Tyre pressures

Submitted: Thursday, Jan 19, 2006 at 20:09
ThreadID: 29886 Views:2301 Replies:11 FollowUps:4
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The great debate continues..............................
At a recent BBQ, two of my mates were arguing over the correct tyre pressure to use on a high speed dirt road with sharp rocks ie: Ooanadata Track.

Mate #1 said to drop the pressures down so the sharp rocks are cushioned against the tyre.

Mate #2 said leave them as they are, reducing the tyre pressure will increase the risk of a rock piercing the sidewall.

I didn't have a clue and thought both had a good arguement, so I did what I thought best .........went to get another beer!

So, the million dollar question is, who is right? Mate #1 or Mate #2?
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Reply By: Darian (SA) - Thursday, Jan 19, 2006 at 20:35

Thursday, Jan 19, 2006 at 20:35
My mind was made up on that long ago - mate 1 ! Can't abide the question though - any road with sharp stones ain't high speed in my books - soften the tyres, slow down, look for (and dodge) those nasty stones and you may not have to get that jack out for ages.................oh....and ....get tyres with a tough sidewall (taking care of mate 2 !).
AnswerID: 149683

Follow Up By: Sand Man (SA) - Friday, Jan 20, 2006 at 00:39

Friday, Jan 20, 2006 at 00:39
Aw Darian,

Jackaroo Owner/Drivers are just so knowledgable.

Couldn't have stated it any better mate:-)

I'm diagonally parked in a parallel Universe!

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FollowupID: 403048

Reply By: Mike - Thursday, Jan 19, 2006 at 20:37

Thursday, Jan 19, 2006 at 20:37
We have taken the advice of the guys who are actually out there done that. Reduce tyre pressures by about 10 psi on dirt/stoney tracks. The risk of sidewall fracture will still exist if you don't drop your speed accordingly. So, the Jackaroo running BFG AT KOs, has 40psi on blacktop 28-30 on dirt (and 80-90KPH). This advice has been backed up by the proprietor/mechanic at both Birdsville and Oodnadatta. I have travelled extensively in the outback, and all the drivers who follow this rule, get less punctures. I have yet to come across anyone with a sidewall fracture due to low pressures.

Happy trails, Mike.
AnswerID: 149685

Follow Up By: Fab - Thursday, Jan 19, 2006 at 21:05

Thursday, Jan 19, 2006 at 21:05
Cheers Darrin and Mike,
Just for the record, when I was referring to "high speed" I meant in the order of 80-100km/h.
Anything more than that is "suicide speed". Not with the wife and kids in the car thanks!
FollowupID: 402982

Follow Up By: Fab - Thursday, Jan 19, 2006 at 21:08

Thursday, Jan 19, 2006 at 21:08
Sorry .....Darian, not Darrin. Hey by the way, a little birdie tells me you're from my old home town, Whyalla! Am I right?
FollowupID: 402983

Reply By: Member - Davoe (Widgiemooltha) - Thursday, Jan 19, 2006 at 22:12

Thursday, Jan 19, 2006 at 22:12
No doubt about it before I knew better I used to run 50 psi in the rear tyres of my campervan because of the weight and suffered 3 irrepairable tread punctures on near new tyres. The problem isnt rocks piercing the tyre but the fracturing of wire plies within due to the shock of rocks hitting the hard over inflated tyre- they literly pop like baloons
AnswerID: 149722

Reply By: Chaz - Thursday, Jan 19, 2006 at 22:33

Thursday, Jan 19, 2006 at 22:33
Hi Fab,
This has obviously been a long standing debate and last August I was able to put it to the test on a drive along the Mereenie Loop road. I pulled up at Kings Canyon and let my D694 Duelers down to 30 hot, say around 26psi cold, and a fellow traveler in his Jeep continued on past with his tires up around 40. I was cruising at around 90 and having a smooth ride when we came across him pulling all his gear out to jack his car up. He’d shredded a rear tire, and the comment that got me was, “Bloody rough road isn’t it”. He said he was only doing 80 and felt every thing in the road, so I hope that answers your question.
I still think it has a lot to do with tire construction and speed, but as stated above, let them down around 10psi for gravel and reduce speed.
I also let them down on the camper.
AnswerID: 149726

