100 series - beefed up coils or airbags

Hi Glen,

The correct way to handle trailer ball weight is NOT to beef up the rear springs, it is to use a proper weight distribution hitch (Hayman-Reese, Trailboss, etc). Yes, stronger springs and/or air springs (Polyair or others) may well return your LC to a level attitude. But they will NOT return the original weight to the front axle and as a result, you will have less braking capacity and possibly less steering force available when towing - when you may well need it most.

Look at it like this: Your Cruiser is a see-saw which pivots about the rear axle. When you put 250kg of down force on the tow ball, you must, by simple physics, be reducing the weight on the front axle by between 50 and 100kg. Even if you lift the sagging rear axle up 70mm with strong springs or air bags, it makes no difference to the weight being supported (or no longer supported) by the axles.

On the other hand, a 250kg weight distribution hitch distributes up to 250kg of ball weight between the tow vehicle front axle, the tow vehicle rear axle and the trailer axle(s). Yes, the weight is still there but it's being shared around. When a weight distribution hitch is properly adjusted, the weight on the front axle is the same before and after hitching the trailer (easily confirmed by measuring the height from ground level to the front guard).

Now, there will no doubt be objections from the camper trailer fraternity that W-D hitch restrict the articulation of trailer hitches in extreme conditions. Fair enough, but what proportion of the time do the vast majority of CTs actually spend in extreme rough road conditions? Even the true adventurers' rigs probably spend 95%+ of their time and kms on the bitumen. And when you do get well off the beaten track (and I don't mean when you first leave the bitumen) and need full articulation, simply remove the W-D hitch. In this situation, it may be advantageous to have Polyairs or similar which can be pumped up to restore your rigs level attitude to tackle the rough stuff without excessive grounding-out.

Stronger springs and/or airbags have a legitimate purpose if you're regularly or permanently carrying a lot of weight in the back of the vehicle. We have a near-permanent load of about 250kg of tools, spares and camping gear in the back of our Discovery. For a couple of years, we handled this with Airlift bags in the rear coils running around 15 to 20 psi. This year we decided the original coils had done enough work at 180,000km and put in Lovells HD springs. These put the Disco back to original ride height + about 20mm, with our 'normal' load in the back. But it will still drop 70-80mm when we hitch up our 2200kg caravan, before the Hayman-Reese hitch is attached. When it is the whole rig returns to a level attitude.

Last thing, Glen; 250kg sounds like a very high ball weight for a unit the size of a Coromal Silouette. I'd guess its loaded weight should be about 1500kg? So, using the conventional wisdom that ball weight should be around 10% of total weight, I'd have thought 150-160kg would be its ideal ball weight? Is there anything you can do about the trailer's weight distribution?

Ian

I Have Polyairs On My 100 TD. I Tow A Kimberly Kamper With Boat And Fully Loaded And I Run Them With !2 lb In Each Bag, Have Had No Problems With Them In The 2 Years Since They Were Fitted.

Hope This Helps.

G'day

I use Polyairs in the rear of the Nissan. They keep the vehicle level without problems. You must keep air in them at all times (min 5-10psi). I use a low pressure pump ( a bicycle pump works fine) to inflate them.

Had a set on a previous vehicle for 9 plus years without any problems.

Regards

Paul

Glen,

I'm on my third set of polyairs in 3 different vehicles I simply would not have a vehicle without them now. If you are going to do a lot of towing then by all means think about Ian's response above as it makes very good sense, but I would still get the airbags as well as the tow hitch. My ball weight is 300+ kgs, depending on how the van is loaded, and have never towed with a tow hitch so I can't comment on their contribution to safe travels but I also have managed to steer a cruiser and my current van around a BIG roo under full brakes without side effects (except dirtying my reg grundies). Just need to drive to your skill level and the road conditions when towing.
Go get the airbags as a prioroty, in my opinion.

Regards Trevor.

Hi Glen,
I am just going to briefly back up what Ian has already said in great detail, he is spot on. Beefing up your vehicles suspension is not the way to compensate for towball download from a trailer. The only proper and safe way to fix your problem is a weight distribution hitch (WDH). This will retain your vehicles steering and breaking capability. You should only consider beefing up your vehicle suspension to increase its offroad capabilities and to allow you to carry a heavy load IN THE VEHICLE (not on the towball).
When you require full articulation in slow OFF ROAD situations, and proper load distribution is not as critical for steering etc. simply remove the WDH.

I would suggest you talk to a towbar specialist for advice as in my experience most 4wd stores do not have anyone who is an expert on proper towing setups and will sell you springs or airbags only, not the proper equipment you require.

Have a look here under safer towing & products, weight distribution: http://www.haymanreese.com.au/index.htm

Cheers,
Stuart

Glen

I have a 100 series l/c and tow a 2.5t bushtracker which has a ball weight of 250kg.

I tried to avoid upgrading the suspension by fitting airbags - it did not work.

The airbags are now inflatable bump-stops.

I reccomend upgrading the suspension ( which is soft in standard form) and using a w/d hitch

Andrew

Glen,

Ian (and others) are spot-on with the advice to fit a WDH hitch to spread the weight. Ask yourself this simple question: how much steering/braking control are you prepared to lose by not fitting one? The answer should be pretty obvious. LOL.

Michael