Homemade Parts!

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Homemade Parts!
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Posted: Jan 24, 2020 at 15:13 Quote
I recently bought the Fox safety needle to start doing work on their nitrogen dampers. If I knew then what I know now, I wouldn't have bothered with the Fox needle. You can build one out of hardware store gas fittings and a hypodermic needle that's easier to use and actually repairable/user serviceable. Just thought I'd post this in case someone else is thinking about getting into nitrogen stuff and trying to figure it all out. Shit was making my brain fizz for awhile...


Posted: Jan 24, 2020 at 15:32 Quote
RunsWithScissors wrote:
I recently bought the Fox safety needle to start doing work on their nitrogen dampers. If I knew then what I know now, I wouldn't have bothered with the Fox needle. You can build one out of hardware store gas fittings and a hypodermic needle that's easier to use and actually repairable/user serviceable. Just thought I'd post this in case someone else is thinking about getting into nitrogen stuff and trying to figure it all out. Shit was making my brain fizz for awhile...
So there's some kind of rubber seal you're piercing with the needle? Also how do you know how much to pressurize the tool before you open the valve / how do you release pressure from the shock?

Posted: Jan 24, 2020 at 17:38 Quote
Pedro404 wrote:
RunsWithScissors wrote:
I recently bought the Fox safety needle to start doing work on their nitrogen dampers. If I knew then what I know now, I wouldn't have bothered with the Fox needle. You can build one out of hardware store gas fittings and a hypodermic needle that's easier to use and actually repairable/user serviceable. Just thought I'd post this in case someone else is thinking about getting into nitrogen stuff and trying to figure it all out. Shit was making my brain fizz for awhile...
So there's some kind of rubber seal you're piercing with the needle? Also how do you know how much to pressurize the tool before you open the valve / how do you release pressure from the shock?

Yeah, if you look up a schematic drawing of a Fox Float you'll see a black rubber plug that's held in place by a threaded steel retainer with a tiny hole in it that you push a needle through. Kind of like a basketball inflator, only thinner. After you fill the system a little white plastic ball gets smashed into the recess where the needle goes in to finish the job.

As for pressure, you set the pressure you want on the gas regulator attached to the bottle. It only takes a moment for the pressure to build and stabilize in the shock after you pierce the plug and open the ball valve at the needle, then you shut off the gas line and pull the needle out. There's a little pop as the needle leaves the plug and a slight hiss as the pressure drops off in the needle as you take it away.

The threaded steel retainer that holds the rubber plug in place also keeps it smashed tight to hold the nitrogen pressure after filling. When you want to depressurize the shock you loosen the retainer and the gas escapes. It's a tiny amount of gas, so you just hear a little puff after the first half turn of loosening the retainer.

I think they could have just used a high pressure rated Schrader valve for the gas fill, but then you'd have end users monkeying with it and that probably wouldn't end well, so I think they deliberately made it expensive and complicated to mess with the damper guts in order to discourage people from doing it Wink

Posted: Jan 24, 2020 at 18:40 Quote
Well thanks for doing it and sharing with us playa!!

Posted: Jan 24, 2020 at 21:34 Quote
whattheheel wrote:
Well thanks for doing it and sharing with us playa!!

Yep, great information. Nice to have a walk-through, beyond just the schematic.

Salute

Posted: Jan 25, 2020 at 4:32 Quote
R-M-R wrote:
whattheheel wrote:
Well thanks for doing it and sharing with us playa!!

Yep, great information. Nice to have a walk-through, beyond just the schematic.

Salute

I'm beginning to think that a lot of the folks who do suspension work and some of the manufacturers also really want it to remain a dark secret art. As I get deeper and deeper in I'm finding conflicting instructions, order-of-operations issues that don't make a lot of sense, little bits that are in one manual for one model of shock but not in others with no explanation why. I'm finding that nItrogen chargning isn't really that hard to DO, it's just hard to find straight answers when you're learning and hard to pin down exactly what you need to buy to do it without just throwing money in every direction.

It's interesting stuff, but frustrating and confusing, too. It's also beginning to make me think that a lot of damper fade issues and other shock problems are traceable simply to low IFP pressures and bubbly oil. For some of my customers this spring I'm gonna recommend a damper oil change first instead of a full rebuild. Cheaper for them, faster and more profitable for me. Don't prescribe chemotherapy for a cold Wink

Posted: Jan 25, 2020 at 6:19 Quote
RunsWithScissors wrote:
R-M-R wrote:
whattheheel wrote:
Well thanks for doing it and sharing with us playa!!

Yep, great information. Nice to have a walk-through, beyond just the schematic.

Salute

I'm beginning to think that a lot of the folks who do suspension work and some of the manufacturers also really want it to remain a dark secret art. As I get deeper and deeper in I'm finding conflicting instructions, order-of-operations issues that don't make a lot of sense, little bits that are in one manual for one model of shock but not in others with no explanation why. I'm finding that nItrogen chargning isn't really that hard to DO, it's just hard to find straight answers when you're learning and hard to pin down exactly what you need to buy to do it without just throwing money in every direction.

