GEN 1 GEN2 Rear Shocks on GEN1 worth it?

[FishFreak]

This is the problem with the Gen 2 shocks on a Gen 1 conversation. Half the people will say it's great and it works and half the people say it won't work. I'm a fan of using the parts that were designed and engineered for my truck. Ford engineers know what they're doing. But do what makes you and your bank account happy.

@FishFreak the Gen 1 shocks are not monotube. There is an internal bypass tube which the shaft/piston/valve assy rides inside. there are no moving parts contacting the 2.5 diameter outer body. This is why i'm curious to know if the Gen 2 bypass tubes are the same diameter. They could be bigger due to there being more space inside, but did Fox/Ford do that? Who knows, but a simple caliper test would answer the question.

@eastreich if you open up a set of Gen 2 shocks i'd be curious to know the ID/OD of the bypass tube as well as the IFP.

Thank you @Jhollowell ! I was wondering what 'internal bypass' meant! I've got more homework to do....

For all intents and purposes, there's not a HUGE difference in the suspension systems of G1 vs G2, I mean, it's not like we're using the G3 rear link suspension coilover in a G1 rear leafspring raptor, right? The design and travel seems very similar. Ford planned from the beginning to make the G1 raptor suspension great, but knew that G2 would have to raise the bar a little with 3.0 shocks, well, to sell us more trucks right?

 

[FishFreak]

@Jhollowell Thank you for the pics and specs. Are you saying that there IS an internal floating piston or air/oil separator like a monotube or is this an emulsion shock where the oil and nitro live together in foamy unhappiness :O ?? Apologize for my ignorance, this is really interesting to learn, and would love a real understanding of how this particular Fox works?

 

[FishFreak]

I think the ride is better too.

I believe Mikra Mfg dynoed both shocks and the GEN2 3.0 had much better longevity as mentioned above.

@FishFreak He is only doing the rear conversion. GEN1 fronts. From what I was told by KHC is that their rear mount relocates the top of the shock upward so it's in the proper operating length opposed to the people that squeezed them into the stock GEN1 mount. So you still hit the oem bump stop rather than collapsing the shock prior to hitting the bump stop. You do get some extra down travel though if you're running Deavers.

All in all I had to rebuild my OEM GEN1 rears every 20k with mostly street driving. If I can get 30k or 40k out of the GEN2 shocks I'm all for it.

Yea that's what I was understanding too, the KHC mount puts the G2 3.0 in the proper place for the oem spring. If you're running Deavers that lift the back end an inch or two, doesn't that negate the need for the KHC mount, and you actually NEED the extra length of the G2 3.0 Fox for that deeper down travel? I was hoping that was the case, save a buck or two and some welding.

I was hoping for similar up front, longer 3.0 shock and an inch and change of lift without KHC upper shock tower destruction kit.

 

[Pacific Wheel]

Yea that's what I was understanding too, the KHC mount puts the G2 3.0 in the proper place for the oem spring. If you're running Deavers that lift the back end an inch or two, doesn't that negate the need for the KHC mount, and you actually NEED the extra length of the G2 3.0 Fox for that deeper down travel? I was hoping that was the case, save a buck or two and some welding.

I was hoping for similar up front, longer 3.0 shock and an inch and change of lift without KHC upper shock tower destruction kit.

Possibly, I'm not super familiar with what's needed to run Deaver +3's. I'm running +2 Deavers (stock height) so the mount was warranted.

 

[Jakenbake]

Yea that's what I was understanding too, the KHC mount puts the G2 3.0 in the proper place for the oem spring. If you're running Deavers that lift the back end an inch or two, doesn't that negate the need for the KHC mount, and you actually NEED the extra length of the G2 3.0 Fox for that deeper down travel? I was hoping that was the case, save a buck or two and some welding.

I was hoping for similar up front, longer 3.0 shock and an inch and change of lift without KHC upper shock tower destruction kit.

If the bumpstop stays in the same location then you would still need the relocated upper mount.

That’s the best of both worlds, get more uptravel, which is very important depending on how you use the truck, and the longer shock will yield more droop.

Also run the gen 2 live valves with eclick.

In fairness I did not go this route with my truck, but had I not gone as far as I did, this would hav even my approach.

 

[Jhollowell]

@Jhollowell Thank you for the pics and specs. Are you saying that there IS an internal floating piston or air/oil separator like a monotube or is this an emulsion shock where the oil and nitro live together in foamy unhappiness :O ?? Apologize for my ignorance, this is really interesting to learn, and would love a real understanding of how this particular Fox works?

yes the oil and nitro are in separate chambers. On the front shocks the IFP (internal floating piston is at the bottom of the shock above the lower shock bolt eyelet.

IFP sits in this housing. If you look close you can see the retaining ring which keeps it from coming out the top. This part threads into the silver shock body and as you can see most of the chamber is inside the shock body as the threads are at the very end.


You can see the bypass tube here with the holes at the top and the shim stack bolted to the side. The shaft and piston slide inside that tube. The triangle cap presses into the bypass tube and that sits on the lip of the lower eyelet so it doesn't contact the IFP. When you fill the shocks with fluid, you have to make sure the shaft is fully extended and the IFP is pushed down about .250" from the snap ring. There should be no air above the IFP. When the shaft compresses into the body/bypass the fluid moves through the valves as well as the bypass holes and shims and the IFP moves down as the shaft displaces the fluid, creating more pressure. Since fluid is not compressible the nitro on the other side of the IFP compresses and lets the IFP move down. As the shock compresses more the nitro pressure increases and stiffens up the shock which keeps you from bottoming out.


