Weighbridge needed in West Sussex

[Keithl]

In theory yes but... the figures for the tyre pressure on each axle are based on that axle being at the maximum allowed weight and as we all know the sum of the two axles permitted weight is typically greater than the GVW to allow for positioning of any load. So if either axle is below the permitted maximum then the tyres on that axle can be run at a lower pressure. 

[colin]

12 minutes ago, Kevjan said:

But surely the manufacturers figure should be what to use or why do they bother publishing them. Kevin 

This is a long argued point, I would say do the manufacturers know what you are putting in your van? The answer to that is no, so they take the worse scenario.

[Kevjan]

So working on the tyre pressure being on what your axle weight at any given time  you would have to weigh your van and adjust the tyre pressure each time you use it.  I would think that most van's either van conversion or coach build are very close to manufacture max weight most of the time. Kevi

[Keithl]

30 minutes ago, Kevjan said:

So working on the tyre pressure being on what your axle weight at any given time  you would have to weigh your van and adjust the tyre pressure each time you use it. I would think that most van's either van conversion or coach build are very close to manufacture max weight most of the time. 

In reality most MH's will remain within a fairly small weight range so not necessary to weigh every time.

Most likely close to max GVW but one axle may still be somewhat below its maximum allowable weight so can run at a lower pressure for an improved ride.

[colin]

2 hours ago, Kevjan said:

So working on the tyre pressure being on what your axle weight at any given time  you would have to weigh your van and adjust the tyre pressure each time you use it.  I would think that most van's either van conversion or coach build are very close to manufacture max weight most of the time. Kevi

I weighed our van then allowed a big margin for 'overloading', and it's still much lower than manufacturers figures, if you have a 'light' chassis it might not be worthwhile. I would note that loading up the van and getting it weighed is no bad thing, many have found they have unwittingly overloaded the van, others have found the van cannot be legally used as a motorhome as there is no capacity to carry anything. 

[Kevjan]

I thought this was about tyre pressure not vehicle weight. Kevin 

[flyboyprowler]

15 hours ago, Derek Uzzell said:

Are you certain about the tyres' specification?

Assuming( from your postings on the earlier thread) that you might be choosing VanContact 4Season tyres with a 225/65 R16C specification, I looked at Continental's current Databook and was concerned that this size of tyres was only shown as 8PR-rated with a load index of 112/110. That load index would restrict a front axle maximum load to 2240kg and a rear (twinned wheel) axle maximum load to 4240kg. 2240 + 4240 = 6480 and - as I think your Flair has a GVW (Gross Vehicle Weight) of 7200k (or 7500kg) - that specification tyre would potentially be unsuitable for the motorhome.

I think it's more likely that your Flair's tyres are 225/75 R16C, as this size is available as 8PR-rated or 10PR-rated. The 10PR-rated version has a load index of 121/120  and that would allow a front axle maximum load of 2900kg and a rear (twinned wheel) axle maximum load of 5600kg. 2900 + 5600 = 8500, so well above your Flair's GVW.

Yes, typo error on my part Derek. 225/75/R16C, 121/120, 10ply.

[Derek Uzzell]

Idle curiosity, but what pressures did you choose to use for the original Michelin Alpin tyres (that presumably had the same size and load index as the Van Contact 4Season tyres) and what pressures do Iveco and/or N+B advise should be used?

(Water under the bridge now, but Avon's AS12 tyres might have been worth considering and - I'm guessing - would have been significantly less expensive.)

[flyboyprowler]

17 hours ago, Derek Uzzell said:

Idle curiosity, but what pressures did you choose to use for the original Michelin Alpin tyres (that presumably had the same size and load index as the Van Contact 4Season tyres) and what pressures do Iveco and/or N+B advise should be used?

(Water under the bridge now, but Avon's AS12 tyres might have been worth considering and - I'm guessing - would have been significantly less expensive.)

I went through much the same process with Michelin when we first got the van as regards tyre pressures and used 4.6 bar on the front, and 4.3 bar on the rear. N & B pressures were given as the maximum weight at well over 5 bar. At maximum axel weights, the Conti tyres would have been at approx 5.3 bar front and 4.6 bar approx for the rear. We are going to N & B at the factory next week so will ask their opinion as they now fit Conti 4 season as standard.

[Derek Uzzell]

The majority of motorhomes are Fiat Ducato-based and the following table is taken from a current Fiat Ducato handbook relating to motorhome chassis.

It should be apparent from this table that, when a Ducato has CP-marked ('camping') tyres, only two inflation pressures are advised - 5.0bar (front) and 5.5bar (rear) for 15"-diameter wheels or 5.5bar (front) and 5.5bar (rear) for 16"-diameter wheels. The vehicle's axle loadings don't come into it - if the tyres are CP-marked, just those two sets of (high) inflation pressures are stipulated.