It's interesting stuff, but frustrating and confusing, too. It's also beginning to make me think that a lot of damper fade issues and other shock problems are traceable simply to low IFP pressures and bubbly oil. For some of my customers this spring I'm gonna recommend a damper oil change first instead of a full rebuild. Cheaper for them, faster and more profitable for me. Don't prescribe chemotherapy for a cold Wink

How much would you charge for a dampener oil change compared to full rebuild? Obviously they save money on the seal kit, but as far as labor for tearing the thing down it cant be much cheaper to just change the oil.
As it stands (unless your customers are quite a bit different then mine) people already run their suspension far longer before servicing then they should.
Most times the customer doesn't care to have it serviced until the shock makes absolutely terrible sounds, or it straight up doesn't work.

Posted: Jan 25, 2020 at 6:33 Quote
Butters has a point there.
Back in my bike shop days, I recall very little maintenance, and a lot of repairs.
To most people it seems that maintenance is another word for unnessesary repairs.

If you actually have a customer that does bring stuff in for service, it's probably right that refilling the nitrogen checking the oil levels will do, but for that to not backfire, you have to be 100% sure that everything else is ok, which isn't so easy without disassembling everything anyway.


Magura Smile

Posted: Jan 25, 2020 at 8:03 Quote
butters1996 wrote:
RunsWithScissors wrote:
R-M-R wrote:


Yep, great information. Nice to have a walk-through, beyond just the schematic.

Salute

I'm beginning to think that a lot of the folks who do suspension work and some of the manufacturers also really want it to remain a dark secret art. As I get deeper and deeper in I'm finding conflicting instructions, order-of-operations issues that don't make a lot of sense, little bits that are in one manual for one model of shock but not in others with no explanation why. I'm finding that nItrogen chargning isn't really that hard to DO, it's just hard to find straight answers when you're learning and hard to pin down exactly what you need to buy to do it without just throwing money in every direction.

It's interesting stuff, but frustrating and confusing, too. It's also beginning to make me think that a lot of damper fade issues and other shock problems are traceable simply to low IFP pressures and bubbly oil. For some of my customers this spring I'm gonna recommend a damper oil change first instead of a full rebuild. Cheaper for them, faster and more profitable for me. Don't prescribe chemotherapy for a cold Wink

How much would you charge for a dampener oil change compared to full rebuild? Obviously they save money on the seal kit, but as far as labor for tearing the thing down it cant be much cheaper to just change the oil.
As it stands (unless your customers are quite a bit different then mine) people already run their suspension far longer before servicing then they should.
Most times the customer doesn't care to have it serviced until the shock makes absolutely terrible sounds, or it straight up doesn't work.

I've been giving that very question a lot of thought in the last couple days. I think I'm just gonna make damper oil change and IFP charge a $40 add to our $60 + seal kit air can service, or $75 as a stand alone service. Either way you need to take the can off the shock to do the damper work or a can service, and once you're already doing a can service adding a damper oil change takes just a few minutes longer and only adds a new rubber pellet and delrin ball and about 30ml of oil to the cost of the job. Total cost out the door for air can service with oil change and IFP charge including tax and parts would be $125.55 at Beanie's Bike Shop in Los Alamos, NM. That price might slide by a couple bucks in either direction depending on the shock, but your basic Float CTD or Monarch would be right there.

Posted: Jan 25, 2020 at 8:07 Quote
Mr-Magura wrote:
Butters has a point there.
Back in my bike shop days, I recall very little maintenance, and a lot of repairs.
To most people it seems that maintenance is another word for unnessesary repairs.

If you actually have a customer that does bring stuff in for service, it's probably right that refilling the nitrogen checking the oil levels will do, but for that to not backfire, you have to be 100% sure that everything else is ok, which isn't so easy without disassembling everything anyway.


Magura Smile

I would totally agree. Having said that... I'm in a town full of um..."interesting" scientists and engineers. It makes the math a little different sometimes. Some of them are the type to say "Just gimme a full rebuild. Do it all. Everything." and there are also the ones who say, "I'm buying a new bike next month, but I'm going to Moab tomorrow. Can you do SOMETHING for me before I go?" I'm wanting to make money on both kinds Wink

Posted: Jan 25, 2020 at 8:37 Quote
RunsWithScissors wrote:
It's interesting stuff, but frustrating and confusing, too. It's also beginning to make me think that a lot of damper fade issues and other shock problems are traceable simply to low IFP pressures and bubbly oil. For some of my customers this spring I'm gonna recommend a damper oil change first instead of a full rebuild. Cheaper for them, faster and more profitable for me. Don't prescribe chemotherapy for a cold Wink

But if the oil is bubbly, aren't the seals already leaking (unless the shock wasn't bled properly at last service)? That way, you would only be buying a little more time before the air gets into the oil again.

Also for an oil change that takes "just a few minutes longer", I'm guessing you're using that manual vacuum bleeder and just the bleed port and not opening the shock? How much of the old oil are you able to get out that way? Not that it really matters, since I imagine the main point is to bleed the shock, but I'm curious.

