Britz's guidance re: tyre pressures in the sand

Submitted: Wednesday, Sep 11, 2013 at 14:38
ThreadID: 104273 Views:3450 Replies:11 FollowUps:14
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Recently, I sent an email to Britz, asking about using reduced tyre pressures on their Bushcamper. It is basically a Troopy and has the standard split rims with tube tyres. Here is the main body of their response:

"Regarding your question we double checked and can tell you that you can let the tyres of the Bushcamper / Toyota Landcruiser down to 25 PSI without getting into trouble even in sand. The tyres are not supposed to get below 25 PSI."

For one thing, it appears the person who wrote the email thinks reducing the pressure in sand is likely to get you bogged!

I personally would run less than 25 psi in the sand, at least with the tubeless radials on my vehicle here in the U.S. But they're saying I shouldn't go below that with the Troopy's set-up.

Is 25 psi adequate for extended sand driving, i.e. the Simpson? (Yes, Britz does now allow their vehicles in the Simpson.) What about extended driving on corrugated roads (such as the AB)?

And why is 25 psi the limit? Is that just a number they plucked out of the air, or is there sound reasoning or science behind it?
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Reply By: Member - Duncan W (WA) - Wednesday, Sep 11, 2013 at 14:53

Wednesday, Sep 11, 2013 at 14:53
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.

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Follow Up By: Dennis Ellery - Wednesday, Sep 11, 2013 at 19:38

Wednesday, Sep 11, 2013 at 19:38
Hi Duncan
I think you must have been unlucky – before I changed over to tubeless – my standard beach pressure on 750R16 split skinnies was 18 PSI. They were a good tyre in sand due to their high profile.
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Follow Up By: Member - Duncan W (WA) - Wednesday, Sep 11, 2013 at 20:08

Wednesday, Sep 11, 2013 at 20:08
Hi Dennis, 750R16 Hankook's were what I was running at the time. Now have Triangles on the splits but rarely use them now.

Now have 16" steel rims with Toyo M55's and if I get a puncture I'll just plug it. Less stuffing around and a lot more user friendly.

Cheers

Dunc

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Reply By: Alloy c/t - Wednesday, Sep 11, 2013 at 14:55

Wednesday, Sep 11, 2013 at 14:55
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] ...
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Reply By: Ron N - Wednesday, Sep 11, 2013 at 17:13

Wednesday, Sep 11, 2013 at 17:13
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.
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Follow Up By: Candace S. - Thursday, Sep 12, 2013 at 00:01

Thursday, Sep 12, 2013 at 00:01
Ron: Thanks for the info, but of course I was not planning to run reduced pressures on the highway or good dirt. I was looking for guidance on reduced pressures for extended sand or corrugation driving. So I wouldn't be performing any sudden evasive maneuvers as you describe.

On the dirt, I run the radials on my own 4WD at 17 psi cold. I won't exceed 32 kph (20 mph) at that pressure.
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Reply By: Member - Scott M (NSW) - Wednesday, Sep 11, 2013 at 18:18

Wednesday, Sep 11, 2013 at 18:18
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.
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Follow Up By: Candace S. - Thursday, Sep 12, 2013 at 00:08

Thursday, Sep 12, 2013 at 00:08
Hopefully that rented 4WD didn't come from Britz: they forbid taking their vehicles on the CSR (as well as to a few other places)!
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Reply By: Ross M - Wednesday, Sep 11, 2013 at 18:32

Wednesday, Sep 11, 2013 at 18:32
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.
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Follow Up By: Dennis Ellery - Wednesday, Sep 11, 2013 at 20:27

Wednesday, Sep 11, 2013 at 20:27
Hi Ross
Your quote “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.”
I think the Britz guy was a silly plucker - probally a clerk at head office giving advice but who has never driven a 4WD – let alone used split rims in sand.
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Follow Up By: Member - Scott M (NSW) - Wednesday, Sep 11, 2013 at 21:58

Wednesday, Sep 11, 2013 at 21:58
"I think the Britz guy was a silly plucker - probally a clerk at head office giving advice but who has never driven a 4WD – let alone used split rims in sand. "

- which was the conclusion we reached over my observation further up.... it's amazing how a bit of bad advice to the ignorant can suddenly become 'gospel' ....
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Reply By: Dennis Ellery - Wednesday, Sep 11, 2013 at 18:41

Wednesday, Sep 11, 2013 at 18:41
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.
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Reply By: Rockape - Wednesday, Sep 11, 2013 at 21:05

Wednesday, Sep 11, 2013 at 21:05
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.