Reply By: Ruth from Birdsville Caravan Park - Friday, Jan 20, 2006 at 08:39

Friday, Jan 20, 2006 at 08:39
Fab, out here where that's all we do have to drive on we go with Mate 1 - as well you will find that mostly we use skinny tyres (yes, even for the sand). The other thing we do out here (even though thousands have driven thousands of miles and never had a problem) is if we are towing a trailer/camper/caravan/horsefloat - we ALWAYS cover the backwindscreen of the vehicle with cardboard to protect against stones being thrown up by rear wheels of vehicle - hitting front of trailer and bouncing against the windscreen and smashing it. Lots of side windows also get broken - especially by those people who fly past you in either direction. Dropping the speed is almost more important than dropping the tyre pressure. Have a good trip. Oh yes, if you are towing something like a caravan - make sure to take extra bits of multi-plugs (electrical), brass (not plastic) water tank bits. Just a couple of hints.
AnswerID: 149786

Reply By: Member - MrBitchi (QLD) - Friday, Jan 20, 2006 at 09:19

Friday, Jan 20, 2006 at 09:19
Reducing tyre pressure will cause the tyre to "bag" but most of the bagging is front/rear, not sideways, so the increase risk to the sidewalls is minimal.

I've tried both methods. Standard pressures gave a harsh ride and cost me 2 tyres on a trip about 3 years ago :-~
Lower pressure (10 psi drop, about 28psi on the Pajero) gives a far better ride and I haven't had a flat since.

AnswerID: 149795

Follow Up By: Kiwi Kia - Friday, Jan 20, 2006 at 18:09

Friday, Jan 20, 2006 at 18:09
I would sugest that you go to a garage, park in front of the air hose and try your idea but use a carpenters square to get a vertical drop from the sidewall to the ground, mark this position with chalk, reduce the pressure and measure the sidewall bulge again. Don't worry about the theory, go and do it and report back here what you have learnt !
FollowupID: 403203

Reply By: Member - Shawsie (QLD) - Friday, Jan 20, 2006 at 10:04

Friday, Jan 20, 2006 at 10:04
I agree with mate#1, recently driven 400km on dirt/gravel at 80/90kph at Winton and let my tyres down to around 26 (down 10psi). Lovely soft ride and no punctures :o)
AnswerID: 149802

Reply By: Darian (SA) - Friday, Jan 20, 2006 at 11:52

Friday, Jan 20, 2006 at 11:52
Not sure if you're talking re Mike or me on the Whyalla conection Fab - negative here re Whyalla - I've been there quite a bit (had family there for 5 years, teaching) - did a lot of tinny fishing there - mecca for serious fishing in my books - best I ever did was get invited onto the Santos jetty in the Xmas hols - heaven - snapper city under there - Whyalla is a good base for serving outback travel and fishing intersts - don't know about all that red dust from Onesteel though (its not just iron oxide -there;s lots of other gear in it, via the pellet plant I'm told) .... would have to live down the other end of the town I think.
AnswerID: 149824

Reply By: johannagoanna - Friday, Jan 20, 2006 at 14:54

Friday, Jan 20, 2006 at 14:54
The best analagy (spell?) I can give you is that of a balloon. If you blow up a balloon really full, you can pop it really easily with anything sharp, however, if you blow it up half way, it is heaps harder to pop the balloon with anything sharp. Try it and see. If you have too much pressure in your tyres (generally above 30psi) you will get heaps more punctures and stakings, drop pressure below 30psi, and you will be lucky to get any!

The other thing is if you don't drop pressures the ride will be horrible. I have been in friends 4WD's that don't drop pressures (about 40psi), and after a day of the dirt, I am so sore I can hardly walk. If the pressures are dropped to below 30psi, then the ride is also heaps better over the rough tracks!

HTH - Jo
AnswerID: 149851

Reply By: Tessysdad - Friday, Jan 20, 2006 at 17:52

Friday, Jan 20, 2006 at 17:52
Hi All,
we might be wrong, but it seems there is no debate here. Did anyone (apart from Mate 2) say that going hard was the way to go. All good advice, especially about keeping the speed down.
Happy camping,
Mike and Jan.
AnswerID: 149885

Reply By: Member - Steve K (WA) - Friday, Jan 20, 2006 at 18:53

Friday, Jan 20, 2006 at 18:53
Hi All,

Just one question about load. I plan to tow a reasonably heavy camper trailer, on road I run at 40 psi rear because of the weight. Offroad any chance of tyre damage at lower pressure due to load and/or assocuiated heat
AnswerID: 149892

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