Towing car on trailer

[tonyishuk]

I chopped out the following from another thread :

 

Having a tonne of vehicle off the ground was positively frightening in cross-winds when passing HGVs on motorway. I frequently had to ease off to counter swaying of the trailer. Perhaps it'd be better with a 4 wheel trailer, but then it's even more of a storage issue on site. Contrast a-frame, the car is so uttlerly stable you need the reversing camera to remind you it's still there.

 

I was wondering if this a common occurance when towing a car on a trailer ? or a more to do with the nose weight and car position on the trailer not being quite correct ?

 

I have tugged a few caravans in my time and know that queasy feeling when passing an HGV (or being white van-ed at high speed).

 

I asking because we are thinking of trailing an IQ auto on a trailer and have not seen any comment before about trailer sway / snaking.

 

Rgds

[Rosbotham]

That's my quote...

 

For additional info on noseweight, I always ran at c100kg noseweight. Max rated on trailer was 110 (or maybe 120). Towbar installers advised to keep noseweight as low as possible as that represented largest strain on the towbar.

 

I struggled to get the noseweight as low as 100kg. (Front engined) car was as far back as it would possibly go on the trailer to achieve that. However that was in-line with how the trailer manufacturers demonstrated it being used - see http://www.bantamtrailers.co.uk/gt.html. Reading posts on another forum from the guy I bought the trailer off, much of the reason he sold it was because he couldn't get the noseweight down to a level he was comfortable with.

 

Bantam trailer by the way...not uncommon (Brian James is same one?).

 

Probably not as much an issue with a rear-engined car such as a Smart.

 

Edit : forgot to add, guy who bought my trailer did so to pull an IQ...sorry, I've not been in contact with him to see how he got on.

 

Paul

[tonyishuk]

Thx for the reply.

 

Intresting to note the noseweight, did you ever try putting the car on backwards to reduce the loading ?

 

Having an Auto IQ, I would have to trailer it, but am beginning to wonder if just not spending the money on a trailer and putting it towards a pre loved A framed Smart may be a better option ?

 

I freely admit I have always been in the "Trailer It" don't "Toad it" camp, but am beginning to change my mind.

 

I suppose one of the benefits of towing the car rather than the trailer is that you do not lose so much payload. The payload is reduced by the weight of the towbar and with an A frame the nose weight is next to nothing ???

 

Assuming a towbar is 60 kg + Noseweight of 100 kg, A 160 kg of the payload is quite a lot. (Have to leave the wife and grandkids behind !)

 

Rgds

 

[Guest JudgeMental]

Sorry to highjack the thread a bit*-) but I know little re towing/nose weight.

 

on a Fiat panel van I intend to fit a tow bar and fit a tow ball bike rack (approx 18kg) and two e bikes (20 kg each without batteries) So that is about 60kg on the tow ball......Will this be OK please :-S

 

Oh! and how will this effect payload? anyone know by how much?

[colin]

If you fit a towball rack to a 'twin' style layout will it interfere with accessing storage area from rear?

Are you getting an L3 or L4 now?

For L3 increases rear axle loading by about 77kg

For L4 about 85kg

How much this affects payload depends on which chassis you have and if you hit limits on axle loading.

[Rosbotham]

I wouldn't claim expertise on these things. As I say, having tried both, I far prefer the a-frame approach, but it's not trouble-free and certainly trailers have their supporters.

 

In terms of the Q about loading the car backwards, a few people suggested it but I can't say I tried it. I sort of felt that given the weight's in the engine (should have mentioned my Fiat 500's a diesel, which doesn't help on this...it's 75kg heavier than the petrol versions), having that hanging over to the rear of the wheels could risk having neglible or even negative noseweight. As I say, didn't try it though.

 

On the impact on payload, I confess I didn't give it any thought at the time. However, mechanics/applied maths would indicate that as well as the reduction of the overall payload, the pivot effect would be to increase the load on rear wheels of motorhome and reduce it on the front. I haven't done the maths but if it's 100kg noseweight, perhaps +140kg on rear, -40kg on front wheels depending on relative distance between wheels versus rear overhang (that's going back to A-level applied maths!). I understand overloading is more commonly an issue at the back end so it'd exacerbate that.

