2008 bt50 daul cab suspension

Submitted: Monday, Nov 05, 2012 at 17:31
ThreadID: 98874 Views:48262 Replies:8 FollowUps:4
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hi team, got rear leaf springs that arnt enough, put iron man upgrade on with adjustable helpers & still bottoms out on stoppers. do i up grade to even bigger leafs or put in airbags. ute has alloy slide on with a roof top tent at rear & with every thing inside is just to much. cheers
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Reply By: M&N's - Monday, Nov 05, 2012 at 18:40

Monday, Nov 05, 2012 at 18:40
M&N's I fitted the polyair big bags [100psi] to my BT50 in 2008. Been towing a 2 tonne GOLF Outback on and of ever since approx 55k.Never inflated them over 35psi and so far[touch wood my head will do] no problems.The dual cab carries about 600 kilos including tow ball weight.There has been plenty of dirt roads in the mix.The reason I don't go over 35psi is because back when fitted there stories of chassis's bending because of to high a pressure and bending around airbag top mount,I suspect more like far too much weight being placed behind the axle of Any dualcab.Happened to a mate's Datsun 720, years ago on a trip to Kowanyama.If you fit bags you will lose the bump stops.You could always leave some weight behind if you're brave enough...Mick
AnswerID: 497973

Reply By: Sand Man (SA) - Monday, Nov 05, 2012 at 19:27

Monday, Nov 05, 2012 at 19:27
I would be a little bit careful.

I seem to recall the potential for bent chassis when airbags are added to a dual cab.
If helper springs are not "helping", I would seek the advice from a qualified engineering firm.

Perhaps ARB, or a similar retailer have the necessary skills to offer good advice.


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AnswerID: 497983

Reply By: disco driver - Monday, Nov 05, 2012 at 19:48

Monday, Nov 05, 2012 at 19:48
If after upgrading the springs it still bottoms out, you're obviously overloaded and probably illegal.
Take some of your stuff out of the slide on
Buy a bigger truck, Cruiser,Patrol, Chev Silverado or F 250.


AnswerID: 497984

Reply By: Member - RobnJane(VIC) - Monday, Nov 05, 2012 at 19:51

Monday, Nov 05, 2012 at 19:51
Hi Ray,

First things first, I suggest you weigh the total of what you are adding to the back of your ute. Don't rely on the weight advised in brochures or data plates for this. Then you or a suspension/spring specialist will be able to determine the best solution.

In my experience I would not be relying on any of the 4wd speciality suppliers for such advice, unless you get lucky all you'll get is a semi informed opinion.

As a thought, adding an additional leaf under the main, plus a reset could well give you a good result. I would not use an airbag in such an installation at all due to peak load concentration when axle is deflecting or using most/all its' travel.

Hope this is of interest.


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AnswerID: 497985

Reply By: AlbyNSW - Monday, Nov 05, 2012 at 20:46

Monday, Nov 05, 2012 at 20:46
I would only be looking at airbags as a fine tuning of your suspension not the main load carrier
I think you need to lighten the load or fit heavier springs
AnswerID: 497989

Reply By: splits - Monday, Nov 05, 2012 at 21:05

Monday, Nov 05, 2012 at 21:05

You are a prime candidate for a bent chassis if you keep going in this direction.
The car in the attached photo does not have air bags. No doubt he has fitted heavier springs though with all of that gear behind the rear axle. Any downward pressure on a chassis behind the axle will cause it to pivot on the axle and try and lift the front. This weight is extreme. The forces generated as all that mass moves up and down will far exceed its static weight and it must have come close to actually getting the front wheels off the ground on some road surfaces. Very few chassis will survive that.

Air bags might have helped a little here. They would have bent the chassis long before he got that far out in the desert and maybe made recovery easier. They are not like an ordinary spring. They get harder as they compress and can become very hard as they near maximum compression. When you overload the car and inflate them far enough to get the car back up level again, you take a lot of weight off the springs and create a new major load bearing point directly above the axle. The chassis now runs from the front suspension then sits on the bags and extends out the back where all the excess weight is bouncing up and down on rough roads. This makes the chassis so much easier to bend.

