Britz's guidance re: tyre pressures in the sand

Candace 25psi may be ok for some conditions other conditions may require less. I tried running my 16 ply rag tyres on split rims at about 18psi in really soft sand and spun one of the tyre on the rim and cut off the valve. So if you are running at low pressures be carfull this doesn't happen. If using radials you may be able to get down to lower pressures but the old tough as nails tyres I was using had little give in them.

Britz are covering their behind by the 25psi , their bush campers are fitted with split rims and tires that don't take to kindly to low pressure due to the design of the split rim [easy to roll tire off the rim if pressure is too low] ...

Candace - In my experience, the major problems that you have watch with greatly lowered tyre pressures, are;

1. Heat buildup in the tyre carcass due to excessive wall flex (this can be rapid and very destructive).

2. Staking of tyres (on sharp rocks and stakes) in rough conditions, due to the increased bulge in the sidewall.

When installing tyres on rims, it takes around 25psi for most tyres seat on the bead. If you run at less than 25 psi, you'd stand a good chance of a tyre bead unseating - particularly if you indulge in an evasive manouvre such as swerving when an animal suddenly appears (and yes, we shouldn't swerve, but sometimes instincts just kick in).

If a tubeless tyre bead unseats, the tyre deflates instantly, unlike the old tubed tyres. This can possibly lead to loss of control, possibly enough vehicle imbalance to cause a rollover, and possible rim damage.

Your speed should be governed by your tyre pressures. If you're running at 25 psi, you'd be well advised to keep your speed down to a maximum of 70-80kmh. Travelling at 110kph at 25 psi would be a recipe for tyre blowout due to heat buildup.

Hmmmmm ... slightly OT ... this topic reminds me of a discussion I had recently after our CSR trip with a chap in Halls Creek in a rented 4wd camper who had 2 blown tyres to repair .... who was also complaining about the corrugations and gear rattling loose.

We asked him what pressure he was running ..... " 60 psi - because that was what the rental company told me to run "

We suggested that if he dropped it to around 40-ish, life might be a bit easier, and then we got into a deep seated debate about why the rental company recommended those pressures.... can't be good for the gear and fitments in the long run. Anyone got any ideas as to why they recommend this?

Back on topic, recently changed my BFT MT KM2's over to tubeless from split rims ... while reading the BFG site to check correct pressures was surprised to read that they claimed you could run them down to 5 psi without compromising seal/bead integrity ...... not that I would be keen to do this.

Candace S.
My point of view is, the tubetype/split rim doesn't have a bead hump and therefore only the tube pressure holds the beads in place, unlike a tubeless which uses pressure and the positive fitment over a larger diameter ie hump.

Since ALL torque is transferred to the tyre through the bead, if it isn't clamped enough by the pressure then it will work loose and possible spin as a result. Once spun there is no tube left worth having and so low pressure isn't a good idea.
Exactly what that critical bead clamping pressure is, I don't know and it all depends on driving attitude to applied power, the terrain and the weight the vehicle and tyres are being asked to carry.

Just deflating a tube type tyre and watching the bead area begin to move away from the rim indicates what happens.

I don't think Britz have plucked the pressure "out of the air" I think it is possible not far above the limit for the situation.

Tyre dia and width also will have some effect too.

My 2008 Troopy came with 750/16 split rims.
I used to run them at 18 PSI on beaches with no trouble – but I was careful not to swing it around corners at a fast pace.
If I got stuck I went down to 10 PSI on a number of occasions – after I got out of trouble onto firmer sand I would put them up to 15, 18 or 20 PSI (depending on the sand) until I got back onto hard ground or bitumen.
But I can see where Britz is coming from – on Fraser Island I seen hired Troopies with almost a dozen backpackers on-board belting along at high speed. A disaster waiting to happen with soft tyres.

No! the person who wrote the email is covering the company and I don't blame them.

He or she says it is ok to run at 12/16/18 psi and there is an accident, guess what the person says to the investigator. They said I could run these pressures. Company now in trouble.

I can run 10psi all day on a split, it is just how I treat the tyre with speed and cornering that will let it survive.

From someone who hates split rims.

The increased weight of the car might also attribute to the recommended higher pressures.

Hi Candace,

A good question. We posted a blog on here a couple of years ago about tyre pressures. It is still valid if you want to have a read http://www.exploroz.com/Customers/49000.875/12/2009/4WD_TYRE_DEFLATION_TIPS_FOR_SAND_and_OFF_ROAD.aspx

Regards

Kurk

All of the above emphasises for me all the reasons I dislike split rims. All the biggest tyre problems I've ever had involved those on split rims. They don't seem to handle lower pressures at all well, leading to blow-outs, which can be quite dangerous at times.

I had always been advise to reduce tyre pressures on dirt roads and tracks, yet if it were not accompanied by a considerable decrease in speed as well, tyre failure was almost inevitable.

When I travelled remote areas for the WA govt in 4wd's equipped with 7.50x16 tyres on split rims we were taught to lower tyre pressures from around 40 psi to 30 on dirt roads such as the Great Central and restrict speed to 100km/hr. That combination always cost a tyre or 2, so eventually we figured it out and stopped it.

Finally we got the instructor to stop advising it, at which point the new advice was, no more than 80km/hr at 30psi or 60km/hr at 20psi. And if you do need to lower pressures to get out of a bog, or up a sand hill etc, then you should re inflate quickly. This seemed to work quite well, if the speed limits were observed. A big if! People are simply going to drive as fast as the conditions allow.

Or more preferably go to tubeless tyres on standard rims. Guess what - problem solved completely.

And, you don't have to worry about the split rim causing catastrophic damage to a person, vehicle or other property if incorrectly fitted during inflation.

So, it seems to me, if you want tyre problems, go to split rims unless you are a very careful driver.

Have just completed the CSR and did the Simpson last year. Ran 22 front and 25 rear for whole trip with no poblems.