JJSL:
Many thanks for the replies, but it would be nice if one of the Vosa guys on here could enlighten me as to why
Rgs
JJSL
Get in touch with VOSA it is what I done after my mot test
Real reason is that someone in the manufacturer’s marketing department is obsessed with the idea that his willy is larger than Mercedes’, Iveco’s or whatever, so he decides that ‘his’ vehicle is going to be an 80 tonner.
JJSL:
Hi,Can someone please explain to me why they do the brake test at VOSA on a 4X2 tractor at the design weight of
44ton when the vehicle plated weight is 40ton max.
I asked the question to the Vosa man doing the brake test, and he said that’s the rules !!! but, you cannot run
a 4X2 in the Uk at more than 40ton, he just turned round and walked off !So, can someone please enlighten me.
Rgs
JJSL
Vehicle manufacturers design their trucks for many different markets, so a while a 4x2 may be limited to 40T in the UK, in another country it may be able to legally run at 44T, so the braking system is designed to run at a maximum of 44T.
There is a bit more scope to change the design weight of trailers as someone quite rightly put earlier as the person ordering can have more input to a trailer spec than a t/unit spec.
I personally keep my trailer axle design weight the same as the max allowed which is 8 tonnes, rather than using the full 9 tonnes the axle manufacturer designed their axles for, and I spec the trailer with a 15 tonne neck, the GVW of the trailer is 36 tonnes (3x8 +15) so the minimum parking brake efficiency is 16% of 36000Kg. The service brake minimum efficiency is 45% of the TAW (16% of 24000Kg).
This makes it easier to get through a brake test.
You’re a bit stuffed with a t/unit as it is type approved to a particular design weight, you can’t change this. Check on the vehicle spec sheet before you buy as to what the design weight is.
There was some talk about changing the MOT test to plated weights rather than design weights, don’t think anything has come of this yet though? I’m sure someone will correct me if I’m wrong!
There is a benefit to a higher design weight than plated weight if you get pulled and found to be overloaded.
This is an old thread but the reason was already mentioned.
It would really â– â– â– â– Geert & Tanja off if you squashed their kids in Rotterdam whilst running your 4x2 at 50tonne because the brakes were only good in the UK
You can do a notifiable alteration and bring the design weight down to the same as gb weights .i think it’s just a paperwork thing as we used to do it to double drive scanias that were 70 t design but couldn’t get through parking brake test
Hi,
Can someone please explain to me why they do the brake test at VOSA on a 4X2 tractor at the design weight of
44ton when the vehicle plated weight is 40ton max.
I asked the question to the Vosa man doing the brake test, and he said that’s the rules !!! but, you cannot run
a 4X2 in the Uk at more than 40ton, he just turned round and walked off !
So, can someone please enlighten me.
Rgs
JJSL
They test at the design weight on the plate. I remember when the first Actros’s came the 4x2 tractors came with a design weight of 60 tonnes for goodness knows what reason, 12 months later it was just about impossible to get them through on the park brake.
Hi i’ve a scania 6wheeler with a GTW 70,000kg■■? even with new drums & shoes i cross everything
on the brake rollers…even with a pass value of 12% on parking
Got an old Daf75 6wheeler with a GTW 29,500kg…pass value of 16% on parking,phewww
Many thanks for the replies, but it would be nice if one of the Vosa guys on here could enlighten me as to why
Rgs
JJSL
JJSL:
Many thanks for the replies, but it would be nice if one of the Vosa guys on here could enlighten me as to whyRgs
JJSL
That would breach the Data Protection Act, abuse their civil liberties, really abuse their human rights, and, really would be asking for a civil servant to put their neck on the line…NOT worth chancing a gold plated pension on a mere haulier 
I suppose for the International hauliers who do go abroad and utilise the design weights instead of some other countries legislation on vehicle weights.
Switzerland used to run at 28tonne but the steep hills and mountain passes possibly needed better brakes & retarders on the trucks than here in the UK, and they could still run outside their own country at 44tonne.
I used to be dismayed when the correct method to downplating a truck was to remove a couple of bolts from the fifth wheel mounting or use lesser ones in the propshaft UJ. At least now it is only a paper exercise.
acd1202:
They test at the design weight on the plate. I remember when the first Actros’s came the 4x2 tractors came with a design weight of 60 tonnes for goodness knows what reason, 12 months later it was just about impossible to get them through on the park brake.
