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Discussion Starter · #1 ·
Just had my bike serviced, mostly suspension. Fork, shock, pivots.

It's a 2019 YT Jeffsy with a 140mm Pike.

I used to put about 75lbs of pressure in it. Today I needed over 90lbs and I plan to add a bit more.

Is this just due to a different viscosity oil used by the shop or ... something else. Is it a problem? The fork seems smooth but it's different so has me wondering.
 

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You have less friction than before your service.

But "needed 90lbs" isn't very descriptive. Needed it for what? Static sag? Mid-stroke support? Bottom out resistance?
 

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Have you tried asking the shop? They may have changed something or it might have been in a really horrible state inside
 

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Could excessive pressure/vacuum trapped on the lower legs cause something like this?

So, prior to service there was trapped air pressure on the lower legs, which acts as additional positive air spring, hence you needed less pressure in the normal air chamber to get same total spring force.

Or now the lower legs have been assembled when air spring and damper shaft was compressed, which might create some vacuum on the lower legs when you pressurizer the air spring, which would show up so that you need now higher pressure in the actual air chamber to get same spring force.

You could try to squeeze small zip-tie between the dust wiper and stanchion tube to release any excessive pressure/vacuum that might be trapped on the lower leg(s)...

Or maybe the more likely scenario is still that the fork was in "not so good condition" prior to the service... :)
 

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Discussion Starter · #6 ·
Good questions, thanks!

It had been 1 year since service. I did the previous shock service myself using SRAM products, about 4 months of riding 2-3 times per week between service.

I needed over 90lbs to get about 30% sag.

I haven't contacted the shop yet, just wanted information before I did that if needed.

I had never heard of the vacuum thing before.
 

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Also unequalized negative chamber may cause the fork to require more pressure, and will also remain compressed even with regular pressure. Usually one needs to pressurize to maximum pressure, cycle the fork a few times to get it equalized, then adjust the pressure.
 

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grease blobs where it shouldn't be either now, or before, can cause changes like this (blocking ports)
 
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Discussion Starter · #9 ·
Also unequalized negative chamber may cause the fork to require more pressure, and will also remain compressed even with regular pressure. Usually one needs to pressurize to maximum pressure, cycle the fork a few times to get it equalized, then adjust the pressure.
Oh interesting, I'll look into this more.
 

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I had never heard of the vacuum thing before.
This is the other most plausible option, if you slowly let the air pressure out, and pull the fork out until you can feel it hit the top out bumper it should stay fully extended (wheel off the ground). If it retracts at all, there is a vacuum in the lowers
 

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Discussion Starter · #11 ·
This is the other most plausible option, if you slowly let the air pressure out, and pull the fork out until you can feel it hit the top out bumper it should stay fully extended (wheel off the ground). If it retracts at all, there is a vacuum in the lowers
Will try this now.

I just pumped it up to about 150lbs (max is 163 per the Rockshox site) and it really raised the fork. Then went down to about 75 and the fork sunk in a lot. I don't recall what markings I should be able to see when the fork is just sitting but it's sunk past the 10% marking.
 

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Discussion Starter · #12 · (Edited)
Yeah it doesn't stay fully extended. Sucks right back up.

OK I pulled hard on the bars with a foot on the front wheel and heard a sucking sound and then the fork stayed extended until I put it on the ground. I then pumped it up and it seemed to still need >90lbs. Let the air out again and it still sucked down until I did the pull hard thing ... so not sure where I am at this point ...
 

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Discussion Starter · #13 ·
Found some videos with the zip tie solution and then this one, which is basically a lower leg service:

 

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Careful taking any tech advice from GMBN!
Stuck down isn’t from a blocked dimple, that can’t happen.
It’s either too much grease in the neg chamber or a damaged quad seal.
Oh I have seen people pour lots of float fluid in to the positive chamber which migrates in to the neg chamber too
 

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What about mounting lowers at full compression? LOL. Not so long ago xfusion showed this way in their service guide.
 

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Discussion Starter · #17 ·
Careful taking any tech advice from GMBN!
Stuck down isn’t from a blocked dimple, that can’t happen.
It’s either too much grease in the neg chamber or a damaged quad seal.
Oh I have seen people pour lots of float fluid in to the positive chamber which migrates in to the neg chamber too
(y) Gotcha. Sounds like I'll need to take it back to the shop.
 
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