My 2015 Ducato-based Rapido 640F coachbuilt motorhome had a GVW (Gross Vehicle Weight) of 3500kg, a Rapido-quoted 'empty' weight of 2865kg and 15"-diameter wheels with 215/70 R15CP tyres. On delivery (and unsurprisingly) the selling dealership had inflated the tyres to (roughly!) 5.0bar (front) and 5.5bar (rear) and it was immediately obvious that the vehicle's steering was unpleasantly light and, on UK rural roads the ride quality was bone-shaking. The Rapido data-plate did specify that those pressures be used when the motorhome was 'fully-loaded', but that was never going to be the case during my ownership period. I chose to use 4.5bar/65psi (front) and 5.0bar/72psi (rear) as those values were well in excess of the pressures advised for the motorhome's weighed axle loadings (and the pressures were easy for me to remember!) This 0.5bar reduction made the steering usefully less light and the ride quality became tolerable (though still harsh).

Historically, motorhome owners have proactively reduced their vehicles' tyre pressures, primarily to obtain a more comfortable ride quality. Recent Ducato-based  coachbuilt motorhomes will have a TPMS (Tyre Pressure Management System) as standard that, presumably, will have been factory-set to 5bar+ pressures when CP-marked tyres are fitted. Surprisingly (to me) this has not generated the level of motorhome forum complaints about overly-high tyre pressures that I had expected.

It is possible to alter the pre-set TPMS data using the appropriate scanning equipment/software (Multiecuscan?) and Fiat Professional agents should be able to do this but may refuse to. But perhaps new owners of TPMS-equipped Ducato-based  motorhomes with CP-marked tyres just live with the harsh ride.

[John52]

I can only add the reason they say pull off the weighbridge and reverse back on is so the scale can be reset to zero in between.  This considerably adds to the time and is only in case a drop of rain or something has fallen on the scale - the difference will be insignificant.

And consider the practicalities when the weighbridge is busy and the vehicles queuing up, as is usual in a scrapyard.  The guys waiting behind may already be a bit peeved you are stopping and weighing twice.  It won't help if you are trying to stop them driving on whilst you pull off, wait for the scale to be zeroed, and reverse back on again.

Its not worth it.

[Brian Kirby]

On 01/11/2023 at 11:04, John52 said:

1  I can only add the reason they say pull off the weighbridge and reverse back on is so the scale can be reset to zero in between.  This considerably adds to the time and is only in case a drop of rain or something has fallen on the scale - the difference will be insignificant.

2  And consider the practicalities when the weighbridge is busy and the vehicles queuing up, as is usual in a scrapyard.  The guys waiting behind may already be a bit peeved you are stopping and weighing twice.  It won't help if you are trying to stop them driving on whilst you pull off, wait for the scale to be zeroed, and reverse back on again.

3  Its not worth it.

1  If the weighbridge is at a scrapyard, or builder's merchant that deals in bulk materials (sand, aggregates, gravel etc.)' all they weigh is the difference in weight between the truck when it arrives, and when it leaves.

For bulk goods, on first arrival the driver goes to the yard office and explains whether, and what, he is collecting/delivering, and they give him an authorisation showing his rej. number, and what he is there to deliver or collect.  From there he goes to the weighbridge.

The operator will record the rej. number of the truck when it arrives, and the weighbridge machine will store that number and the vehicle weight.

The truck will then go and deliver whatever it is carrying, or collect whatever it is collecting, following which it will again pass over the weighbridge.

On the second pass the weighbridge operator will again enter the truck's rej. number and the machine will retrieve its arrival weight and compare that to its new, departure, weight.  If the truck is heavier when leaving it will obviously have collected goods, if lighter, it will have delivered goods.  In both cases it will print a "ticket" showing the arrival weight, the departure weight, and the difference between the two, either negative (collection) or positive (delivery).

The driver will then take the ticket and his authorisation statement back to the office where he will either be paid, or pay, whatever the cost per tonne for those goods was agreed when he first arrived.

So, when weighing a motorhome to get axle loads all that is usually done is to ask the weighbridge operator to set his machine for a delivery.  Then, drive fully onto the platform and stop as centrally as possible.  The operator records your rej. number and takes that weight.  You then advance just enough to take the front wheels just clear of the platform, leaving the rear wheels as close as possible to the platform centre.  The operator then takes that weight.  As above, the machine will then deduct the second weight from the first, and print your ticket with your rej. number on it.  You then have an "official" (the machines are periodically checked for accuracy by local weights and measures inspectors) record of your actual laden weight (the first weight), your rear axle weight (the second weight), and your front axle weight (the first weight minus the second weight).

Nothing needs to be re-set, and the whole operation only takes as long as the weighbridge machine takes to record the two weights, deduct t'other from which, and print the ticket, which takes only minutes.

2  I haven't used a scrapyard weighbridge, only "heaviside" builders yard weighbridges.  The queue problem has never materialised because I'd phone beforehand and ask when the machine was usually quiet.  No queue behind, the operator knew what was required and, consequently, the whole operation was quick.

It may be that John52's scrapyard has an older machine (this was a modern, electronic machine which weighed me reasonably accurately as I walked across the platform to explain to the operator what I wanted!) but no-one was disrupted or agitated as it was so quick.

The bit above about centring the van and keeping the rear axle a central as possible relates mainly to mechanical weighbridges, which are a bit less accurate around the platform ends.  So if you don't know whether the weighbridge you are using is mechanical or electronic just seek the advice of the operator regarding where to stop while explaining what you want.

