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Thread: Letting tyres pressures down

  1. #1
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    Letting tyres pressures down

    Hi all
    I just thought that I would pass on this bit of info that I learnt today.
    I'm currently on a driver CSE and one of the civie instructors was talking about letting tyres down for rough/soft ground. This particular instructor was a policeman and later a police driving instructor. He said that the police do not teach letting down the tyre pressures in soft ground. And indeed when called over to Bribie or Fraser never let pressures down unless bogged and then reinflated immediately. The reason is that they are gazetted roads and to drive on low pressures is illegal. He said if you are involved in an accident the first thing they check is tyre pressures and if low you will be charged. He also said if you where involved in a fatal accident you could be charged with culpable driving. The problem arises because nowhere does the tyre placard say that the tyres can be safely lowered below the manufactures recommended pressures.

    I got to thinking about this. I have been told by the guys in the club. I've read it in 4WD monthly. Even Pat Calligan has said so on his show. But NEVER have I been told officially that letting tyre pressures down is a legal practice.
    So my point is, just cos you've been told. Don't make it right.

    Thoughts?
    Regards

    Nino.

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    I doubt its so clear-cut as travel speed is also a consideration when determining suitable tyres pressures. Traveling at 80 kph on under-inflated tyres could be considered as culpable but at 40 kph would be a totally different situation.
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    I would class the term "Recommended pressure" as advisory only & not categorically stating not to go below a certain pressure. It's also "recommended" to rotate tyres at certain mileages too but it's not illegal not to. Tyres have a top speed rating code number as well but they don't have a minimum speed code now, do they?
    Steve

  4. #4
    DiscoMick Guest
    Wouldn't it depend on whether an investigator found that the lower tyre pressure caused or contributed to the accident?
    If you rolled a tyre off a wheel, then that would be clear cut. If a vehicle swerved and rolled, did the lower tyre pressure cause the rolling? Was the vehicle speed reduced after the tyre pressure was lowered, which would be a reasonable precaution to take, or did the driver coontinue to go at the same speed despite the lower pressure?
    That police rule sounds more about the police service wanting to avoid being held responsible if a cop followed a recommendation to lower the pressure on sand, and something went wrong, than about what's best in the situation. Bureaucracies always want to cover their bums. If a cop was injured after following a recommendation to lower pressures, then the police service might go down big in a compensation case. It would want to avoid that.

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  5. #5
    Tombie Guest
    The individual you got your information from is wrong!

    Under ADR 23 and 24 the recommended pressures are on the door sticker.
    These are recommended for the vehicle load under normal use - Off-road is not considered normal use.

    There are no laws regarding minimum pressures, there are laws on negligence.
    Driving on a completely flat tyre at 110km/h leading to an accident obviously falls under these.

    Instructors like the one you mention are frustrating, because they are spreading misinformation and scare mongering..

    Essentially - he's full of it!

    A local trainer / assessor and of SAPOL and other government departments just confirmed my suspicions...

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    Quote Originally Posted by Tombie View Post
    The individual you got your information from is wrong!

    Under ADR 23 and 24 the recommended pressures are on the door sticker.
    These are recommended for the vehicle load under normal use - Off-road is not considered normal use.

    There are no laws regarding minimum pressures, there are laws on negligence.
    Driving on a completely flat tyre at 110km/h leading to an accident obviously falls under these.

    Instructors like the one you mention are frustrating, because they are spreading misinformation and scare mongering..

    Essentially - he's full of it!

    A local trainer / assessor and of SAPOL and other government departments just confirmed my suspicions...
    So does this mean I can keep driving to the servo after being offroad with the tyres at 15PSI or do I have to start using the little compressor at the end of the track?

    Cheers
    Will

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    Quote Originally Posted by Tombie View Post
    The individual you got your information from is wrong!

    Under ADR 23 and 24 the recommended pressures are on the door sticker.
    These are recommended for the vehicle load under normal use - Off-road is not considered normal use.

    There are no laws regarding minimum pressures, there are laws on negligence.
    Driving on a completely flat tyre at 110km/h leading to an accident obviously falls under these.

    Instructors like the one you mention are frustrating, because they are spreading misinformation and scare mongering..

    Essentially - he's full of it!

    A local trainer / assessor and of SAPOL and other government departments just confirmed my suspicions...
    Hmmmmm. Some very valid points. And good ones from you tombie. I did mention that at Bribie there is a sign that says to let tyre pressures down. But the point he was trying to make was that they are gazetted roads.
    I certainly think that I want to ask some more opinions of the traffic police and decide from there. It does contradict everything I've been told in regards to off road driving.
    I'm really not sure what I think. And with all due respect to your friend, it's one cop does and one cop doesn't. Further info required I think.

  8. #8
    JDNSW's Avatar
    JDNSW is offline RoverLord Silver Subscriber
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    Further to the above - both my Landrovers (1970 2A and 1986 110) have emergency soft pressures specified on the tyre placard, and these are also listed in the 1981 Series 3 owners manual I have.

    So it seems that for many Landrovers, as long as you stay above the pressures specified in these placards and manuals, there should be no legal repercussions.
    John

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  9. #9
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    I would make the assumption that your friend in question is generalising and in doing so erring on the side of safety.
    He quite possibly knows that in general, "Common sense" is well and truly a thing of the past in these days of high power advertising and misinformed Peer pressure.
    Every instructor worth his salt I have had anything to do with would tell you that letting tyres down too low can be extremely dangerous in many conditions, involving the danger of incurring instability, rolling tyres off the rims or spinning wheels inside the tyre, and with these inherent dangers well in mind, will instruct on the minimalist side of things.
    It only takes a couple of pounds pressure difference to give the maximum traction possible (and that can simply defined as applying the maximum amount of tyre on the ground in the direction of travel.) Any deflation above this % deflection equation and you are simply wasting your time and money, offering rolling resistance and flotation rather than traction. This is the reason why tractors have large diameter driving wheels, and why crawler tracked vehicles are so capable.
    In an instruction scenario, especially a limited time frame one as I presume yours is, any instructor would have to gloss over what is really a rather complex portion of an advanced course and generalise.
    Most vehicles today are engineered and equipped from the factory with tyres that offer the best traction/flotation equation for general use and lets be honest, 99% of these vehicles will never see a difficult track in their lives, so I feel that he is quite within his rights to state what he has stated, rather than plant suggestive seeds in over receptive minds that in some cases will be exaggerated beyond any realms of common sense or safety down the line.
    Regards
    Glen

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    Quote Originally Posted by MR LR View Post
    So does this mean I can keep driving to the servo after being offroad with the tyres at 15PSI or do I have to start using the little compressor at the end of the track?

    Cheers
    Will
    Common sense would dictate that if you had to travel more than a couple of hundred meters on bitumen @15 psi then maybe you should take the time to air up.
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