To let down or not to let down?

[TerryO]

Forgetting sand driving for a moment, what is the general opinion about lowering tyre pressures when heading off road?

I often read on here about lowering tyre pressures as a good thing before heading into the sticks. I recently did an off road driving course with the Range Rover Club and the instructor, a hard arse old bugger, said if you want to get flat tyres that could be avoided then let down your tyre pressure before you head in.

He strongly recommended that you only let down tyre pressures when you need to, not before.

So if you don't mind what is the general opinion and first hand experiences of the members?

Cheers,
Terry

[Slunnie]

Do you mean in scrub or fast dirt like the Oodnadatta Tk?

[Sleepy]

Yes as Slunnie is eluding, it depends on the terrain. If I am trundling through the high country in low range - I am more confident pre-emptively dropping to say 18 to 20 psi - will go lower if it gets ugly.

If I am belting along an outback track (50 to 80 kmh), with worn out tree roots sticking up and threatening my tyre walls, I may wait.

[LOVEMYRANGIE]

Letting your tyres down in say, a rocky or rough slow track allows your tyres to deform over sharp objects and spread the weight over the deformed surface and give more contact area for traction rather than a hard tyre which will carry all the weight and load on one very small point on the tyre, opening up the chances of punctures or tears.
As to what pressure, that depends wholly on what the actual conditions are.

For fast surfaces, generally keep to std pressure as this will avoid the feeling of driving a wet sponge on oiled glass!

Cheers

Andrew

[beefy]

i always let them down at the start. if you wait until your already bogging down its getting close to being to late.
keith

[Slunnie]

Fast dirt like the desert tracks I will drop from full pressure (approx 40psi loaded) down to about 34psi to soften up the tyres a bit and allow them to absorb some rock impact. When 4WDing I drop to about 20psi with a radial tyre. On sand I'll head to somewhere around 15-16psi or about 10-12 with a bias tyre.

I let them down early, because its when you don't that you come unstuck by getting stuck, damaging tyres and/or breaking it.

[TerryO]

Sorry I should have been more specific.

I'm talking low range rough scrub or rocky area driving.

Just to add to the discussion I also read recently a 10 to 15 year old LR book on how to drive your LR in different off road conditions.

From memory it said that you don't let your tyres down in rocky off road conditions.

Cheers,
Terry

[V8Ian]

Slunnie, you're the only other person I know who thinks like me. As I was about to post; on rough tracks such as The Cape or Strez, I let my tyres down to become the first part of the suspension. True it will shorten the life of the tyres, but they are cheap and easy to replace in comparison to the whole car.

[Sleepy]

Sorry I should have been more specific.

I'm talking low range rough scrub or rocky area driving.

Just to add to the discussion I also read recently a 10 to 15 year old LR book on how to drive your LR in different off road conditions.

From memory it said that you don't let your tyres down in rocky off road conditions.

Cheers,
Terry

Yes, I go down to 20 to 25 psi to start with - you can really feel the difference in controlability of the vehicle.

To tell you the truth Terry, I have read lots too, but the best rule is the one you prove yourself - just give it a go. Take a compressor and see what you think of various pressures - different tyres will make a difference too.

You shouldn't be worried too much about rolling off the rim until you are under about 18psi. As for tyre damage by foreign objects - it'll happen, it's just a matter of when. :-(

[TheLowRanger]

I will nearly always let down my tyre pressures pre-emptively at the start of heading off road. Depending on how loaded I am, or if I am towing, I normally run my tyres between 32-38psi. On fast corrugated dirt (like the Gibb and nearly every other road up here) I will drop them around 5-6psi to help take some of the harshness out of the corrugations and also to help the tyres to conform around sharp rocks etc to avoid punctures. I will also limit my speed to a maximum of 80kmh. On true off road conditions including mud, shale, rocks etc. I would normally run around 20-25psi depending on load and conditions. On sand I would drop to a maximum of 18psi but normally 16psi. I have done around 60k km's in the last couple of years with a good portion of that on second rate Kimberley roads and station tracks, have not suffered any tyre damage yet.

