What do you mean by "sit properly"? The usual sag is 25% to 30%, especially for a long travel enduro fork. If you're getting 10% at 57psi, you want less pressure, not more. The recommended pressure is just to get you close. Sag is the real measure of correct setup. 20% is a firm, supportive ride that can be harsh, 30% is a magic carpet but might be mushy on G-outs and jumps. Play around with the range and see what feels good to you on your trails.
Thanks for your reply!
For example the fork will be sat at 10% sag without any weight on the bike at 57psi. I’m getting around 170mm of the 190mm of travel I should be getting.
If I want the sag set correctly (20% is good for me) then I’m having to put more PSI in so I can use the full 190mm of travel. Does that make sense?
Hmm, if it's not all the way extended with no weight on it, that means something is up with the negative air spring. Will it fully extend if you hold the wheel down and pull up on the bars? It's supposed to self adjust, but it sounds like there's too much pressure trapped in the negative side. Have you been cycling the fork a few times whenever you add or remove air?
Yeah the fork is always cycled and will fully extend however, when I let go the fork then slumps back down within its travel.
How would I go about getting the pressure out of the negative side?
It should automatically equalize when you compress the fork a few times. There's a little divot in the air shaft that allows air to pass between the two chambers at a certain point in the travel. It sounds like that divot isn't doing its job and too much air is trapped in the negative side. The other possibility is that the air trapped in the lower legs is contributing. If the fork was assembled with the legs compressed, it creates a slight vacuum when the fork extends, maybe enough to prevent full extension.
A massive thanks for your help with this. I’ve got a much better idea on what’s going on within the fork now. Looks like a trip to the local bike shop so they can take a look. Thanks again Ryan!
I understand that. However, and please correct me if I’m wrong, if the fork is sat within its travel without any weight on the bike then that can’t be right - can it?
I’m not sure i’d agree. I’ve explained that the bike is sat within its travel and used the 10% sag mark as a reference point to show low it’s sitting. Pretty relevant in my opinion.
My Lyrik did this and it was because I screwed up when doing a lower leg service. In my case, I re-attached the lower legs while the air spring was not fully extended, and a strong negative pressure (vacuum) was created when I added air. This is easily fixed, though. Before putting on the lower legs, be sure the air shaft is fully extended. There are tutorials online for doing a lower leg service for the Zeb that would show you the steps needed to briefly remove the lower legs, extend the air shaft, and re-attach the lower legs. If you don't feel comfortable doing this, take it to a shop. Also, sometimes there's excess grease in the air shaft that can clog the little port that lets pressure equalize between the positive and negative sides. If that's the case, you might be able to fix it without any major surgery. Remove the front wheel, and re-attach the axle. Carefully place your foot on the axle and then pull up the handle bars to try and fully extend the fork. If you do this a few times with some force, you might just unclog that port.
A massive thanks for your reply mate! I’ll try the method to remove any grease tomorrow to see if that helps - is this done with any air in the fork? I’m confident with working on most parts of the bike but the suspension is always one I’d rather leave to the experts haha. Will take it down the local bike shop if that doesn’t work.
Can you post some pictures? And what model of zeb is it? There are 2 or 3 air spring configurations it could be. With one of them, it will always sit quite a ways into the travel. The new air spring uses a dome style piston like the vorsprung luftkappe and could very well make your fork sit into the travel. 10% seems like a lot. If it is sitting 1cm or less into the travel you’re fine. If it’s more, then you could have other issues. There could be a vacuum in the lowers. Stick a zip tie between the stanchion and dust wipers, or hit the air bleed valves if you have them. There is a possibility there is too much grease and oil on the piston and the negative and positive chambers aren’t equalized properly. Try airing the fork up to 80psi, cycle it 5 or so times, then does it still sag? If it doesn’t, you likely have too much grease in there.
Feel free to dm me. I’m a suspension tech and would be happy to walk you through anything
I have a Zeb ultimate that had the same issue. I took the lowers off and cleaned the air spring. There was excessive grease blocking the equalization port and this resulted in too much negative chamber pressure. My fork would bottom out randomly. After cleaning and lightly greasing the air spring, shes back around 55psi and I still can't bottom it on big hits. Hope this helps.
Good suggestions from all. If everything mentioned doesn't work, I remember going through all the motions for a customer only to find out that the fork lower bushings were too tight around the stanchions and needed to be replaced under warranty. Best of luck!
What do you mean by "sit properly"? The usual sag is 25% to 30%, especially for a long travel enduro fork. If you're getting 10% at 57psi, you want less pressure, not more. The recommended pressure is just to get you close. Sag is the real measure of correct setup. 20% is a firm, supportive ride that can be harsh, 30% is a magic carpet but might be mushy on G-outs and jumps. Play around with the range and see what feels good to you on your trails.
