This is a very very helpful thread.
Cheers to the OP for asking the question, and to everyone who answered, particularly wheel nut for that formula. I’ve been driving 7yrs and never had anyone explain it to me in terms as crystal clear as this. I like having things set out unambiguously, precisely and methodically. But whenever I’ve asked other drivers for help on weights/overloading the answers have always been somewhat vague, and, a lot of the time, even conflicting.
A very common occurrence for a bottom-of-the-ladder agency driver is transport managers who try to bully you into taking the load regardless. I’ve sometimes felt like I didn’t have much of a leg to stand on in those situations.
But that diagram & formula really gives me some peace of mind from now on.
Thanks again.
Peter Smythe:
The answer is a bit simplistic
It’s also very good! Many drivers struggle with this concept. It’s known as diminishing load and the example I use is 25 ton of sand in 1 ton bags spread evenly accross a trailer bed. All is fine until you take around 10 ton from the back. At that point the drive axle of the unit will be overloaded.
By the way, this is one of the subjects often dealt with in the much maligned periodic training driver cpc; but isn’t it good to know?!
Sorry Pete but would like to see your workings out on this, according to my calculations ( which might be wrong )
if the trailer was 12m long and wheelbase was 10m with a payload of 24 ton ( to make working out easier )
This makes 12 rows of two bags, centre of load is 6m, wheel base is 10m
rear load base (4)/ wheel base(10) x payload (24)= 9.6 ton on front
take 10 bags of leaving 14
rear loadbase (3.5)/ wheel base(10) x payload (14)= 9.1 ton on front
so not over axle weight, as I said might be wrong 
hi peeps and thanks in advance on any advice,sorry but am slightly confused on this topic,been driving a Mercedes Atego 815 for some time now,it has a Box Body,and my loads have been nothin much more than a 1500kg.
Im going to be getting busier in the run up to Christmas,and want to make sure im staying within the law with regards to my load weight.
The truck weighs 5.2 ton unladen,i have seen the plate by the drivers door,and this is the following info on it:
Permissable total weight-7490kg
Permissable Combination weight-10990kg
Axle 1-3400kg
Axle 2-5000kg
And so i am under the impression that maximum load i can carry including fuel etc is 2290kg.So if my load weighs more than this i am breaking the law?But then the axle weights are confusing me with the total of them being 8400kg …just wanna keep road legal;)
Hi Telrea
If the vehicle weighs 5.2tonne unladen then Yes you can only carry 2290kgs of payload as the entire vehicle including load, fuel, driver, spare wheel etc must not exceed 7490kgs.
The seperate axle weight limits are there to ensure the whole load is distributed over both axles and not just in 1 place on the vehicle. The axle weight is the maximum that can be transmitted to the road surface if only that axle were weighed on its own (Vosa will have scales made for this purpose).
You would not be able to load both axles down to their permitted maximum at the same time as this would exceed the total permissable weight.
It is possible for a vehicle to be perfectly legal in all respects to axle and total weights but after unloading part of the load it may exceed an axle limit. This is due to the see-saw effect. (if 2, 10 stone people sat on a see saw it would be balanced but if 1 got off, despite only half the original load remaining the see saw would be overloaded at 1 end). It would then be neccessary to redistribute the remaining load evenly over the loading area.
The combination weight only applies if you are towing a trailer.
The answer is a bit simplistic but I hope it helps
Regards
John
The answer is a bit simplistic
It’s also very good! Many drivers struggle with this concept. It’s known as diminishing load and the example I use is 25 ton of sand in 1 ton bags spread evenly accross a trailer bed. All is fine until you take around 10 ton from the back. At that point the drive axle of the unit will be overloaded.
By the way, this is one of the subjects often dealt with in the much maligned periodic training driver cpc; but isn’t it good to know?!
Calculation of axle loads
This is copyright material from Kogan Page written by David Lowe who taught me all I know, the book will cost you 55 quid but if you click on my link it may explain the theory of working out axle weights. I have just enquired about the 2011 issue of Daves book, the best knowledge in the industry!
Thanks everyone the examples have made the whole thing alot easier to understand…cheers!!
This is where we need Rog
DAF95XF:
This is where we need Rog
I’ll finish that sentence for you Stu… 
… to over-complicate something already adequately explained by Malc’s reference to David Lowe.
The only thing I’d add to what’s already written is that the extra allowance on each axle comes in very handy when a load is of irregular shape or is composed of materials of different densities, provided that the permitted GVW isn’t exceeded.