Fox Coil Over Questions

[blakrapter]

Hi everyone,

Couple of quick questions for you guys. First, what type of seals does Fox use around the shaft of their 2.0 coil overs (where the shaft slides in and out of the body)? Is it just an O ring, or is it a seal similar to a grease seal and hydraulic cylinder seal that is tapered so that it "flares" for a tighter seal when pressure is applied?

Also, are there any good coil overs that can be run upside down (body down)? I am not jumping or racing the truck, so the res isn't really necessary except to separate the oil from the nitrogen. I believe the bilstein 6100 coilovers can be run upside down. Whats the general opinion on them?

Thanks.

[mattb]

Appearently "Tinman" is actually working today. John must be crackin' the whip.

[tinman]

Matt ,sometimes i do have to work (unlike you lol) and i already talked to this gentleman on the phone.

[Kritter]

Youve got a wiper seal which is what you see on the outside, a U-cup, and a dynamic O-ring made of nitrile or Viton depending on the application and a DU bushing.

There should be no issues mounting your shock upside down but why? With a coil over your diameter is consistent so you have no advantage of flipping it upside down.

Most race shocks without external reservoirs still have internal reservoirs...the ones that dont are emulsion shocks and you should stay away from them.

[blakrapter]

Thanks for the reply Kritter and thanks for the info on the phone "tinman". To the others reading, the reason I asked about the seals is because I will be making an airstrut out out it and did not want the 200 psi air to leak into the shock. I know the pressures in the shock are at a min of 200 psi, but if the seals were directional, it could cause a leaking problem.

As mentioned, they will be used to make an airstrut, and the bag must be mounted at the top for clearance issues, which is why it will be run upside down.

On more question for you guys that I forgot to ask Fox while on the phone. Is a 2.0 going to be large enough for a 4wd 2500HD? I will not be jumping at all, only on road and light offroad (mud, rocks, nothing really dynamic), the only reason I am looking at race shocks is because I need a coil over and need long travel. Fox, King, RaceRunner, etc are the only ones that make a shock with the travel needed and a body that can handle the loads. I would rather not use a 2.5 if possible because they are significantly more expensive and may cause other problems with the bag. I am not sure if the larger size is due to its damping capabilities, or its load handling capabilities. A 2.0 should be capable of handling my damping needs (I think), but what about the 7500-8000 lb truck? I need a shock with ~8" of travel that can handle axial loads of about 3000-3500 lbs. The high loads and lower travel is due to control arm mounting...

Thanks

[FullsizeFun]

I would go with a 2.5" for sure, no question about it.

[Chris_Wilson]

Internet opinions can be worth less than the time to read them but here's mine.
The size of the shock has little to do with what valving you can put in it.
The size has a lot to do with how much work it can do without overheating.
For an application with little dynamic action, a small bore shock can work
just fine as long as it's valved for the application. So I think a 2.0 will work fine
after it's valved correctly.

[blakrapter]

Chris and Fullsize,

Thanks for the replies. Fullsize, is there any specific reason you would recomend the 2.5? Chris, I tend to agree with you, thats why I origionally planned to run 2.0s, however, my experience with suspension work has been with mini baja cars that weigh ~450 lbs, so I am in another ballpark now :) Thats why I am asking for opinions. I am sure the Fox guys can tell me for sure, but I thought it might be a good idea to talk to some of you who may be running coilovers on your personal heavy vehicles. I know a lot of people put them on lifted trucks (even 2 and 3 shocks per wheel), which IMHO is a little overkill b/c very very few ever see mud, much less air...

[Kritter]

"I need a shock with ~8" of travel that can handle axial loads of about 3000-3500 lbs. "

In rebound a shock will often pull over 3500 lbs of load at a high shaft speed (40ips and above) to put that into perspective if I recall correctly a shock valved for a tundra in the stock location will pull over 5000lbs on rebound over 40ips.

Pull testing of a monotube shock will exceed 15k lbs force before the shock pulls apart. The factory twin tubes that come stock on vehicles will exceed 8-12k lbs before pulling apart.

You want a shock with acme threads for the coil adjuster as they are stronger then standard 60 degree threads.

If you are supporting the vehicle with this contraption of yours...shaft diameter is going to be your limit. Get a 7/8 shaft min if this shock is holding up the vehicle.

[blakrapter]

Thanks again for the reply and info. I was not sure how much force the shock actually saw when damping the suspension. I was pretty sure it was high, but I have never read anything about the numbers. We wanted a shock dyno on the race team I was on, but couldn't afford it. They are pretty sweet machines though.

