<span class="highlight">tyre</span> <span class="highlight">pressures</span>

Just driving on dirt roads it is uneccessary IMHO.

The purpose of lowering tyre pressures is to increase grip in rough, slow going. If you're not having traction problems, leave them where they are.

A lot of good dirt roads can be travelled at speeds approaching those you would use on a sealed surface. Hence running the tyres at 25 psi may damage the tyre through overheating.

Cheers,

Jim.

Jim & Cheryl,
It depends on a number of factors, weight being carried, type of vehicle, road conditions & type of tyres.
To give you an example, we went on a camping trip up through the gulf country, on bitumen I ran 40psi, on good dirt I went down to 35psi and on rocky type dirt roads I went down to 28-30psi depending on the type of rocks etc..
Never had any problem.
You will need to experiment a bit to find what suits you and your vehicle, just remember whwn lowering tyre pressures you can be exposing your walls to possible damage from rocks so drive accordingly.

Hope this helps

Franga

While using BFG's for years now, I've always lowered my pressures on 'gravel roads'. I took that advice on pressures from people who live and work in the outback. 28 front and 30 rear is my approximate pressure - you need to couple that plan with conservative driving too - The tyre walls do bulge at lower pressures, and are susceptible to heat build up and stick and stone attack as a result - that is largely taken care of by good tyre choice, reduced speed and stone dodging. Works for me. After 8 years in the Jackaroo towing campers, I've had one flat (a budget Kelly LT tyre -on the trailer) - fingers are crossed now that I have the heavier 'Cruiser.

Personally I drop my pressures depending on the road condition, corrugated, rock, sand.

25 sounds a bit low to me I run mine around 28 and adjust from there. Again it will depend on your vehicle and the weight you are carrying.

My run into Birdsville earlier this year and down the Birdsville track my pressures where at 30 - 32 and it was a easy comfortable ride. You could have left them at normal as the road was fantastic. Driving around the Flinders I had 24 - 26.

Just remember the lower the pressure the lower the speed.

Have a safe drive.

Brian

Tyres are like balloons - blow up a party balloon as far as it will go, and another with far less pressure, then prick both with a pin.

You don't have to be einstein to know which one will explode with the slightest prick and which one will indent quite a way before it goes.

On gravel roads, stones and sticks are the pin - the higher the pressure in your tyres, the easier it is to have a sharp stone cut through. Lower pressure allows the tyre to deform around the object more, more often than not preventing the blowout.

I like 28-30 psi on gravel and that's good for speeds up to 100k when conditions permit. Highway I use 40psi, sand as low as 15psi if needed.

When we do a trip we drop pressures on the tyres depending on load and type of tyre.

For a fully loaded 4x4 for the cape with a good set of rubber I suggest 27 front and about 32 rear that is a hot tyre pressures this will drop about 4psi per tyre when cold. Some people go lower and same don't like to adjust.
The lower pressure's give a bigger foot print and smooth out the corrugations.

At these pressure's we don't see any troubles and don't travel over about 80k/h

I go a lot lower than this and no I havnt had side wall blow outs side wall dammge.

All the best
Eric

Jim & Cheryl
Imagine a balloon blown up very tight, then try poking a biro point into it , it won't depress very far before it bursts, Then let 1/3 of the air out and try the pen again , it will depress much further before it punctures , Tyres are the same . so when on stoney tracks run at about 28/30 psi , and don't run over the big rocks .

The balloon theory sounds great, but tyres are not balloons.

The weakest point of the tyre is the sidewall. When pressures are dropped the sidewall bulges out, becoming exposed to nasties that are on the ground.

When pressures are high the sidewalls stand more upright and the nasties only contact the tread which is designed for that purpose.

The balloon theory sounds great, but tyres are not balloons.

The weakest point of the tyre is the sidewall. When pressures are dropped the sidewall bulges out, becoming exposed to nasties that are on the ground.

When pressures are high the sidewalls stand more upright and the nasties only contact the tread which is designed for that purpose.

