Coromal suspension conversion

[Graeme]

The original independent suspension on my 1990 pop-top had too little movement and rode too harshly. Step 1 of the upgrade plan was to replace the suspension with soft off-road springs and shocks using a live axle. Step 1a is to relocate the coupling from on top of the draw-bar to below it to level the van. Step 2 is to fit X5 rims the same as I have fitted to the D4 especially if parallel bearing hubs can be produced.

The original van...
https://www.aulro.com/afvb/images/imported/2013/01/199.jpg

and its suspension...
https://www.aulro.com/afvb/images/imported/2013/01/200.jpg

new springs...
https://www.aulro.com/afvb/images/imported/2013/01/201.jpg

and shocks...
https://www.aulro.com/afvb/images/imported/2013/01/202.jpg

X5 wheel position mock-up...
https://www.aulro.com/afvb/images/imported/2013/01/203.jpg

A test run without the coupling mount having yet been relocated revealed that it tows and rides exceedingly well at least at speeds up to 100 kph over the local B-grade sealed roads and light corrugations and pot-holes on unsealed roads. The van doesn't jump around anymore nor tug on the D4 and the mattress now stays put even though it only sits on an un-edged base. The springs are Vehicle Components 608 series (60mm x 8mm) 850 mm long 1.6T rated with 1 leaf removed which is expected to be the same as their 1.3T springs. The removed leaf will be refitted later if significant weight is added.

The X5 rims have more offset than the HT rims so a longer axle is needed but will have to wait to see if 1.6T parallel hubs can be shoe-horned into the X5 rims.

[TerryO]

With that much extra ground clearance now you will have to buy one of those fold up steps so you and your good wife will be able to get into it. ...;)

cheers,
Terry

[Graeme]

Already splurged $7 on a step...
https://www.aulro.com/afvb/images/imported/2013/02/1382.jpg


The lowered coupling...
https://www.aulro.com/afvb/images/imported/2013/02/1383.jpg

[3 Lions]

Good job:BigThumb:

Col

[Graeme]

Parallel bearing hub-drums are on order. The hubs have the 78mm dia "Ford" boss and will be supplied with 14mm studs on 5 x 120mm PCD, but with the studs not fitted. I'll then have the boss machined to 72.5mm to suit X5 rims. There won't be a lot of metal around the outer bearing but very little less than what's around the inner bearing so hopefully will be strong enough. Once I'm happy with the hubs a longer, parallel bearing axle will be obtained.

The guards are in the process of being modified to allow for LT245/70-17 tyres. The original plastic wheel guards will be refitted, albeit with a 25mm spacer, which will hide the trimming and clear the wider tyres.

Pics later.

[Graeme]

Parallel bearing hub converion for LR /X5 rims:

Parallel bearing hub boss originally machined to 80mm for Ford but drilled to 5 x 120mm PCD for 14mm studs:
https://www.aulro.com/afvb/images/imported/2013/02/1021.jpg



Now with 72.5mm boss for X5 or LR rims:
https://www.aulro.com/afvb/images/imported/2013/02/1022.jpg
The experienced machinist thinks there's plenty of metal around the bearing (6.7mm). I hope he's right.


X5 rim fitted to the parallel bearing hub. Can't loose the grease cap as it can't get past the rim.
https://www.aulro.com/afvb/images/imported/2013/02/1023.jpg



Test fit of D4 rim to parallel bearing hub:
https://www.aulro.com/afvb/images/imported/2013/02/1024.jpg
To fit it would need the outside edge of the boss rounded a little more, a special grease cap made from the combination of a standard hub's cap and a parallel bearing hub's cap to fit through the rim's cap hole and the studs shortened by about 5mm. However as I would need the rims to be spaced outwards 10mm to get acceptable spring/tyre clearance on the axle made for X5 rim fitment, the studs would be OK as would the boss edge but still require a custom cap.

A new axle is on order.

[Redback]

Great job Graeme, van is coming along nicely, are you getting a new longer axle so you can fit the LR rims at a later date??


I'll have to get that engineers number if I ever go to electric brakes, I sorted my hubs yesterday, fitted a new backing plate mount, the type that goes over the square section of the axle, this allows us to keep the backing plate we were supplied with, just need to do the shackle bushes and it's done.

Baz.

[Graeme]

The current axle is for Ford bearings and is too short for X5 or LR rims even if standard 5x120 pcd hubs with 14mm studs were to be used due to the more positive offset and wider X5 and LR rims. This axle was obtained to check that the new suspension didn't introduce any undesireable characteristics because if it did then the old suspension would have been refitted and the van sold. This axle and the 14' rims may be refitted and the guard spacers removed when the van eventually gets sold. The enlarged wheel openings are not visible with the original guards fitted.

