Longer Travel fork with more sag VS Shorter travel fork with less sag. What difference does it make?

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Longer Travel fork with more sag VS Shorter travel fork with less sag. What difference does it make?
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Posted: Jan 19, 2022 at 6:20 Quote
Cpembo6 wrote:
Hi Vbar. I kow you've menteioned that it is not viable to run the fork at RockShox suggested pressure (78psi), becuase you are already runnin it at 65psi and it's already too harsh.

Have you actually tried it at 78psi?

Sometimes air pressure and fork setup doesn't work how we assume. I have a Lyrik that I ran at low pressure for ages and always complained that it was way too harsh. Eventually I put an extra 10psi in it and brough it up to RockSHox recomendation, and it was amazing!
My theory is that at a lower pressure, the fork blows through the midstroke, straight into the end stroke where it gets a bit spikey (due to the fork having much less positive volume when in the end stroke - regardless of spacers). When I increased the air pressure, I got much better midstroke support which stopped it from diving into the spikey end stroke. It would only get to the end stroke when I really needed it (e.g. taking a decent hit, landing a drop etc) and ramp up nicely.

I'm no expert, but I've learned a few things through trial and error. Try having a play with higher pressure and see what it does.

This is a good point. I know OP said they are at 15% SAG with lower pressure already but it could be a situation where they are measuring SAG incorrectly might as well try at the recommended pressure before spending any money

Posted: Jan 19, 2022 at 22:05 Quote
ssantana wrote:
Cpembo6 wrote:
Hi Vbar. I kow you've menteioned that it is not viable to run the fork at RockShox suggested pressure (78psi), becuase you are already runnin it at 65psi and it's already too harsh.

Have you actually tried it at 78psi?

Sometimes air pressure and fork setup doesn't work how we assume. I have a Lyrik that I ran at low pressure for ages and always complained that it was way too harsh. Eventually I put an extra 10psi in it and brough it up to RockSHox recomendation, and it was amazing!
My theory is that at a lower pressure, the fork blows through the midstroke, straight into the end stroke where it gets a bit spikey (due to the fork having much less positive volume when in the end stroke - regardless of spacers). When I increased the air pressure, I got much better midstroke support which stopped it from diving into the spikey end stroke. It would only get to the end stroke when I really needed it (e.g. taking a decent hit, landing a drop etc) and ramp up nicely.

I'm no expert, but I've learned a few things through trial and error. Try having a play with higher pressure and see what it does.

This is a good point. I know OP said they are at 15% SAG with lower pressure already but it could be a situation where they are measuring SAG incorrectly might as well try at the recommended pressure before spending any money

Hi there!
I have seen all the videos on YouTube on how to set sag.
Truth is that what i measure is not consistent because the fork is not diving into the travel smoothly and 100% freely.

But what can i do?

For instance my rear dhx2 coil when i move my body on the front or rear even slightly, it is affecting the sag instantly.

On the fork if i move my body very very slow towards the front or the rear the fork may not dive at all.

Its like having to much friction.
So yes maybe i am measuring the sag incorrect but what else can i do?

Posted: Jan 20, 2022 at 0:37 Quote
Dont measure sag, for that exact reason. Put the recommended air in the fork, ride a familiar trail and see if it works well or not, then add more or less air depending on how it feels.

Read this and follow the instructions -https://www.shockcraft.co.nz/technical-support/setup-suspension/suspension-setup

Posted: Jan 20, 2022 at 5:52 Quote
TimMog wrote:
Dont measure sag, for that exact reason. Put the recommended air in the fork, ride a familiar trail and see if it works well or not, then add more or less air depending on how it feels.

Read this and follow the instructions -https://www.shockcraft.co.nz/technical-support/setup-suspension/suspension-setup

Ok man thanks for the comment.
BTW before my test with 75psi which the fork was surprisingly soft i did this:

https://www.youtube.com/watch?v=Zqes1rwG-iI&lc=UgwLBK2RBEEgSSSRIsh4AaABAg.9XIyMgmHtlb9XMMIhtw1lS

The trick with the zip tie to remove air from lowers. But i didnt hear any air coming out so i didnt even mention it.

