Member Since: 02 May 2023
Location: Trowbridge
Posts: 141
Roof load - what is actually the law?
I know this has been covered many times and I know the manual says 75kg. But as far as I can tell it isn't actually illegal to ignore a rule in your handbook, right? i.e the handbook has many rules which I think can legally be ignored. i.e 'don't dismantle the fuel system' was the first thing I just saw. I don't think the police could very well fine you for doing a fuel system repair on your driveway.
The highway code says 100kg is the actual limit for roof loads so would that actually be the actual max legal amount?
Practically speaking though having the increase in roof limit to 100kg is the difference between a roof tent and an awning or just a roof tent.
I guess if you're ignoring stuff in the manual it probably would be considered a modification by the insurance provider so that's what it might come down to - although they'd presumably need to justify refusing a claim to be related to that 'modification'.
Wonder if anyone has any insight on this from this perspective?
1st May 2024 5:37 pm
KevinD3
Member Since: 05 Aug 2020
Location: Sutton Coldfield
Posts: 1236
Deffinate not an expert, you’ll need to wait for one of those to get back from work but the roof load is dynamic and I think the 75kg is based average speed and conditions as wind etc has an impact on the actual weight felt by the car.
A 75kg load on the roof may exert a virtual load of more than 100kg at 40mph (I’m making these numbers up but the theory is sound) and 150kg at 70mph due to the resistance against wind.
150kg loaded correctly may be fine on a flat tarmac road but rip the roof off or roll the car on a dirt track as it makes the vehicle top heavy.
You’re right about the roof tent example. If 75kg is the limit of a static load, Roof tent may be 60kg, well within the limit…..as long as you don’t sleep in it! Add two “pleasantly plump” people in the mix and you’ll have 200kg - 260kg on her roof..waaaaaay over the 75kg 2008 HSE Stornoway Grey
My Wife thinks the D3 is a hobby, The D3 thinks the wife is 💕
1st May 2024 6:00 pm
rrhool
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4441
Re: Roof load - what is actually the law?
bensla wrote:
I know this has been covered many times and I know the manual says 75kg. But as far as I can tell it isn't actually illegal to ignore a rule in your handbook, right? i.e the handbook has many rules which I think can legally be ignored. i.e 'don't dismantle the fuel system' was the first thing I just saw. I don't think the police could very well fine you for doing a fuel system repair on your driveway.
The highway code says 100kg is the actual limit for roof loads so would that actually be the actual max legal amount?
It's all good until something goes wrong, and you are stood in court explaining why you ignored the manufacturers advice! I'm not suggesting anything will go wrong, but in the eyes of the law, if you ignore advice, you are open to prosecution.Richard
D3 SE 2007. Triumph 2.5Pi 1973. Ferguson TEA20 1948.
Discovery 2 4.0 ES 2001- Gone
Discovery 1 300Tdi ES '95 - Gone
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Member Since: 02 May 2023
Location: Trowbridge
Posts: 141
Yeah I'm thinking the way forward is to check if it's an allowable modification with insurance. i.e roof cargo up to 100kg. I'll phone a mod friendly insurance tomorrow.
If there were an issue then it's an insurance get out by ignoring it & leaves you open to Dangerous Driving - fine/point/poss sentence & void insurance (Unsecured load/overloaded/dangerous load)
Weights are worked out on a number of factors, all too complex for me but essentially it's:
* The way weight changes when in motion, factors such as acceleration/deceleration/pitch/yaw/gravity etc, etc.
It's been shown that weight can increase by up to x10, that 75kg suddenly becomes a lot more, this obviously increases your CoG & affects handling.
* The way a load affects what is the inbuilt 'cocoon' designed to protect occupants in the event of a roll-over
The other thing to remember is that there's a max of 8 M6 bolts going into captive nuts that are only spot welded to the roof panel.
General accepted/suggested rule of thumb is to decrease load by 1/3 if off road.
So if you buy a rack that is rated to 300kg it doesn't matter because the defining factor is the vehicle/lower weight - the rack does nothing to alter the physical structure only decreases your payload as its weight is to be subtracted from the 75kg.
So, 75kg - Frontrunner (38kg) = 37kg payload, approx 1 x 19" rim with a new AT Tyre
Prospeed approx 25kg
Out-Rack 24kg.Paul.
06 Java Black HSE - gone
12 Baltic Blue HSE - gone
15 Fuji HSE Lux
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Traxide/Luna hybrid & Yellow top
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+ some other stuff
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1st May 2024 8:51 pm
HairyFool
Member Since: 04 Jan 2023
Location: Essex
Posts: 596
I am not convinced the limits are calculated with any degree of precision as the dynamic loading often bears little relation to the static load, 75Kg could be significantly higher over a pot hole.
I wonder about roof boxes with inverted aerodynamics. They exert higher downforce at speed but what actually is it at 70Mph? Even if the manufacturer did wind tunnel testing the true force is going to vary according to the height of the rails above the roof.A visitor from the dark side, my other vehicle is an MG5 EV
Static load is irrelevant in many ways as you can’t move ‘it’ from A to B.
At best the vehicle is designed to take its own weight as a minimum in the case of a roll-over so exceeds any Dynamic rating.
Interesting to note that the Merc C-class is as std 75kg, however the stiffened AMG version is given a 200kg load rating 🤷♂️Paul.
06 Java Black HSE - gone
12 Baltic Blue HSE - gone
15 Fuji HSE Lux
Club Biscuits, mmmm nice!
Traxide/Luna hybrid & Yellow top
Some Prospeed bits
+ some other stuff
Club N.E.R.D.s.
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