I’m having problems with my fork after installing a longer airshaft. The fork won’t extend fully unless a lot of pressure is built up inside. I’ve followed the MBR video on this, the only difference being i don’t have a bike stand so i’ve done it with the fork fitted to the bike and the bike upside down.

Is the fact the fork doesn’t want to extend fully a tell-tale sign of anything in particular? I’m hoping it’s obvious to somebody. It needs about 90 PSI to push it fully out. At my normal 60PSI it won’t go past (lower than) 20% sag.

I compressed the lowers fully and vented the air out of the chamber, and then as advised did this also to the end of each rod to remove pressure in the lowers too.

Any techs about? Just to clarify; forks are 27.5 150mm and i’ve fitted a 27.5 160mm/29 140mm shaft.

Cheers

Not familiar with the exact fork, but can you not refer to official SRAM service documents? It may be that assembling it the wrong way up does have an effect, check in their guide.

Sounds like you have grease in the transfer port. Does the problem clear temporarily if you pull the fork to its max extension?

Most folk think the fork should be fully extended when the do the bolts up so you don’t create a negative airspring in the lowers.

Where is the transfer port? I’ve not opened up the damper side, only replaced the air shaft, cleaned and lubed the foam rings, fresh butter on the wipers and air piston.
If i pull the fork to max extension i can feel it pulling back which it does when i let go. Feels like there’s too much vacuum in the lowers.

The transfer port is in the air spring side. Take the lowers off and remove the air piston. You’ll feel a little bump inside the stanchion about 20mm from the bottom on the inner centre part. Spray with IPA and clean and don’t overly grease the air spring piston seal head.

chickenman – Member

Most folk think the fork should be fully extended when the do the bolts up so you don’t create a negative airspring in the lowers.

I rekon this is your issue, the Sram docs tell you to do the bolts when fully extended.

If that doesn’t work, then as above the transfer port would be where I’d be looking.

Stripped back down. The air shaft was fully in and when trying to pull it out, even with the top nut/cap removed, it felt like it was pulling a vacuum and wouldn’t extend. Removed air shaft and it gave a big pop as pressure was relieved.
So that groove inside the stanchion is the transfer port? That would make sense if air is getting sealed where it shouldn’t as it’s rammed with grease.
So what felt like negative pressure was actually positive on the back side of the piston?
Nice one. Thanks for the help.
You always learn something when you **** up!