Just had a win raising my silhouette camper & want to tell the world.
Anyone interested how we did it simply without buggering up the wheel geometry, ask & you shall receive.
Foz
Vic41 said
10:13 PM Apr 21, 2014
Fire away Foz, I am sure there would be many here who would want to know, probably haven't seen your post yet
ColB said
09:06 AM Apr 22, 2014
Would be interested Foz, for sure
Aus-Kiwi said
01:19 PM Apr 22, 2014
Larger dia wheels ?
Foz said
06:32 PM Apr 24, 2014
As you probably already know the Coromals have a triangular frame pivoting from the van centre to a leaf spring set up at the wheels.
All sorts of suggestions have come up from increasing wheel size to building a separate hanging frame from which the complete suspension system attaches.
Have been pondering how to do it as you can't sling the axle under the leaf pack & there is nothing really substantial on the caravan frame where the pivots sit.
So..............
At the wheel end, the stub axle is welded in to the triangular frame.
Cut the old stub off flush with the end of the frame, leaves about 120mm stub, weld brand new stub axles to the bottom of the leftover originals. Weld your new brake backing plate supports to the new stubs. Fit longer U bolts. Dab of paint & she's done.
The amount of solid steel to weld to (ie: the two stub axles) provides a really strong joint that can't be beat.
Making sure your measurements are written down before you start is helpful, taking some photo's for later reference once you've cut all the good bits off is also a good idea.
Total cost 2X 50mm stubs "B" type Ford $60
2X brake backing plates, pre drilled $5
2X extended U bolts $9
Grinding discs, welding rods etc approx. $10 Total $84
If you're not confident doing the modification yourself a mate who runs an engineering shop estimates about 4.5 hrs from wheels off to wheels on. This makes the total cost for the mod approx. $450 - 500 taking in to account you'll be paying a premium for the parts if the shop supplies them for you.
And it road tests beautifully, doesn't whack the driveway on the way in & now I need to buy a step for the door.
03_troopy said
06:50 PM Apr 24, 2014
Well done Foz. Sort of like a drop axle but off independently slung stubs? How much height did you achieve, 40mm to 50mm? Or am I picturing it wrong?
As the engineer said...........you could go up to 100mm by duplicating the set up with a dummy stub/spacer with a gusset to each side of the A frame. Plenty of strength there to absorb the twisting effect.
I'm more than happy with the 50mm plus running high wall L/T tyres gives me an extra 30mm.
Keeps the camper roof just level with the ute canopy for aerodynamics.
JustJim said
01:50 PM Apr 27, 2014
Foz..
You may be interested to know - the type of suspension on your Coromal is called a - 'Symons Knee'. (Possibly - 'Symonds')
I believe it was designed by a bloke named Brian Symons, back in the 1960's. It was fitted on trailers initially and appeared on caravans in the 1970's.
The Symons Knee suspension has the advantage of not suffering from axle steer.
Axle steer is a problem with 'live axle' caravans (beam axle and leaf springs)..
A van is far more likely to roll over with a 'live axle' suspension. With a live axle van, if the van sways to one side and the spring compresses, the axle shifts position on one side and steers the van offline, which magnifies the sway.
With a Symons Knee suspension, if the spring compresses the wheel doesn't change direction as it does with a beam axle (although the camber changes), so the sway isn't magnified.
The disadvantage of a Symons Knee suspension is the limited wheel travel and the somewhat high wear rate if used on rougher roads.
A well designed coil spring independent suspension overcomes both the wear rate and wheel travel problems and gives the contents of the van a much smoother ride - but at a price.
The only reason all caravans don't have independent suspensions fitted is price.
Beam axles and leaf springs are by far the cheapest - and the most inferior suspension.
It's interesting that Jayco are now very serious about fitting independent coil spring suspension on their vans. It probably won't be too long before the new suspension is fitted right across the Jayco range.
