Axle mounting on springs

Submitted: Monday, Jan 12, 2009 at 19:37
ThreadID: 65061 Views:15837 Replies:11 FollowUps:4
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I have asked many people this question (even trailer retailers) and still can't get an educated answer. Plenty of guesses but no substance to any of the theories. So can someone please explain to me why I can't mount my trailer axle under the leaf springs in order for it to ride at a more level height behind the 4wd rather than having them mounting on top of the springs.

Thanks
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Reply By: Member - Nick (TAS) - Monday, Jan 12, 2009 at 19:39

Monday, Jan 12, 2009 at 19:39
You mean a spring over conversion.Quite common on leaf sprung vehicles but Im not sure its totally legal.
AnswerID: 343944

Follow Up By: Member - Nick (TAS) - Monday, Jan 12, 2009 at 19:45

Monday, Jan 12, 2009 at 19:45
Legal thing was for vehicles, not trailers.
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FollowupID: 611807

Reply By: Olsen's 4WD Tours and Training - Monday, Jan 12, 2009 at 19:41

Monday, Jan 12, 2009 at 19:41
You can and many do.
AnswerID: 343946

Reply By: Member - Tony B (Malanda FNQ) - Monday, Jan 12, 2009 at 19:43

Monday, Jan 12, 2009 at 19:43
I might be proved wrong - but no reason I would say. I made a boat trailer back quite a few years ago and made it this way, spring still works the same. Just have to watch your center of gravity, so you can not make it too much higher. You have to do a bit of modification to the center bolt as well. Wait to see what other say - there may be some rule. Regards Tony
AnswerID: 343948

Reply By: Peter_n_Margaret - Monday, Jan 12, 2009 at 19:44

Monday, Jan 12, 2009 at 19:44
My off road trailer is that way.
So is the OKA. That is the way it was built.

Cheers,
Peter
OKA196 Motorhome
AnswerID: 343949

Reply By: Willem - Monday, Jan 12, 2009 at 19:47

Monday, Jan 12, 2009 at 19:47
Dunno about rules......................My trailer has springs over axle. I did the job....and it hasn't broken yet...surprise, surprise....lol
AnswerID: 343952

Reply By: 96 GXL 80 series - Monday, Jan 12, 2009 at 19:59

Monday, Jan 12, 2009 at 19:59
There is less weight on the "U" bolts that way as the axle is taking all the weight.

Some also do it that way because of spring travel with the load they are carrying.

It not only lifts the trailer height but allows more weight to be carried due to spring travel.
AnswerID: 343955

Follow Up By: disco driver - Tuesday, Jan 13, 2009 at 15:16

Tuesday, Jan 13, 2009 at 15:16
It does NOT allow more weight to be carried.
All it does is allow a bit more spring flex before anything bottoms out.
The Tare and Aggregate (or whatever the trendy new terms are) weights do not change simply because the axle is now under the springs.

Disco.
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FollowupID: 611982

Follow Up By: 96 GXL 80 series - Tuesday, Jan 13, 2009 at 15:25

Tuesday, Jan 13, 2009 at 15:25
It is usually the axle to bottom out, if on top of the spring so if under the spring you can get a bit more load on.

Plus a lot more height travel in rough terrain if axle is mounted under the spring.
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FollowupID: 611984

Reply By: DCTriton - Monday, Jan 12, 2009 at 20:00

Monday, Jan 12, 2009 at 20:00
I was offered spoa by the manufacturer of my 8x4 tandem, measured up and it wasn't necessary but in this light I would say it's legal...
AnswerID: 343957

Reply By: Member - shane (SA) - Monday, Jan 12, 2009 at 20:04

Monday, Jan 12, 2009 at 20:04
When you have the axle under the spring the weight is down on the axle and the centre pin. when you have the axle on top the weight is all on the u bolts,nuts and plate. this could be as much as 1-2 tonne as some people just keep piling it on. If you think about it its a lot of weight hanging on eight mild steel bolts. This is as simple as i can explain it.
cheers.shane.
AnswerID: 343960

Follow Up By: Member - Graham H (QLD) - Monday, Jan 12, 2009 at 21:30

Monday, Jan 12, 2009 at 21:30
Hopefully they would be bright enough to use high tensile bolts
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FollowupID: 611838

Reply By: Member - Roachie (SA) - Monday, Jan 12, 2009 at 22:01

Monday, Jan 12, 2009 at 22:01
Like the others have said.....it's the best way to have it set-up. I did my box trailer 6 months ago... no brakes on this trailer and it took me a couple of hours.

Too easy

Roachie
AnswerID: 343999

Reply By: Ozhumvee - Tuesday, Jan 13, 2009 at 08:13

Tuesday, Jan 13, 2009 at 08:13
Easily and cheaply done at home with basic tools.
Just check that the centre bolt in the spring is not bottoming out in the hole in the spring pad which is welded to the axle.
If it is you will have to clamp the spring pack with a large G clamp and turn the bolt over so the head is back in the hole in the pad.
Don't be tempted to grin the excess thread off the end of the centre bolt as then you will find it nigh on impossible to start the nut if you ever have to disassemble the spring pack as even when clamped the springs are slightly apart requiring the extra length to start the nut.
Peter
1996 Oka Motorhome

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AnswerID: 344039

Reply By: Member - Matt (Perth-WA) - Tuesday, Jan 13, 2009 at 12:49

Tuesday, Jan 13, 2009 at 12:49
As the other have said..of course you can do it...the only time it can become an engineering drama is when there are brakes fitted. This can alter the operation of the brakes (cable/hyd) and torque (brake) reaction of the axle.

Point to note is if you have bump stops fitted, make sure you adjust them to still contact the axle/spring at the original distance so they can do their job.
Otherwise to may find over compression and contact with wheel/axle/spring/guard etc with the trailer or wheel arch if you ever hit a large washout etc.

All the best

Matt.
AnswerID: 344087

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