Air Shock Tuning

[jevyguy]

I have 2x14" race runner air shocks on the back of my J pickup that are in need of tuning and wanted some advice from those who have done some themselves. I currently have about 4" of shaft showing charged with about 425psi (which seems like a lot.)

I know that I need to add oil, but how much (total) oil are you finding to work well? I know it all depends on what vehicle, but I have a sway bar and still get a bunch of sway.

Also what weight of oil are you putting in the shocks that is working well? Do they come with 5wt from the factory? Is regular motorycycle fork oil what I should use?

 

[neagtea]

2 inchers seem a little small for a J truck.

 

[Herzog]

Yeah you are probably running close to max weight if not over. Try maxing out the oil if you dare, that's a lot for those 2" shocks.

Basically, with the shaft all the way in -> fill it up until starts to drip out... then measure how much you were able to fit so you know if you have air trapped or not. You will then be able to run a little less nitrogen pressure to get the ride & height you want.

 

[jevyguy]

Yeah you are probably running close to max weight if not over. Try maxing out the oil if you dare, that's a lot for those 2" shocks.

So what exactly is the "dare" factor I need to be worried about?

I am sure they are close to being maxed out weight wise, but even on the rear? The bed and frame are bobbed almost 20".

So do you know how much oil they hold maxed out? 5wt or 10wt?

 

[Herzog]

So what exactly is the "dare" factor I need to be worried about?

I am sure they are close to being maxed out weight wise, but even on the rear? The bed and frame are bobbed almost 20".

So do you know how much oil they hold maxed out? 5wt or 10wt?

Honestly, no idea. I have heard of people exploding shocks with too much oil & weight. Sounds scary but I've never witnessed it.

I don't know how much your 14" 2.0's will hold. My 16" 2.0's held about 450ml if I remember correctly. So you might be close to 425ml. 5wt is what I use with good results. No idea what will happen if you change the oil weight.

 

[greenjeep]

I just installed some Fox 2.5x14 on my CJ, and I was worried about getting the right mix of oil and nitrogen, also. It seems like everyone has a different opinion, but Steve Nantz of the Moab 4x4 Outpost says you must keep the factory set oil in the shocks or it will screw up the valving, and can ruin the shock. Poly Performance shows what they "should" have, although all of them actually had different amounts.

For a Fox 2.5x14 it says 585cc (fromHERE)

For Fox 2x14 it says 300cc (HERE)

For nitrogen I started with 300psi then let it out until it's about 1" over desired ride height, it should settle about that much.

All of this is about Fox shocks, but I assume Race Runner is similar.

 

[Herzog]

They are probably designed to only have the factory amount of oil, but act more like pressured rams than they do shocks with factory oil and anything over 270psi (my opinion and experience).

I'm also convinced that I'm running way too much weight even on the front of my 2.0 shocks, but maxing the oil out up front sure has made a night and day difference with those. My buggy is NOT heavy by any means.

So far so good for me. Next time I will be using 2.5's or even trying out coil-overs.

 

[J Kimmel]

I tuned mine with trial and error...I spent an afternoon at a friends shop with a lift so I could put the truck on and fill them up, and then drive it around the back to see the differences.

I have racerunner 16" 2.0 in the rear, and 16" 2.5's in the front of my Toyota. Here is where I started on mine and where I am now.

front 260psi +30cc oil
rear 180psi +40cc oil

Keep in mind the "+" is over the stock level

now I am at

front 160psi +100cc oil
rear 130psi +70cc oil

So what did it accomplish? Well, the ride height is about 1-2 inches lower. I have about 3-3 1/2 inches of shaft showing front and rear. But the biggest improvement is that now it has almost no body roll Before I brought it into the shop I ran it around in the field behind the shop. It got a decent amount of roll in the dirt, and a TON of body roll on pavement. Now when I run around the field, it stays perfectly level. rears won't bottom out, and the front will bottom softly(as opposed to periodic hard bang I got in Moab).
Getting off my trailer, I have to make a right turn on the street going into my garage, normally I have to back up and adjust unless I want it to sit a foot high on the passenger side, and this time I pulled in there was no noticeable roll


Oh ya, I also added 45cc of oil to my front air bumps, and aired them up to 60 psi, so it should prevent the "soft bottom" I was getting in the front



Its not a plug and play thing unfortunately, I hoped it would be but it wasn't. Now that I had it out a few times un-tuned, and then since I have, its night and day and totally worth the effort it took. It rides smooth, I can go faster than most on bumpy fire roads and it feels very stable on off camber spots. The suspension works while allowing the body to remain reletively level.

My truck is on 42's, the rock I am on in this pic is probably 44-46 inches tall?


Hope this helped

 

[jevyguy]

Your postings give me great hope so thanks for all of the replies.

Just some info for those who want/need to know:
2x14" RaceRunners come from the factory with 225ml of oil.
Maxed out they hold 300ml.
I am going to run 290ml in mine. I'll post my findings

 

[jevyguy]

Well I can say that adding oil really helped out a BUNCH. The truck felt stable and performed great the whole weekend. Has way less sway, but really stiffened up the ride (prob not a bad thing)

 

[Herzog]

Good to hear! You might be able to find a sweet spot in there somewhere. Maybe slightly less oil to loosen it up a bit? Or just be content cause it can be a pain to do all over again.