[Slunnie]

Slunnie, you're the only other person I know who thinks like me. As I was about to post; on rough tracks such as The Cape or Strez, I let my tyres down to become the first part of the suspension. True it will shorten the life of the tyres, but they are cheap and easy to replace in comparison to the whole car.
Up at the cape we ran around everywhere fully loaded on Simex tyres at 20psi. There is no way in the world I would do it any differently up there as the corrugations are that bad. That probably equates to about 25psi in a radial. We passed a Pajero up there that had cracked its axle in half! If you don't drop the pressures everything in the body and suspension will just get chopped out.

I hear of some people running full pressures, but none of the roadhouses that I have stopped at anywhere have advised high pressures on these roads, and most advise anything from slightly lower and down.

[GS-ADI]

I like 22ish in mud
Depending on the tire, some like to be hard to throw mud out of the nubs. Some like to be softer, so it rolls out when the tire bends from being flat
There is a lot of ifs in that,
You might be somewhere where clearance is more important then grip,.
Or it could be sharp rocky stuff,
You can always let more air out if it gets too tricky,.
Not so much fun replacing a shredded tire
The type of tires too,. I remember a old tire repair guy (wall welds) he had a pioneer beard and all, saying about how some AT tires have wire
That kinda looks like this
XXXXX
then when the pressure is down for too long the wire stretches and can break, making it look like this
\ / \ / \ / \ /
/ \ / \ / \ / \
wich is all fun and games untill your driving home from the beach at 110 on the freeway, and the tire blows apart, and flips your truck
:) He made the wire look with his hands when telling the story, and is a rubber repair guru:D,.. So he seemed to know his stuff,.. Except he said he never goes under 20 on the sand because of this,. So I feel for his rigg, what ever it is, must rev its poor tits off,

[Slunnie]

I like 22ish in mud
Depending on the tire, some like to be hard to throw mud out of the nubs. Some like to be softer, so it rolls out when the tire bends from being flat
There is a lot of ifs in that,
You might be somewhere where clearance is more important then grip,.
Or it could be sharp rocky stuff,
You can always let more air out if it gets too tricky,.
Not so much fun replacing a shredded tire
The type of tires too,. I remember a old tire repair guy (wall welds) he had a pioneer beard and all, saying about how some AT tires have wire
That kinda looks like this
XXXXX
then when the pressure is down for too long the wire stretches and can break, making it look like this
\ / \ / \ / \ /
/ \ / \ / \ / \
wich is all fun and games untill your driving home from the beach at 110 on the freeway, and the tire blows apart, and flips your truck
:) He made the wire look with his hands when telling the story, and is a rubber repair guru:D,.. So he seemed to know his stuff,.. Except he said he never goes under 20 on the sand because of this,. So I feel for his rigg, what ever it is, must rev its poor tits off,
Was he talking cross plys or radials?

[GS-ADI]

No idea :( I really dont know anything about it,.. but it seemed like something that would be good to ask when buying some tires, what happens inside the tire at different pressures would be good information to have,
I wouldn't think they would all be the same, ??

[V8Ian]

Was he talking cross plys or radials?
Must be talking radial, never heard of steel belted cross plies.

[GS-ADI]

Radial tire - Wikipedia, the free encyclopedia

keep in mind these blokes sell these tires so there is more bias in the report then bias in the tire :)

Michelin AG - Advantages - Bias vs Radial (http://www.michelinag.com/agx/en-US/products/advantages/bias_radial/bias_radial.jsp)

[isuzurover]

Fast dirt like the desert tracks I will drop from full pressure (approx 40psi loaded) down to about 34psi to soften up the tyres a bit and allow them to absorb some rock impact. When 4WDing I drop to about 20psi with a radial tyre. On sand I'll head to somewhere around 15-16psi or about 10-12 with a bias tyre.

I let them down early, because its when you don't that you come unstuck by getting stuck, damaging tyres and/or breaking it.

Pretty much what Slunnie said. Except that when on really hard low range stuff I will let my tyres down as low as 7 psi (radials, no bead locks - but I know my tyres are a tight fit on my rims).

I have never staked a tyre at 7psi, but have staked one at higher pressures.

[blitz]

I agree with Slunnie, tyres are a part of your suspension - actually a vital part of the suspension and often over looked as such. My father is an old bushy but try as I might to explain this to him, he would run his tyres at 200 psi if they could take it, excpet in sand and then he lets them down .

Tyre pressure depends on the terrain you are in, there is no real hard and fast mesure for what pressure you need for each situation as the weight of the vehicle, the width and diameter of the tyre and the weight positioning in the vehicle are vital to tyre pressure.

