Trailer load placement vs Tongue weight limit dilemma
Discussion
i might be in a pickle and looking for informed opinions... i'm an inexperienced tower.
my towing car (bmw 4 series) has a tongue nose weight limit of 75kg.
i also do have very firm bilstein b14 suspension on it.
i have a double axle trailer, and a mid-engined radical, around 650kg and it's centre of gravity being slightly rearward. It's also 4.1m long, and my trailer bed length is 4.27m. Combined weight of trailer + load = 1150kg, so that's 70% of my car's weight.
Apparently a suitable tongue weight should be 10-15% of this, so 115kg to 173kg....this is way above the car's limit of 75kg.
Loading the car in backwards, so, rear first, i went for a drive for the first time. Everything felt fine, nothing alarming, it felt safe to drive, nothing to comment or report on, though i didn't do any 60mph motorway runs.
i then checked my tongue weight, which was literally, off the scale. Using my cheap mechanical weighing scale with 135kg limit, the needle just went straight round and through the limit. I therefore don't know exactly what the reading is, but was definitely over 135kg.
i measured it by placing a scale under the trailer hitch, stacking up a load of wood on the scale until the height was the same as my towbar, then lowered the trailer onto it.
So then i loaded the car facing forwards, and this took the reading back down to 70kg. At this point i only have mabye another 10-15cm of space to move the car further forward.
It was fairly disconcerting - on the motorway at 55mph it felt ok, though i felt some marginal tugging every so often over bumps, which i'm sure i didn't feel before.
Over more bumpy A and B roads it wasn't comfortable, and there was some noticeable tugging. Nothing to cause me to have to apply any steering connection or anything dramatic, but i just felt like the car wasn't happy.
I'm aware that it's best practice to follow the 60/40 rule with 60% of the weight positioned towards the front of the trailer. That would mean the radical has to be loaded rearwards.
I think for the tongue weight to be anywhere near the official handbook limits, id' have to position the car so the front splitter is sat slightly out the back of the trailer.. not ideal.
is it safe to have the tongue weight at 90-120kg when the manual says the limit is 75kg? All to ensure better trailer weight distribution?
does fitting significantly stiffer suspension increase the tongue weight limit?
As long as the car steers and brakes safely, that's what matters, right?
or do i now need to get a longer trailer and a tow car with higher tongue limits - which would be a disaster and something i really want to avoid. I've had my 440i over 4 years and dont want to replace it with anything.
maybe i should just ensure the rear ride height of my car with the trailer hitched up remains roughly the same and the car is level, and that would be a good check?
over to you guys
my towing car (bmw 4 series) has a tongue nose weight limit of 75kg.
i also do have very firm bilstein b14 suspension on it.
i have a double axle trailer, and a mid-engined radical, around 650kg and it's centre of gravity being slightly rearward. It's also 4.1m long, and my trailer bed length is 4.27m. Combined weight of trailer + load = 1150kg, so that's 70% of my car's weight.
Apparently a suitable tongue weight should be 10-15% of this, so 115kg to 173kg....this is way above the car's limit of 75kg.
Loading the car in backwards, so, rear first, i went for a drive for the first time. Everything felt fine, nothing alarming, it felt safe to drive, nothing to comment or report on, though i didn't do any 60mph motorway runs.
i then checked my tongue weight, which was literally, off the scale. Using my cheap mechanical weighing scale with 135kg limit, the needle just went straight round and through the limit. I therefore don't know exactly what the reading is, but was definitely over 135kg.
i measured it by placing a scale under the trailer hitch, stacking up a load of wood on the scale until the height was the same as my towbar, then lowered the trailer onto it.
So then i loaded the car facing forwards, and this took the reading back down to 70kg. At this point i only have mabye another 10-15cm of space to move the car further forward.
It was fairly disconcerting - on the motorway at 55mph it felt ok, though i felt some marginal tugging every so often over bumps, which i'm sure i didn't feel before.
Over more bumpy A and B roads it wasn't comfortable, and there was some noticeable tugging. Nothing to cause me to have to apply any steering connection or anything dramatic, but i just felt like the car wasn't happy.
I'm aware that it's best practice to follow the 60/40 rule with 60% of the weight positioned towards the front of the trailer. That would mean the radical has to be loaded rearwards.
