I’ve had a Pike for a few months. At first I would use most of the travel on every ride and all of it on some rides, but recently it seems that I never use that last inch. So, today, I took off the top cap to see if there were any tokens in there (there aren’t) or if any oil had migrated into the ait chamber (it hadn’t although there is plenty of grease down there). But even with the cap off it wasn’t that easy to fully compress the fork. So, I stuck a zip tie down between the stanchion and the dust seal and sure enough there was a hiss and the fork compressed easily.

So, what’s going on there then? Have I “fixed” it or is there something blocked? It’s a solo air fork, so I wonder if there is something stopping the positive and negative chambers from equalizing properly?

So, what’s going on there then? Have I “fixed” it or is there something blocked? It’s a solo air fork, so I wonder if there is something stopping the positive and negative chambers from equalizing properly?

Grease can block the port between the pos and ng chambers. I believe the fix was pump them to high psi and pull fork up. Should get s hiss or something.

Thanks. The more think about it the more sense that makes. When I put it back together it seemed to have sucked down a bit and took more air to get it back to the normal sag. I guess putting the zip tie down while compressing the fork let more air into the negative side, which is now trapped.

If I pump it up hard then do the zip tie trick it will presumably get most of the air out of the negative side. Then a bit of vigorous bouncing might clear the blockage. Otherwise I guess it’s a strip down job.

Well, pumping them up to 110psi and bouncing them around the garden didn’t do much good. Not too surprising really. If hitting rocks at speed doesn’t free them up I guess there is not much I can do by riding it around the garden.

Thinking about it some more I’m not sure what’s going on when I slip a zip tie down between the stanchion and the wiper seal. That’s letting ait in and out of the lowers right? But that’s not the same as the negative chamber, which is presumably sealed.

So, is my problem that air is trapped in the lowers? If so, is there a port somewhere that is supposed to allow this air to escape?

My understanding of these issues is that a blocked air transfer port between positive and negative air chambers is different to trapped air in the lowers.

I’ve experienced the forks sucking down with no load- this was fixed by pulling up on the forks (to fully extend). I could hear a short hiss- this worked and has not happened again.

Trapped air in the lowers can be caused if the lowers are installed without any air in the chamber. MBR video recommends releasing all the air and compressing the forks when installing lowers. I’ve had issues when following their instruction but no issues when following TFTuned instructions of adding just enough air to prevent the air spring compressing when installing lowers. Had no issues having built them this way. Not sure if this solves your problem but worth a try- and the zip tie trick may solve it anyway but not tried that

My understanding of these issues is that a blocked air transfer port between positive and negative air chambers is different to trapped air in the lowers.

Yes, I’ve done a bit more digging on this and it seems to be a known issue, but a lot of online discussions are confusing as they mix up the issue of air getting trapped in the lowers with transfer between the positive and negative chambers. As far as I can tell these are different issues.

The positive and negative chambers both live in the stanchion on the air side and should be sealed (I think). At full extension there is a small groove that balances the pressure between the two sides and this can get blocked (e.g. with grease).

However, hard as it may be to believe, it would appear that the dust and wiper seals are now so good that they are effectively air tight, so the lowers are also a sealed system. Since the volume of the lowers changes as the forks are compressed they act as another air “spring”. There are two things that can happen here. First, as in my case, the pressure in the lowers can increase with use (for reasons I don’t understand) and prevent you getting full travel. Sticking a zip tie down between the seal and the stanchion can release this pressure and restore travel. Second, if you do the zip tie “trick” at full compression or have the forks compressed when you assemble them, you can have a negative pressure in the lowers, which will cause the forks to suck down.

So, it seems to just be an unintended consequence of improvements in the dust and wiper seals. The solution would be to put a pressure release valve in the lowers, which fox apparently do with their 40 series forks, but that’s not common.

I hope that’s some help to somebody and I’m sure that, if there are errors in my understanding, somebody will be along soon to correct them.

However, hard as it may be to believe, it would appear that the dust and wiper seals are now so good that they are effectively air tight, so the lowers are also a sealed system. Since the volume of the lowers changes as the forks are compressed they act as another air “spring”. There are two things that can happen here. First, as in my case, the pressure in the lowers can increase with use (for reasons I don’t understand) and prevent you getting full travel. Sticking a zip tie down between the seal and the stanchion can release this pressure and restore travel. Second, if you do the zip tie “trick” at full compression or have the forks compressed when you assemble them, you can have a negative pressure in the lowers, which will cause the forks to suck down.

So, it seems to just be an unintended consequence of improvements in the dust and wiper seals. The solution would be to put a pressure release valve in the lowers, which fox apparently do with their 40 series forks, but that’s not common.

I hope that’s some help to somebody and I’m sure that, if there are errors in my understanding, somebody will be along soon to correct them.

To my understanding that’s spot on and yes symptoms can be similar to the blocked port issue.

Mine were sitting about 20mm too low in the fork leg, and got info here and sorted it. Pumped the PSI up to about 150, pushed the front wheel and pulled the stem away from each other and got the little ‘pist’ sound, put them back to the usual 75psi and they are now fine. Rode them on Sunday and all good.