Tyre Pressures

colinm said:
That is not correct, the law (Regulation 27(1)(b) of the Road Vehicles (Construction and Use) Regulations 1986) states "a motor vehicle cannot be used on a road if a tyre is not so inflated as to make it fit for the use to which the vehicle is being put".
With the tyre manufacturer giving the pressure to be used for the given load, that is the correct pressure to use.
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The ' ... use to which it is being put' would surely make a prosecution difficult? My car has 3 tyre pressure settings, IIRC, depending upon the load and number of passengers being carried. So, if I am stopped at the Recycling Centre exit [made 60+ trips in last 4 months after house move , I would need to reduce the pressures by x psi on warm tyres with guessing the adjustment ...

The same applies to the M/home if the water tank, lpg and the diesel is well down during a trip, and I am stopped after a refill with an increase of perhaps 100kg-130kg

Steve
 
marchie said:
The ' ... use to which it is being put' would surely make a prosecution difficult? My car has 3 tyre pressure settings, IIRC, depending upon the load and number of passengers being carried. So, if I am stopped at the Recycling Centre exit [made 60+ trips in last 4 months after house move , I would need to reduce the pressures by x psi on warm tyres with guessing the adjustment ...

The same applies to the M/home if the water tank, lpg and the diesel is well down during a trip, and I am stopped after a refill with an increase of perhaps 100kg-130kg

Steve
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All (most?) cars now have a data plate that has 3 pressures, something along line of, light loading, heavy loading, and eco. At any one time it's highly unlikely these will be the absolute ideal pressure, but they will all be 'fit' for purpose.
 
I have seen folk here driving with tyres comming or the rims, a lady driving in the wet with hand brake on and back wheels locked for miles, folk waving at her and she just gave a nice wave back, as a rule police here dont bother until there is a crash. and even then if no one is injured they say sort it yourselves.
So tire pressures here to many is a kick at the wheels test.
 
colinm said:
All (most?) cars now have a data plate that has 3 pressures, something along line of, light loading, heavy loading, and eco. At any one time it's highly unlikely these will be the absolute ideal pressure, but they will all be 'fit' for purpose.
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Not in the case of a revised loading [full car to empty car in my Recycling Centre example] or in the case of the M/Home with the payload changed significantly by a refill of water, lpg and diesel [a common 3 factor alteration when we are away on long trips, starting off with little gas and water, and refilling at the last garage before the upcoming aire with water, gas, diesel and supermarket supplies to minimise the daily shopping by bike. A change of payload by 130Kg-150Kg is quite common for us.

Steve
 
My late brother used to drive from Teesside to Norfolk then increase his car tyre pressures next day "because I might take you and your wife out". Then he would reduce the pressure just before his return journey.

I just used to laugh behind his back.

When I bought Goodyear's via the internet for my MH last year the Manager rushed out when I turned up to say they had a limit of 72psi. I wasn't bothered because my axle loadings suggested 48 psi front and 56 psi rear: I had used those pressures for over 10y on two sets of non-CP tyres with no ill effect. I believe that tyre wear is not a big problem because most of us need to renew tyres due to age rather than low tread depth.
 
marchie said:
Not in the case of a revised loading [full car to empty car in my Recycling Centre example] or in the case of the M/Home with the payload changed significantly by a refill of water, lpg and diesel [a common 3 factor alteration when we are away on long trips, starting off with little gas and water, and refilling at the last garage before the upcoming aire with water, gas, diesel and supermarket supplies to minimise the daily shopping by bike. A change of payload by 130Kg-150Kg is quite common for us.

Steve
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The tyre pressures I use are for the maximum expected load, that includes full water, full waste, full gas, etc, if we're going to South Wales in the autumn I even allow for 100kg of anthracite on the return journey, at anyone one time it's highly unlikely we will be up to those loads, and even if we where, we would still be running much less than the manufacturers allow for with their tyre pressures, in our case because the van is built on a Maxi chassis and plated for 4.5t total axle loads, but overall plated (and used) at 3.5t, this is very common for XLWB Ducato's as at one time the XLWB was only made as a Maxi chassis.
 
Tyres fitted to commercials will often have a much larger change in payload than MH's ever do. Take a tipper for eg.
The correct pressure for such a vehicle would be calculated from it's max payload, on the return journey when empty, the tyre will technically be over inflated, that is not ideal, but as Colin points out, still fit for purpose..
 
marchie said:
Not in the case of a revised loading [full car to empty car in my Recycling Centre example] or in the case of the M/Home with the payload changed significantly by a refill of water, lpg and diesel [a common 3 factor alteration when we are away on long trips, starting off with little gas and water, and refilling at the last garage before the upcoming aire with water, gas, diesel and supermarket supplies to minimise the daily shopping by bike. A change of payload by 130Kg-150Kg is quite common for us.

Steve
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And as a percentage of the total weight, that is what?
 
marchie said:
Just shy of 5%, and, according to the Owner's Manual, enough to raise the risk of a blowout

Steve
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And if inflating for that maximum load, any serious disadvantage tyrewise if you're slightly low on water/diesel?
 
I am no expert but don't see how tyre pressure 5% off target is a risk of blowout.


My trike runs at 10psi on the rear car tyres which on a car would be expected to be around 30psi. I am thinking of dropping the pressures a little more yet but need to check if I get any wheel spin within the tyres. In any event I am running at least 60% less than the same tyre would be on a car.

To my mind, (which is suspect) I would say tyre condition, loading, speed and heat have more effect on a blow out than tyre pressures. I will add that porous wheel or a slow puncture can/will reduce pressures while travelling and so could cause a blowout but I am using the 'tyre condition' clause for that. :)
 
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