reasoning behind the suspension brick on the S18.

[Ek.]

Wait (sorry for double posting)...

Since it only seems to be the bottom chamber that you need to inflate without weight on the shock... Can't you already access the valve for that one without putting weight on the suspension? 

Would this sequence work for optimal performance and ease of inflation?

1. Sit on the wheel or insert the block.
2. Pump the top chamber to your desired pressure.
3. Take out the block and/or unweight the wheel.
4. Pump the lower chamber to your desired pressure.

Sorry for my ignorance, but I was under the impression that it was only the top valve that would disappear under the shell. 

If that's the case then I guess it would be easy to follow the OP's recommendation regardless!

[enaon]

15 minutes ago, Ek. said:

You are therefore recommending that no matter how difficult or easy it is to inflate the bottom chamber without the block, it should always be inflated with the suspension not under weight in order to maximise performance. Doesn't seem to matter as much for the top chamber.

Thank you, this sums it up. 

5 minutes ago, Ek. said:

Would this sequence work for optimal performance and ease of inflation?

1. Sit on the wheel or insert the block.
2. Pump the top chamber to your desired pressure.
3. Take out the block and/or unweight the wheel.
4. Pump the lower chamber to your desired pressure.

Yes, the only reason I suggest one should use the hole on the side to pump the upper valve, it that it is a good way to verify the suspension arms move all the way up. If the do not, access is not possible, iI think it is best not to overlook it, it is easy to fix. 

[Ek.]

If I understand your last point correctly: as an additional consideration, if you are unable to inflate the upper chamber when not under weight (through the hole in the casing) it would mean that your suspension is not extending as far as it should. Therefore an additional recommendation is to fix the "middle rear fender screw lug" as per point 6 in this post:

The reason I'm interested, BTW, is that I hope to get the S18 as my next wheel and I'd like to understand these issues even though they will be dealt with expertly by my local wheel dealer

[enaon]

59 minutes ago, Ek. said:

If I understand your last point correctly: as an additional consideration, if you are unable to inflate the upper chamber when not under weight (through the hole in the casing) it would mean that your suspension is not extending as far as it should. Therefore an additional recommendation is to fix the "middle rear fender screw lug" as per point 6 in this post:

Allmost. If all is working good, the arms will go up anyway, will hit the fender, make some noise, but it is bearable. I think it better to cut it though, there was a case where the o-ring got damaged from the fender.  

There are two reason that the arms will not go up freely, misaligned suspension columns, or blocked shock. 

The columns are easy to fix, release the pedal hanger screws, it will move freely, tighten again one by one, both sides at the same time while fully extended. 

the shock is easy to fix too, just don use the brick on the down/negative chamber.

 

I think you will enjoy it

 

ps. the "almost" part was to say that the plastic is not that important, otherwise if you follow that guide from fbhb you are covered, with the exception of the cable rubbing issue, I like my solution regardless if the cable rubs or not, it also keeps the shoe clean, I also have one on the other side 

 

 

 

also, if everything else is ok and you only need to do the fender plastic part, you can do it using a hot blade without dismantling the s18, the plastic is very soft, will melt like butter. 

Edited April 21, 2021 by enaon

[mrelwood]

1 hour ago, Ek. said:

Not sure why your one point, made over and over, hasn't been clear to people

Quite simple really. It’s against how the laws of physics work, as far as us humans understand them.

That’s why this thread has turned into (unintended?) comedy for some readers.

[enaon]

24 minutes ago, mrelwood said:

Quite simple really. It’s against how the laws of physics work, as far as us humans understand them.

That’s why this thread has turned into (unintended?) comedy for some readers.

it's nice you are having a good time. 

you still do not understand what I am saying though, tragedy and comedy are close. It should not make any difference you are correct, but it does. If one, like myslf, wants 100psi on the bottom chamber, he will put 150 in to accommodate for the loss when taking the pump out, like I did. This will result in putting over 250psi in the bottom chamber, 5 times over the shock manufacturer recommendation. Even if one then reduces pressure to 100, a stiffness will remain, my guess is something leaks. Don't imagine leds lighting up and signs sayin "I am stuck". It is noticeable if one cares to see it, easy to see if another s18 is there to compare 

Edited April 21, 2021 by enaon

[Zopper]

22 minutes ago, enaon said:

If one, like myslf, wants 100psi on the bottom chamber, he will put 150 in to accommodate for the loss when taking the pump out, like I did. This will result in putting over 250psi in the bottom chamber, 5 times over the shock manufacturer recommendation. Even if one then reduces pressure to 100, a stiffness will remain, my guess is something leaks. Don't imagine leds lighting up and signs sayin "I am stuck". It is noticeable if one cares to see it, easy to see if another s18 is there to compare 

Sorry for joining so late, but what will the pressure of the bottom chamber will be if you pump it extended to the recommended value and then you jump and it bottoms out? Or if you let a super heavy friend to stand up on it? It will be exactly the same 250 psi you are pumping it to when compressed. 

