Lowering tyre pressure not the answer?

[Simon]

Heading to Arkaroola in the 110 with trailer in tow, there had been some talk from others at the previous camp not to lower tyres despite it being dirt / stones all the way from Copley. Thinking was it increased the risk of sidewall damage too much.

I was running pretty close to highway, just under 30 front and trailer, just under 40 rear.

Pulling into Arkaroola a trailer tyre was going down rapidly, with a hole on the inner wall. Annoying as it was a near new Continental AT.

The guys here reckon 37 is what they use on the station vehicles.

Think I'll be running higher on the way out, seems lower pressure may not always be good

[vnx205]

seems lower pressure may not always be good

Maybe it is just that lower tyre pressures are not a 100% guarantee that you will not suffer tyre damage.

It may still be the case that lower pressures reduce the probability of damage PROVIDED you slow down.

I saw a suggestion recently that your speed in km/h should not exceed three times the tyre pressure in psi. That sounds pretty close to the mark in a lot of situations.

EDIT: I hope that not very many people read the post before I remembered to include the words "three times". It makes quite a difference.

[PAT303]

If you ask 20 different people about tyre pressure you will get 20 different answers,there's nothing saying you would not have got tyre damage running any other way. Pat

[Eevo]

I saw a suggestion recently that your speed in km/h should not exceed the tyre pressure in psi. That sounds pretty close to the mark in a lot of situations.

what?!?

if i want to do 100km/h i need 100psi?
i generally drive around on about 40psi


you sure you dont mean kpa? (kpa doesnt work anyway)

[vnx205]

what?!?

if i want to do 100km/h i need 100psi?
i generally drive around on about 40psi


you sure you dont mean kpa? (kpa doesnt work anyway)

See the edit I did on my earlier post.

33 psi would be enough to do 100 km/h.
40 psi would be good for about 120 km/h
I didn't read my post carefully enough. Sorry about that.

[Eevo]

I didn't read my post carefully enough. Sorry about that.

all good!

however i wouldnt be doing 60km/h on 20psi

having said that, i once did 1000km @ 120km/h on 16psi by accident :angel:

[Blknight.aus]

Of those 20 people and their 20 different opinions not one of them will give you this bit of advise.

Slow the hell down.

ID love to have had the cost of the new tyre donated to me every time Ive been hassled for going slowly only to pass the hassler on the side of the track later with them changing a staked tyre. (actually the same could be said for suspension components, loss of vehicle controls, fuel stops)

Slow down, it costs less and is usually quicker at the end of the day.

[fitzy]

I was at mount Augustus last year and talking to the station owner. He runs 50 psi on all his station tracks and roads out there, he said the higher pressure has reduced damage and punctures significantly . I tried it and he is right for that country and type of roads but higher shock temps , higher bush and suspension wear rates put me back to lower pressures.
This is in the Gascoine region of w.a.

[PAT303]

Of those 20 people and their 20 different opinions not one of them will give you this bit of advise.

Slow the hell down.

ID love to have had the cost of the new tyre donated to me every time Ive been hassled for going slowly only to pass the hassler on the side of the track later with them changing a staked tyre. (actually the same could be said for suspension components, loss of vehicle controls, fuel stops)

Slow down, it costs less and is usually quicker at the end of the day.

Going slow on corrigations doesn't work. Pat

[Eevo]

going fast means less steering and breaking.

[Tombie]

In most circumstances 75-85km/h suits most corrugated surfaces.

[Tombie]

Of those 20 people and their 20 different opinions not one of them will give you this bit of advise.



Slow the hell down.



ID love to have had the cost of the new tyre donated to me every time Ive been hassled for going slowly only to pass the hassler on the side of the track later with them changing a staked tyre. (actually the same could be said for suspension components, loss of vehicle controls, fuel stops)



Slow down, it costs less and is usually quicker at the end of the day.


Pressures down - speed no more than 90km/h has always been my standard practice.

I have been known to go a little quicker, but not sustained and no corners!!!!

[MrLandy]

In all my years driving central and northern Australian rough, rocky, corrugated roads, I've found higher tyre pressures much more reliable. 35-45psi (depending on load). This coupled with the right tyre choice (best IMO 10ply Bridgestone 661 235/85R16) and correct speed for conditions (usually around 80km/he on corrugated fast dirt, means fewer punctures. I believe Flat vertical sidewalls are always better except in very soft sand. And narrow tyres are better than wide.

[steane]

I've come across a property owner in the Flinders who told me to put more air in not let it out. I compromised and only let half of what I'd planned to out. He said that sliced sidewalls is a daily occurance with city folk who all let their tyres down on arrival..Many don't listen to him and many leave needing a new tyre or two.

The roads around his property were quite rocky/flinty.

[Blknight.aus]

In my experience most stakings are on the exit of corners and usually wind up being a rear or trailer tyre, and typically enter on the shoulder of the tyre.

one of the more educational things you can do is grab a good trusted friend and have them drive your car for you on sealed roads with varying tyre pressures, loads and speeds to see what the tyres are doing and where they are being placed.

With that up your sleeve, watch the way a rally car spits rocks on a grabel road. Then have a look at the underside of a car thats rently been on a gravel road but hasnt been cleaned. Something causes all the little didts in the dust on the underside between the wheels.

unless the road surface wont take the weight of the vehicle a higher pressure is better.

with modern tyres my money is generally on road pressure for anything hardpack when I dont need the extra flex in the sidewall or treadface to keep the contact patch sound. But I also gnerally only hang around the 80kph mark if Im on gravel. Good for fuel, tyres, suspension, fatigue and it helps keep the dust down.

[Simon]

I perhaps should also have said, speed was no higher than 80 at any point and more typically 60 to 70.

On a side trip in just the 110 yesterday afternoon I ran 40 front and 45 back. No punctures but ride much harsher. Had some scrapes on the sidewalls still. Would they have been a puncture at lower pressures? Who knows.

[wrinklearthur]

What are your thoughts on the 4 P.S.I. rule?

It seems to work for me.

[POD]

What are your thoughts on the 4 P.S.I. rule?

It seems to work for me.

My thoughts are: "What is the 4psi rule?"

[TwoUp]

4psi is to do with heat. To find the optimum tyre pressure by checking the cold pressure versus the run hot pressure. I agree, to an extent, without regard to sand and very difficult off road.


Cheers,

[Simon]

Kept pressure up and managed to avoid any further sidewall issues through rest of the Flinders. Some pretty rough roads.

Stopped at Port Augusta to get new tyre fitted. He looked at the load rating (114) on existing and said that was far too weak, the walls needed to be stronger. I must admit I was not aware the Contis came in higher ratings, but the new one is 120 and he said they go higher

[Eevo]

but the new one is 120 and he said they go higher

120 is a good number

[Blknight.aus]

the 4psi rule is good for most on road and some sand (sustained low speed at a constant stable sand temp) conditions but not much chop otherwise.


Normally for road use if you have your pressure right once the temp comes up you go over your target pressureby 4 psi. if you start at 28 and you chekc them after an hour and yovue got 32 and you get 32 gain an hour later youve got the pressure about right for your current operating conditions.

My caveat for using it in sandy conditions is that the pressure rise should get you to your target pressure. but you have to be careul if your target pressure is lower than 15 psi or you air up hot tyres to a low pressure on a hot day