Back Heavy and Poor Traction

[Davenjo]

I have a T30 Highline SWB 150DSG Panel Van which has been prefessionally converted to a full blown camper. In addition I carry 3 bikes (about 40Kg) on a rear door mounted rack and tow a boat trailer with around 30Kg of down force.

With this set up a large proportion of the weight is over/behind the back wheels which is leading to a low back end ("saggy arse syndrome" as Walski puts it) and very poor traction when pulling away and I think the van, with all my gear, would become pretty much useless with the slightest bit of snow or ice.

Would uprating the rear suspension help with this problem and provide more traction on the front? If so what do I need to look at so as not to affect any warranties and/or insurance.

(For info; I asked similar in another thread in the Camper Van forum earlier but feel it sits better here and will, hopefully get me more response).

 

[former member]

I think a California gets T32 suspension (or similar); maybe a T30 isn't beefy enough?
Any idea what the overall weight is now it's been converted. Anything from the conversion company? I should think it's their responsibility to convert the van safely.
You can get vehicles weighed to see what the weight is on each wheel; maybe do this. If it's really back heavy, something needs sorting because that'll have a dangerous effect on handling.

 

[Davenjo]

The normal base vehicle Hillside use is a T28; with the conversion weight coming in at around 2300kg giving around 500kg for user payload - with my T30, even with addition of DSG and tow bar, I should still have over 500kg to play with. I don't think the overall weight is an issue its the position of it over and behind the rear wheels. Without the bikes and trailer its not a problem.

 

[former member]

How big is the boat? I don't know the details but with caravans, it's critical you get the nose weight right as well as all up weight. The tow bar height is important too.

I know with our boat trailer, it wasn't properly balanced so we had to adjust it to get it spot on. It was really hard to manually lift the tow hitch beforehand; once adjusted it was easy and that was only a 900ish kg Salcombe Flyer (14ft speed boat).

Can't see 40kgs of bike/rack making a difference.

 

[Davenjo]

Trailer has a plated gross weight of 400KG with payload of 300kg so assume trailer weighs 100Kg. My boat is around 90kg fully rigged plus around 60kg gear so I'm around the 250kg mark - I think the important thing here is the nose weight which last time I weighed it was around 30kg. Surely with the bikes hanging out beyond the point of the tow ball, their weight is having as much, if not more, effect than the trailer on my "saggy arse"?

 

[Keeff]

I used to do a lot of towing with my old Renault trafic and that was OK in the dry but in the wet it would wheel spin when pulling away and up hill with a car on the back was nearly impossible . You could fit t32 rear springs or just load the van with as much weight up front as you can. Fitting a good set of tyres and not using summer racing ones will really help.

 

[Davenjo]

I used to do a lot of towing with my old Renault trafic and that was OK in the dry but in the wet it would wheel spin when pulling away and up hill with a car on the back was nearly impossible . You could fit t32 rear springs or just load the van with as much weight up front as you can. Fitting a good set of tyres and not using summer racing ones will really help.

Thanks. The problem is most of the weight is in the conversion, i.e. bed, cupboard units, gas locker, etc.. most of which sits over the back axle so I'm limited with what I can move forward. Happy to look at T32 springs and struts but would like to know if this is the best way to go as I will be reliant on someone else doing and need to get it right first time.

 

[former member]

Trailer has a plated gross weight of 400KG with payload of 300kg so assume trailer weighs 100Kg. My boat is around 90kg fully rigged plus around 60kg gear so I'm around the 250kg mark - I think the important thing here is the nose weight which last time I weighed it was around 30kg. Surely with the bikes hanging out beyond the point of the tow ball, their weight is having as much, if not more, effect than the trailer on my "saggy arse"?

How you tried it with just the bikes loaded then just the trailer hitched to work out which is having more effect? That's quite a light boat so shouldn't be causing issues; the towing weight of a 150/204 is pretty high.

Still don't think either should be causing you so much trouble though - the vans are pretty front heavy so it should take a lot to tip that weight bias over to the rear.