[Brian Kirby]

On 29/10/2023 at 23:26, Kevjan said:

I thought this was about tyre pressure not vehicle weight. Kevin 

It was/is, Kevin.  But to get the optimal tyre pressures for your van you need to know the actual, fully laden, load on each axle.  The optimal tyre pressure follows that weight.

In your first post you said "Hi all, i took my Peugeot Boxer to the weight bridge when we first got it, I only weighed the total weight which was 3440 kgs that was half tank water, full tank fuel, 2 people and everything to go away for 2 week's so not far from the max gross weight so i run the tyre pressure at the Peugeot recommended laden weight, surely that is the correct thing to do. Kevin.

So, do you always travel with your fresh water half full, and how do you know that is is half full?  Many vans have 100 litre tanks, and water weighs 1kg per litre.  So were you to fully fill your tank the total weight of the van would increase by how much? 

Moreover, the weight on the rear axle could possibly increase by the same amount, as many water tanks are close to the rear axle.

Also as Keith said above, if the van is close to its assumed MAM of 3,500kg, it had only 60kg of payload "spare" when at the weighbridge.  The usually indicates the the rear axle would have been close to its maximum permissible load.  So, unless the weighing takes place with a measured amount of water in the tank, and you also get the actual rear axle load in that condition, you risk overloading the rear axle, which means the rear tyres would be under-inflated for that load which, depending on degree of overload, may result in dangerously overheating rear tyres, but is also illegal.

It is these variables that mean you need to know both axle loads to be confident that the manufacturer's tyre pressures are the correct pressures to use.

[John52]

Well yes Brian I am probably out of date as usual.  Because the weighbridge I operated wasn't digital.  It had a big central dial and a big 5 position lever at the side you set to the weight range 0-10 tonnes, 10-20 tonnes etc up to 50 tonnes.

There was one where I worked so I was able to play around with it - trying just pulling forward to weigh the rear axle.   Then trying pulling off and reversing back on again (this is where I envisaged the following vehicle driving on before you had finished.)  It made little or no difference to the indicated weight.

[Kevjan]

So Brian what I said before about having to weigh and adjust your tyre pressure each time you use your van would be right. As for axle overload most vans if you add the total max load of both axles together it is normally well over the gross weight of the van so I dought very much you would overload either.  As for water I always put in 2 x 20 ltr cans of water before travelling so it is always about the same. Kevin 

[colin]

13 minutes ago, Kevjan said:

So Brian what I said before about having to weigh and adjust your tyre pressure each time you use your van would be right. As for axle overload most vans if you add the total max load of both axles together it is normally well over the gross weight of the van so I dought very much you would overload either.  As for water I always put in 2 x 20 ltr cans of water before travelling so it is always about the same. Kevin 

And I would say there is no need for adjusting tyre pressures for every journey, I have checked our van loaded for touring then adjusted tyre pressures to allow for a bit of overloading, and these are still far below the Fiat/Globecar figures.

If you look at the data plate on a car you will see it usually gives three different tyre pressures, light load, heavy load, economy.

[Brian Kirby]

5 hours ago, Kevjan said:

So Brian what I said before about having to weigh and adjust your tyre pressure each time you use your van would be right. As for axle overload most vans if you add the total max load of both axles together it is normally well over the gross weight of the van so I dought very much you would overload either.  As for water I always put in 2 x 20 ltr cans of water before travelling so it is always about the same. Kevin 

Not really.  🙂 

As Colin says above, if you add an upward  tolerance for load variations, and then take the appropriate pressure for that load, you will almost invariably be able to run at pressures below the van manufacturers published pressures, with benefit to handling and comfort.  

As Keith said, the van manufacturer has no knowledge of how you may load the van, so can only recommend pressures suitable for the maximum permissible load on each axle.  As the base for your motorhome is a commercial vehicle, built to carry a wide range of loads, its suspension and tyres are specified to cope with a wide range of axle loads.   As you say, the maximum front axle load plus the maximum rear load invariably exceeds the GVW for the van by a substantial margin.  That is to allow for load distribution within the van.  However, once you have the van fully laden as you will use it, those loads are unlikely to vary significantly, so can, with Colin's upward tolerance added for good measure, be assumed to be fairly constant.  The only time you should then need to re-check the axle loads and alter the pressures is if you add, or remove, significant weight to/from the van.

Don't be too confident that the axle loads will not be exceeded!  🙂  You haven't said what your van actually is, save that it is on a Boxer base.  Many coachbuilt vans have rear chassis extensions that increase the rear overhang, making overload of the rear quite common with motorhomes, so better safe than sorry?  Re the water, then you travelling water load will be consistent.  

[flyboyprowler]

We are just starting our first trip on the new tyres. Definitely quieter than the Michelins they replaced,  and from starting from cold, the pressures rose by .7 Bar on the trip to Dover, and set the TPMS off. The Michelins rose a lot less on route and the O.A.T. Was around 8.5 degrees. The ride quality also feels smoother, but that could be imagination!