Generally speaking, high pressure on hard ground and tarmac, a bit lower on corragations to allow for more side wall flex (to much and the side wall flexes to much and will over heat and bugger your tyres)

Sand let them down so that you inclease you footprint and lower your weight to surface area load.

Sharp stones and sticks, avoid the bloody things, but if you cant then slow and lower pressure so that the tyre can flex around the object, but expect to get holes.

Mud, I have been playing in mud for the last 25 years and I feel that tyre pressure has little to do with success, I will probably get plenty of arguments from this, but, big block tyres and full noise to keep the tread clean is the main criteria. I feel that of all the terains I have driven in mud is the hardest and the one which leaves the least room for error. In fact unless you really need to mud is not the fun that it looks like in videos, it's bloody hard work, hard on your vehicle and you. but if you have something like a suzuki sierra very modified then it's fun - BUT not your daily drive as it will kill it.

I guess what I am trying to say is that you will have to experiment to see what works best for you and your vehicle. Take all advice with a grain of salt as unless it is an identical vehicle then you can only use the advice as a guide and that of course includes me.

Have fun as it's all part of the learning curve

Cheers Blythe

[land864]

On a recent trip to Mt Skene in Victoria , in a Leaf sprung :eek:Stage One I ran 35 psi on the way up the hill over some rough roads and it shook the ' you know what ' out of me , the passenger and the vehicle.

Coming back down I deflated to 25 psi and it made a heck of a diffrence in comfort factor.

Heading up to the Oodnadatta track and Mereenie loop soon towing a camper trailer.

Will try them at 30 in the rear and 25 in the front.

Pete

[TerryO]

The reason why I brought this topic up is that there are quite different opinions on what is the right way to go which is confusing if your a newbie and many people on this website are newbies.

As I said I had already read what was an official Land Rover off road driver instruction book that I was given to me by the previous owner of my D1. The book was some 100 pages long and said exactly the same as John the RRC instructor regarding driving over rocky or extremely rough (dry) terrain in low. I had considered that even though it showed classic Range Rovers and old D1's as examples in the book they, being Land Rover, should know what they were talking about even 15 to 20 + odd years ago when the book was printed.

The instructor who did the course I was on from the RRC is an older bloke who has been around for many decades and what he said made sense to me anyway at the time about punctures and the negatives of lowering your underside mechanicals height by lowering tyre pressures which makes it easier to damage axles etc.

What I've read and what I was told by a professional instructor does seem at odds with the experiences of many very travelled and very experienced people on this website though. So as a newbie to this great pastime it does create some confusion about what is the right way to go. If there is such a thing.

I do understand that concept of tyres being a integral part of suspension as I am involved quite heavilly with motosport of the two wheel kind where suspension and tyre selection and pressure is everything if you want to go fast and lessen the risk of crashing. But in this instance I'm not talking about going fast I'm talking about crawling over rocky rough terrain in low.

Personally I struggle some what with the concept that it is a case of whats right for each individual is the way to go. Obviously tyre construction is now far superior to what was around 20 years ago but unless the whole concept of off road driving has changed dramatically then what was right 20 years ago should still be the same today.

I thought if I brought the topic up it might cause some sole searching about accepted norms and if they are correct or not and this might make it a bit clearer for a newbie trying to move forward.
It's interesting though that no one has really said yes to leaving their tyres at normal road pressures in rough terrain at very slow speeds though.

I did wonder if the older members who have been doing this for decades were of the same opinion as the younger members who might have been around for only a few years?


Cheers,
Terry

[Litlbee]

Have a look at this link. It could be helpful.

Direct 4WD - Tours in the Australian Outback (http://www.direct4wd.com.au/tours/TYRE%20PRESSURE.htm)

Cheers,
Gary

[Bush65]

Fast dirt like the desert tracks I will drop from full pressure (approx 40psi loaded) down to about 34psi to soften up the tyres a bit and allow them to absorb some rock impact. When 4WDing I drop to about 20psi with a radial tyre. On sand I'll head to somewhere around 15-16psi or about 10-12 with a bias tyre.

I let them down early, because its when you don't that you come unstuck by getting stuck, damaging tyres and/or breaking it.


