BT50 2013 suspension upgrade

My bt50 has a constant 300kg load in the tray with approx 100kg in front of the rear axle. No front bar or winch. My off-road van has a 200kg ball weight. Spoke with 2 companies today re a suspension upgrade.
No.1 suggested 300kg rear springs to take care of the constant payload with airbags to take care of the van when touring
No.2 suggested 300 - 600kg rear springs with no airbags
Can anyone please comment re which setup is most desirable or alternatives? Not interested in WDH due to their off-road limitations.
Looking forward to some sage advice
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Reply By: Member - willawa - Friday, May 02, 2014 at 18:59

Friday, May 02, 2014 at 18:59
Hi tg123
for what its worth,I looked at a number of systems for my Colorado in 2012 and ended up fitting 'Super Springs' ,lifted the rear 2" with no significant change to the front .
the advice I was given that air bags tend to put extra pressure on the real axle .
I tow a Ultimate CT with a loaded rate of 1800kgs and a fully loaded tub ( fridge,tools camping gear ,tools , etc etc )
May be worth a look.


AnswerID: 531696

Reply By: disco driver - Friday, May 02, 2014 at 19:39

Friday, May 02, 2014 at 19:39
Before you go getting a new suspension or, heaven forbid, airbags you should check the speci's for your towbar and the allowable ball weight as 200kg may be at the upper limit for the BT50.
Assuming that is within speci's the next thing to consider is a spring upgrade. Many companies can do this but it pays to explain what your proposed vehicle use will be,(%on road, % off road and usual tray loading when seeking advice.

AnswerID: 531697

Follow Up By: tg123 - Friday, May 02, 2014 at 19:56

Friday, May 02, 2014 at 19:56
Allowable ball weight is 350kg
FollowupID: 814739

Reply By: Sinkas - Friday, May 02, 2014 at 20:02

Friday, May 02, 2014 at 20:02
The current BT50 has a maximum ball weight of 350kg. Airbags should be avoided due to placing point loads on the chassis where it is not designed for. You might like to talk to Ultimate Suspension as they have BT50/Ford Ranger kits that they have invested a lot of R&D into. (I have no affiliation).
AnswerID: 531699

Follow Up By: WBS - Saturday, May 03, 2014 at 07:36

Saturday, May 03, 2014 at 07:36
I'm mystified how an the airbag that fits inside the coil spring puts point load where it is not designed for? Aren't they putting the load in the same places as the springs or do you mean the extra load from the airbag is putting too much point load on the spring housing? Please enlighten me

FollowupID: 814776

Follow Up By: Slow one - Saturday, May 03, 2014 at 08:03

Saturday, May 03, 2014 at 08:03

The BT50 has leaf springs on the back, so you are placing load on the chassis where it was never designed to be.
FollowupID: 814780

Follow Up By: 671 - Saturday, May 03, 2014 at 21:08

Saturday, May 03, 2014 at 21:08
WBS posted:
I'm mystified how an the airbag that fits inside the coil spring puts point load where it is not designed for?
An air bag and a coil spring are both springs but they are not the same type. A coil spring is linear meaning it will keep on compressing in direct proportion to the load on it i.e double the load and you will double the amount it compresses.

An air bag is exponential and will keep on getting harder as it compresses. The more you compress it, the more it will resist further compression. They usually start getting hard when they are about 40% compressed and can be like a rock at 60%.

Your standard bump rubbers are also exponential and do the same thing which is why they will bring the downward movement of the chassis to a very sudden stop if the coil, or leaf spring, bottoms out on severe bumps. When you put an air bag inside a coil, or between a leaf spring and the chassis, you are really installing an oversize bump rubber. If you have enough pressure in them, which is often the case when they are being used to lift an overloaded car, they can stop a falling chassis well before it would normally reach the original bump rubbers. This can easily lead to chassis damage.

Few people seem to realise that when a falling chassis is suddenly stopped, whatever is behind the rear axle will want to keep falling. The forces generated increase by the square of the distance from the axle back to wherever the weight is or right back to the tow ball if you are towing something. That distance is like a lever sticking out the back of the car and we all know how big weights can be lifted easily with just a little effort on the end of a long lever. As the rear of the chassis slams down, the leverage on the end of the chassis rocks the car on the axle and tries to lift the front placing tremendous stress into the chassis around the axle or, as in the case with air bags, right on the bag mounting point.

The tow ball on these type of utes is usually around 1.2 metres behind the axle so a weight of 350kg on the ball, which is the Ranger's maximum, can become 504 kg when the rear wheels drop suddenly into a washout or whatever on a track. The weight of whatever is in the tray plus the rear of the tray and even part of the chassis itself is also falling and will be adding to the downward force so the total amount will be well above 504kg.

What is needed here is a WDH. It is a lever, not a spring, and will lift the rear of the chassis and transfer some of the weight back onto the front wheels. Air bags and heavier springs simply lift the car a little higher and make it look better from side on but they can not transfer weight. You still have all that weight behind the axle wacking the end of the chassis down on rough surfaces. That is why there have been so many broken chassis over the years and they have not all been in the bush. The last one that I saw was on a 2wd tradies ute earlier this year in the middle of Canberra. It was the same old story i.e far too much weight too far behind the rear axle.