 

On an A-frame, I guess superficially it'd be part of the weight of the a-frame (given it's supported between the toad and the motorhome). So not much at all...10-20kg at most?

 

One thing I perhaps should have mentioned. My trailer was a Bantam GT that started life as a Bantam Smart and was rebedded to become the GT by Bantam for the original owner. However I can't think that this would be material to any of this...to all intents & purposes the trailer was life an "off the shelf" GT.

 

Paul

[tonyishuk]

From my caravaning days; towballs generally seem to be around 75 to 90 kg capacity. BUT the weight is specified by the towbar maufacturer in conjunction with the vehical manufacturer. (Some cars go as low as 50kg, or have a recommendation that a towbar cannot / should not be fitted)

 

This information should be availiable from suppliers.

 

Other m/homes with Alko chassies ect where the towbars are "one-offs" there is probably no specific nose weight specified.

 

From a towing, handling point of view 75 to 90 kg seems about right.

 

Having had a Discovery that could take a weight of 150kg, the handling at that weight made the outfit unstable and only to be used at low speed.

 

As mentioned above in the thread, the weight + a bit more (because the weight will be transferred from the front axle) is transfered to the back axle, so makes the front end & steering lighter.

 

Rgds

 

 

 

 

[tonyishuk]

Hi,

 

Our replies crossed about the same time !

 

I suppose its a matter of asking the right questions from the trailer suppliers, possibly trying the car on a trailer with a nose weight guage and consider replating the m/home,

 

I sm starting to think investigating A frames might be worth while.

 

Rgds

[Brian Kirby]

Recommendation (Caravan Club) for caravan towing is that for stability, 7% of the actual laden weight of the trailer should fall onto the hitch.  The French seem to reckon 10%, but they are allowed to tow up to 130kph on autoroutes.  This higher speed will tend to magnify slip stream effects.

One thing no-one has mentioned is motorhome rear overhang.  For stable towing, this should be a short as possible.  Motorhomes with long rear overhangs have considerable lateral movement over road irregularities, and are more prone to HGV etc slipstreams, due to the amount by which the bodywork projects behind the rear axle.  These lateral movements transmit to the relatively short car trailer, causing it to wander, in turn pulling the rear of the motorhome around.

Golden rule for easy towing?  Short tow vehicle, minimal overhang, long trailer.  Think artic.   Motorhome towing car?  Hmmmmmmmmmm!  Cart before horse?  :-)

[Rosbotham]

Funny you should mention that Brian. I'm not an ex-caravanner so not an expert at pulling trailers. However, I did find reversing the trailer with the motorhome a bit of a nightmare compared to towing with a car, because the slightest variation of steering was amplified by the overhang. It always struck me that the reversability or otherwise of a-frames was a bit of a moot point, because the alternative of a trailer wouldn't be particularly maneouvrable in the confines of a single-track road if you met something coming the other way.

 

Returning to the noseweight, agree with what you've said, but car+trailer=1300kg, and max noseweight of the alko trailer-chassis is approx 120kg. It's all very tight...

 

Paul

[John J Thompson]

We tow a BANTAM "Smart Car"trailer with a Diesel Smarty,

 

It is as stable as a rock behind my Hymer S700 which has a massive rear overhang. I can see it in my rear view camera but that is the only way I know it is there.

 

John

[tonyishuk]

Brian Kirby - 2010-09-26 4:49 PMOne thing no-one has mentioned is motorhome rear overhang.  For stable towing, this should be a short as possible.  Motorhomes with long rear overhangs have considerable lateral movement over road irregularities, and are more prone to HGV etc slipstreams, due to the amount by which the bodywork projects behind the rear axle.  These lateral movements transmit to the relatively short car trailer, causing it to wander, in turn pulling the rear of the motorhome around.

Golden rule for easy towing?  Short tow vehicle, minimal overhang, long trailer.  Think artic.   Motorhome towing car?  Hmmmmmmmmmm!  Cart before horse?  :-)

Food for thought !!Overtaking trucks on the Peage with our Rapido (no trailer) we counted "one - two" as the front slipstream hit the side of the M/home and we felt the wobble !Maybe tugging a trailer, our overtaking days may lessened.Back to the slide rule for working out shear forces & moments and pivot point loads on static frames ! Hated it at Uni !Rgds