Jim
-- Edited by JustJim on Sunday 27th of April 2014 02:20:31 PM
Foz said
07:19 PM Apr 27, 2014
Thanks for that Jim, a little info doesn't hurt anyone eh?
This suspension is so simple & if you can't fix it with a welder & a bloody big hammer you're not doing it right.
I notice from your comments re; Jayco that they may be moving to a more complex suspension system.
All Ok I guess until you do break it, as you do.
Then it's a long way to the Jayco dealer as I'll bet the little thingamebob that fits in to the whatsit is exclusive to Jayco only & has to be imported from "that" country that makes everything for the whole world now.
Live axle & leaf springs are so............easy to jerry up &/or replace bits almost anywhere up the track.
Oh well, price of progress I suppose.
regards,
Foz
PeterD said
08:44 PM Apr 27, 2014
JustJim wrote:
The Symons Knee suspension has the advantage of not suffering from axle steer.
Axle steer is a problem with 'live axle' caravans (beam axle and leaf springs)..
Where did you glean this gem? Axle is only of concern on steering axles.
JustJim said
08:30 AM May 1, 2014
Foz
I've heard your reasoning many times over the years and it's an opinion still held by many. Maybe one day you'll see the benefits of better design and superior performance.
I did suggest using a 'well designed' independent coil spring suspension.. In any market imitators turn up, and there are some poor designs on the market, which give the good ones a bad name.
Keep in mind leaf springs are more likely to break than coil springs, especially with the harsh treatment springs get on rough tracks and corrugations.. If you're in the fortunate position to be able to weld if you're stuck in some remote place, you could probably weld any steel item.
Good design and good engineering should be paramount.Add correct rating, and it means failures are no more likely than the suspension on your vehicle.
Few people would be happy with a sixty year old suspension design on their vehicle, yet they defend an older inferior design on their caravan - mainly with the reasoning that when it breaks (not if it breaks) they can weld it up.
Vehicle manufacturers have been modifying and improving suspensions for over a century now. If they didn't we would still be using full elliptic leaf springs and tiller steering on our vehicles. Imagine that on your new Landcruiser.
Ask yourself why the better built caravans, and the so called 'off road' caravans are all using independent suspensions. It's not to save money - It's to improve performance and safety, to improve the ride quality, and with the right design it improves reliability as well.
Peter..
That gem is fact. When a van with leaf springs on a beam axle sways to one side and compresses one spring, the axle steers the van offline.
If you do some thinking about the function of a leaf spring under compression and rebound you'll understand about axle steer.
Think about what happens to the axle position when you flatten a semi-elliptic leaf spring, with the van swaying to one side.
Jim
Foz said
08:22 PM May 1, 2014
Ta folks,
Had a mate who was a school teacher.
Went to school for 12 yrs, uni for 4 yrs then started in the classroom.
Taught for 30 yrs..........then...................................... given the job as careers advisor as his life experience best qualified him for that role. Hah Hah Hah!
He was of the opinion each & every child should be a teacher, rather a narrow perspective.
There are many "school teachers" out & about eh?
Just saying..................
remo said
06:17 AM Sep 10, 2015
Hello FOZ, any chance of some pics of your axle mods? Did the axle end up under the spring pack?
cheers.
Foz said
09:04 PM Sep 10, 2015
Sorry, no pics.
However...............you can not move the axle below the spring pack. This upsets the wheel geometry.
The old stub axle (cut down) just becomes the 50mm spacer between the beam axle & the new stub axle.
Looking at the axle from front or rear of van you have the beam axle on the top. The cut down stub under it. The new stub axle welded to the bottom of the cut down stub axle so you have 3 layers of 50mm steel top to bottom, beam axle, spacer, new stub.
You achieve a 50mm lift.
Higher profile tyres an extra 30mm, overall lift 80mm
Good luck with it all
drewgarth said
11:30 AM Jul 23, 2025
G'Day all,
Hopefully no one minds me digging up this old thread.
