressure to lowers would result in either no effect, or it getting slightly softer, by comparison. I have the same problem with my fork (not a Pike), but it's in the shop to figure out which seal is leaking.

If you have the old air spring handy I would start there to isolate it. You could be burping the seal head at the shaft, or the seal head rocking in the stanction under load. Could even be the foot nut itself (I believe RS uses a hollow air shaft as part of their negative volume, so a torn o-ring on the footnut could be a leak point).
Click to expand...
I have installed the old original air spring.

After cycling through various pressures 80 psi gets 30%
There is something wrong with the Debonair. Based on research you should in theory run MORE psi to set the desired sag setting where I have been consistently lower as documented above.
I'm going to take this out for a shorty bumpy ride, and see how it holds up.
 
#28 ·
The low initial spring pressure is most certainly a function of the pressure not equalizing into the negative properly. Once you did get it equalized, and the pressure was in the 'normal' range for the desired sag, the later harshness is almost certainly air leaking out of the negative and into the lower leg. (which you confirmed by being able to burp the seals, as well as a decrease in spring pressure). Exactly why/where it's leaking - who knows.
The main change of C1 was to move the position of the piston head relative to the equalization dimple. Is your C1 a complete assembly or a rebuild/upgrade? Just curious if there's some combination that could put your piston starting height above the dimple...
 
#29 · (Edited)
By original air spring do you mean you installed the 2019/2020 Debonair or the original black seal head spring the bike came with?

IMO the 2019/2020 Debonair is superior to the 2021 revision. With the 2021 version the taller end-cap equates to a reduced negative air chamber volume. So, with 2021 the fork sits higher on it's sag indicators but the smaller negative volume now makes the fork firmer off it's initial travel.

2021 is great if you're more worried about your travel and your head angle seemingly being off, while 2020 rests 8mm into it's travel but rides great.

Edit. Here's a video complaining that the Pike feels harsh and stiff with the 2021 Debonair spring, compared to the 2020 version. Starts at at about 13 minute mark.

 
Discussion starter · #31 ·
Rick Draper said:
Why are you installing the lower legs with the fork fully compressed?
Click to expand...
It seemed like the right thing to do. I'm open to suggestions

The below pic is a combination of photos
I installed the original 2016 air assembly that came with the fork, and set sag after cycling it many times as seen in previous post.
When I first started rolling on the trail i was riding over small roots at low speed and watching the fork move into it's travel
All seemed well.
I climbed up to a trail that is short and rooty, and ran that twice and checked sag which is the picture on the left. You can see it's already losing it's sag position. I rode out again riding over small roots, and it felt noticeably harsher, and I could no longer see the fork moving when hitting these small bumps.
The middle photo is after getting home, and checking again. No big difference.
The 3rd photo on the right is the real twister.
I burped the seals with an audible hiss, and checked sag again assuming I would have gotten some of it back, but oh no. It's now harsher with less sag. I then checked air pressure, and it was just shy of 80.
WTF
 
Discussion starter · #32 ·
I'm running out of things to try
OK put the B1 air spring back in.
This time I installed the air spring the opposite of what I did in post #22 in response to what Rick Draper said.

I found a place with a series of curbs I could ride back and forth on like it was a mini rock garden. Fork felt super plush at first but it didn't take long for it to start to firm up when it did I went back to the garage
Image on the left is initial setup 50 PSI to hit sag
Image in the middle is sag measurement after riding around for 10 minutes
Image on the right is fork with zero PSI on the air spring.
Shouldn't there be vacuum on the negative side that pulls the fork back up to top?
This is why I was installing the piston compressed before.
 
#33 ·
When you did a leak test with the lowers off, were you able to eqalize the negative pressure and then cycle the air shaft? I still think your negative is leaking into the lowers - if there's little to no pressure left in there it won't pull the fork up. If you let the air out slowly it will also balance as it bleeds typically. Usually only sucks up if you drop the pressure fast (and get it past the dimple).

The real question is where/why is it leaking...?
 
Discussion starter · #34 ·
InVeloVeritas said:
When you did a leak test with the lowers off, were you able to eqalize the negative pressure and then cycle the air shaft? I still think your negative is leaking into the lowers - if there's little to no pressure left in there it won't pull the fork up. If you let the air out slowly it will also balance as it bleeds typically. Usually only sucks up if you drop the pressure fast (and get it past the dimple).