This is why i'm curious as to whats inside the Gen 2 shocks. All the magic is happening inside the bypass tube and within the IFP. If those are the same diameter between Gen 1 and 2 i would find it hard to believe there's much performance difference. Obviously the shim stack and valves (hole diameter) will likely be different, but a 1.8" valve and a 2" bypass tube will move the same fluid, regardless of how big the shock body is. I'm sure there was some marketing involved going to "3.0" shocks. bigger is always better, right?

 

[FishFreak]

yes the oil and nitro are in separate chambers. On the front shocks the IFP (internal floating piston is at the bottom of the shock above the lower shock bolt eyelet.

IFP sits in this housing. If you look close you can see the retaining ring which keeps it from coming out the top. This part threads into the silver shock body and as you can see most of the chamber is inside the shock body as the threads are at the very end.

You can see the bypass tube here with the holes at the top and the shim stack bolted to the side. The shaft and piston slide inside that tube. The triangle cap presses into the bypass tube and that sits on the lip of the lower eyelet so it doesn't contact the IFP. When you fill the shocks with fluid, you have to make sure the shaft is fully extended and the IFP is pushed down about .250" from the snap ring. There should be no air above the IFP. When the shaft compresses into the body/bypass the fluid moves through the valves as well as the bypass holes and shims and the IFP moves down as the shaft displaces the fluid, creating more pressure. Since fluid is not compressible the nitro on the other side of the IFP compresses and lets the IFP move down. As the shock compresses more the nitro pressure increases and stiffens up the shock which keeps you from bottoming out.

This is why i'm curious as to whats inside the Gen 2 shocks. All the magic is happening inside the bypass tube and within the IFP. If those are the same diameter between Gen 1 and 2 i would find it hard to believe there's much performance difference. Obviously the shim stack and valves (hole diameter) will likely be different, but a 1.8" valve and a 2" bypass tube will move the same fluid, regardless of how big the shock body is. I'm sure there was some marketing involved going to "3.0" shocks. bigger is always better, right?

Very nice, so it is a monotube-style design where the IFP keeps the oil from foaming, a common problem with twin tube or emulsion shock designs? Thanks for taking the time to explain, appreciate it!

....so at the same time the piston is pushing the IFP down in the compression stroke, the piston is allowing some fluid to flow back through it's holes to damp it's movement, as welll as some oil is forced back through the bypass holes in the cylinder wall at various travel points right? You were talking about shim stack bolted to the side of the cylinder as a sort of bypass right? ...and are there also compression/rebound shim stacks on either side of the piston, like is common with most monotube shocks?

 

[FishFreak]

Now I see why Mikra Mfg charged so dang much for that G2 3.0 shorter eye retrofit kit, it's quite involved, and includes a new piston cylinder to match the shorter height, with adjusted bypass points as well. Needs to be installed by someone like yourself @Jhollowell ?

Anyone heard from Doug at Mikra lately? His kit looks more attractive after seeing this teardown.

Although it doesn't look too hard to freshen these shocks if you've got the time, know-how and special pin wrench tools? Where are you getting the rebuild parts and oil? I know of a 4x4 shop that has nitrogen gas....

 

[Jhollowell]

Very nice, so it is a monotube-style design where the IFP keeps the oil from foaming, a common problem with twin tube or emulsion shock designs? Thanks for taking the time to explain, appreciate it!

....so at the same time the piston is pushing the IFP down in the compression stroke, the piston is allowing some fluid to flow back through it's holes to damp it's movement, as welll as some oil is forced back through the bypass holes in the cylinder wall at various travel points right? You were talking about shim stack bolted to the side of the cylinder as a sort of bypass right? ...and are there also compression/rebound shim stacks on either side of the piston, like is common with most monotube shocks?

I think you got it. The IFP acts like a hydraulic/pneumatic bottom out resistor. As the shock compresses the shaft moves into the body and displaces the oil. The IFP moves down in its chamber giving the displaced oil a place to go as well as increasing the air pressure below it, subsequently making the shock a little stiffer and keeping the metal parts from contacting each other. When we talk about the "shaft piston" its really 2 sets of shims on either side of a valve body. The valve body has holes in it that are partial blocked by the shims (thin round pieces of steel). As the fluid flows through the holes it starts to bend the shims, which opens the holes a little more and lets more fluid through. This is where tuning comes in. You can change the thickness and diameter of the shims to make them easier to bend (softer) or harder to bend (stiffer) and you can also change the number and sequence of the shim stack. This is where trial and error and just good ole experience comes in. I don't fully understand how the bypass works but i think you have it right where the holes allow more fluid to flow out of the bypass and the shims on the side do the same thing, just at a different pressure.

Here is the "piston assembly" that is on the end of the shaft. This is NOT the IFP. The shims you can see here control the rebound and you can see how they partially cover the holes in the valve. The large holes that you can partially see are for your compression stroke.

Here is one side of the valve. you can see 8 different holes, 4 compression and 4 rebound

here is the compression shim stack. generally 2x as many compression shims than rebound.


I started a thread showing the different shim stacks for different trucks just because i like to document stuff and compare.
https://www.fordraptorforum.com/threads/fox-2-5-shim-stack.96415/

 

[FishFreak]

This is where the 'art' part of shock valving comes in! Insert info here on alternative shim tech like flutter stacks...???