Monday, Nov 08, 2021 at 18:32
Its the amount of load that the spring pack is designed to carry and maintain the nominal ride height. The stock springs may be able to carry 600kg, but the back end will sag and you will be intimate with the bump stops over lumps and undulations as the spring pack isn't up to it.
Springs are manufactured and given a 'rate', which is how much they will deflect with a given force applied. A spring pack that is made to carry more load will have more leaves and/or heavier leaves to support the weight without deflecting as much as a thinner leaf, but will be a horrible, bone rattling ride with no load onboard.
A replacement pack that is designed to give 50mm lift (pretty much the industry standard) and 0- 300kg will sit 50mm higher when empty and probably close to factory unladen height with the 300kg on board. The 300+ will be stiffer, so will sit 50mm higher than stock with no load and won't settle much with 300kg onboard, but will be much happier carrying that load over bumps and undulations without compressing to the bump stops as once they compress there are more leaves to bear the load and resist compression.
I have
Tough Dog 0-300kg comfort springs in the back of my BT50 (same vehicle, but different) under an alloy tray. The ally tray is around 100/150kg lighter than the style side body, so I'm a bit ahead there. My camping set up is around 450-500kg fully loaded and with that on the back it sits bang on the height it left the factory.
I find them much better than the factory springs as they are a bit taller, so when empty they have more flex to soak up the bumps, but then load carrying leaves can then come into play and it is rare that I hit the bump stops, even when fully loaded. Its not passenger car smooth, but pretty good. Before I fitted
the springs and had the same load on it was often nudging the bump stops, even on reasonably good roads and the back end felt like it was wallowing around as
the springs just weren't up to the job.
The big question is how much 'stuff' do you constantly have in the back? If you motor around basically empty, then the 300+kg will probably be too much and the 500+kg will probably rattle your teeth loose as they will be very stiff. We have them under a Patrol fire truck and with less than a full
water tank, you just about need a kidney belt.
It might also be worth going and seeing a
suspension specialist (not Pedders), I had a bit of an idea what I wanted, so went and saw Climax
Suspension in Berresfield (bit of a drive for you), He listened to what I had to say, put me straight and got me exactly what I actually needed.
AnswerID:
638530
Follow Up By: Member - Scruffy - Tuesday, Nov 09, 2021 at 11:12
Tuesday, Nov 09, 2021 at 11:12
Thanks for your response Hoyks. I have Ironman 0-300kg Heavy Duty leaf springs on the back with Foam Cell shocks. When fully loaded it travels beautifully but 80% of the time I carry golf clubs so its a bit arse up and can loose traction...thats ok I can deal with that but I would like to know if 0-300kg additional means I can exceed GVM slightly if I have to.
cheers
FollowupID:
916988
Follow Up By: Member - silkwood - Tuesday, Nov 09, 2021 at 14:53
Tuesday, Nov 09, 2021 at 14:53
" I would like to know if 0-300kg additional means I can exceed GVM slightly if I have to."
No, unless certificated for this... or, yes, but not legally... your choice.
Cheers,
Mark
FollowupID:
916992
Follow Up By: Hoyks - Tuesday, Nov 09, 2021 at 17:58
Tuesday, Nov 09, 2021 at 17:58
GVM is the legal maximum your vehicle and load can weigh.
Unfortunately, putting springs under it that are optimised for the load you regularly carry doesn't give you any extra credits to exceed GVM.
You can get engineering done to increase the GVM a bit, but you're still at the mercy of what the vehicle was designed to carry when it left the factory. more load is going to put the chassis, drive line and brakes under extra load, so its a far bet something is going to give.
FollowupID:
916996