EAS spring rate

[prelude]

Hi all,

Last weekend I was able to do a nice trip for the first time in a looong time. I came across plenty of ancient cobblestone roads in france which must be centuries old by now. Anyway, it was a good test for my suspension setup and I have some observations / questions.

When I went over some large bumps I noticed the car beginning to bottom out whereas the other cars in the convoy seemed to have less of a problem with it. My P38 was loaded to the brim with 4 people and gear. I think it is safe to say I was pushing GVM limits.

With normal springs, the spring rate is linear. Loading up spring fitted vehicle will lower it of course but the spring rate will remain the same. More weight with the same spring rate will make the car dip further and faster. Now, air springs. I was/am under impression that the springs rate will vary with the air pressure inside the springs. When you load up a vehicle with EAS it will simply pump more air into the bags to level the car with the side effect of making the springs firmer. This process I think is relational, ie. more load, equally firmer spring so nothing changes.

I guess with more load I would need to alter the terrafirma adjustables to a stiffer setting (shocks) but I found that driving over cobblestone roads (basically stone currogated roads). was still somewhat harsh so I would like a softer setting on my shocks. It could also be that the high setting (not the wading setting) of the EAS needs to be even higher but thus far I find this the best height to have the most flex, pumping up the air bags any further will start eating into the total wheel travel. Also, there are limits as to where you can set the height with the EAS system.

Anyone have any ideas on this? If it turns out that my heavily laden P38 is just to soft it would mean I'd have to ditch the EAS system and that would be a real drag since it is one of the prime reasons I keep pushing on the with P38 to begin with :)

Cheers!
-P

[deano2469]

hi pelude, sorry i'm not going to answer your question but am hoping someone might. I have lifted my rig with 2 inch blocks under the springs, needed longer sensor arms and bump stop blocks too. Also i have longer airbags, like gen 3 but cheaper they are a lot longer. As such the numbers on the eas settings are similar to standard as it has no idea on the real height of car. i have terrafirma shocks as well and set them at 2 all the time..i find it too hard, will prob change to 1 when car is running again. i set car about 2 inches higher than stock..haven't loaded it up yet and would be keen to hear what might happen. I did raise the stock height by an inch with standard springs and it had no real change to handling. I might feel it when i tow camper trailer ,not sure yet.

[prelude]

Deano,

2 is pretty soft already :) I usually have them set to 3 on the highway and am often too lazy to crawl under a (by then already) dirty car to switch them to a softer setting. I think 4 for the highway might work when the car is (over)loaded, it helps with body roll in corners.

Now, back to the air springs; the arnott gen 3's are non linear to begin with. The lowest setting, the range in which the spring will live in highway mode, has a broader internal flange then the high setting make the springs effectively stiffer when they are beginning to bottom out if I remember and understand it correctly. I am not sure if your non gen 3's are constructed the same way?

In any case, I found a diagram for the gen 2's online whilst I was searching for a good comparo with the gen 3's and I think I'm going to contact arnott to find out if they have a similar sheet for the gen 3's available.

Cheers,
-P