Air down- When?, how much?

[Chaski]

What is the recommended tire pressure to air down when going off road?  Should I air down every time I go off paved road surface?

 

[Cynic-al]

Depends on what your driving on and how low your can go with your wheel tyre combo without them coming off. No point doing it unless you have to as it's just hassle. Mine used to sit somewhere between 10 and 30 on wheels with beadlocks on the outside.

[Dave W]

It depends on the surface you're likely to drive on and if you're running tubed tyres, tubeless or bead locks. It's only something you can learn with experience as their are no hard and fast rules. It can also vary with tyre patter and size !

That said, if I'm running on and off road, such as on a green laning trip, I usually run at around 24psi as a decent pressure for road use that's good for most off road scenarios. If I'm running off road all day, such as at a trial, I'll drop them as low as 12psi if I'm running tubed tyres or 16psi for tubeless, any lower than that, especially with tubeless and no beadlocks means you risk knocking the tyre off the bead if you hit a bump or slide sideways into an edge. With beadlocks I'll run as low as I feel necessary depending on the terrain. I've even taken the valves out all together when running in deep sand and sand dunes where steering isn't an issue.

Running on wet grass or in sand or mud you can run lower pressures than you would if you were on a rocky track where too low a pressure might encourage cuts in the tyres or even pinch punctures.

[miketomcat]

The only time I've aired down was in Russia at ladoga. The main reason is I can't be bothered and I have no sensible way of pumping them back up. Don't get me wrong it works I know that but we punched 3 tyres off rims in the space of 2 miles. We were running 16psi and believe me putting a tyre back on full of mud, in a rut with an electric compressor is not my idea of fun.

Mike

[Mo Murphy]

On my 90 I run 30 psi and round and that seems to get me through most things on and off road. Never bother airing down the tyres. 

Mo

[Chicken Drumstick]

In very wet sloppy mud airing down will make a big difference. Or if you are rock crawling. Other uses maybe less so, but anytime you want to elongate the tyres foot print its good. 

 

Tyre type/make will also have a bearing. 25-28psi works well as a general all round pressure for any use, road and off. But some tyres are pretty stiff, and dropping down pressures a bit will make no odds really. In fact, unless I'm dropping them down to 15psi, i tend not to bother.

But tbh, unless you have a real need to air down, then don't, unless you are running 40psi or something. And don't air down low if you have no means of inflating the tyre again. 

[Hybrid_From_Hell]

Airing down on standard rim or with tubes less than 20.psi can see tube valves torn off etc.

 

Les than 20 look at beadlocks or double. Internal beadlocks strauns etc

[Ex Member]

I go to 15 psi regardless at the start of the day.   It is nice and safe.  You have to try hard to drop a bead.  Go lower when needed.  I've run down to 5 when needed in the winter without beadlocks.    Carry a compressor so you do not need to worry.  People that do not air down do not do any real off roading.

[elbekko]

I usually run 1.4-1.5 bar off-road, never had issues except for some dirt in the bead. It makes a huge difference.

[David Sparkes]

Gentlemen, the post is full of assumptions, that is the first, and I hope the others are as inoffensive!

As I post this, 8 replies, ranging from 'never' to 'always', so that will clarify matters for the OP :-)

Actually, the OP, Chaski, has been a naughty person, in that his Location has not been entered into his Forum Profile.
Looking at his profile I see his other topic is Driving down steep wet clay mountain roads.  Highly significant information, which he also left out of this topic.

Now we have a better idea of what he means by going ' off paved road surface', people can read through his posts in the 'steep wet clay' and perhaps take that into account in any additional replies.

I'm in Derbyshire, and can say I have no experience of steep wet clay roads.
I do have experience of airing down in my own car, and it was very useful.
I've also seen one example of two bog standard Series 2s (1960s Leaf springs). One went up a wet limestone rock very easily on road treaded tyres at 22 psi, the other struggled greatly on chunkier treaded tyres at 30 psi. Set at 30 psi "because he had been humping heavy loads, had inflated the tyres to cope, and hadn't bothered to go back to standard pressures" before this green lane trip.
IE Over pressure was positively harmful.
No-one in the group had a tyre pressure gauge, my excuse being that I was a passenger. I'll try and remember next time!!

So, if I may be so bold, should Chaski air down before driving on steep wet clay mountain roads?

Regards.

[Hybrid_From_Hell]

^^

 

 

In answer I would say no so much airing down as not to be hard as can be, but, running less air than is recomended is a risk of loosing tyre off rim, the MORE you air down the GREATER the risk of loosing the connection of tyre to rim, a little reduction does make a bit of a difference as oppossed to rock hard, but, in my experience a littlke less say 20-25 is about it. 

 

I lost tubes where the V8 and the tyres grip span the now aired down tyre slicing off the vlave stem, similarly on un tubed tyres something was able to get between the wall and the lower pressured tyre and all the air escaped.

so, in answer "Less than rock solid, maybe 20-25.

 

Staun air valves are fab for dropping pressures down tro a preset limit, and a cheap small compressor to bring them back up.