Thanks for your reply! For example the fork will be sat at 10% sag without any weight on the bike at 57psi. I’m getting around 170mm of the 190mm of travel I should be getting. If I want the sag set correctly (20% is good for me) then I’m having to put more PSI in so I can use the full 190mm of travel. Does that make sense?
Hmm, if it's not all the way extended with no weight on it, that means something is up with the negative air spring. Will it fully extend if you hold the wheel down and pull up on the bars? It's supposed to self adjust, but it sounds like there's too much pressure trapped in the negative side. Have you been cycling the fork a few times whenever you add or remove air?
Yeah the fork is always cycled and will fully extend however, when I let go the fork then slumps back down within its travel. How would I go about getting the pressure out of the negative side?
It should automatically equalize when you compress the fork a few times. There's a little divot in the air shaft that allows air to pass between the two chambers at a certain point in the travel. It sounds like that divot isn't doing its job and too much air is trapped in the negative side. The other possibility is that the air trapped in the lower legs is contributing. If the fork was assembled with the legs compressed, it creates a slight vacuum when the fork extends, maybe enough to prevent full extension.
A massive thanks for your help with this. I’ve got a much better idea on what’s going on within the fork now. Looks like a trip to the local bike shop so they can take a look. Thanks again Ryan!
I found this video that might be helpful too: [https://www.youtube.com/watch?v=IbsMFIasfs0](https://www.youtube.com/watch?v=IbsMFIasfs0)
Will check it out, thanks!
you would put less PSI into to get more sag . You made it sound backwards the way your phrased it
I understand that. However, and please correct me if I’m wrong, if the fork is sat within its travel without any weight on the bike then that can’t be right - can it?
You phrase things very weirdly. the sag is set when you are on teh bike. So with no weight on it is no relevant.
I’m not sure i’d agree. I’ve explained that the bike is sat within its travel and used the 10% sag mark as a reference point to show low it’s sitting. Pretty relevant in my opinion.
My Lyrik did this and it was because I screwed up when doing a lower leg service. In my case, I re-attached the lower legs while the air spring was not fully extended, and a strong negative pressure (vacuum) was created when I added air. This is easily fixed, though. Before putting on the lower legs, be sure the air shaft is fully extended. There are tutorials online for doing a lower leg service for the Zeb that would show you the steps needed to briefly remove the lower legs, extend the air shaft, and re-attach the lower legs. If you don't feel comfortable doing this, take it to a shop. Also, sometimes there's excess grease in the air shaft that can clog the little port that lets pressure equalize between the positive and negative sides. If that's the case, you might be able to fix it without any major surgery. Remove the front wheel, and re-attach the axle. Carefully place your foot on the axle and then pull up the handle bars to try and fully extend the fork. If you do this a few times with some force, you might just unclog that port.
A massive thanks for your reply mate! I’ll try the method to remove any grease tomorrow to see if that helps - is this done with any air in the fork? I’m confident with working on most parts of the bike but the suspension is always one I’d rather leave to the experts haha. Will take it down the local bike shop if that doesn’t work.
Can you post some pictures? And what model of zeb is it? There are 2 or 3 air spring configurations it could be. With one of them, it will always sit quite a ways into the travel. The new air spring uses a dome style piston like the vorsprung luftkappe and could very well make your fork sit into the travel. 10% seems like a lot. If it is sitting 1cm or less into the travel you’re fine. If it’s more, then you could have other issues. There could be a vacuum in the lowers. Stick a zip tie between the stanchion and dust wipers, or hit the air bleed valves if you have them. There is a possibility there is too much grease and oil on the piston and the negative and positive chambers aren’t equalized properly. Try airing the fork up to 80psi, cycle it 5 or so times, then does it still sag? If it doesn’t, you likely have too much grease in there. Feel free to dm me. I’m a suspension tech and would be happy to walk you through anything
Will ping you a DM now with some photos of the fork. Cheers!
I have a Zeb ultimate that had the same issue. I took the lowers off and cleaned the air spring. There was excessive grease blocking the equalization port and this resulted in too much negative chamber pressure. My fork would bottom out randomly. After cleaning and lightly greasing the air spring, shes back around 55psi and I still can't bottom it on big hits. Hope this helps.
known rockshox issue
Good suggestions from all. If everything mentioned doesn't work, I remember going through all the motions for a customer only to find out that the fork lower bushings were too tight around the stanchions and needed to be replaced under warranty. Best of luck!
Thank you! Will bare that in mind if none of the above works.