The reason why I brought this topic up is that there are quite different opinions on what is the right way to go which is confusing if your a newbie and many people on this website are newbies.

As I said I had already read what was an official Land Rover off road driver instruction book that I was given to me by the previous owner of my D1. The book was some 100 pages long and said exactly the same as John the RRC instructor regarding driving over rocky or extremely rough (dry) terrain in low. I had considered that even though it showed classic Range Rovers and old D1's as examples in the book they, being Land Rover, should know what they were talking about even 15 to 20 + odd years ago when the book was printed.

The instructor who did the course I was on from the RRC is an older bloke who has been around for many decades and what he said made sense to me anyway at the time about punctures and the negatives of lowering your underside mechanicals height by lowering tyre pressures which makes it easier to damage axles etc.

What I've read and what I was told by a professional instructor does seem at odds with the experiences of many very travelled and very experienced people on this website though. So as a newbie to this great pastime it does create some confusion about what is the right way to go. If there is such a thing.

I do understand that concept of tyres being a integral part of suspension as I am involved quite heavilly with motosport of the two wheel kind where suspension and tyre selection and pressure is everything if you want to go fast and lessen the risk of crashing. But in this instance I'm not talking about going fast I'm talking about crawling over rocky rough terrain in low.

Personally I struggle some what with the concept that it is a case of whats right for each individual is the way to go. Obviously tyre construction is now far superior to what was around 20 years ago but unless the whole concept of off road driving has changed dramatically then what was right 20 years ago should still be the same today.

I thought if I brought the topic up it might cause some sole searching about accepted norms and if they are correct or not and this might make it a bit clearer for a newbie trying to move forward.
It's interesting though that no one has really said yes to leaving their tyres at normal road pressures in rough terrain at very slow speeds though.

I did wonder if the older members who have been doing this for decades were of the same opinion as the younger members who might have been around for only a few years?


Cheers,
Terry
I'm with Slunnie.

Probably that book's remarks are based on recommended highway pressures that are lower than we use. Like Slunnie, I use about 40 psi on the highway and the pressure definitely needs to be lower than that on our sharp, rocky outback roads - if not the rocks will damage the tyres.

[George130]

I run 40 to 50 psi on the road.
Fast dirt I don't bother lowering the pressures.
If low range and playing then I drop then to 25 at first and then lower as I start to have less grip than those with me (Hapens most trips). I find I often end up around 18 by lunch.
On sand I have been down as far as 12.

Only ever had punctures on road and normally by nails.

[DeanoH]

I did wonder if the older members who have been doing this for decades were of the same opinion as the younger members who might have been around for only a few years?


Hang on, I'll just park the walking frame...................

Back in the 'good old days' all we had were 600/650 or if you were really wild 750 16 non radial tubed tyres on skinny rims. You had bar treads for off road work, really scary on sideways slopes or highway pattern. Dunlop Roadtrack Majors probably the first go at an AT type tyre but were pretty forgettable on the dirt and the bitumen, then Bridgestone bought out their Jeep Service tyres, probably the best AT type tyre of its day. Had them on the SIIA going up the Cape in 1979.

Rims were a lot diferent then too. If you let your tyres down too far you'd end up spinning the tyre on the rim. If you were really lucky the valve bit got broken off the tube. If not you had to figure how to get a pumped up tyre to bits without access to the valve.

I pretty well agree with Slunnie on this issue. With modern tubeless tyres on wide rims my rule of thumb would be say 75% of normal pressure on dirt, less on rocks where you're only doing 20 k's or less and whatever you're game on sand but definitely 50% or less. By normal I mean what you would run on bitumen with the same load. The bagging of the tyre is more important than the psi number. Look at the tyre as you deflate and use the tyre gauge to read what you consider OK rather than just picking a number.

Put rocks through two tyres on our recent Central Australia trip. First flats I've had in over 10 years. First was just out of Mt Dare on very rocky road. 26 psi on the front LHS @ 30KMH. Rock through the side wall 10mm from the tread, hole about pencil size. Tyre not ruined as I picked it straight away, largish patch with a tube now becomes a spare, 2000 Km old Cooper ST. The second was going into Mornington Wilderness Camp off the Gibb River Road 3000 K's later. Best road we'd travelled on for days, 10mm long cut in the exact centre of rear RHS tyre in the 'valley'. Was towing the van so had pressure up to 36 psi. Saved this one too. Lucky we'd just stopped for SWMBO to take a photo and picked up the deflating tyre when I did a walk around. Really lucky, usually you pick up a flat rear, especially when towing when its trashed. A couple of plugs in this one and changed it at the camp. Spare no 2 is now a 5000 Km old Cooper ST. Sometimes its just the luck of the draw. Can't really go crook, 2 flats in 10 years and over 500,000 Km can't really go crook.