The new axle will be made to accept the parallel bearing hubs and at a length to give enough spring clearance for the X5 rims, keeping the wheels in as much as possible but still requiring a 25mm spacer for the guards. LR rims will use the same axle but require 10-15mm spacers to give tyre/spring clearance and will require the plastic gaurds to be spaced out even further to accomodate wider tyres. I hope not to need to fit LR rims - they would protrude a fair way out from the sides as the wheel wells were not designed to accomodate such wide tyres.

Edit: The 255/55-19 tyres don't protrude any further out as they're no wider so no extra guard spacer is req'd.

The only reason my hubs needed machining is because I wanted to use parallel bearing hubs to get the large outer bearing that is much better able to withstand the leverage of the 30/31" tyres with the anticipated load. This bearing configuration is rated at 1600 kg for large diameter tyres. The hubs were special order from Melbourne Trailer & Van Supplies in the same way as your's - having 5x120mm pcd 14mm holes in a hub they normally supply with a different pcd and/or stud dia. Subsequent machining was straight-forward - reduce the boss to 72.5mm dia please! Melb Trailers were fussing too much about reducing the boss dia so I didn't persist in trying to get them to do it.

Did Melb Trailers not want to swap the backing plates?

[Redback]

They said only the 10" hubs have the flat backing plate, the 9" hubs have the raised backing plate, so they sent me the new mounts, it's worked out well, so it's all good now.

Baz.

[Graeme]

The suspension and wheel conversion is done except for mudflaps and new rear stabiliser legs. The van is slightly nose down at normal height but level at +30mm. Guard spacers were not required due to mounting the guards' lower edge level with the van side lower edges rather than 30mm below, along with some judicious trimming of the fibreglass guards to ensure the tyres can't touch. It rides twisty, bumpy sealed roads at 100 kph and gravel roads with small bumps and pot-holes and minor corrugations at 90 kph (I didn't want to go faster) and meanders along my rough driveway magically - I'm chuffed!
https://www.aulro.com/afvb/images/imported/2013/02/497.jpg

[Redback]

Looks great Graeme, always good when it tows well, nothing worse than a bad handling trailer

Baz.

[Graeme]

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.

[Geedublya]

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

[Graeme]

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

[TerryO]

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

[Graeme]

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

[Graeme]

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.
https://www.aulro.com/afvb/images/imported/2013/08/1513.jpg

[loanrangie]

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.
https://uploads.tapatalk-cdn.com/20220403/65f849ddca62b082b32687ecdb778507.jpghttps://uploads.tapatalk-cdn.com/20220403/1292b6ec42bc4e3d7a6db6b717944590.jpghttps://uploads.tapatalk-cdn.com/20220403/578929d165d0e1ae9b9e575a8ff9b858.jpghttps://uploads.tapatalk-cdn.com/20220403/86b5871bbbc82376007ba5777c4a8f15.jpg

[Graeme]

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!

[loanrangie]

Did you need to replace the spring hangers or was it a bolt in solution ?

[Graeme]

Normal longitudinal spring hangers with weight spreading pads were fitted well away from the original retaining brackets.

[Graeme]

Here's a pic using the original 14" rims.

[loanrangie]

Here's a pic using the original 14" rims.

Were both hangers added or the fronts still the originals ? , not something i would need to do right away but planning it out for now.

[PhilipA]

177897Funny most people with Coromal experience seem to think that the the Coromal suspension is far superior to solid axle. I cannot really comment as I have always had independent suspension on first my camper trailer then my 2002 Coromal 505 Pioneer XC. No skipping side ways on corrugations particularly on corners, it just follows. One wheel off the bitumen onto a broken shoulder , no problem.

To raise a Coromal all that is necessary is is weld blocks between the suspension pivot points and the centre cross member and also under the spring shackles.

Mine is high enough with nothing hanging down to catch anything. Mine has 2 tonne hubs so no possibility of later LR hubs.

I have to say my Coromal is amazingly stable when towing on bitumin or in dirt.

The only mod I may make is to switch to 7 inch rims from 8 inch as the 265.75R16 tyres are very close to the spring hangers and I may fit 235 85r16s. So close with my Toyo muds with big Side Biters , that I fitted 7MM spacers. Second hand 16x7 rims with 0 offset are like hens teeth.
Regards PhilipA

[Graeme]

All new hangers. The original springs were very short and didn't have hangers as such, just captive brackets to stop the springs from dropping down.

