Helper air springs

[Snagger]

Has anyone ever tried them?

I'm trying to reduce the body roll on my 109 (fitted with parabolics, so not dissimilar roll to a coiler) when cornering and on side slopes, but may have problems with fitting the 109 ambulance anti-roll bar due to the depth of the rear fuel tank (not fitted to ambulances). If I fit an anti-roll bar, it would have to be so much lower than on an ambulance that it may foul the top of the rear ends of the leaf springs when articluating.

Do the helper air springs help significantly with body roll (not just tail sag)? Do they have to pumped up to silly pressures to do so, making the ride unbearably harsh?

 

[TeriAnn]

Has anyone ever tried them?

I'm trying to reduce the body roll on my 109 (fitted with parabolics, so not dissimilar roll to a coiler) when cornering and on side slopes

Sorry, no help with helper springs, but you brought up the single reason I never switched to parabolics, they have a lot less resistance to lateral twisting than a solid pack of semi-elliptical springs. Having a very active phobia of drop offs, body lean is an important attribute to me.

I chose to stay with the stock spring design and make modifications to allow them to flex more. Part of the solution is to pick springs that provide the best flex for the weight they need to carry without being overstressed. Thankfully LR has a lot of different springs for different load ranges.

The other important part is to minimize the leaf to leaf friction to enable each spring leaf to flex easily. For that I use UHMW (ultra-high molecular weight) Polyethylene plastic sheets layered between spring leaves where they contact one another. This plastic provides a low friction surface, similar to Teflon tape, but with a much higher abrasion and puncture resistance. It was designed specifically for commercial use on chutes, packaging lines, slides, and anywhere high pressure metal to metal sliding contact occurs. It also provides sound dampening, eliminating squeaks and rattles caused by adjacent parts movement. The plastic's temperature range is -40 to +225 degrees F.

The plastic tape I like is 0.005" thick, comes on a 3 inch wide roll and has 1.5 mils of acrylic adhesive. It can be purchased from McMaster Carr (http://www.mcmaster.com/) and is part number 76445A24 (You can do a part number search on their site to find the tape).

You disassemble the spring pack and stick the tape to the top side of each individual leaf, except for the top leaf of course. This tape virtually eliminates the friction between adjacent leaves in the leaf pack and dramatically increases the spring's ability to react to bumps in the road.

To that I added the greasable poly bushings which allow for greater rotational movement than the stock bound bushings and longer shackles.

I ended up with much better spring articulation than I had with new springs without increasing body roll. I've had the plastic sheets in my springs for just over 10 years now and they have held up very well so far.

I have a friend with a Land Rover Dormobile and new parabolic springs. Just for the fun of it we piled into his Dormobile, drove a windy road followed by an offroad track then repeated the drive in my Dormobile and compared subjective notes. For ride comfort and articulation we could not tell any difference between either vehicle. But the Dorme with parabolics had noticeably more side sway. The test of course was very subjective and had a jillion other factors involved that were ignored but the overall feel was that the ride was similar except for the side sway.

I hope you are able to find someone who can provide help with your side sway problem.

 

[revor]

I rebuilt the standard springs for mine (very light) and another (very heavy) 109 much the way TeriAnn did and they worked very nicely on the heavily loaded truck with good control and decent articulation.
On my 110 I decided to use a lighter rate spring in the rear because of it's multi purpose use I also hate sway bars so mine (it only came with a rear) is removed. I think they are a great way to help your springs.

I will use air bags to help the springs when the load is heavy. My first attempt didn't work out so well but with a few minor tweaks they will be good to go. I am using a 4" air spring with an 8" stroke. The suspension will cycle the air bags in the upper 8" of travel and will unseat for the remaining 4" of downtravel. I calculated that I would need about 30 PSI of air in the springs to increase load capacity 1000 pounds.

One thing that aire springs will do if plumbed together is work exactly the oposite of a sway bar. If you can imagine being on a side hill the weight of the vehicle is all on one air spring trying to compress it, as you compress the air in the downhill air spring it's moving to the other side air spring extending it. For that reason I planned to plumb my springs seperately.

 

[ntsqd]

What's happening is that the old springs had more spring rate than just that needed to carry the load, so they also worked to add roll stiffness to the rear suspension.

In going to the parabolics you've reduced the rate to the point where that roll stiffness is now missing (I'm interpolating here). You could add air springs and they can be made to increase the roll stiffness. However, you would be partially negating the results of going to the parabolics in the first place. If the load exceeds the spring rate and the rear sags too much, then air springs are ideal because of their adjustability. To simply control body roll a sway-bar/anti-roll bar is the most desired method as it only affects body lean and has no loading carrying spring rate.

Are there other sway-bar/anti-roll bar options available to you? There are always custom parts, but if there is an off the shelf solution it is likely to be less spendy than going custom.
If custom is the only solution then I would look into the components used in racing. As a starting point for that:
http://www.1speedway.com/Swaybars.htm
http://www.colemanracing.com/catalog/index.php?cPath=49_1409

 

[Snagger]

I went over to parabolics about 10-11 years ago, replacing some very rusted and burst standard springs. Never having had new standard spring, I can't make any direct comparisons.

I have been very pleased with my parabolics - being TI Console HD units, they were about the most expensive on the market, but gave good handling up until my rebuild. Now, on the new 1-ton chassis and long shackles and a lot of extra weight in the vehicle (sound proofing, extra fuel tanks, a bonnet mounted spare, the roof rack and more), the raise CoG is producing more roll. IOt's not terrible when lightly loaded or empty, but is very unpleasant when heavy.