The shock won't die because of 250 psi. The problem would be if you pumped it to 250 psi expanded and then compressed it, causing it to go over 500 psi. This is the pressure that will damage it. If the shock is built to be pumped to 100 psi expanded, it must be ok with 250 psi compressed, or it would break on the first bottoming out.

Edited April 21, 2021 by Zopper

[enaon]

7 minutes ago, Zopper said:

Sorry for joining so late, but what will the pressure of the bottom chamber will be if you pump it extended to the recommended value and then jumps and it bottoms out? Or if you let a super heavy friend to stand up on it? It will be exactly the same 250 psi you are pumping it to when compressed. 

The shock won't die because of 250 psi. The problem would be if you pumped it to 250 psi expanded and then compressed it, causing it to go over 500 psi. This is the pressure that will damage it. If the shock is built to be pumped to 100 psi expanded, it must be ok with 250 psi compressed, or it would break on the first bottoming out.

I am not sure what the recomented values are, I do not think anybody is, because the brick doubles/halfs that, and it's not clear if they want us to use it on the bottom chamber. 

The shock's manufacturer has a chart, he says 75psi for 220lbs on the bottom chamber, KS says 100, that equals to over 200 if the brick is in place. 

I am not talking about permanent damage, but it get stiffer until done all over again, very easy to understand if using the pirelli, it needs all the sensitivity available. 

Edited April 21, 2021 by enaon

[enaon]

to explain how i came to notice it, we saw that my friends s18 was not moving all the way up freely, we had to pull it up. Also, the speed dial was behaving different, like it was a different shock, we were laughing with Chinese QC and looking to see if it was a different model. 10 cliks from slow on my s18, was like 10 clicks from fast on the one inflated with the brick. We checked pressures, we were at the same levels. I even let the air out of his down chamber, and it did not completely released, it still needed some pulling to fully extend. Only after I released air from both chambers and did it all over without the brick I was able to get the same behavior. 

 

[enaon]

45 minutes ago, Zopper said:

The problem would be if you pumped it to 250 psi expanded and then compressed it, causing it to go over 500 psi.

it is the other way around with the bottom chamber, pressure drops as it compresses. 250psi uncompressed is 120 compressed. 

[Zopper]

11 minutes ago, enaon said:

I am not sure what the recomented values are, I do not think anybody is, because the brick doubles/halfs that, and it's not clear if they want us to use it on the bottom chamber. 

The shock's manufacturer has a chart, he says 75psi for 220lbs on the bottom chamber, KS says 100, that equals to over 200 if the brick is in place. 

I am not talking about permanent damage, but it get stiffer until done all over again, very easy to understand if using the pirelli, it needs all the sensitivity available. 

I think you still don't see the point. The brick doesn't halves anything. 

If the expanded chamber has 100 psi and compressed 250 psi, it doesn't matter at which state of compression you pump it as long as the pressure is matching the degree of compression. If you pump expanded it to 100 psi and compress it, it gets 250 psi. If you compress it empty, pump it to 250 psi and expand it, it gets 100 psi. It's absolutely the same pressure and if the shock is fine with 100 psi expanded, it means it was built for the higher pressure when compressed.

See the picture. This is the pressure space of our imaginary chamber that has 100 psi expanded and 250 psi fully compressed.

As long as you are on the blue line, everything is ok and it doesn't matter where exactly is the point you used to fill the chamber. You can pump it at 250/full, at 100/none, at 175/half, and you are still good. You are still at exactly the same pressures. If the 250 psi would wear out some seal, it would happen even if you pumped it to 100 psi expanded, because it gets to those 250 when it compress.

