Tyre pressures

Kdc.. Thank you for that information. It seems to me then that the Peugeot system is rather more practical and less likely to be triggered by something other than a sudden loss of pressure.

Please, please, please let this eternal thread go to bed!!
The pressure of a tyre is purely a function of the weight applied to it, end of story
The only variables are the construction of the carcass and the number of plies inside it.
The English Electric Lightning, which I worked on for some time, tyre was very small for the weight of the aircraft as it had to retract into a very thin wing, it was 16 ply, from memory, and inflated to 230Psi  with Nitrogen. The average life of the tyre was between one and four landings depending on pilot skill.
So, in a nutshell, you need to know the accurate axle weight of your vehicle, divided by 2, then you know the weight the tyre has to carry, now, surely, the manufacturer should be able to quote a pressure for that tyre to carry that weight????????????

woodlice wrote:Cymro, what was your vehicles original plated pressures? Mine are 65 - 72

Woodlice: Just been to check. On my Nuevo ES the doorplate says Front 72.3 psi [5Bar +/- 0.05] and Rear 79.5psi [5.5bar].

On Continental Vanco Campers - having weighed my van in holiday trim - I run at 53:73.

Cymro

Cymro thanks, so you dropped the front by about 15psi. Just trying to figure out how low you might be able to get away with without triggering the tpms warning.

IanH wrote:
The pressure of a tyre is purely a function of the weight applied to it, end of story

Or is it more a function of the mass of air pumped into the tyre?
Doesn't a tyre have the same pressure when not fitted to the van and hence bearing no weight?

Don, if the tyre is set to a pressure and then you increase the weight the pressure will increase.

woodlice wrote:Don, if the tyre is set to a pressure and then you increase the weight the pressure will increase.

so you can't check the pressure of the spare without fitting it on the van?

woodlice wrote:Cymro thanks, so you dropped the front by about 15psi. Just trying to figure out how low you might be able to get away with without triggering the tpms warning.

As I mentioned, Woodlice, the alarm was triggered when I dropped the tyre pressures to 55:75. I don't know how much above those figures the TPMS was originally set at by Peugeot. All I know is that, having dropped to 55:75 and thereby triggered the alarm, I wasn't able to reset the alarm merely by restoring the tyre pressures to the high pressures on the door plate - it needed a visit to the dealer to reset it. And so, when I was there, I instructed them to lower the TPMS trigger pressures to about 5psi lower than the pressures at which I wanted to run the vehicle. So they reset the TPMS to 50:70, and I run at just under 55:75.

Cymro

Found this on MotorhomeFun forum from Continental. They seem only too willing to help. What a refreshing change!
Added middle bit myself to assist Nuevo Lancashire owners to get a grip of the subject.
Also found in one Auto-Sleeper handbook "Increase the tyre pressure (by approximately 2 bar above the standard pressure) to prevent the tyres from becoming flat."
Unbelievable or what....... I kid you not.................


Continental 215/70 R15 109 R CP Tyre Pressure
Advice from Continental regarding Tyre Pressures for their Vanco Camper Tyres:-

It is extremely likely that the relevant information supplied with the chassis is documented for use as a commercial vehicle, therefore proposed before the conversion to a motor home. For this reason, Continental tyres would always recommend having the motor home weighed on a weigh bridge at your heaviest travelling weight, including liquids to achieve specific axle weights. In some cases the coach builder will also put their recommended pressures on the vehicle plate. However, the majority put this to the maximum inflation pressure of the tyre to cover all loads being applied and not specific loads which often, are not near the plated weight you actually travel at. The volume and pressure of the inflation medium is what carries the load and if it is not sufficient then the tyre can suffer damage, hence why it is extremely important for the correct loads to be obtained, in order to inflate the tyre correctly. Experience shows that due to the weight distribution of vehicles in the leisure industry such as motor homes the likelihood of overloading or uneven weight distribution tends to put a greater load on the rear axle rather than on the front axles, where the weight tends to remain more consistent. It is true that when braking occurs the weight transference is to the front, but this only tends to be for short periods, whereas overloading on the rear axle can be present over long periods, when the tyres are rotating at high speed. This is the main reason that with CP Camper type tyres the inflation pressures at the rear is deliberately set higher. Although this also has a bearing on the contact area when negotiating grassy parking areas and also to the sidewall deflection, which influences the body roll.