 

[Pauly]

I would have a chat with your local dealer and your converter and probably a local garage/suspension place if you have one and see what they say

 

[Keeff]

Don't fit front strut as you want the front soft and the rear are a quick fit . You could have a look at rear coil overs as you could adjust them when towing .

 

[VanBlanc]

T30 is about right for a conversion. I did the sums on our our T5.1 and including the conversion, 2 people and fully laden ready to go there was only about 100kg left on a T30 so it would be daft to do a conversion on a T28.

Its surprising just how quickly the weight adds up for example 2 adults will go a couple of hundred kilos, a couple of teenagers perhaps another 100kg and so on. Even the dog who is 12.5kg and 4 weeks of his food adds up to 60kg. Add fuel, a tank of water and so on and bobs your uncle. Check your ride height and see how much you have already lost from the base van and then do it again with the van laden.

Next problem is perhaps how far behind the rear axle the weight is because of the leverage. Don't forget that the van will have been designed to carry the weight as an average between the axles and not 800mm behind the rear axle. But as we discussed elsewhere on here getting the weight forward is a good idea in any case.

 

[VanBlanc]

Actually it might help you to make / get a bike rack for boat trailer and put the weight on that axle so taking it off the tow ball?

 

[Walski]

You should be ok with a T30. I nearly got a T28 but my conversion guy talked me out of it saying T30 is best at a minimum. He thought fully loaded we'd be close to if not slightly over 2.8t.

I've got a public weigh bridge at a quarry just a mile or so from me so I might try to get on it Thurs/Fri next week as I'm off work and see what it weighs. I'm quite interested for the load ratings of the tyres.

 

[Davenjo]

You should be ok with a T30. I nearly got a T28 but my conversion guy talked me out of it saying T30 is best at a minimum. He thought fully loaded we'd be close to if not slightly over 2.8t.

I've got a public weigh bridge at a quarry just a mile or so from me so I might try to get on it Thurs/Fri next week as I'm off work and see what it weighs. I'm quite interested for the load ratings of the tyres.

I'd be interested to see what t comes out at.

 

[Davenjo]

I've just ordered some caravan scales so I can check the loading on each wheel and have a play with the weight a bit to see if there is anything I can do to balance the load better before looking at stiffer suspension, etc..

 

[chriscroft]

I've just ordered some caravan scales so I can check the loading on each wheel and have a play with the weight a bit to see if there is anything I can do to balance the load better before looking at stiffer suspension, etc..

You certainly need to check the axel/tyre loads on the rear. And whilst uprated suspension will help handling/safety etc, it won't re-distribute the weight between the front/rear axel to help fwd traction. Only altering the overall load or load position will do that.
We upgraded our tyres on our fwd T5 to All-Terrains, it made a huge difference on soft surfaces. In fact there are some really good all-season+all-terrains now, which will improve traction in mud/snow/ice/grass/wet, they really do make a difference.
Or you could fit an A-frame/Bull Bar, filled with lead shot on the front, also helps with stray cows

 

[Davenjo]

My "Caravan Weight Check" scales arrived earlier and I have been having a play with them. As loaded, but without the bikes/trailer, after some serious rounding up, and splitting the weight between wheels based on where it would be place in the van, for the things I couldn't readily lay my hands on, I got a total weight up to around 2964 kg with the weight pretty evenly distributed between wheels and axles at 1504kg front and 1460kg rear - both well within the 1610kg/1600kg axle limits. The 40kg for the bikes and around 40Kg for the trailer downforce would take me over the 3000kg limit but I'm not too concerned with overall weight as there were some major over-guesstimates in there (60kg for luggage for instance - well over the top!!) and I don't need to always carry the 70+ litres of water the tank holds. However, I still think that it is the position of the bikes and trailer well behind the back axle that is causing the problem.

What I think is happening is that the weight behind the back axle is having a pivot effect and, as well as the extra 80kg for bikes and trailer, it is causing some weight to be lifted off of the front axle and down onto the rear axle - with the result that I'm ending up with somewhat less than the 1504kg on the front and it being transferred to the rear, potentially putting more on it than the legal/safe rear axle limit of 1600kg for my van? I'm not sure of the physics here but it sounds reasonable to me?? I'll do another test at the weekend to include everything.