But i still have a question:
What if you try to remove air from lowers but having the fork a bit compressed?
Isn't it this way going to generate a negative chamber effect?
So wouldn't it increase even more the small bump sensitivity?

Someone in the comments is asking this.

Posted: Jan 20, 2022 at 9:15 Quote
Ok first of all i would like to thank each one of you for your comments your help and your kind support.

But eventually I believe I have shorted out the issue. It must have been the air trapped in the lower legs.

I see huge difference on how the fork behaves when I equalize the air in the lower legs (and I see now why fox uses equalizer valves in their 38s).
The difference is amazing.

If I remove the air from the fork and sit on my bike's frame and compress the fork all the way down and if I equalize the air in the lower legs when the fork is completely pushed down, and if i pump the fork afterwards with 78 psi I can almost use full travel just by pushing the fork down with my hands...

Which means I could easily bottom out this way in a trail.
So what I eventually did is I pumped the fork to 78 PSI i sat slightly on the frame to force the fork to 20%sag and then i equalized the air in the lower legs.

As soon as I get it to a ride on my local trails I will report back to you.

Posted: Jan 20, 2022 at 9:42 Quote
You need to equalise the fork without your weight on it, and not by shoving a ziptie down the stanchion. That's a surefire way to eventually ruin your seals.
Equalise it by pumping up the fork to 30psi or so, fully compress the fork, then push the lowers away from the crown. You should hear it slightly hiss. Pump another 30 or so, repeat. Set your final psi and go ride it.

Posted: Jan 20, 2022 at 10:51 Quote
TimMog wrote:
You need to equalise the fork without your weight on it, and not by shoving a ziptie down the stanchion. That's a surefire way to eventually ruin your seals.
Equalise it by pumping up the fork to 30psi or so, fully compress the fork, then push the lowers away from the crown. You should hear it slightly hiss. Pump another 30 or so, repeat. Set your final psi and go ride it.


I equalized with my weight on holding the fork at 20% Sag.

The way you describe will not equalize the fork in my case.
My fork had trapped air in the lowers. So when I was removing the air from the fork it was standing high in its travel alread, so pushing the lowers away was not possible because they were already away from the crown.
What you describe maybe could work when you have no air in the lowers and they tend to suck the fork down.

But again in my case I was pushing my fork through its travel and the air was not getting out from the lowers.
I was forced to use the zip tie although you are right this could damage the seal but i used a very small one.

Posted: Jan 20, 2022 at 12:47 Quote
Vbar wrote:
TimMog wrote:
You need to equalise the fork without your weight on it, and not by shoving a ziptie down the stanchion. That's a surefire way to eventually ruin your seals.
Equalise it by pumping up the fork to 30psi or so, fully compress the fork, then push the lowers away from the crown. You should hear it slightly hiss. Pump another 30 or so, repeat. Set your final psi and go ride it.


I equalized with my weight on holding the fork at 20% Sag.

The way you describe will not equalize the fork in my case.
My fork had trapped air in the lowers. So when I was removing the air from the fork it was standing high in its travel alread, so pushing the lowers away was not possible because they were already away from the crown.
What you describe maybe could work when you have no air in the lowers and they tend to suck the fork down.

But again in my case I was pushing my fork through its travel and the air was not getting out from the lowers.
I was forced to use the zip tie although you are right this could damage the seal but i used a very small one.

I'm by no means a mechanic but I think you two are talking about two different things. One is negative air pressure the other is air in the lowers.

The zip tie trick should remove the air pressure built up in the lowers but this is not something you should constantly be doing. Once you have air out of your lowers though you shouldn't just pump up your air pressure straight to your riding psi as that will not properly equalize the positive and negative chambers of your air piston. You should slowly add air and every 20-30 psi give the fork a good couple of cycles through the travel until you hit your riding pressure

Posted: Jan 20, 2022 at 13:46 Quote
ssantana wrote:
Vbar wrote:
TimMog wrote:
You need to equalise the fork without your weight on it, and not by shoving a ziptie down the stanchion. That's a surefire way to eventually ruin your seals.
Equalise it by pumping up the fork to 30psi or so, fully compress the fork, then push the lowers away from the crown. You should hear it slightly hiss. Pump another 30 or so, repeat. Set your final psi and go ride it.


