Thread: Shocks needed?

"and uses quite short leaf springs"

Even without photos I imagine this is the issue at hand - especially if you have reset the springs with more camber. Is each leaf pack suspended off the chassis rail longutudinally with shackles? Or do the leafs run transverse? If the former, in the process of resetting the springs you have also shortened their eye to eye distance which will suare up the shackle leading to a harsher ride.

Either way dampers will most likely do very little as I would be guessing the wishbones will be moving very little. Get on the guard and jump up and down. My guess is most of your "suspension" will be tyre sidewall deflection.

So rather than fabricating damper mounts, maybe look into changing the springs out for longer more compliant leaf packs that still offer the ground clearance you want but actually travel! And whilst doing this incorporate dampers.

Steve

The short (22" contact area to contact area) and therefore stiff springs are necessary due to the very limited axle travel.

The spring packs are longitudinal and sit in moveable holders mounted to the chassis but they don't have shackles. The extra camber is due to more height, albeit only 1 inch, because the wishbones pivot longitudinally from in towards the centre of the van similar to vehicles, but only have 1 wishbone per side instead of 2. The springs previously flexed as evidenced by the U-bolt marks on the chassis and I suspect they have only been restored to their new condition.

Perhaps the tyre pressures aren't appropriate as they were lowered from my initial 45psi to 40psi to reduce tugging as wheels exitted depressions, but lowering improved the van's impact on the D4. Using higher pressures to stop sidwall flex isn't really an option because of the increased tugging. The van doesn't have guards but I doubt that jumping up and down would simulate road movement anyway. I might see if I can get someone to follow me to check for tyre bounce vs spring movement though.

No more travel is possible because the higher the van is raised, the more positive the camber gets, so longer, more supple springs aren't an option unless the suspension is changed to trailing arms or a live axle. Coromal vans still use this or very similar suspension although larger, longer wishbones and longer springs are used on their XC range so I'm surprised that my van doesn't ride better than it does.

I'm not inclined to spend much money, time or effort on trying to improve this suspension if there's little likelihood of reasonable success, hence the inquiry about the effects of fitting shocks to short, stiff springs.

I agree with Steve, shocks won't help much, actually they may even make it worse.

Take a leaf out of the pack or as Steve has said, change to a longer leaf pack and use the eye to eye shackle setup, using rebound springs, no need for shocks with these leaf springs, I'm assuming you have a slipper spring setup at the moment, going on this statement although I may have misread this (The spring packs are longitudinal and sit in moveable holders) this will have the benifit of a softer less bouncy ride and it will also lift your van up, also with this setup it makes lifting or lowering the vans height easier, it's just a matter of changing the length of the shackles.

One thing you may want to look at before fitting larger wheels, is the inner guard space, a lot of the older style poptops don't have any margine to do this, also these older van don't react well being taller and can sway when being towed, you could end up with a much worse setup.

I would also lower your tyre pressures, 40psi seems a bit much on a van that's about 1t to 1.5t, our camper is 1.3t to 1.5t and I run around 35psi.

Baz.

Graeme the description that you give is typical of mainly tyre bounce not suspension, and agree with the other posters not much you can do with short stiff leaf set up.
To be compliant leaves need to be long and soft and preferably not too many leaves. They can still be strong e.g. many heavy trucks are 2 or 3 leaf in the front but long, and give quite a soft ride.

DD

Thanks everyone for the suggestions.

I acknowledge that the springs are too short for a decent ride but I can't do anything about the springs without scrapping the inboard-mounted wishbones because the camber goes more positive the higher the axle sits.

The tyres are only 14" LT with a LI of 102 at 65 psi so 35 psi may be too soft but I can drop them and see if the increase in contact patch length is too great. However I suspect softer tyres would create more bounce rather than less as the tyres aren't skipping over bumps from being too hard but more likely they are too soft for the springs.

I've already taken measurements for duplicating the chassis and fitting trailing arm independent long leaf spring suspension and fitting 31" tyres. Its a fair amount of work and will destroy the van's resale value (not that it cost much anyway) so I need to be sure the conversion is worthwhile. I'd like even a temporary improvement so that we can determine if we can make sufficient use of the van to keep it, although the current poor ride is a deterrant to doing so. I'm not inclined to do half a job and just fit a live axle to use long springs without strengthening the chassis, lowering the drawbar and fitting larger wheels and brakes.

The task now is to determine if the bounce is from the tyres or from the springs.

Just a quick point... You have mentioned several times about swapping to a live axle. I am guessing you mean a lazy axle or solid axle. LIve axle denotes that it is driven.

I've always known live to describe the suspension characteristic of the axle for when its not independent, drive/driven and lazy describing whether or not the wheels can drive the vehicle and solid or or otherwise for the construction of the axle, but perhaps these terms are not the general interpretation. Anyway, I meant a single axle attached to the 2 springs.

Graeme,
with the right choice of spring (my current fav is 78/79 tojo rears) and dampers
I can get a solid axle setup to ride almost as smoothly as any coil/independent/solid setup.

The issue with a van will be guard clearance for such a long leaf (need 1200mm)
Travel is still constrained to 100mm up and 100mm down.

In no way would fitting a solid axle be a half job as long as its done right.
I imagine the outer chassis rails of your trailer will be sufficiently structural to take the loads of long leaves.

Have a look over in the "fishing" section at "offroad baot trailer" I just posted some pics of a recent conversion to 78 rears. This thing rides like a dream weighing in at 700-800kg.

S