I have a Seka 520 and i am keen to look into raising the ride height.
I like the simplicity of what Foz has done, though conceptually i have a challenge.
It looks like the suspension spring pack on the single axle are eye to eye which constrains the geometry.
If i was to add the additional stub axle in, i cant see how this would work, without also dropping the spring pack down by the same amount.
What am i missing?
I welcome any thoughts on this.
cheers
Rusty W said
07:43 PM Jul 24, 2025
Just weld a spacer to the chassis rail where the spring eyes mount. That was done to my Coromal before I bought it and apparently the way to do it if u look on the Coromal forum. No stub axle cutting and welding.
drewgarth said
06:38 AM Jul 26, 2025
Useful to know :) i guess just adding the spacer cha gesture the camber a little. New stub plus plus spacer would keep the camber roughly the same. Nice to have options and thanks for the reply :)
Burt65 said
08:06 AM Jul 28, 2025
JustJim wrote:
The Symons Knee suspension has the advantage of not suffering from axle steer.
Axle steer is a problem with 'live axle' caravans (beam axle and leaf springs)..
-- Edited by JustJim on Sunday 27th of April 2014 02:20:31 PM
Live Axle??? In a Coromal caravan??? Can you show us the picture of the Coromal caravan with the differential?!?!
PeterD said
11:59 AM Jul 28, 2025
Burt, I missed out answering this within a timely period, but as you have broached the subject, here goes.
Coromal suspension pictures. That is a Coromal sales brochure, but if you scroll down you will see pictures of both the new coils spring suspension and the leaf spring suspension that is the subject under discussilon.
Regarding axle steer, see - Caravan and tow vehicle dynamics - It is covered in the paragraphs under the heading "Need for steered wheel stability." If you read the whole article, you will gain a lot of knowledge regarding car and trailer suspension.
Burt65 said
02:36 PM Jul 28, 2025
PeterD wrote:
Burt, I missed out answering this within a timely period, but as you have broached the subject, here goes.
Coromal suspension pictures. That is a Coromal sales brochure, but if you scroll down you will see pictures of both the new coils spring suspension and the leaf spring suspension that is the subject under discussilon.
Regarding axle steer, see - Caravan and tow vehicle dynamics - It is covered in the paragraphs under the heading "Need for steered wheel stability." If you read the whole article, you will gain a lot of knowledge regarding car and trailer suspension.
Thank you, Peter, for your reply. Being a mechanic, I'm well aware of all sorts of different axles setup.. Hence, my question about the "live axle" JustJim mentioned in his old post.. I have yet to see a live axle on a caravan of any brand... That's why I was interested to see a caravan with a "Live axle".
Now regarding the conventional setup of axle and leaf springs, and the mentioned "axle steer", I would like to add that we are talking about a couple of degrees of either toe in or toe out and only when the wheels are not on the same plane... It is there, for sure, but not a real crisis situation issue or as bad as painted by JustJim... If it was a severe issue, by now all caravan would have independent suspension...
PeterD said
07:38 PM Jul 28, 2025
I should have also pointed out that Jim has not been active for a while. From his profile - Last Access 06:35 Mar 15, 2015
Hi all,
Just had a win raising my silhouette camper & want to tell the world.
Anyone interested how we did it simply without buggering up the wheel geometry, ask & you shall receive.
Foz
Fire away Foz, I am sure there would be many here who would want to know, probably haven't seen your post yet
As you probably already know the Coromals have a triangular frame pivoting from the van centre to a leaf spring set up at the wheels.
All sorts of suggestions have come up from increasing wheel size to building a separate hanging frame from which the complete suspension system attaches.
Have been pondering how to do it as you can't sling the axle under the leaf pack & there is nothing really substantial on the caravan frame where the pivots sit.
So..............
At the wheel end, the stub axle is welded in to the triangular frame.
