Tyre Pressures Symbol (again!)

I am still not happy with the tyre pressures set by my Autosleeper agent.  They feel too hard when set at 65 psi   
I have looked for a weigh bridge near by without success.

If you have a 2011 (or near) Symbol and have weighed it and done the sums maybe you could share your findings. 

Any help will be much appreciated.

Whilst info from another Symbol owner is awaited, can you say what make, and size, tyre you are using?
Cymro

Cymro wrote:Whilst info from another Symbol owner is awaited, can you say what make, and size, tyre you are using?
Cymro

They are Pirelli Chrono 225/70  x 15".

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

JandJ wrote:Use Tyresafe [You must be registered and logged in to see this link.]

Thanks for that  but surely that will only be right if I know what the actual axle loads are not the theoretical maximum loads. My thoughts are that even when loaded for a tour they wont be at maximum.

The difference between the actual axle weights and maximum limits will be relatively small.

Do the check on the site using the MRO, (theoretical minimum value), MTPLM (theoretical maximum) and Max Axle weights for the base vehicle (absolute maximum) .

How much does it vary?

I just googled your area and three weigh bridges available if no good go on your county council website they will have a list that you can use

chrisk wrote:I just googled your area and three weigh bridges available if no good go on your county council website they will have a list that you can use

I have been down that route. The gov. map is not accurate. Among other things it lists a company that manufactures weighing equipment not public accessible weighbridges. The nearest I could find is in Romford. 
 County Council web site search produced no results. 

Just thought that if another forum member has done the research with a similar van it would save a bit of hassle.

I took my 2016 Symbol to a weighbridge, fully laden, full of fuel and gas and 25% fresh water, two people plus dog and it weighed 1610kg front and 1494kg rear. My tyres are Bridgestone Duravis Light Truck 215/70 15c. 109/107S. I contacted Bridgestone UK who recommended 3.3 bar front and 3 bar rear. Hope this helps.

Thank you TJB.    That would confirm what I thought.  My tyres are far to hard. Your figures give 47 front and 43 rear. As we rarely travel fully laden I will contact Pirelli to see what they suggest.

Thanks again.

Those figures put into the Tyresafe utility give 54 front 49 rear, nowhere near the 65 they were which is often the marked maximum. By maths they should be 51/47. Sounds like the engineer put them to the max which is fine to bed the beads in but should then be reduced to the required value 

When I fitted my Firestones (part of Bridgestone) I asked them the same question but they came back with "as per vehicle manufacturer specification".

Have just tried 50 front and 48 rear. Already feels much better. I await response from Pirelli for their settings

Have mine at 50psi all round makes life easier as recommended by my local garage
David

Have mine at 50psi all round makes life easier as recommended by my local garage
David

The tyres fitted to my 2009 Symbol are Bridgestone Duravis Light Truck, 215/70R15 C 109/107 S.

I have been advised by Bridgestone that the minimum pressures should be:
Front axle at 1740 kg = 54 psi per tyre
Rear axle at 1560 kg = 46 psi per tyre
Rear axle at 1650 kg = 59 psi per tyre

If going on long motorway journeys they recommend that the pressures are boosted by 2 psi per tyre to cope with the continual high speed running.

In touring trim my van weighs in at:
Gross weight: 3460 kg (van has been uprated to 3500 kg)
Front Axle: 1760 kg (max plated weight 1850 kg)
Rear Axle: 1700 kg (max plated weight 2000 kg)

I set my pressures at:
Front 57 psi
Rear 60 psi

I find the steering too 'skittish' if the front pressures are too high.

Maybe this helps.

G

The difference in pressure between the two rear loads seems excessive, nearly a 30% increase for only 100kg I get 50 and 53

I make the fronts should be 56psi so OK

But the rears 54psi. Why a higher pressure when it is a lower load?

"I find the steering too 'skittish' if the front pressures are too high"


Entirely reasonable. At too high a pressure the contact area reduces so less traction, also the sidewalls cannot deform to side loads as well and maintain contact in the turn

Sorry, the rear axle at 1650 kg should have read 50 psi.

My mistake.

G

Pirrelli have just responded with 47 psi for both front and rear.

Will try that next trip.

Thank you all for your contributions to the thread.

A couple of PSI either way is not going to make that much difference.

I used to take 3 or 4 measurements and take the mean as the value. Since been told take the highest, the gauge itself is most likely accurate enough but its the precise process that produces the error. It may under read as a result but never over read so the highest will be the best tvalue.

Following this thread with interest as l've always experimented with tyre pressures on my vehicles, but a friendly boy in blue pointed out to me that the manufacturer's recommended pressures as displayed on the vehicle door pillar are gospel as far as they are concerned. Stray too far from that, be involved in an accident or even just a vehicle spot check and you could be in trouble. Comments?

No, they would still have to show that it left the vehicle in a dangerous condition.

If you can show that there was sound engineering reasoning and/or authoritative technical advice then it in itself is not a fault. I used to build rally cars which in the main had no applicable "B" post label to refer to yet were fully road legal.

All these after market alloy wheel makers would have little market for their products if they could not be used.

PS I have no such label on the "B" so they would be somewhat stymied, neither on the van nor on my new SEAT. (it's in the fuel filler flap)

Jarjar wrote:a friendly boy in blue pointed out to me that the manufacturer's recommended pressures as displayed on the vehicle door pillar are gospel as far as they are concerned. Stray too far from that, be involved in an accident or even just a vehicle spot check and you could be in trouble. Comments?

I tend to agree with the boys in blue. It's difficult to believe the figures on the door pillars are wrong.
Underinflated tyres may be comfortable but they are prone to over heating (blowout) and do not keep their shape if you need to swerve.

Ok. So my Sussex states 59 front and 65 rear. I have Michelin Agilis Camper tyres. Michelin (and Tyresafe) say rear should be 80psi on camper tyres on all motorhomes irrespective of axle weight. I have an accident, insurance assessor knows that Michelin say 80 but I've put 65 in. Do I get insurance claim rejected for having 65 in or do I get done by police if I put 80 in?

AutoSleepy_Don wrote:Underinflated tyres may be comfortable but they are prone to over heating (blowout) and do not keep their shape if you need to swerve.

Absolutely! But who would in their right mind underinflate just to be comfortable? Over inflation can be just as problematic as far as handling is concerned

C & U regulations on Tyre Pressures only says - CL 27 (b)

(b)the tyre is not so inflated as to make it fit for the use to which the motor vehicle or trailer is being put;

Whatever that means.