BUT if you take the "half" pressure and pump to that while expanded, 175/none, then you moved outside of the safe space and now you are going to have high pressure that can cause trouble. This is why the "manufacturer recommendation" is e.g. 100 psi - because it's for the "none" line. But as you can see, even 250 psi is fine if the shock is fully compressed at the moment.

Now, in a shock, there is a second chamber, so you have two these charts and change in one changes the other, so it's harder to get on the blue line, as you have to start with a different pressure that will be the resulting one.

20 minutes ago, enaon said:

to explain how i came to notice it, we saw that my friends s18 was not moving all the way up freely, we had to pull it up.

I'm not sure what was the cause of this behavior, but my guess would be that the pressures weren't the same after all. Or that you measured it at different compression levels. The only way how the degree of compression when pumping it could cause something would be if the inlet inside of the chamber wasn't at the bottom, but at a side and got blocked by a seal. In that case, the air might find a way in the wrong direction. But I think that this would cause much bigger problems.

 

 

[enaon]

1 minute ago, Zopper said:

If the expanded chamber has 100 psi and compressed 250 psi, it doesn't matter at which state of compression you pump it as long as the pressure is matching the degree of compression. If you pump expanded it to 100 psi and compress it, it gets 250 psi.

nice, I heard that about 10 times, I say it does, if one cares to try, and he finds it does, I would like to know why. 

 

you have the pressures mixed up, it is the other way around.

[Zopper]

1 minute ago, enaon said:

it is the other way around with the bottom chamber, pressure drops as it compresses. 250psi uncompressed is 120 compressed. 

This doesn't change anything except the polarity. You are still moving on the line, it's just rotated. (Or invert the y axis and the line stays where it is.)

2 minutes ago, enaon said:

nice, I heard that about 10 times, I say it does, if one cares to try, and he finds it does, I would like to know why. 

I would try it if I had S18 and not V11. I even formulated a hypothesis what could be the cause if your observation is universal. But I see just one point of weird data, so until others chime in with similar experience, I keep betting at something like "wrong pressure for the compression level." Sorry. :-)

[enaon]

14 hours ago, Zopper said:

This doesn't change anything except the polarity. You are still moving on the line, it's just rotated. (Or invert the y axis and the line stays where it is.)

14 hours ago, enaon said:

it changes the fact that by having the brick there, you allow yourself to easily go beyond the shock limits. You can easily put in 150 with the brick on, you do not understand that something bad is happening. But if you try to put 250 in while extended, you will understand that you should not, it needs a lot of force. This is the bottom/negative chamber we are talking about. 

This thread is really only for people that can actually test i think, talking about it makes no point I am afraid. 

Edited April 21, 2021 by enaon

[Kagenin]

Well, I just ordered some 90-degree valve extensions without seeing the thread-through-the-hole trick.

I'm gonna do some testing as well.  With the block, I'm running at 250/150, which was what Doug at RevRides recommended in our email dialog when I bought it (we both weight about 150 lbs).  It'll be interesting to see how that changes without the block.

I'm just all about the experimentation, finding what feels best.

On 4/21/2021 at 12:39 AM, enaon said:

it still needed some pulling to fully extend

This makes think that the axle isn't shimmed properly, causing some rubbing in the suspension tubes, but I could very well be wrong.

[Tawpie]

I'm into the way back time machine because I just got an S18 and am fiddling with the shock pressures and had an ah-ha moment. I'm usually on the short bus and am late to this game so all'y'all probably already know this.

Using the brick helps you get consistent air pressure readings because it puts the suspension's air cylinders in a volumetric configuration that is fixed by the brick. What counts is how many air molecules you have stuffed into that volume and you must fix the volume in order for air pressure to be an indicator of the number of air molecules you have in there. The 160psi figure that KS recommends for my weight only applies when the brick is in place. If I'm sitting on the wheel, the psi to achieve my target sag will be lower. If the wheel is on its side completely unloaded, the psi will be lower still.

The mtn bike gurus always start and usually end with setting sag (upper/positive chamber). They rarely if ever, mention positive chamber psi. From what I've read, the lower/negative chamber is mostly there to reduce stickshun so arriving at precise psi settings on the lower/negative chamber doesn't seem to be terribly important. Yes yes yes, the relationship of positive chamber to negative changes where on the non-linear response curve you're operating and that can be important too (the fully compressed end of the curve can be very harsh). Rebound speed is controlled by the red dial and in my short time messing around, it can make a dramatic difference.