This is the exact reason why!
On a trailer from europe, your’ll find that on the chassis data plate the TAW (design total axle(s) weight) the design weight will be 9000kg and the legal weight will be 8000kg , if you look at say a Gray & Adams your’ll find the design weight will be 8000kg and the legal weight will 8000kg!! Its just a matter of putting the correct information on the data plate to help at MOT time!! The design weight can be anything as long as it more than whats on the plate!
If the design weight was 9000kg this would give total axle weights of 27000kg thus meaning to pass you would need to achieve 45% for service (12150kg) and 16% for parking (4320kg)
So in the case of the Gray & Adams trailer on service brake the specified efficiency is 45% of the TAW (45% of 24000kg=10800kg) and a 16% of the TAW (16% of 24000kg=3840kg) on the parking brake.
The figures are substanially lower and therefore more achievable!! Trailer wheels will normally lock unless there a weak springed chamber!!
Trailers are also tested with no load!! Where as a 4x2 will be tested with the load simulator, but 6x2 on air suspension has to tested with a loaded trailer because the load simulator doesnt put enough weight on the middle axle!!!
To use the example of the actros above, a pass on service brake for a tractor unit is 50% of the GVW (design goss vehicle weight) so that would be 30000kg on the rollers, where as if it was tested at the legal weight which iirc is 8000kg (front axle) and 12000kg (back axle) which is 20000kg it would have to achieve only 10000kg on the rollers which is easier to achieve!
This is my understanding but if i’m wrong i’m sure someone will be along shortly and tell me!
olds’kool:
Trailers are also tested with no load!! Where as a 4x2 will be tested with the load simulator, but 6x2 on air suspension has to tested with a loaded trailer because the load simulator doesnt put enough weight on the middle axle!!!
Tankers had to be loaded for MOT and the load simulator cannot be used obviously, so we put water in them overnight or ran them in with a load of non hazardous edible. However with the water we were not so bothered about accuracy and have often struggled up Rudston Walk near Beverley with 32 tonne of H20 inside the tank, the advantage was that there was no product swill and the trailers sailed through the test 
olds’kool:
acd1202:
They test at the design weight on the plate. I remember when the first Actros’s came the 4x2 tractors came with a design weight of 60 tonnes for goodness knows what reason, 12 months later it was just about impossible to get them through on the park brake.This is the exact reason why!
On a trailer from europe, your’ll find that on the chassis data plate the TAW (design total axle(s) weight) the design weight will be 9000kg and the legal weight will be 8000kg , if you look at say a Gray & Adams your’ll find the design weight will be 8000kg and the legal weight will 8000kg!! Its just a matter of putting the correct information on the data plate to help at MOT time!! The design weight can be anything as long as it more than whats on the plate!
If the design weight was 9000kg this would give total axle weights of 27000kg thus meaning to pass you would need to achieve 45% for service (12150kg) and 16% for parking (4320kg)
So in the case of the Gray & Adams trailer on service brake the specified efficiency is 45% of the TAW (45% of 24000kg=10800kg) and a 16% of the TAW (16% of 24000kg=3840kg) on the parking brake.
The figures are substanially lower and therefore more achievable!! Trailer wheels will normally lock unless there a weak springed chamber!!
Trailers are also tested with no load!! Where as a 4x2 will be tested with the load simulator, but 6x2 on air suspension has to tested with a loaded trailer because the load simulator doesnt put enough weight on the middle axle!!!
To use the example of the actros above, a pass on service brake for a tractor unit is 50% of the GVW (design goss vehicle weight) so that would be 30000kg on the rollers, where as if it was tested at the legal weight which iirc is 8000kg (front axle) and 12000kg (back axle) which is 20000kg it would have to achieve only 10000kg on the rollers which is easier to achieve!
This is my understanding but if i’m wrong i’m sure someone will be along shortly and tell me!
That’s pretty much bang on the nail, if you’re in a position to buy a trailer from new don’t forget you can get the manufacturer to put the axle design weight the same as the plated weight (i.e. 8000kg for a triaxle) it just makes it easier getting through a loaded test, although the only downside is that if the axle weights ever increased from 8 Tonne you’d be a bit stuck