Cut the old stub off flush with the end of the frame, leaves about 120mm stub, weld brand new stub axles to the bottom of the leftover originals. Weld your new brake backing plate supports to the new stubs. Fit longer U bolts. Dab of paint & she's done.
The amount of solid steel to weld to (ie: the two stub axles) provides a really strong joint that can't be beat.
Making sure your measurements are written down before you start is helpful, taking some photo's for later reference once you've cut all the good bits off is also a good idea.
Total cost 2X 50mm stubs "B" type Ford $60
2X brake backing plates, pre drilled $5
2X extended U bolts $9
Grinding discs, welding rods etc approx. $10 Total $84
If you're not confident doing the modification yourself a mate who runs an engineering shop estimates about 4.5 hrs from wheels off to wheels on. This makes the total cost for the mod approx. $450 - 500 taking in to account you'll be paying a premium for the parts if the shop supplies them for you.
And it road tests beautifully, doesn't whack the driveway on the way in & now I need to buy a step for the door.
Well done Foz. Sort of like a drop axle but off independently slung stubs? How much height did you achieve, 40mm to 50mm? Or am I picturing it wrong?
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'day Troopy,
You got it. Gets 50mm minimum.
As the engineer said...........you could go up to 100mm by duplicating the set up with a dummy stub/spacer with a gusset to each side of the A frame. Plenty of strength there to absorb the twisting effect.
I'm more than happy with the 50mm plus running high wall L/T tyres gives me an extra 30mm.
Keeps the camper roof just level with the ute canopy for aerodynamics.
Foz..
You may be interested to know - the type of suspension on your Coromal is called a - 'Symons Knee'. (Possibly - 'Symonds')
I believe it was designed by a bloke named Brian Symons, back in the 1960's.
It was fitted on trailers initially and appeared on caravans in the 1970's.
The Symons Knee suspension has the advantage of not suffering from axle steer.
Axle steer is a problem with 'live axle' caravans (beam axle and leaf springs)..
A van is far more likely to roll over with a 'live axle' suspension.
With a live axle van, if the van sways to one side and the spring compresses, the axle shifts position on one side and steers the van offline, which magnifies the sway.
With a Symons Knee suspension, if the spring compresses the wheel doesn't change direction as it does with a beam axle (although the camber changes), so the sway isn't magnified.
The disadvantage of a Symons Knee suspension is the limited wheel travel and the somewhat high wear rate if used on rougher roads.
A well designed coil spring independent suspension overcomes both the wear rate and wheel travel problems and gives the contents of the van a much smoother ride - but at a price.
The only reason all caravans don't have independent suspensions fitted is price.
Beam axles and leaf springs are by far the cheapest - and the most inferior suspension.
It's interesting that Jayco are now very serious about fitting independent coil spring suspension on their vans.
It probably won't be too long before the new suspension is fitted right across the Jayco range.
Jim
-- Edited by JustJim on Sunday 27th of April 2014 02:20:31 PM
This suspension is so simple & if you can't fix it with a welder & a bloody big hammer you're not doing it right.
I notice from your comments re; Jayco that they may be moving to a more complex suspension system.
All Ok I guess until you do break it, as you do.
Then it's a long way to the Jayco dealer as I'll bet the little thingamebob that fits in to the whatsit is exclusive to Jayco only & has to be imported from "that" country that makes everything for the whole world now.
Live axle & leaf springs are so............easy to jerry up &/or replace bits almost anywhere up the track.
Oh well, price of progress I suppose.
regards,
Foz
Where did you glean this gem? Axle is only of concern on steering axles.
Foz
I've heard your reasoning many times over the years and it's an opinion still held by many.
Maybe one day you'll see the benefits of better design and superior performance.
I did suggest using a 'well designed' independent coil spring suspension..
In any market imitators turn up, and there are some poor designs on the market, which give the good ones a bad name.
Keep in mind leaf springs are more likely to break than coil springs, especially with the harsh treatment springs get on rough tracks and corrugations..