 

Anything less than the correct pressures will absolutely wear tyres oddly and quite fast on tarmac, and effect handling !Q

[FridgeFreezer]

13 hours ago, Red90 said:

People that do not air down do not do any real off roading.

Bit of a sweeping "f***k you" to a lot of people isn't it? Care to define what does count as real off-roading?

[Chicken Drumstick]

19 hours ago, Hybrid_From_Hell said:

Airing down on standard rim or with tubes less than 20.psi can see tube valves torn off etc.

 

Les than 20 look at beadlocks or double. Internal beadlocks strauns etc

Can't run beadlockers for ALRC events and we can air down to 12psi. Occasionally you'll see someone pop a tyre off the rim, but not all that common tbh. Ive often run 15psi and never had an issue. 

[Daan]

what a load of cold air! Yes airing down makes a big difference, and I usually do it if i go offroad. If you have an old tyre on a rim, chances are they are rusted stuck to the rim. No way that ever comes off, even if you want it to....

Inner tubes are the way to go if you want an easy solution. Fit the tyres dry (no soap), I have run this successfully to 8 PSI during the Croatia trophy.

Other solutions are beadlocks obviously or sikaflex the tyres to the wheels. I believe some comp safari guys use this idea.

 

Daan

[Chaski]

Air down, When and how much?

Thank you all for your input on this topic. So I just purchased a set of BF Goodrich AT KM2 for my Landrover Defender 110. Drove from Lima to Huaraz, Peru all tarmac. They are currently set at 35PSI. So my next question is : Should I be running les than 35PSI even if I am on tarmac? It appears that it really is subjective as to to how much air one wants to use. 

I was impressed by the way they handled on tarmac. These tires were recommended by some of the responders to my topic "Steep downhill, clay,mud

[Hybrid_From_Hell]

OK. 

 

This is how to determine how much pressure in each tyre

Get some tyre chalk

Find a dead straight quiet road.

 Stop.  

Mark front 2 tyres across from shower to shoulder with chalk.

Drive 50 yards or even less

Must be dead straight.  The story get out and look at line

If centre worn away lower pressure

If edges not centre add air. Repeat until line is worn off pretty much across entire tread 

Then measure pressure and note down. 

Then do same to rear

 

That then right pressures all around

 

Nige

 

[deep]

59 minutes ago, Chaski said:

Air down, When and how much?

Thank you all for your input on this topic. So I just purchased a set of BF Goodrich AT KM2 for my Landrover Defender 110. Drove from Lima to Huaraz, Peru all tarmac. They are currently set at 35PSI. So my next question is : Should I be running les than 35PSI even if I am on tarmac? It appears that it really is subjective as to to how much air one wants to use. 

I was impressed by the way they handled on tarmac. These tires were recommended by some of the responders to my topic "Steep downhill, clay,mud

I assume (from the other thread) that you mean MT KM2, not AT!  35 p.s.i. is fine for the rear, too much for the front (28-30 is better).  It does depend on your load but it's the rear that you would adjust more (32 if empty, as much as 40 if loaded).  Make sure your gauge is accurate!

Lots of variation in the recommendations above and it seems they mostly need qualifying, according to people's uses.  

There are so many factors to take into account, mostly rim type, tyre type and size, intended use and horsepower.  People with large engines and lead in their feet can, indeed, get a tyre to spin on a rim in "lubricating" conditions with as much as 20 p.s.i. on board, especially if it is an over-sized, mega-grippy tyre. That is pretty unusual, unless you are talking about very intense (competitive) off-roading, in which case they should have some sort of bead lock fitted anyway.  

The tyres you have on standard Defender rims will be perfectly fine at reasonable off-road speeds down to 15 p.s.i., assuming you are going tubeless, and you will really benefit from the extra floatation and grip.  In this case, the extra flex will help loosen that claggy mud.  My own approach is to just drop to 20/24 (front/rear) initially, because that is safe, and only go down further if I am in danger of getting very stuck.  I still wouldn't go less than 15 p.s.i. with tubeless tyres. 

I once drove up a trials section that had been totally chewed out by previous competitors.  I aired the Series 3 (with tubes) down to 3 p.s.i. and just walked slowly up in low first, no trouble at all.  Conversely, I once bought a Range Rover with very soft-walled snow tyres and they came off the rim at 20 p.s.i. crossing a rocky river.  The tyres just weren't up to it at all.  The same rims with BFGs worked at 10 p.s.i. with tubes.

[honitonhobbit]

On wet clay mountain roads you need bite. Airing down can provide this but as the side wall of the tyre flexes all over, your directional stability is severely compromised. \often resulting in a relatively uncontrollable skid. Airing down in sandy or dusty deserts is good - bigger footprint = more floatation and sand is carp for directional stability anyways

Airing down on rock seems to work for the chaps in the colonies, but airing down on gravel/shale/rock is pointless to the point of being a Trumpism

Every make of tyre behaves differently and can vary in pressures to the next tyre. Every size of tyre is the same. For example a Michelin XCL 7.50x16 will stay on the rim at 9psi, whereas a Michelin XM&S in a 205/80x16 will fall off the rim at 20psi.