In the case of this Ranger in question, and all other cars, the maximum tow ball weight will most like come with a few restrictions. The manufacturer may say a hitch must be used or it is for good sealed roads only and must be reduced as road surfaces get rougher. The only way to find out is to ask the manufacturer, not the dealer. They don't put specifications like this in the hand books because there are too many variables involved to try and cover them all.
FollowupID: 814879

Reply By: gbc - Saturday, May 03, 2014 at 04:57

Saturday, May 03, 2014 at 04:57
My ranger does similar stuff. I went to Midas and they set it up perfectly on comfort lift springs. My ball weight is a little lower than yours though. Don't be afraid of airbags with springs they will do the job well in your case.
AnswerID: 531713

Follow Up By: Sinkas - Saturday, May 03, 2014 at 09:11

Saturday, May 03, 2014 at 09:11
Regarding your comment about the airbags, I had better give back my engineering degree then! There are plenty of warnings on forums about not using airbags with leaf springs with at least one case of a broken chassis at that point that I can recall. I understand the fact if you use airbags with light loads you will get away with it, but that is not what people do - they load em up. The real test is to get it in writing from Mazda if they will honour your warranty with airbags.
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Follow Up By: gbc - Saturday, May 03, 2014 at 10:09

Saturday, May 03, 2014 at 10:09
Nothing wrong with up rated springs and airbags for the variable loads. I've run a whole fleet with them. When clowns overload a standard flogged out suspension then expect airbags to replace them and then go off-road in an overloaded vehicle, clowns get what's coming to them. I've seen the internet pics and they deserved what they got in most cases.
Do what you like with your engineering degree, but waving in peoples faces whom you've never met is setting yourself up for a big fall IMHO.
FollowupID: 814799

Reply By: evaredy - Saturday, May 03, 2014 at 12:21

Saturday, May 03, 2014 at 12:21
I had my 2013 Dmax suspension upgraded and also had the GVM upgraded at the same time.

First off, let me state that I am no mechanic by any stretch and this is what I have been told and what I have read when researching my upgrade.

As far as Airbags are concerned, there have been many that have caused major failure with the chassis, this is because they are overloaded and it is generally not recommended to use them in modern dual cabs.

As far as the suspension is concerned I went with Old Man Emu and it was fitted by ARB. I had the 300 kg constant put in and it made a huge difference to the handling and driving, I am very happy with it.

You need to be aware of how it will affect the front steering components, tail shaft etc. The Dmax could not be raised very high at the front because it would introduce a lot of problems with the various components.

I think you would be happy with a constant 300 kg setup, similar to mine.
AnswerID: 531732

Reply By: tuck - Saturday, May 03, 2014 at 12:47

Saturday, May 03, 2014 at 12:47
Have a 2013 bt50 extra cab. Had my ARB man at Murray Bridge upgrade suspension
OME shocks to suit .Increased leaf springs on back to 600 kilo above normal as carry a slide on camper fully loaded around 1000 kilo . Rides excellent loaded . Springs designed with extra leaves to take weight when applied . When not loaded there are 2 leaves which arent taking load so therefore allows ride to not be so rough. If the ride was not suitable we could have taken one leaf out. However unloaded we are mainly on bitumen ,we let tyres down to around 30- 32 and is definitely not rough. Coils on front to suit with steel B/B and winch . Have whole set up increased 50 mm above standard as we do a reasonable amount off road work. Was not happy with bags as when loaded forums indicate suspensions are too rigid with pressure all at one point . (thats my interpretation)
AnswerID: 531735

Follow Up By: tg123 - Sunday, May 04, 2014 at 10:23

Sunday, May 04, 2014 at 10:23
Thanks all for your input. Still confused!! Does anyone know who sells/installs Ultimate Suspension in Adelaide?
FollowupID: 814893

Follow Up By: 671 - Sunday, May 04, 2014 at 14:35

Sunday, May 04, 2014 at 14:35
tg123 posted:
Thanks all for your input. Still confused!!
The first thing that you have to do is find out if the weight that you have behind the axle is too much to be unsupported . On my 4x4 ute it is because the hand book clearly states that a WDH must be used for any tow ball weight over a certain amount. Your weight is well over my unsupported limit but it may not be for your car so read the hand book carefully and if the information is not there then ring the manufacturer on their customer information number which will be on their website. If you are over and you ignore it then no amount of custom suspensions are going to save your chassis if the car is driven in the right conditions. A short run down an average dirt road every second weekend to your favourite camping area will most likely never worry it but long repeated Outback trips or a run along the Canning or Anne Beadell for example could easily result in disaster.

This article is always worth reading in cases like this. It will also give you a brief insight into what changing suspension design can do to the car's handling.
FollowupID: 814936

Reply By: evaredy - Sunday, May 04, 2014 at 11:03

Sunday, May 04, 2014 at 11:03
Why are you still confused, what don't you understand?
AnswerID: 531798

Reply By: shane c9 - Sunday, May 04, 2014 at 20:18

Sunday, May 04, 2014 at 20:18
Your bt50 has rear leaf springs and if is a bit saggy in the rear and is still under warranty go to mazda as I did and make a polite complaint about it and they will possibly replace the two lower spring leaves with thicker mazda ones like they did for me under warranty your chassis is not designed for airbags and fitting them will void your warranty I have seen numerous other leaf sprung chassis with airbags get bent they are perfect with coil springs as the chassis was designed for this application
AnswerID: 531856

Follow Up By: 671 - Sunday, May 04, 2014 at 22:25

Sunday, May 04, 2014 at 22:25
they are perfect with coil springs as the chassis was designed for this application
Unfortunately Shane nothing is perfect for a car that has too much weight too far behind the rear axle. There would be no chassis damage if owners would only realise this. You could fit the finest heavy duty aftermarket leaf springs, coil springs, air bags, blocks of wood or who knows what else between the chassis and the axle and you are still left with that weight hanging out the back unsupported and flexing the end of the chassis up and down as the car bounces along rough roads.

WDH manufacturers claim their products will transfer weight from the rear axle to the front and they are right. I have yet to see any spring or air bag manufacturer claim their springs will transfer weight anywhere other than straight up.
FollowupID: 815010

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