The real question is where/why is it leaking...?
Click to expand...
I think your right. It's the only thing that makes sense, and since the fork feels great for 5 minutes then starts to get bad something is pressurizing.
3 different air springs though.
I'm shopping for a new fork
 
#35 ·
Mick-e said:
I think your right. It's the only thing that makes sense, and since the fork feels great for 5 minutes then starts to get bad something is pressurizing.
3 different air springs though.
I'm shopping for a new fork
Click to expand...
Seems odd, but it would seem to imply an issue in the stanction - possibly a scratch near the seal head o-ring or out of round. They're pretty simple machines on the air side - only places for the air to go are around the seal head, through the seal head, or out the air spring shaft (through the foot nut).
As you say, if it was the seal head or foot nut you would think one of the 3 airshafts would be in ok shape...
 
Discussion starter · #36 ·
InVeloVeritas said:
Seems odd, but it would seem to imply an issue in the stanction - possibly a scratch near the seal head o-ring or out of round. They're pretty simple machines on the air side - only places for the air to go are around the seal head, through the seal head, or out the air spring shaft (through the foot nut).
As you say, if it was the seal head or foot nut you would think one of the 3 airshafts would be in ok shape...
Click to expand...
I'm going to do an experiment that is slightly dangerous but worth the risk, and will hopefully narrow some options.
I'm going to remove 1 oil seal at time and ride the bike to see if it packs up.
I'll start with the damper side.
Pull lowers, remove seal, install lowers, and ride.
I'll ziptie a paper towel over the opening to prevent big splashes of oil from getting out, or large debris getting in.
This will tell us whether the issue is in the lowers or not.
 
#37 ·
Have you taken the ramp control out of the fork yet? Does your damper have the upgraded seal head at the bottom and have you blead/checked the damper to make sure that it is not over filled due to ingesting oil through the lower seal?
 
Discussion starter · #38 ·
minimusprime said:
Have you taken the ramp control out of the fork yet? Does your damper have the upgraded seal head at the bottom and have you blead/checked the damper to make sure that it is not over filled due to ingesting oil through the lower seal?
Click to expand...
No I haven't
I'll do the ramp control swap first. I don't see how it could be the problem, but why not test the theory just to remove the variable.
I don't have a way to bleed the damper. It is on my list of options.
I wanted to try this no seal test. If the fork still packs up and gets stiff with no seals in place then I can eliminate the lowers as the issue, and something has to be inside.
The damper is a 2.1. I don't know about it's seal head.
 
#39 ·
I don't think there's a need to remove the dust wipers (ie: 35mm outer seals). All they do is keep bath oil in and dirt out. They've not intended to seal air in the fork, although they happen to trap air in the lowers. If you run the fork without the air side wiper (which I don't recommend), I suspect the harshness is likely to go away but you will slowly lose main spring pressure as the negative leaks to atmosphere and the positive bleeds to negative via the eq port.

When you do the zip tie bleed, I'm presuming you only get a hiss on the air side and not the damper side, correct?
 
Discussion starter · #40 ·
Most current test.
Here's my procedure. With bike in the stand. Let out air from air side. Remove air head (MRP Ramp). Flip bike over so forks are parallel to the ground (this allows me to remove lowers without losing any oil). Lossen retaining bolts, whack gently with hammer to release tension. Pull lowers, which magically resets everything.
Install lowers, torque retaining bolts, flip back to regular position, install air head, and in this case that would be the OEM airhead with 1 token.
Add 30-40 psi with bike in the stand, remove from stand and cycle fork, and add to 50-60 psi, cycle fork, and check sag, adjust PSI as needed

After and extended "rock garden" test I fork stayed consistent.
Is it possible the MRP ramp is the root cause? :confused:
I'm going to take the bike to a trail, and do some laps on a rooty section and see what I discover

See below for my testing grounds
The neighbors down the street must think I'm insane.
I rode back and forth on those things 20 or times this morning.

Oh and to comment on burping the lowers. I get a "psst" from both sides
 
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