The 69 psi written on the side of the tyre is for the Northern American market only and the inflation pressure of the tyre can exceed this value within its safety operating range.
Based on the following: ContiVanco Camper 215/70 R15 (CP*) 109 R tyres. (*CP- Camper) (Single fitment (S) = two wheels per axle.

Now my bit:-
From Handbook - The Lancashire EK has a MTPLM of 3300 kg ( RunW 2852 + PL 448)
Axle Weights: (Running order should be inclusive of driver, passenger and liquids?)
Front, in Running Order 1309 kg
Rear, in Running Order 1543 kg

Though tables do not cover such a light axle load for the front of 1309 kg; we have from the Continental Chart:
1425 kg Axle Load for pressure of 3.0 bar or 44 psi
1520 kg Axle Load for pressure of 3.25 bar or 47 psi
1615 kg Axle Load for pressure of 3.5 bar or 51 psi
This is a lot different to the 74 psi as supplied by Auto-Sleeper dealer.

The Continental Chart (Single fitment (S) for the rear axle load of:
1595 kg Axle Load for pressure of 4.0 bar or 58 psi
1675 kg Axle Load for pressure of 4.25 bar or 62 psi
1755 kg Axle Load for pressure of 4.5 bar or 65 psi
1830 kg Axle Load for pressure of 4.75 bar or 69 psi
However Tyresafe recommend 80 psi – the maximum safe pressure for this tyre – single fitment - for all rear axle loads which is at odds with Continental and would give a very harsh ride.
Any vehicle design engineer will tell you that the tyres are part of the suspension system and thus operate in synergy with tyre pressures and load to give the desired ride and handling. Simply inflating tyres to the maximum allowed does not concur with common sense though does comply with avoiding any responsibility. The 74 psi as supplied in running order by Auto-Sleeper dealer gives horrendously harsh bone shaking hoppy ride at rear accompanied by very loud rattling.
You will find that many people on forums report that they use (Nuevo) 50psi front and 60psi rear – I think that I will now reduce my pressures down to this level in stages as it concurs with rear axle Continental Chart for 100 kg or 220 lb payload biased to the rear axle. First will try 55psi front and 68psi rear. (written by me – John, who would not consider loading any vehicle to anywhere near its maximum 450kg PL equivalent to mass of six extra people!)
ps; I was alarmed by the body roll with all tyres at 74psi – are they supposed to be like this? Still, I am used to and love, the sharp precise steering and taught handling of a hot hatch back! Must get to a weigh bridge soon.


Missing chart should be inserted here -

Now back to these nice, very helpful Continental people:-

I hope this helps and any further enquiries (no matter how small) please do not hesitate to ask, we are always happy to help!

Visitors Address: Continental Tyre Group Ltd DC2 Castle Mound Way Rugby United Kingdom CV23 0WB
Direct Line: +44 (0)1788 566240 Fax: +44 (0)1788 517731
E-Mail: administrator.technical @conti.de
Web: [You must be registered and logged in to see this link.]

The Continental chart is noted in the Fact Sheet sub-forum, and here.
[You must be registered and logged in to see this link.]

72.3 : 79.5. Says the door plate. 
Cymro

Hey Peter L,

Thanks for the link as I was squinting a little on that other post as the chart degraded under enlargement.
Did not and still do not know how to access the sub forum you talk of?
If you have it from the horses mouth why are we not fully sorted with tyre pressures by now????  
Have you or any other member confirmed axle loads on a weigh bridge?

thanks again - John  

The factsheet sub section can be found about half way down home page but here is the tyresafe factsheet link

[You must be registered and logged in to see this link.]

Thanks Paul,

Had the leaflet but now used the calculator.
This gives 44psi front and yes you guessed it 80psi rear in running order axle loads per handbook.
Guess I will not bother with it again and stick to tyre Manufacturer chart - Continental.
Just been out for a spin having reduced all pressures from 74psi.
Front now 60psi and rear at 69psi - Wow - what an improvement.
Tyre wall and footprint visibly different.
The tyres are now getting to work in harmony with load, springs and dampers for first time 
Still rattles but not with such harsh intensity.
Body roll seems about the same and steering much smoother.

Will reduce further when I have loads from weigh bridge. 
Feel in control now.

Thanks to all - John & Maggie