The dampers are Pro Comp ES9000s, which were fitted during the rebuild, replacing the 3000s that were fitted when I first changed to parabolics. I can see how the damping rate would affect handling in short turns and sweves, but sustained turns and side slopes need another solution.

I have three anti roll bar options:

1) 109 ambulance, using all the standard Series roll bar parts and some extended drop-mounts to fit the bar to the chassis immediately below the fuel tank (have a look at the pictures);

2) since I plan to fit a set of coiler axles (modified to suit the leaf springs), I could use the same custom drop mounts to use a standard Defender/Discovery/RRC rear anti-roll bar;

3) I could modify the exhaust so that it runs out of a side exit before entering the chassis void with the rear axle, so that a DiscoveryII anti-roll bar could be mounted on the rear face of the chassis cross member ahead of the axle (the left arm of the bar would occupy the space currently occupied by the exhaust), using custom brackets for the chassis and on the top of the axle.

Each has its own advantages and disadvantages. The best solution seems to be "number 1" because I already have everything except the drop mounts, it allows the use of standard Series axles as well as leaf-modified coil axles, and the bar is dead straight under the fuel tank. "2" would be an easy fit once the axles have been swapped, but would not permit the refit of Series axles without its loss, and the kink in the centre of the bar could foul the tank. "3" involves a lot of custom fabrication of mountings and chassis bracing, and a lot of re-routing and refabrication of the exhaust, but has the big advantage of acting as an anti-torque or anti-tramp bar if connected directly to the top of the axle with rose joints, rather than using vertical links with multiple joints.

If using the helper air springs, I was going to do so with independent inflation to prevent the air running from one to the other - even though they should help with roll a bit when connected as the down going side tries to over-inflate the upgoing side (of the body), preventing cross-feeding of the springs would give better roll control. It's an expensive solution, though, and could result in being unusably harsh except when very heavy, which would defeat the object of the excercise.

Here are some LR manual diagrams of how the ambulance roll bars fit (note the lack of a rear fuel tank):

 

[Snagger]

For those that are curious, this is how the front anti-roll bar is set up on the ambulance, and the airsprings I was considering:

 

[revor]

Keep in mind that most if not all " really comfortable" cars use air springs so the ride need not be too harsh.
And... Most heavily laden vehicles with varied loads also use air springs for both comfort and protecting load contents.

Tuning a steel spring for a specific load or condition is sort of a permanent thing, to a point an air spring is infinitely variable so in theory tuning it for varied loads and comfort should be easier.

 

[kellymoe]

I had air bags inside my rear coil in my 130 to help with body roll. By adjusting the PSI through a valve in the back of the bumper I could really dial in the ride for hwy. and trail. Unfortunately after a years of constant rubbing they gave up the ghost. Worked great while I had them.

 

[silvergrand]

I added Air Lift 1000 rear bags to my '01 WJ. I have added a fair amount of "bolt" on items over the past several years and the full size (265/70/17) spare is mounted on the rear bumper. I found that at highway speeds, with a full load in the jeep when I went over a depression the rear tires would bottom out on the Custom 4X4 rear bumper. Didn't hurt the bumper (too thick) but I did'nt like "flintching" when I saw a bump coming up.
Easy addition, did it in my home garage, no problems. Lifetime warranty!

 

[Snagger]

Thanks for those links, ntsqd. A friend had suggested using custom bars that clamped to the leaf springs, both near the axle and near the spring eye. I haven't seen them, but he assures me they're commonly used on muscle cars.

I think I may have a solution that would use just the standard parts I alread have and a pair of chassis mounting plates identical to those in the drawings I linked to. By fitting the roll bar itself in a reversed configuration, it'll sit immediately in front of the bump stops with the arms pointing aft. It'll clear the dampers in that position, and the vertical links and spring plates would be as per LR's design. I have to check that the diff couldn't hit the centre of the bar on simultaneous full compression of both springs. but I don't think it will. The only alteration it looks like I need to make are to the exhaust, relocating the muffler box to the intermediate pipe and routing it through the arched cross member instead of under it - the muffler is currently in the way of this solution. It might even be possible to just use a slimmer muffler, though, and leave the rest of the system as it is.

 

[ntsqd]

You're welcome. Perhaps they'll help someone else in the future.

GM A-Body cars use the method your friend describes, but those are rear coilers and the bar is attached to the lower links (double converging 4 link system). I can not recall ever seeing such done on a leaf sprung muscle car of U.S. mfg. There may be some aftermarket bits that do this, would be very low on my list of options.

The bar and the chassis do not care which end is mounted to what. The only consideration would be if the idea of adding the weight of most of the bar and it's mounts to the unsprung axle weight is appalling for some reason. Somehow I'm not getting the idea that a lap in anger around Silverstone is high on the agenda.....

There is value in using stock parts if they can be made to work.

 

[Snagger]

There is value in using stock parts if they can be made to work.

Not least when it comes to insuring the car - British insurers tend to baulk at modifications, an at least half the companies won't even insure a 4x4 if it's fitted with a bull bar, never mind suspension or engine alterations. the premiums for those companies who do cover modified vehicles can start expanding rapidly unless you can point at something and say "LR fitted them as an option".