AnswerID: 517976

Follow Up By: Candace S. - Thursday, Sep 12, 2013 at 00:13

Thursday, Sep 12, 2013 at 00:13
LOL, well why do you think I wrote the email? I wanted a written response I could refer back to if necessary! ;)

I already hate split rims too. If these things were equipped with tubeless, I wouldn't have needed to ask for any advice: I would know from experience how to manage the pressures off the pavement.
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Reply By: Member - Craig F (WA) - Friday, Sep 13, 2013 at 14:12

Friday, Sep 13, 2013 at 14:12
The increased weight of the car might also attribute to the recommended higher pressures.
AnswerID: 518069

Reply By: BluePrint Industries Pty Ltd - Friday, Sep 13, 2013 at 20:35

Friday, Sep 13, 2013 at 20:35
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
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Follow Up By: Candace S. - Saturday, Sep 14, 2013 at 12:59

Saturday, Sep 14, 2013 at 12:59
I've seen that before. Most of it is basic information I already know from experience (see my original post). It is the split rim/tube tyre combination that I'm unfamiliar with.

"...if you are running Split Rims then you need to be careful that you do not go too low as you can pop the tyre off the rim very easily."

How low is too low?
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Follow Up By: Candace S. - Saturday, Sep 14, 2013 at 13:06

Saturday, Sep 14, 2013 at 13:06
P.S. I own a set of the Trailhead deflators mentioned in that article. I adjusted them to drop my tyres (tubeless radials, of course) down to 17 psi cold, which is what I use on rougher roads and sand.
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Reply By: Member - Paul B (WA) - Saturday, Sep 14, 2013 at 09:03

Saturday, Sep 14, 2013 at 09:03
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.
Paul B Kalgoorlie

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Follow Up By: Candace S. - Saturday, Sep 14, 2013 at 13:02

Saturday, Sep 14, 2013 at 13:02
I don't like them either. But that's what comes on the vehicle and it's not feasible for me to change them out on a rental. I'm just trying to figure out how to live with them for my trip!

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Reply By: Member - DingoBlue(WA) - Sunday, Sep 15, 2013 at 09:21

Sunday, Sep 15, 2013 at 09:21
Have just completed the CSR and did the Simpson last year. Ran 22 front and 25 rear for whole trip with no poblems.
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Follow Up By: Candace S. - Sunday, Sep 15, 2013 at 11:34

Sunday, Sep 15, 2013 at 11:34
On split rims/tube tyres? What size?

I've noticed the ones on the Troopy are rather skinny compared to the tubeless tyres I'm used to seeing on 4WD's. Makes me wonder how a tubeless at a given pressure would perform compared to a skinnier tube tyre at the same pressure...
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Follow Up By: Member - DingoBlue(WA) - Sunday, Sep 15, 2013 at 17:54

Sunday, Sep 15, 2013 at 17:54
Don't like split rims.
Tyres on 100 series Landcruiser - BFG LT 265/75R16.
Have used 22 and 25 on Connie Sue, Anne Beadell, Googs Track, Gunbarrel, Simpson and CSR without any problems whatsoever.
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Follow Up By: Candace S. - Monday, Sep 16, 2013 at 00:34

Monday, Sep 16, 2013 at 00:34
So, sounds like you found that 25 psi was good for the Simpson and some of the other tracks I'm interested in. It was low enough to avoid bogging in the sand and to soften the ride on the corrugations?

(I'm still concerned about the fact the tube tyres will be so skinny, and that I might have different results at the same pressures).

I've gathered that 25 psi on a split rim should be high enough to avoid any of the dire problems mentioned here such as spinning the tyre/tube on the rim. Even if run for long distances (such on the Simpson or the AB).
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Follow Up By: Member - DingoBlue(WA) - Monday, Sep 16, 2013 at 09:08

Monday, Sep 16, 2013 at 09:08
Hi Candace,
22 and 25 psi were fine. No bogging and softened the corrugations. Could probably lower a few psi more but depends on the load you're carrying and the speed you're travelling.
The split rim 'skinnys' shouldn't cause a problem at 25 psi and will increase the footprint at that pressure. Most people believe that tyres 'bag' out thus increasing the footprint but in fact the contact area lengthens which gives you the increased contact area.
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