If the pivot effect from the load behind the rear wheels is causing the problem would uprated suspension on the rear stop the weight being lifted off of the front axle so much or just give me a higher pivot point and potentially cause the front wheels to lift even more??

(My head now hurts!!)

 

[chriscroft]

My "Caravan Weight Check" scales arrived earlier and I have been having a play with them. As loaded, but without the bikes/trailer, after some serious rounding up, and splitting the weight between wheels based on where it would be place in the van, for the things I couldn't readily lay my hands on, I got a total weight up to around 2964 kg with the weight pretty evenly distributed between wheels and axles at 1504kg front and 1460kg rear - both well within the 1610kg/1600kg axle limits. The 40kg for the bikes and around 40Kg for the trailer downforce would take me over the 3000kg limit but I'm not too concerned with overall weight as there were some major over-guesstimates in there (60kg for luggage for instance - well over the top!!) and I don't need to always carry the 70+ litres of water the tank holds. However, I still think that it is the position of the bikes and trailer well behind the back axle that is causing the problem.

What I think is happening is that the weight behind the back axle is having a pivot effect and, as well as the extra 80kg for bikes and trailer, it is causing some weight to be lifted off of the front axle and down onto the rear axle - with the result that I'm ending up with somewhat less than the 1504kg on the front and it being transferred to the rear, potentially putting more on it than the legal/safe rear axle limit of 1600kg for my van? I'm not sure of the physics here but it sounds reasonable to me?? I'll do another test at the weekend to include everything.

If the pivot effect from the load behind the rear wheels is causing the problem would uprated suspension on the rear stop the weight being lifted off of the front axle so much or just give me a higher pivot point and potentially cause the front wheels to lift even more??

(My head now hurts!!)

No, altering the suspension will not effect how the load is distributed between the axels.
Your thoughts re the bikes etc is totally correct.
The calculation is quite easy its just a "moment calculation" or "Lever arm" calculation
If you put extra weight behind the rear axel, not only does all that extra weight go straight onto the back axel load, just as you thought, it also redistributes load from the front axel, onto the rear axel.
So if you add 60kg 1 metre behind the back axel, and distance between the front and rear axel is 3metres, the net effect is you redistribute (60kg*1m)/3m = 20kg from the front axel to the rear axel; So the rear axel now weighs 60Kg+20kg=80kg more; And the front axel weighs 20kg less. Simpels (I think)

 

[chriscroft]

No, altering the suspension will not effect how the load is distributed between the axels.
Your thoughts re the bikes etc is totally correct.
The calculation is quite easy its just a "moment calculation" or "Lever arm" calculation
If you put extra weight behind the rear axel, not only does all that extra weight go straight onto the back axel load, just as you thought, it also redistributes load from the front axel, onto the rear axel.
So if you add 60kg 1 metre behind the back axel, and distance between the front and rear axel is 3metres, the net effect is you redistribute (60kg*1m)/3m = 20kg from the front axel to the rear axel; So the rear axel now weighs 60Kg+20kg=80kg more; And the front axel weighs 20kg less. Simpels (I think)

And now you've got the scales to check my maths

 

[Davenjo]

No, altering the suspension will not effect how the load is distributed between the axels.
Your thoughts re the bikes etc is totally correct.
The calculation is quite easy its just a "moment calculation" or "Lever arm" calculation
If you put extra weight behind the rear axel, not only does all that extra weight go straight onto the back axel load, just as you thought, it also redistributes load from the front axel, onto the rear axel.
So if you add 60kg 1 metre behind the back axel, and distance between the front and rear axel is 3metres, the net effect is you redistribute (60kg*1m)/3m = 20kg from the front axel to the rear axel; So the rear axel now weighs 60Kg+20kg=80kg more; And the front axel weighs 20kg less. Simpels (I think)

Thanks for that - whilst not changing the weight going through each axle, and assuming when I do the weight checks I am still within the limits for the rear axle, would uprated suspension and the resultant more level van, improve traction?