I equalized with my weight on holding the fork at 20% Sag.

The way you describe will not equalize the fork in my case.
My fork had trapped air in the lowers. So when I was removing the air from the fork it was standing high in its travel alread, so pushing the lowers away was not possible because they were already away from the crown.
What you describe maybe could work when you have no air in the lowers and they tend to suck the fork down.

But again in my case I was pushing my fork through its travel and the air was not getting out from the lowers.
I was forced to use the zip tie although you are right this could damage the seal but i used a very small one.

I'm by no means a mechanic but I think you two are talking about two different things. One is negative air pressure the other is air in the lowers.

The zip tie trick should remove the air pressure built up in the lowers but this is not something you should constantly be doing. Once you have air out of your lowers though you shouldn't just pump up your air pressure straight to your riding psi as that will not properly equalize the positive and negative chambers of your air piston. You should slowly add air and every 20-30 psi give the fork a good couple of cycles through the travel until you hit your riding pressure


This is exactly what i did.
https://youtu.be/LlcCiPj74KQ
Check at 14:40
Only i did it with the zip tie because zeb doesn't have equilization valves.

I compressed with my weight at about 20% sag and then equalized.

So this means that now the lowers of the fork act like a negative chamber from 0-20% of the travel (sucking the fork) and from 20-100% travel the act as a positive chamber pushing the fork to extend.

Also in zeb the hole that balance the negative and positive chamber is in alignment with the sealhead when the fork is fully extended. So you dont have to compress a few times the fork evey 20-30 psi while pumping it up on order to equalise the chambers (this is according to rockshox)

But maybe you are correct and the other guy is talking about the negative chamber of the fork (but this is not equalized with zip tie).
Nevertheless i am talking about the trapped air in the lowers.

Posted: Jan 21, 2022 at 4:23 Quote
That is not how you equalise your fork, as you're right, they will equalise by themselves at full extension.
If you want them to feel more supple off the top, you need to add some tokens to decrease your positive volume (your negative become relatively larger in comparison)
Amazingly, you'll keep all your travel and it'll be softer at the start, at the expense of ramp up at the end.

Stop setting your air pressure while on the bike, and stop shoving zipties down the seals.

Posted: Jan 21, 2022 at 7:18 Quote
Vbar wrote:
ssantana wrote:
Vbar wrote:



I equalized with my weight on holding the fork at 20% Sag.

The way you describe will not equalize the fork in my case.
My fork had trapped air in the lowers. So when I was removing the air from the fork it was standing high in its travel alread, so pushing the lowers away was not possible because they were already away from the crown.
What you describe maybe could work when you have no air in the lowers and they tend to suck the fork down.

But again in my case I was pushing my fork through its travel and the air was not getting out from the lowers.
I was forced to use the zip tie although you are right this could damage the seal but i used a very small one.

I'm by no means a mechanic but I think you two are talking about two different things. One is negative air pressure the other is air in the lowers.

The zip tie trick should remove the air pressure built up in the lowers but this is not something you should constantly be doing. Once you have air out of your lowers though you shouldn't just pump up your air pressure straight to your riding psi as that will not properly equalize the positive and negative chambers of your air piston. You should slowly add air and every 20-30 psi give the fork a good couple of cycles through the travel until you hit your riding pressure


This is exactly what i did.
https://youtu.be/LlcCiPj74KQ
Check at 14:40
Only i did it with the zip tie because zeb doesn't have equilization valves.

I compressed with my weight at about 20% sag and then equalized.

So this means that now the lowers of the fork act like a negative chamber from 0-20% of the travel (sucking the fork) and from 20-100% travel the act as a positive chamber pushing the fork to extend.

Also in zeb the hole that balance the negative and positive chamber is in alignment with the sealhead when the fork is fully extended. So you dont have to compress a few times the fork evey 20-30 psi while pumping it up on order to equalise the chambers (this is according to rockshox)

But maybe you are correct and the other guy is talking about the negative chamber of the fork (but this is not equalized with zip tie).
Nevertheless i am talking about the trapped air in the lowers.