I think for the tongue weight to be anywhere near the official handbook limits, id' have to position the car so the front splitter is sat slightly out the back of the trailer.. not ideal.
is it safe to have the tongue weight at 90-120kg when the manual says the limit is 75kg? All to ensure better trailer weight distribution?
does fitting significantly stiffer suspension increase the tongue weight limit?
As long as the car steers and brakes safely, that's what matters, right?
or do i now need to get a longer trailer and a tow car with higher tongue limits - which would be a disaster and something i really want to avoid. I've had my 440i over 4 years and dont want to replace it with anything.
maybe i should just ensure the rear ride height of my car with the trailer hitched up remains roughly the same and the car is level, and that would be a good check?
over to you guys
Edited by wioifoiee on Sunday 5th June 17:54
Do you have a big wing on the car on the trailer? At speed that can have an effect, reducing the nose weight and causing the trailer to feel light?
If you go too heavy on the nose weight, you get a very unpleasant oscillation when you go over bumps as the trailer bounces and pushes the rear of the car up and down.
I've found a position on my trailer where it feels really stable regardless of speed and that's where I set it everytime now.
If you go too heavy on the nose weight, you get a very unpleasant oscillation when you go over bumps as the trailer bounces and pushes the rear of the car up and down.
I've found a position on my trailer where it feels really stable regardless of speed and that's where I set it everytime now.
How is the attitude of the trailer when hitched to the car, viewed from the side? Is the trailer level or is it sloping down from the hitch, and low at the rear?
The Radical is going to have to go on backwards in my opinion for stability but you will obviously want to reduce the tongue weight from it’s current very high level.
The Radical is going to have to go on backwards in my opinion for stability but you will obviously want to reduce the tongue weight from it’s current very high level.
I've done a lot of towing with a variety of tow cars with rally and track cars on the trailer, sometimes probably illegally in terms of towing capacity of the tow car, trailer and what's on it but what you are doing sounds very safe.
Google suggests the towing capacity of your 440i is 1700kg and you are well below that, sounds like you have a decent double axle trailer, I would just make sure you haven't got too much nose weight, as others have said put the Radical on backwards. I used to load it all up and attach the trailer to the tow hook, if I could lift the tow hook a little by hand it was about right, I'm not very strong so if I could lift it a bit then it couldn't be too heavy.
If it drives fine then I'm sure it's ok.
Google suggests the towing capacity of your 440i is 1700kg and you are well below that, sounds like you have a decent double axle trailer, I would just make sure you haven't got too much nose weight, as others have said put the Radical on backwards. I used to load it all up and attach the trailer to the tow hook, if I could lift the tow hook a little by hand it was about right, I'm not very strong so if I could lift it a bit then it couldn't be too heavy.
If it drives fine then I'm sure it's ok.
thanks for all the inputs,
i towed the car back home today, loading it in rearward put putting it as far back on the trailer as possible (so the nose was hovering in line with edge of trailer)
Visually there appeared to be absolutely no change in ride height of the rear of the car, unloaded or loaded.
I also did the 'hand feel test' as described above and could pull up without much issue, again there wasn't any change in perceptible feel when pulling up, either loaded or unloaded.
And hey presto the car felt absolutely fine over the rough B roads and I could cruise easily at 55-60 on motorway without my ass clenched.
I guess the 75kg towball limit must be ultra conservative on my car. I'll stop shopping around for an Evoque now, thank god.
i towed the car back home today, loading it in rearward put putting it as far back on the trailer as possible (so the nose was hovering in line with edge of trailer)
Visually there appeared to be absolutely no change in ride height of the rear of the car, unloaded or loaded.
I also did the 'hand feel test' as described above and could pull up without much issue, again there wasn't any change in perceptible feel when pulling up, either loaded or unloaded.
And hey presto the car felt absolutely fine over the rough B roads and I could cruise easily at 55-60 on motorway without my ass clenched.
I guess the 75kg towball limit must be ultra conservative on my car. I'll stop shopping around for an Evoque now, thank god.
Edited by wioifoiee on Tuesday 14th June 14:43
Gassing Station | Track Days | Top of Page | What's New | My Stuff