As for the shaft, it will not be supporting the vehicle, the airbag will. The bag will basically surround the shaft, so the bag itself is supporting the load. I would prefer a 7/8 shaft, and may end up spending the money to get it. However, the 7/8" shaft shocks in the 2.0 series start at 10 or 12 of travel I think. I will need to move up to a 2.5 to get a 7/8" shaft with 8" of travel... My main concern with the 2.5, other than cost of course, is the size of the body. I don't want to drill any larger hole than necessary in the bag top and bottom plates. I am already pushing it with drilling 2" holes in it.

Thanks for the info and suggestions. Keep them coming.

[FABRICATOR]

In rebound, the shock basically sees no more than the spring tension. You could install an air bag directly on the shock instead of modifying an existing one. Things like this have been around a while. Airbagit.com and others sell parts.
http://airbagit-store.com/productImages/AIRSTRUT%2D4%2EJPGhttp://airbagit-store.com/productImages/BAGA%2D2400BARE%2EJPG

[blakrapter]

Thanks for the info fabricator. Unfortunatly, I have been unable to find a bag that is designed to be placed over a bag or strut that has enough travel or load capacity. Most are 1500 lb bags for hondas and other imports. The pics on the left you posted are from AIM. I don't really trust any of their stuff, nor can I get any specs out of them for those particular struts, so I will assume they are no good. I have used AIM before with poor results, and most everyone I talk to has had similar experiences with them (they also trade under chassis tech, airbag it, truckstuff I think, and many others). I am trying to build what they are selling, just with a longer travel, higher load capacity, and higher quality.

Thanks

[Scott_F]

How do you plan to seal the air bag to the shock body? Have you looked at the integrated unit that King makes for Funco?

[FABRICATOR]

It should not be hard to secure the bag to the shock body. The end that goes on the shock end may need a bolt up device. I don't know of anyone else who sells just the bag. It might have to be removed from an existing unit.

Then you could plumb it for anti-body roll...
http://www.funco-motorsports.com/images/FrontEndClose.jpg

[blakrapter]

Fox doesn't do it for Funco. Funco uses king shocks and make their own adapters/plates. They won't tell me how they did it, nor will they sell a set for any price. It has to be bought with the car... Not sure if their bags meet my load requirments either. However, what they are doing is what I need, just with the proper stroke and bag.

My plan is to remove the eylet and have a new eyelet with intgrated plate machined to replace it. That plate will then bolt to the bag with a seal around the shock shaft because a hole will have to be drilled in the bag plate to accept the shock shaft. At the other end, a larger hole will be drilled in the other end bag plate to accept the shock body. Then a threaded tube will slide over the shock body from the shaft side and seal to it using an o-ring around the base of the shock body. The tube will have a flange on it to bolt the bag to. Another seal will be used at the bag/tube interface to prevent leaking... Its hard to explain in words, but really pretty simple assuming I can get the geometry of each part correct.

Thanks for the replies, keep them coming.

[Scott_F]

Isn't this what I said? Do you know you can buy bags from Firestone with a bolt on bead plate instead of the crimp on style? This might make your adaptation easier.


Fox doesn't do it for Funco. Funco uses king shocks.

[Scott_F]

FAB, you caught my eye with this comment. Please elaborate...


Then you could plumb it for anti-body roll...

[blakrapter]

Scott,

Sorry, I misread your post. However, king is only suppling the shock, they are not making the adapters and bags; thats my understanding anyway.

I was unaware of a bolt on plate rather than crimp on style. How is the reliability and what are the max pressures? I have not been able to find out much info on firestone bags. Their website only lists their larger bags for trucks. Do you know where i can get technical info on those bags?

I too noticed the anti-body roll comment. I can see how you could make it worse, but I cannot figure out how to improve it. I am very anxious to hear.

Thanks.

[Scott_F]

You can order the Firestone catalogs, or go down to a truck fleet supplier and see if they have them. I prefer to keep the bags and shocks separate. The only advantage of combining them is if there are serious space constraints.

[partybarge_pilot]

King is making the adapter plates. Funco takes a reguler bag and hole saws the top and bottom plates. The adapter plates have an o-ring in them. They also use a longer shaft (2" I think).

[blakrapter]

partybarge,

thanks for the info. Im going to have to give King a call again. See if I can convince them to do the same...