I just watched that video and that sounds like terrible and hacky advice. Shame on bikeradar for doing that. That it not a normal process and you shouldnt be doing that to make your fork work.

EDIT: After doing some digging I don't even see how that would do anything meaningful. If your seals aren't airtight the "negative" pressure you put in will eventually equalize and if your seals are airtight then you shouldn't be getting a lot of air in your lowers after a service since "all" the air is removed when your service your lowers so its already at a negative air pressure

Posted: Jan 21, 2022 at 7:54 Quote
TimMog wrote:
That is not how you equalise your fork, as you're right, they will equalise by themselves at full extension.
If you want them to feel more supple off the top, you need to add some tokens to decrease your positive volume (your negative become relatively larger in comparison)
Amazingly, you'll keep all your travel and it'll be softer at the start, at the expense of ramp up at the end.

Stop setting your air pressure while on the bike, and stop shoving zipties down the seals.


I think i have confused you.
My apologies.

I am not setting my air pressure while sitting on my bike.
I pump my fork normally without sitting on my bike.

I am equalising the lower legs (removing the trapped air) when sitting on the bike exactly as on the video i posted.
And this is something that you will not need to do it more than a couple of times during a service period.

Posted: Jan 21, 2022 at 8:14 Quote
As has been pointed out, you don't need to do that at all if you've serviced them properly, and you shouldn't do it while weighting the bike. The ziptie trick is a quick hack, and is done without weight on the bike - you're just making more problems for yourself.

Posted: Jan 21, 2022 at 8:21 Quote
ssantana wrote:
EDIT: After doing some digging I don't even see how that would do anything meaningful. If your seals aren't airtight the "negative" pressure you put in will eventually equalize and if your seals are airtight then you shouldn't be getting a lot of air in your lowers after a service since "all" the air is removed when your service your lowers so its already at a negative air pressure


The seals are indeed airtight thats why air is trapped. Otherwise it would constantly equalise.

ssantana wrote:
the air is removed when your service your lowers so its already at a negative air pressure

Well thats a good point now and the answer is no its not negative while servicing the fork.
It's exactly at atmospheric pressure when installing the lowers. And when assembling the lowers both shafts (damper and air shaft) are both fully extended.
And that means that the moment you start to compress the fork air pressure starts to build up inside the lowers.

Remember air shaft and damper shaft are fully extended when installing the lowers.
So by default while assembling the fork you trap air.

In order to service them and not trap air inside, you have to compress the lowers a bit and then tight the bolts after you have allowed the air to get out by compressing a bit the shafts (airshaft and damper shaft) otherwise you are always trapping air inside the lower.
In my case is obvious to me now that i had air trapped in my lowers from day 1 (directly from rochshox).

Thats why it was impossible to use the fork with 78 psi. It was amazingly harsh.
And it is not now.

I was removing all the air from my fork (from the top valve) and the fork was still standing high in its travel. I was also removing the top cap completely to change tokens and the fork was still standing high like it was pumped with air. You could literally compress it and it was bouncing back (and i thought it was from the damper) but eventually it was from the air inside the lowers.

Maybe also i had from day one damaged air shaft and air leaked from the shaft to the lowers. I dont know.

Posted: Jan 21, 2022 at 12:05 Quote
TimMog wrote:
As has been pointed out, you don't need to do that at all if you've serviced them properly, and you shouldn't do it while weighting the bike. The ziptie trick is a quick hack, and is done without weight on the bike - you're just making more problems for yourself.


Hi.
Really thanks for your efforts and your kind help.
I am paying attention to what ever you say.

But on the other hand i can't hide what i have seen and what i have felt today in my ride.
Maybe there is something else going on here, but i can't figure it out. The only explaination to me is trapped air in the lower legs.

Today in my ride for the first time i was riding the Zeb and the fork amazed me in every aspect.
Plushness support pumpingnness.

At last this fork is working as expected and as it should be.
78psi used and used almost 80% of my travel without gaps drops etc. Just rocky trail riding.

Last time with 78 psi the fork was terrible and couldnt be ridden.
Thanks to all of you for your kind help.
In case i have any additional findings i will report back.

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