The prime reasons for replacing the suspension was because the suspension had grossly inadequate travel and the van was very choppy on all but smooth surfaces, jigging the D4 excessively. Later Coromal springs and arms wouldn't fit because they were all longer.

[loanrangie]

177897Funny most people with Coromal experience seem to think that the the Coromal suspension is far superior to solid axle. I cannot really comment as I have always had independent suspension on first my camper trailer then my 2002 Coromal 505 Pioneer XC. No skipping side ways on corrugations particularly on corners, it just follows. One wheel off the bitumen onto a broken shoulder , no problem.

To raise a Coromal all that is necessary is is weld blocks between the suspension pivot points and the centre cross member and also under the spring shackles.

Mine is high enough with nothing hanging down to catch anything. Mine has 2 tonne hubs so no possibility of later LR hubs.

I have to say my Coromal is amazingly stable when towing on bitumin or in dirt.

The only mod I may make is to switch to 7 inch rims from 8 inch as the 265.75R16 tyres are very close to the spring hangers and I may fit 235 85r16s. So close with my Toyo muds with big Side Biters , that I fitted 7MM spacers. Second hand 16x7 rims with 0 offset are like hens teeth.
Regards PhilipA

Yes i was looking at the pivot points and agree that it would be easy enough to go that way, looks like we will be buying it so will look at it properly when we get it home.
Using my spare 18" wheels would be ideal but 15 or 16's may be easier to fit but not something i'd do eight away, fitting a 12V system is first priority and then a diesel heater.
If it wasn't for the pesky 2 money pits (kids) your van would be perfect for us.

[PhilipA]

I
f it wasn't for the pesky 2 money pits (kids) your van would be perfect for us.

There is one layout that has a front "diner" type layout , which can easily covert to a bed for smaller kids.

505 Seka Pioneer XCs are like hen's teeth and highly sought after. Mine was the only one for sale in OZ at the time and I went to Yarrawonga for it.

Join the Facebook Coromal Owners group and you will access lots of good info and ideas.
Regards PhilipA

[loanrangie]

[COLOR=#333333]I

There is one layout that has a front "diner" type layout , which can easily covert to a bed for smaller kids.

505 Seka Pioneer XCs are like hen's teeth and highly sought after. Mine was the only one for sale in OZ at the time and I went to Yarrawonga for it.

Join the Facebook Coromal Owners group and you will access lots of good info and ideas.
Regards PhilipAMine are 19 and 15 so a bit big for most kid beds, I expected to be looking at 2 berth vans but they had other ideas.
Just one exactly the same as yours for 25k which is 10k more than the one we are looking at.

[PhilipA]

If you plan any dirt road travel, it is worthwhile to buy the Pioneer XC version as it has a stronger chassis, all the furniture is bolted to the walls and floor, and has the larger hubs and stronger longer springs. They also have 16x8 wheels and 265 75r16 tyres with a 120 load rating. They are also lighter than most other off road caravans. Mine is 1280Kg tare AFAIR with 1860 GVM. In addition the cutaway at the back will enable travel through washaways and creek crossings that will damage straight caravans .
You would have to watch the load rating on your proposed tyres as the bigger vans are heavy and have only 2 tyres ( or I guess 4 if you get a tandem) . I like the singles as you can turn the thing by hand if necessary in a tight spot. I think that the main reason stated for tandems is if you get a blow out. IMHO much overstated if you change tyres every 8 years or so. 20 year old tyres are common on vans and surprise surprise they sometimes blow out.

I can recall going to Lorella springs in NT and a bloke with a Bushtracker ( tres expensive) had his microwave drop out onto the floor. In a Coromal XC it is bolted down.
Regards PhilipA

[loanrangie]

I want an off-road van but not a dual axle behemoth but the wife wants a family van even though the eldest is unlikely to come with us very often, not much choice in our price bracket for off-road vans. I've just about talked myself out of the above fan for now.

[PhilipA]

Put them in a swag under the awning!
Regards PhilipA

[loanrangie]

Put them in a swag under the awning!
Regards PhilipAThat was my plan but almost 19yo princess won't have it and wife doesn't accept my reasoning [emoji34].
Was going to be just in time for an Easter get away but princess's birthday is Easter Saturday and she doesn't want to go away now.

[loanrangie]

Problem solved, just found a 2004 17ft jayco freedom semi off road van with the same internal bunk fit out as the coromal we looked at.
Deposit paid and will collect before the weekend, happy with the 16k price as well. Van is very neat and tidy and well looked after.
https://uploads.tapatalk-cdn.com/20220405/32e5d616cb25c84263b0489263afb75a.jpg