How much weight do you have in the front of your car? If you are going by the maximum carrying capacity of the car then don't forget that includes five heavy people in the cabin. You can't put a little bit in the front e.g. just a couple of average size people, and bring it up near GVM by putting everything else in the back. Many people do that then find the rear is dragging on the ground. They think the car is just under GVM therefore it must have a crappy suspension so they rush out and buy heavier springs or air bags then find the chassis bends. That convinces them the whole car car is no good and they vow never to buy that brand again

These cars are not designed to carry the weight you have behind the axle. That is why the motor industry makes utes ranging in size from your BT50 to Landcruisers to F250s to heavier trucks. The trick is to buy the right size one then head off into the bush with maximum safety and reliability.

AnswerID: 497992

Follow Up By: Whirlwinder - Monday, Nov 05, 2012 at 22:48

Monday, Nov 05, 2012 at 22:48
Well said splits and easy to follow. I have been saying the same for 10 years having seen my first bent chassis.
I often drive a Ford Ranger dual cab with a canopy body and find it jerks back and forth continually and is a pain to drive any distance. I hate to think what it would be like on rough dirt roads loaded for a trip.
FollowupID: 773930

Follow Up By: Ross M - Tuesday, Nov 06, 2012 at 09:28

Tuesday, Nov 06, 2012 at 09:28

I think the comment there would be:

BRAVO well done.

I didn't know Mazda made a tipper model.
Is that a slide on camper or a slide off. Unsure which at the moment.

Your comments show the things which can and do happen when people try to use the full manufacturers load ratings as everyday usage.
Many have the opinion that manufacturers ratings are ok to follow, re loading and towing weights.
Your posts tend to suggest a great deal of caution should be observed.
I like the part where you said, a 4wd store isn't the place to go for suspension advice. Oh so true.

It is good to see comments from someone who has an understanding of the dynamic performance issues, most don't, and not just the static loading, she'll be right recommendations.
FollowupID: 773940

Follow Up By: olcoolone - Wednesday, Nov 07, 2012 at 08:00

Wednesday, Nov 07, 2012 at 08:00
Ross..... no Mazda don't make a tipper model.

But Toyota makes a Hilux tipper model as pictured above!
FollowupID: 774008

Reply By: Ashez H - Monday, Nov 05, 2012 at 23:31

Monday, Nov 05, 2012 at 23:31
Maybe have a look at Geoff M's (Vic) comments and experiences with his BT.
Surely the chassis can be reinforced? Not sure how much it would cost though?

AnswerID: 497998

Follow Up By: splits - Tuesday, Nov 06, 2012 at 07:47

Tuesday, Nov 06, 2012 at 07:47
"Surely the chassis can be reinforced"

You can reinforce anything, even your lawn mower chassis, but why go to all that trouble when there standard cars that will do the job? 4wd owners are notorious for buying cars that are a couple of sizes too small. They then "upgrade' them and wonder why things break out in the bush.

Chassis problems are not the only issue here. Have you ever wondered what all that weight hanging off the back will do to the on road handling of the car? It has been designed to understeer. If you stiffen the front springs or sway bar, you will transfer more weight to the outside wheel in corners and it will understeer a bit more. If you stiffen the rear end without doing the same to the front you will increase the weight on the outside rear wheel plus alter the front to rear tyre slip angle ratio and most likely change the car from understeer to oversteer. That is a lot more difficult for the average driver to handle, particularly on wet roads. It would be even worse with all that weight swinging the tail of the car around.

That car will handle that weight easily in standard form if he spreads the weight between the car and a small trailer. If the bare camper is not too heavy then it will work. If it is then he has got the wrong car.
FollowupID: 773935

Reply By: olcoolone - Tuesday, Nov 06, 2012 at 07:42

Tuesday, Nov 06, 2012 at 07:42
The best thing to do is take your BT50 to a weighbridge and weigh what is over the front axle and then what is over the rear.... this will give a suspension place an idea of what is where.

Make sure you don't exceed the axle ratings and then set about balancing the weight across both, grab a piece of paper write down and calculate known weight left to right (don't forget to include the fuel tank and fridge when full)..... this will make your BT50 a lot more stable and safer...... basically divide your vehicle into four squares, front left, front right, rear left, rear right.

Try and move heavy items into the centre of the vehicle.

Once you have done this then it's time for suspension.

Too many people without thinking; setup vehicles with too much weight on the back or one corner.

We do this to all our 4x4's and our businesses field service vehicles.
AnswerID: 498007

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