You will get different answers depending on which state you're in (geographically speaking!)

The South Aussies have outback roads with bigger gravel - sharp stones have a habit of going through the tread - made worse by overloading, high speed and high pressures. If you lower pressures to 25, then thats one factor you've minimised. If you cut your speed to 80, and keep the weight under control, you're very unlikely to get a puncture on the sharp gravel roads.

Most West Aussie outback gravel roads are better maintained with finer gravel - so you'll find that the west aussies are more likely to keep their pressures up and travel like the clappers.

The Victorians................well, they usually drive on bitumen or mud! Put them on an outback road, they will go flying past you, and then stop ahead to fix a tyre.

The other upside to lowering pressures is that the ride is better, you're suspension has less work to do, and you're less likely to break stuff on your 4wd.

The downside to lowering pressures is that you increase the work done by the sidewall, and in hot weather, and working hard, its possible to cause delamination of the sidewall.

Its all a compromise, but I lower mine to 25-28 on most gravel roads.

I am a firm believer of higher pressure's.

Now I have proof that they work and not a theory.

12 sets of 265/75/16 Bridgestone A/T duellers 694s, over 6 Toyota's 1 80 series 1 75 series 1 78 series and 3 100 series.

70% of the use is on corrugated dirt roads 6 months of the year Daily, I currently run 4 cars this year they averaged 35000 km each since June until yesterday.

In this time I had 2 punctures 1 blow-out (and the first in all 12 sets).

The blow-out was caused by one of the punctures, I run my pressure's at 40 psi front and 42 psi rear, the only time I changed them was on Fraser Island.

One of my guides saw that the tyre was going down at Jim Jim falls car park, then when he got to the camp ground 1/2 an hour latter he said it didn't look as if it had gone down any more so decided to continue, so with the tyre having a puncture and going down he kept going on a corrugated dirt road and got a blow-out.

The puncture was a nail in the tread and the blow-out was a side wall there was no damage were the nail was, so the first time I have had a blow-out with these tyres is when the pressure was low I will leave the conclusion to you.

Cheers Steve.

HI Jimbo,
Its good to see someone else not dropping tyre pressures on gravel roads.I have done thousands of k's on rough gravel and never had problems.On the contrary I have seen a lot of people with tyre damage due to too low pressures on the stony stuff.It's just my experience and I will stick with what works for me.Just completed over 20000ks to CapeYork and back without one puncture.More importantly is not taking a chance with half worn tyres.

Learned long ago that all the nasties on roads are mostly on the surface. Thus the less contact you have with the surface the better. For this reason :
1. pump your tyres up to the manufacturers max.
2. use verrrry skinny tyres
3. never drive when it's hot because the tyre might overheat
4. go like hell on corrugations because that way you'll miss all the nasties in between (maybe 90% saving here)
5. avoid biros

That's the theory and it works in practice because I've got lots of experience.

Phil's idea that you might put pressures down to also conserve suspension and other bits is only worthwhile if you are thinking of surviving.

A few other ideas:
1. It's worthwhile checking pressures during the day - in summer months or when doing hard work, it's not uncommon to find they have far greater pressure than starting pressure
2. corrugations are better at reduced pressures
3. serious climbs on dirt or sand will also be easier with reduced pressures
4 the ballooning effect is not an issue for most 'mid-pressure range' considerations
5. because kms of dirt can turn to other conditions, I run the Troopy down at 28 front 35 rear for most general track driving. If long stretches of highway become the go, then Up go the pressures to 32front 55rear. In fact I'll use these higher pressures until I encounter first warnings of potential probs.

Cheers
Chris

I'll put in a vote for the low pressures.....The nissan and boat in the rig pics went to Kalumburu last year. The road was quite bad, but ran about 20 puond in the trailer, 28 pound in the rear of the car, and 25 pound in the front. Much more comfortable on the bad bits - comfort for me = survival for the boat/trailer!