Posted: Jan 25, 2020 at 9:08 Quote
Pedro404 wrote:
RunsWithScissors wrote:
It's interesting stuff, but frustrating and confusing, too. It's also beginning to make me think that a lot of damper fade issues and other shock problems are traceable simply to low IFP pressures and bubbly oil. For some of my customers this spring I'm gonna recommend a damper oil change first instead of a full rebuild. Cheaper for them, faster and more profitable for me. Don't prescribe chemotherapy for a cold Wink

But if the oil is bubbly, aren't the seals already leaking (unless the shock wasn't bled properly at last service)? That way, you would only be buying a little more time before the air gets into the oil again.

Also for an oil change that takes "just a few minutes longer", I'm guessing you're using that manual vacuum bleeder and just the bleed port and not opening the shock? How much of the old oil are you able to get out that way? Not that it really matters, since I imagine the main point is to bleed the shock, but I'm curious.

What I'm seeing so far is making me believe that gas transfer across the IFP is somewhat inevitable due to the pressures involved and the fact that IFPs are typically sealed by a single O-ring. Rockshox famously found out just how little an o-ring works on IFPs with the first Reverbs. Reverbs run at lower pressures than a Float CTD. They had TWO o-rings in the early model IFPs and they still had air leak problems that caused posts to squat. Soooo..... my thinking on this is that if gas transfer is inevitable, make the gas nitrogen and figure out how to make damper oil changes cheap and fast.

Now as to the HOW... that's gonna depend on the model. In line shocks like Float CTD, Monarch RL, etc. you have to remove the damper seal head to reset the IFP height in the damper body, so you just pour the old oil out and wipe everything off. With something like a Float X that has a piggyback reservoir you can latch on to the bleed port with your vacuum rig, pull a vacuum on the shock and work the damper back and forth several times to eject the old oil. The tiny film of residual oil left behind isn't gonna be the end of the world and the vacuum will bust all the bubbles and take the air out.

I'm not saying this is all you ever need to do to a damper, I'm just saying it's not that hard to do, and sometimes it's all you really need. For a lot of my customers, time is more important than money and they'll drop $40 or $50 on a service with a same day turnaround.

Posted: Jan 25, 2020 at 9:22 Quote
RunsWithScissors wrote:

What I'm seeing so far is making me believe that gas transfer across the IFP is somewhat inevitable due to the pressures involved and the fact that IFPs are typically sealed by a single O-ring. Rockshox famously found out just how little an o-ring works on IFPs with the first Reverbs. Reverbs run at lower pressures than a Float CTD. They had TWO o-rings in the early model IFPs and they still had air leak problems that caused posts to squat. Soooo..... my thinking on this is that if gas transfer is inevitable, make the gas nitrogen and figure out how to make damper oil changes cheap and fast.

That's incorrect. The pressure difference across the IFP is pretty close to zero, if you count out the pressure difference resulting from the friction of the O-ring.
This is so no matter how high the pressure of the IFP is.
In fact if anything, the issue would be from incorrect oil levels, that causes the IFP to bottom out, when the shock is fully extended. The very second the IFP bottoms out, you'll see nitrogen pass the seal, and then it's over.

The short version:

The shock ran out of oil, and the IFP bottomed out, causing the nitrogen to pass the O-ring and get into the oil.

Magura Smile

Posted: Jan 25, 2020 at 10:03 Quote
Mr-Magura wrote:
RunsWithScissors wrote:

What I'm seeing so far is making me believe that gas transfer across the IFP is somewhat inevitable due to the pressures involved and the fact that IFPs are typically sealed by a single O-ring. Rockshox famously found out just how little an o-ring works on IFPs with the first Reverbs. Reverbs run at lower pressures than a Float CTD. They had TWO o-rings in the early model IFPs and they still had air leak problems that caused posts to squat. Soooo..... my thinking on this is that if gas transfer is inevitable, make the gas nitrogen and figure out how to make damper oil changes cheap and fast.

That's incorrect. The pressure difference across the IFP is pretty close to zero, if you count out the pressure difference resulting from the friction of the O-ring.
This is so no matter how high the pressure of the IFP is.
In fact if anything, the issue would be from incorrect oil levels, that causes the IFP to bottom out, when the shock is fully extended. The very second the IFP bottoms out, you'll see nitrogen pass the seal, and then it's over.

The short version:

The shock ran out of oil, and the IFP bottomed out, causing the nitrogen to pass the O-ring and get into the oil.

Magura Smile

You could very well be correct. I'm still learning this stuff as I go. One thing I'm seeing consistently though is oil with bubbles, no matter the age of the shock and regardless of whether it's been serviced in the past. I suspect that the pressure within the IFP might spike hard enough under big hits to cause burping even with enough oil in the system, but I need to break open more shocks to feel confident about this.

Regardless of where they come from or what they're made of bubbles in damper oil definitely affect performance and cause noise, and they seem to be in every shock I take apart regardless of age or prior maintenance, so I'm thinking that the IFPs just leak a little and it's not the end of the world and not something that necessitates a full rebuild every time you see them. Some of the time, I think an oil change and IFP recharge is all that's worth doing.


 
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