Thread: Coromal suspension conversion

Thanks Baz. Swapping out an independent system for a live axle system had me wondering if it was the right decision but live axles are used so widely that it was bound to be an improvement due to using far better springs and shocks. I've been wanting to do a loop through Willandra and Mungo NPs as a trial but wasn't game to take the van in its old form on those western gravel roads.

Hi Graeme,

I want to upgrade my Goldstream camper suspension and bearings similar to what you have done.

At the moment it is running ford bearings on a 45mm axle and 10" brakes with slipper springs.

I want to go to parallel bearings on a 50mm axle with 12" brakes and long soft off road springs.

What weight is your van? Are 10" brakes large enough running 30" tyres. I'm running 31" and was advised that 10" was too small for the ATM I want (1700kg).

Why did you go for Vehicle components springs? I'm looking at ALKO or Alloy Industrial Springs as well.

I wasn't considering running the X5 wheels as I didn't think it could be done. How have you resolved the bearing cap issue?

Are you getting the caravan re-rated? If so could you PM me your engineers details.

Thanks Geoff

I initally wanted to fit 12" brakes because I was allowing for an ATM of 1.8T. Vehicle Components show that 10" brakes are normally only sufficient for 1.4T with 30/31" tyres although also stating that the legislation only requires "sufficient braking" or similar wording. I'd like to have the ATM upgraded to 1.6T but 1.4T will do. X5/LR rims wont fit hubs with 12" brakes. The caps for the 1.6T parallel bearing hub and the 1.5T hub fit the X5 rims. The cap modificiation would only be required if I wanted to fit LR rims, if it is indeed feasible. The nut fits inside the small cap but the split pin may grab.

I've only seen parallel bearing hubs rated at 1.6T and only with 10" brakes. The 1.5T hubs for 12" brakes use a larger inner bearing but a Holden inner as the outer so using a Ford inner as the outer (the same as a parallel hub) the max load would be increased to more than 1.6T due to the inner being larger than that of the parallel bearing hub. The axle would need to be machined to 35mm for the Ford inner bearing rather than 31.75mm for a Holden inner, thus creating a 1.6+T hybrid bearing axle/hub. The 1.5T hub has the same dia boss as the 1.6T parallel bearing hub so it could be machined to fit X5 rims too, although the similarly-reduced outer bearing wall thickness may prevent an increased load capability - indeed even the 1.6T rating might be compromised. As the 1.5T inner bearing is only 3mm larger in radius the hub should still be able to be drilled to 120 PCD for 14mm studs as there is plenty of room in the parallel bearing hub.

The 2T hubs use a much larger outer bearing with a boss that is far too large for X5 or LR rims. Furthermore due to the larger inner bearing (89mm OD), a PCD of 120mm is probably impossible due to interference with the inner bearing housing. I was informed that the parallel bearing hub could not be drilled to Commodore pattern but the person must have thought I wanted to fit Comomdore rims with their small registers (holes). (Edit: This has no bearing on what can be done to the hubs though, only to not necessarily take a statement as gospel.)

According to Vehicle Components, a 45mm square axle is rated at 2T as long as the tyre centreline doesn't exceed 190 mm from the chassis, although it should be the spring. May as well save weight and money where possible.

I used Vehicle Components springs because they are thicker and use 1 less leaf than Alko for the same load rating and therefore I expect them to be softer.

As my van is pre-compliance plate (and therefore no manufacturer ATM), the ATM is determined by a blue-slip inspector using RTA guidelines for the most limiting factor - coupling, safety chain(s), springs, brakes and tyre load rating.

HTH

On tandem axle van most van builders use 10" brakes for up to around 2.8 ton, over that they use 12" brakes. So the info you found of needing 12" brakes on a van around 1.4 sounds right.

I know on our van even when it's fully laden the 10" brakes stop it really well.

cheers,
Terry

There's a Desert Sky model with 10" electric brakes for a 1.6T GTM although it has 29" tyres.

A pic of the van on its first real outing. It rode the pot-holes, ruts and rocky track very well with nothing inside having moved, including the unrestrained mattress on the island bed.

Thread revived from the dead, looking at upgrading from our camper trailer and 2 vans are in our price bracket. A jayco 17ft off road and coromal 17ft non offroad model, i prefer the jayco but the boss doesn't like the internal layout as there isn't an option for another bed (or 2). The coromal has bunks and will suit our needs but i really wanted the extra ground clearance which is how i ended up here - googled coromal spring over conversion.
The coromal is a 2003 and has the same independent/leaf spring suspension as your van has so looks like its doable, do you still have the van Graeme or moved on to better things ?
I have a spare set of 18" rims so using them on the van would be ideal.

I no longer have the van primarily as my wife wanted a van with an ensuite.

PS The extra 3ft makes quite a difference to available space!