If you're in the fortunate position to be able to weld if you're stuck in some remote place, you could probably weld any steel item.
Good design and good engineering should be paramount. Add correct rating, and it means failures are no more likely than the suspension on your vehicle.
Few people would be happy with a sixty year old suspension design on their vehicle, yet they defend an older inferior design on their caravan - mainly with the reasoning that when it breaks (not if it breaks) they can weld it up.
Vehicle manufacturers have been modifying and improving suspensions for over a century now.
If they didn't we would still be using full elliptic leaf springs and tiller steering on our vehicles.
Imagine that on your new Landcruiser.
Ask yourself why the better built caravans, and the so called 'off road' caravans are all using independent suspensions.
It's not to save money - It's to improve performance and safety, to improve the ride quality, and with the right design it improves reliability as well.
Peter..
That gem is fact.
When a van with leaf springs on a beam axle sways to one side and compresses one spring, the axle steers the van offline.
If you do some thinking about the function of a leaf spring under compression and rebound you'll understand about axle steer.
Think about what happens to the axle position when you flatten a semi-elliptic leaf spring, with the van swaying to one side.
Jim
Had a mate who was a school teacher.
Went to school for 12 yrs, uni for 4 yrs then started in the classroom.
Taught for 30 yrs..........then...................................... given the job as careers advisor as his life experience best qualified him for that role. Hah Hah Hah!
He was of the opinion each & every child should be a teacher, rather a narrow perspective.
There are many "school teachers" out & about eh?
Just saying..................
Hello FOZ, any chance of some pics of your axle mods? Did the axle end up under the spring pack?
cheers.
Sorry, no pics.
However...............you can not move the axle below the spring pack. This upsets the wheel geometry.
The old stub axle (cut down) just becomes the 50mm spacer between the beam axle & the new stub axle.
Looking at the axle from front or rear of van you have the beam axle on the top. The cut down stub under it. The new stub axle welded to the bottom of the cut down stub axle so you have 3 layers of 50mm steel top to bottom, beam axle, spacer, new stub.
You achieve a 50mm lift.
Higher profile tyres an extra 30mm, overall lift 80mm
Good luck with it all
G'Day all,
Hopefully no one minds me digging up this old thread.
I have a Seka 520 and i am keen to look into raising the ride height.
I like the simplicity of what Foz has done, though conceptually i have a challenge.
It looks like the suspension spring pack on the single axle are eye to eye which constrains the geometry.
If i was to add the additional stub axle in, i cant see how this would work, without also dropping the spring pack down by the same amount.
What am i missing?
I welcome any thoughts on this.
cheers
Live Axle??? In a Coromal caravan??? Can you show us the picture of the Coromal caravan with the differential?!?!
Burt, I missed out answering this within a timely period, but as you have broached the subject, here goes.
Coromal suspension pictures. That is a Coromal sales brochure, but if you scroll down you will see pictures of both the new coils spring suspension and the leaf spring suspension that is the subject under discussilon.
Regarding axle steer, see - Caravan and tow vehicle dynamics - It is covered in the paragraphs under the heading "Need for steered wheel stability." If you read the whole article, you will gain a lot of knowledge regarding car and trailer suspension.
Thank you, Peter, for your reply. Being a mechanic, I'm well aware of all sorts of different axles setup.. Hence, my question about the "live axle" JustJim mentioned in his old post.. I have yet to see a live axle on a caravan of any brand... That's why I was interested to see a caravan with a "Live axle".
Now regarding the conventional setup of axle and leaf springs, and the mentioned "axle steer", I would like to add that we are talking about a couple of degrees of either toe in or toe out and only when the wheels are not on the same plane... It is there, for sure, but not a real crisis situation issue or as bad as painted by JustJim... If it was a severe issue, by now all caravan would have independent suspension...
I should have also pointed out that Jim has not been active for a while. From his profile - Last Access 06:35 Mar 15, 2015