Trashed one tyre on the front when we were nearly home, on a rock on the edge of the road which would have trashed most tyres regardless of pressure. A mate did the same trip on the same tyres the year before, and had 3 punctures through the tread, on brand new tyres. He was carrying a bit more weight than me (well, probably a lot more), and was running over 40 pound.

At work, the pressures are usually 40 pound, and not a lot of extra weight in most vehicles. Generally pretty good life from the tyres (bridgestone 235/85r16 from memory), usually puncture through the tread when they get a bit worn. not many sidewall cuts, but a few.

I'd sacrifice the rare sidewall cut for the comfort, and less strain on everything else (especially the boat!)

Cheers Andrew

Tyre presures are a very personal thing.
I personally lower my pressure down to 25/28psi if doing extensive gravel and believe the thoery about the biro, my normal road pressure is 36/38psi on 235/85 16's which have tubes and I find that there is less sidewall movement (better handling)for normal situations, more presure load depending.
With the lower presure on dirt my vehicles handling noticeble detirates, so its driven accordingly.


Shane

Jimbo, Eric & Chris

The Higher pressure's are the way to go.

What pressure you use depends on, Vehicle load, tyre type, air temps, road surface to be traversed and speeds to be driven at.

Now please everyone READ MY LIPS:

There is no magic chart or crystal ball that you can look up for your situation, because every rig is a INDIVIDUAL SITUATION that must be assessed on a case by case basis.

As long as you take into account the factors in para 3 above, add a bit of common dog and all will be ok.

Oh!by the way, tyre monitors added to your rig's will frighten the be-jessus out of you dudes who like the lower pressures.

If you want to get into any sort of debate of the virtues of high or low pressures in tyres on gravel road, just call into the Pink Roadhouse at Oodnadatta. The owner will in no uncertain terms given you his opinion on the subject.


Floody

Well, this is rapidly developing into post pi$$ing competition post,eh!

From a lifetime on cattle stations, from the Kimberley to Channel country, I'd say it is all up to the individual.

If you want to hammer along, then run GOOD tyres @ 40 psi. If you're content to smell the roses, then by all means spend your day airing up, down or whatever, and run in the high 20's or so.

The Wifes 80 series runs tyres @ 32 psi, all the time, whether it be the Birdsville Track, Winton-Jundah road or Landsborough H'way, to Brissy. The only flats have been nails, or welding rods, and we've never had a blowout.

The work utes are a different matter. Varying loads, different drivers and variable terrain, with sticks, old fencing material and other rubbish to damage them. Keep these tyres around 40 psi, to match the loads and speeds. Even then there is the occassional "death", of even new rubber. Summer heat is a big factor, if one is in a hurry to get to town, and the tyres suffer.

hooroo...

My vote goes with the high pressure party. My experience includes
only about 1/2 mill offroad ks operating a hilux based sprayrig at
15 kph. I threw tyres away weekly until getting to 50 psi plus. Now hardly ever have any sort of tyre grief. Brand of tyre makes
no difference either...big dollar Coopers or budget , I threw them all away, stuffed by stones & sticks, until finding the best pressure for the conditions.
The owner of an independant tyre service in Alice told me to never run my (Jackaroo) just fitted BFG a/t less than 38psi unless in sand.
Sprayrig now runs Firestone Firehawks at 50/55 psi virtually
trouble free. No one will ever win this argument but experience,
not hearsay, will always be my guide....oldbaz.

Great thread guys, at least we now know who is resonsible for the corrogations!

My experience won't let me do it myself but I've been on trips with folks that like 40+ on dirt. They didn't get any punctures either but my bullbar didn't fall off, shocks still worked and family did not insist on stopping every 40 minutes for respite.

I like Jol Fleming's (Direct 4WD) contact patch method:

180 - 200mm Tread length is good for most roads, inc the sealed

220 - 250mm Corrugated Dirt Road

300mm Sand Dunes, including the trailer.

400mm about 7 or 8 psi, When yr really in ‘it’

OT