One place to be careful is creek crossings. Water makes a good lubricant when you want to stick a rock through a tyre, helps it along nicely.

Get a good tyre gauge and when travelling, be pedantic about checking your pressures. Check tyre pressure first thing in the morning when cold and visually whenever you stop. Its worth it. I also touch the rim centres looking for heat from a failing wheel bearing. Only takes a minute but can save a heap of grief.

Another thing. When you get new tyres make sure you get new 'black things' that hold the tyre valve. These can fail too and cause your tyre to be just as flat/trashed.

Met a bloke at Halls Creek who'd been told to pump his tyres up hard by the staff at El Questro when he rang from Kununurra about road conditions. He didn't know any better and assumed it was good advice. Got half way to El Questro and turned back as the ride was too hard, changed his travel plans and went down the bitumen instead of the GRR. Sure he was inexperienced but had his holiday plans scuttled by some ignorant idiot at El Questro. He was driving a Toyota Kluger with Cooper ST's, perfect for the GRR I would have thought.

One of the benefits of the D2 & P38A rims, with the Coopers, is that the tyre is a real tight fit. Makes 'em a bugger to change but you can let 'em down heaps before they pop off the rims. 14psi is the lowest we've run in the sand on the loaded D2 with no problems.

My two bobs worth

Deano

[TerryO]

Thank you Deano, I hope it is a LR walking frame you are using? ;-)

Your post makes very interestng reading. Its always good to have an explanation as to why something is better or works when compared to something else.

And thank you to everyone else who has taken the time to answer my questions to date.

I note that there is a very similar discussion that started soon after this one did in the Discovery 2 discussion area and the last post on the topic, so far, is from Sanbar who had just done a Land Rover course where the instructors had told them all to use highway pressures off road. The reason he gave, I'm not sure if he was being sarcastic or not, was the instructors didn't have a compressor with them to pump the tyres back up ...Hmmm!

While the instructors I did my course with carried everything and were happy to show us all they still basically gave the same advice about running highway pressures especially on rocky surfaces.

I just checked and the official Land Rover Off Road Driving Guide book I quoted from originally about running highway pressures on very rocky surfaces was written in 1993 for those who may be interested.

I'm not trying to say or offering an opinion about who is right and who is not, if there is such a thing, but for a relative newbie it is confusng when professional instructors and a official LR books say one thing, but nearly everyone elses vast experience says something else.

I'm not trying to push any viewpoint on this rather I have always thought it best to ask questions rather then just accept what your told especially when the answers you are given are contradictory.


cheers,
Terry

[Bush65]

What do they and the other posters mean when saying 'highway pressures'?

I use about 40 psi for highway trips. I find the tyres roll easier (so probably some fuel saving), the vehicle steers and handles better. Wear is uniform over the width of the tyre tread - no indication of over inflation.

That pressure is to high on rocky outback roads. It is uncomfortable and the sharp rocks that you often encounter will damage the tyres - I have seen new, good quality, tyres cracked badly in the base of all of the tread grooves by a few hours at too high a pressure on the Plenty Highway.

I just went and looked at the placard in my disco - it recommends 26 psi front and 34 psi rear.

Now that is not far off what I would run on a rocky outback road when I have the camping gear in the back. But it is not what I would run on the highway.

[dullbird]

I run 40 on the roads and usually drop between 26/22 off road

[isuzurover]

I run:
40-46 psi on the highway
~30 on high speed dirt roads (unless they are perfectly smooth)
~16-20 on sand/beach
As low as 7 psi in "extreme" offroad conditions.

[waz]

It's not just tyres we need to care for. Wheel spin damages tracks. I pressure down early as it makes progress in tough stuff more controllable and means I'm not spinning wheels trying to do sections that would be easier with lower pressure.

I speculate that the Land Rover manual may have been written for UK terrains. (perhaps a lot more mud)

W