Driving skills, steering type (ram/ps/manual) all give varying results

The whole idea comes form the olden times when tyres where cross-ply and had big old stiff side walls, so airing down was the only way to get more traction. In these modern times with so many sizes of tyre, it's almost pointless unless in competition

Worth noting it saps engine power, can trash the tyre, valve, ps, braking efficiency - so all in all unless you are competing, driving across a desert with skinny tyres or just plain bored - maybe opt away from doing it

 

[tacr2man]

Chaski , the question you are asking , is not necessarily being addressed by the answers you have received above (mainly) due to your location .  "off road" in UK is a very limited duration activity , and mostly at very low speeds .  I believe  from my experience in Australia , and the similarity of travel where you are , that airing down will not be in the main feasible.    Airing down is greatly affected by speed and duration due to the effect that both will have on heat build up and possibility of damage to tyre casing . 

Airing down can greatly help flotation eg in sand  , and to a degree in mud , where it also helps with tread cleaning , these are both utilised at a very low speed. For normal travel on muddy roads , or hard stony desert tracks then tyre pressures are normally operated at very similar to tarmac highway levels, not for exactly the same reasons.  In my previous answer to your question re tyres etc , I advised you of the limited possibilities open to you , and in this answer , I hope you see that airing down other than to get you moving again isnt an answer . HTSH   

[HoSS]

On 10/13/2016 at 3:47 AM, Red90 said:

I go to 15 psi regardless at the start of the day.   It is nice and safe.  You have to try hard to drop a bead.  Go lower when needed.  I've run down to 5 when needed in the winter without beadlocks.    Carry a compressor so you do not need to worry.  People that do not air down do not do any real off roading.

Red not only is your opinion incorrect with reference to some of the more experienced folk here, you manage to make it rude and insulting as usual. 

[Cynic-al]

I used to be able to put tyres back on rims with my on board air system with a 24 litre tank but I've found electric compressors are often lacking in flow to get them back on unless you can hold the tyre against the rim tightly for a long time. Guess it depends on the tyre and rim though.

[Tal]

For me if I have to get home afterwards I dont mess with air pressure at all. if I slip then I get out chuck some gravel or anything else handy in there and carry on at a lower speed or ratio.

Basically If I come upon anything I can't get around with whatever tyre I happen to have on, I blag my way through.

[deep]

On 10/17/2016 at 1:23 AM, HoSS said:

Red not only is your opinion incorrect with reference to some of the more experienced folk here, you manage to make it rude and insulting as usual. 

Well, Red could have phrased it better but I'm amazed that a few people who consider themselves experienced actually haven't experienced the MASSIVE difference in traction/mud clearing/floatation you get when airing down.  Sand, soft gravel, mud and the sort of conditions the original poster faces are all common off-road situations that benefit hugely from controlling your air pressure and not relying on the higher pressures that are used to keep your tyres cool in (totally different) fast, on-road use.  Even driving across hot, stony Australian deserts, the locals universally recommend no more than 28 p.s.i., in order to allow the tyres some give on the nasty, sharp rocks you can find there.  It certainly worked for me (I did a 31,000 km explore of Aussie once, taking in a hefty range of desert conditions, so think I am qualified to offer an observation).

"Experience" means you have done something and learnt from it!  If you've only experienced conditions which are fine with your tyres running at high pressures, you'd have to admit that experience is pretty limited, surely?  I'm not trying to be rude or aggressive, it's just that I am baffled that anyone can use the term "experienced" without acknowledging something which is one of the most basic rules of off-road driving and has been for maybe a hundred years (look up 1920s Dodge going off road on youtube and prepare to be amazed).

[miketomcat]

I'm not taking this personally. I have aired down however in the UK off roading is predominantly for fun and short. Out of a 100 mile greenlane trip your likely to do 60 miles on road. A site day there is only likely to be 10% of the site where airing down will make any difference. So yes I'm lazy and don't bother but I also don't bother to drive some where I'm going to spend 4 hours trying to get out of. 

It does work and makes a big difference  but I would only use it on prolonged off road use and probably only drop to 20 psi.

Mike

[Chicken Drumstick]

2 hours ago, miketomcat said:

I'm not taking this personally. I have aired down however in the UK off roading is predominantly for fun and short. Out of a 100 mile greenlane trip your likely to do 60 miles on road. A site day there is only likely to be 10% of the site where airing down will make any difference. So yes I'm lazy and don't bother but I also don't bother to drive some where I'm going to spend 4 hours trying to get out of. 

It does work and makes a big difference  but I would only use it on prolonged off road use and probably only drop to 20 psi.

Mike

Green laning shouldn't require you to sit down massively low. Although mid 20's psi is more sensible than 40+ for that sort of use. 

But by the same measure, you also don't need Insa Turbo Special Tracks, a 2" lift or a tray back to go green laning either. 

But there are plenty of off road sites in the U.K. That you can benefit greatly from airing down. If you CCV then more the fool you if you run 25+psi....