 

Edited October 20, 2021 by Tawpie

[enaon]

8 hours ago, Tawpie said:

If the wheel is on its side completely unloaded, the psi will be lower still.

read carefully the thread, what you say applies for the top chamber, the bottom one is the opposite, gets to higher pressure when you take the brick out, if you put 100psi in with the brick, it  is like putting 250 with out it, out of limits, an internal leak will happen, and your shock will need constant refilling. It's been verified now, but I cannot really say more on the matter, other than trash the brick, buy yourself an valve extender if you must. 

 

this brick is the reason I find it hard to believe @Jack ex-KS statement that the s18 is an internal design. I cannot see how one designed a hole on the side to access the valve, yet failed to inform his colleagues, and they had to resolve to a brick that is bricking the shock. 

Edited October 20, 2021 by enaon

[Tawpie]

16 hours ago, enaon said:

what you say applies for the top chamber, the bottom one is the opposite, gets to higher pressure when you take the brick out

Agreed. I should have been more specific on that point. I was sharing my ah-ha that the brick lets you put the suspension into a known position so that when you pump to a certain psi the next time, it'll more closely match the setup you did before. Sitting on the wheel as EUCO recommends, works fine but you can't "reuse" your psi readings directly. Both techniques work, but will show different upper/positive chamber pressures for a given amount of sag.

You still want to set the upper/positive pressure to achieve the desired sag—the brick helps you do this over and over pretty much the same, then the lower is set to overcome stickshun.

Edited October 21, 2021 by Tawpie
typos. can't typ

[enaon]

2 hours ago, Tawpie said:

Sitting on the wheel as EUCO recommends

no comment 

 

I wish you all the fun riding your new s18 

[enaon]

I have added tpms support for the watch, and took the opportunity to measure the s18 shock chambers. 

I wanted to verify what seemed obvious, on all s18's I have seen that have used the brick method at least once, I was sure the sock was gone, yet as this topic proves, it was difficult to communicate it. 

I hope this will serve for others to avoid the same mistake.
I started with 35/160, 8 hours later it is at ~110 each, the chambers have internal leak.

https://streamable.com/mmwck2
 

8 hours later

https://streamable.com/f8ovo4
 

[EUC Forest]

My shock is shot...doesn't hold any pressure in the bottom chamber. I can't say with certainty what went wrong (not big jumps for sure), but I did pump with the block to 100-150 PSI always.

I am getting the 38RC as a replacement, hopefully this issue is reduced with just one chamber to pump, the second one being automatic.

[mrelwood]

On 1/7/2022 at 10:24 AM, EUC Forest said:

My shock is shot...doesn't hold any pressure in the bottom chamber. I can't say with certainty what went wrong (not big jumps for sure), but I did pump with the block to 100-150 PSI always.

I am getting the 38RC as a replacement, hopefully this issue is reduced with just one chamber to pump, the second one being automatic.

Shocks can be repaired. Maintenance and repair seems to be a regular thing in the MTB scene, and detailed guides are widely available in YouTube.

I can’t see how rare but regular shock disassembly and maintenance shouldn’t be a thing with suspension EUCs as well.

[Alrog]

On 4/21/2021 at 10:25 AM, enaon said:

it changes the fact that by having the brick there, you allow yourself to easily go beyond the shock limits. You can easily put in 150 with the brick on, you do not understand that something bad is happening. But if you try to put 250 in while extended, you will understand that you should not, it needs a lot of force. This is the bottom/negative chamber we are talking about. 

This thread is really only for people that can actually test i think, talking about it makes no point I am afraid. 

I tested it on my S18, and I’m totaly agree with Enaon: my S18 suspension was not working well before ! And now it’s really smooth, a game changer! Follow Enaon’s instructions to respect your suspension. Thanks a lot Enaon!!!! 

[enaon]

5 hours ago, Alrog said:

I tested it on my S18

thank you for testing.

[EUC Forest]

On 1/10/2022 at 4:29 AM, mrelwood said:

Shocks can be repaired. Maintenance and repair seems to be a regular thing in the MTB scene, and detailed guides are widely available in YouTube.

I can’t see how rare but regular shock disassembly and maintenance shouldn’t be a thing with suspension EUCs as well.

Tried to open the air can on the 36RC, just can't bare handed...also I didn't find any replacement o'rings etc for the DNM shocks if needed.