insufficient payload

[RonB]

When faced with the same problem on a previous van I often wondered why there was no double fixed/mono wheeled trailer on the market as it would take all the agro out of reversing the unit. I took it that there was some technical reason and they were not allowed. Why are they not more popular as they look the ideal solution for motor bikes/scooters?

[tonyishuk]

Well at least it saves about 5ft on a ferry price :->

 

Rgds

[Brian Kirby]

The short answer, I think, is that some kind of trailer is your only practical option.

Your van is based on a light chassis, and has a substantial rear overhang.  Even with rear axle upgrading, if possible (which I doubt), the extra weight so far back would be liable to cause stability problems, and also quite severe traction problems. 

The scooter would be at somewhere around 50% of the van's wheelbase behind the rear axle.  A towbar mounted rack, for reasons stated above, would be very liable to overload the towbar itself in terms of its downforce limits, and the weight of the scooter plus that of the rack would be very challenging to stabilise when perched only on a towball. 

A proper, chassis mounted, scooter rack would be, I think, your only option - but would need to be purpose made for your van and would be quite heavy in itself.  Due to the need to extend the rack well forward beneath the rear of the van, for strength, the rack would be liable to grounding.

However, if you already have insufficient payload to carry the scooter alone, it is pretty much a racing certainty that your rear axle is already at, or above, its permitted load limit.  Irrespective of the solution you adopt, therefore, I would suggest you check this with the van fully laden, as it may preclude even the addition of a towbar.  Why?  The towbar alone may take your rear axle overweight, but any trailer will need to exert some additional downforce on the towball, or you risk instability of the trailer, and this added load is likely to be the clincher.

The castoring type trailer, while apparently attractive, must place somewhere around 50% of its self-weight, plus 50% of the scooter's weight, onto the rear mounting points on the van, which will themselves add weight at the rear.  Ask the trailer manufacturer how much load it transfers to the tow vehicle: he should know.

The point of all this is that loads added behind the rear axle add more than their self weight to the rear axle load, with the difference subtracted from the front axle load.  If I'm roughly right about the ratio of overhang to vehicle wheelbase (50%), then the self weight of your scooter + rack, or rack + trailer noseweight (i.e. the towball downforce), or transferred load from a castoring trailer, will be multiplied by 150% at the rear axle, with 50% coming off the front axle.  That is to say, the 100Kg scooter alone, with an overhang at 50% of wheelbase = 150Kg at the rear axle and -50Kg at the front axle.

Be very wary of claims to be able to re-plate the van.  If it has previously been downplated from a higher MAM, which I think extremely unlikely, it should be possible to re-plate it back to its original capacity. 

It may be possible to upgrade the rear axle capacity, and so gain MAM, but expect springs to need to be replaced, possibly tyres, and maybe brakes.

Otherwise, all most re-platings achieve is to add together the maximum permissible loading for the front and rear axles, which will invariably exceed the original plated MAM, and declare these as the new MAM.  Thus, the MAM increases, but neither axle can carry more load than before.  This creates great loading difficulty when trying to take advantage of the increased capacity, since any added load will almost invariably be unevenly spread between the two axles, with one, or the other, becoming the limiting factor before the new MAM is reached.

Your van's capacity seems liable to be limited now by its rear axle load limit, and this would most probably remain unaltered whatever increase in MAM may result from the re-plating.  In short, you could spend a few hundred pounds on re-plating and gain no benefit whatever.

If the castoring trailer places too much load on the rear a conventional trailer might work, but do check the present rear axle load very carefully, take account of the self-weight of the tow bracket + ball, and then add approximately 7% of the combined self-weights of trailer plus scooter, as the necessary downforce at the towball.

If it will take it, be prepared to spend around £300 + fitting to add air assisters to the rear suspension.  These will not enhance the rear axle load carrying capacity, but should counter any tendency for the tail to drop and cause grounding problems with the tow bracket.

Otherwise, and probably simpler in the long run, change the van for one with a much shorter overhang and a higher permissible rear axle load.  A cheaper alternative would be for your wife to drive the van, with you following on the scooter (or vice versa)!  :-)