Mud Tyre Pressures

Submitted: Tuesday, Jan 27, 2009 at 22:54
ThreadID: 65471 Views:2186 Replies:6 FollowUps:1
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Gidday all,

We have all been there, some more than others, you are bogged to the eyeballs and it does not look good. Should I have dropped my tyre pressures from around 36 to whatever so that I can get across the mud or do I leave them as is so that they can bite. I maybe wrong but I let my pressures down to about 12 psi so that I could float across. Unfortunately this did not help as I was in one of those bottomless bogs.
After we got the vehicle out after a lonnnng time, one of the people that assisted me said that I should have left the tyres at 36 so that the diffs would not bottom out and the tyres to bite.
I am no expert, so what do you do?

Thanks in advance.

Greg
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Reply By: Member - Kiwi Kia - Tuesday, Jan 27, 2009 at 23:14

Tuesday, Jan 27, 2009 at 23:14
Hi Greg, Hmmm, depends on how deep the real soft stuff is. If you bottom out on the diff or chassis and the tyres have still not managed to bite the bottom then I don't believe that tyre pressure will matter. If the tyres can bite down through the soft stuff then the longer the tyre footprint (low pressure) the better. Sometimes you may find that you can 'make ground' by swinging the steering from side to side so that the side of the tyres can bite the sides of a rut. If you do this with a heavy foot and real low pressure then you risk breaking the bead away from the rim. I don't think that there is only one answer for all conditions however I would generally lower pressure to about 16 myself

.
AnswerID: 346243

Reply By: Geoff (Newcastle, NSW) - Tuesday, Jan 27, 2009 at 23:48

Tuesday, Jan 27, 2009 at 23:48
Hi Greg,
The way I look at it, anything that is driveable can be driven more easily with less air in the tyres.

Of course, if the mud or sand or ruts are bottomless then the above theory is way out the window.

Geoff

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AnswerID: 346244

Reply By: Off-track - Wednesday, Jan 28, 2009 at 00:26

Wednesday, Jan 28, 2009 at 00:26
Personally I leave them as is, doesnt seem to make much difference and the extra time taken friggin around with muddy valves can be better spent using other methods.
AnswerID: 346256

Reply By: P7OFFROAD Accredited Driver Training - Wednesday, Jan 28, 2009 at 08:35

Wednesday, Jan 28, 2009 at 08:35
If you have already broken the crust, I haven't found there to be much real difference.


If it's wet black soil and you haven't broken the crust then lowering pressures will make a massive difference



cheers

Dave
AnswerID: 346280

Reply By: GregF - Wednesday, Jan 28, 2009 at 10:07

Wednesday, Jan 28, 2009 at 10:07
HI Greg
I lived in Darwin for over 30years. Most weekends out on Marrikia Plains, pig or goose shooting. My experiances were that once you have gone through the Blacksoil crust you be just about Nackered.
Had all sorts of 4 by4s and tyre set ups, still got stuck. May be I should have let the Tyres down abit. I rented out an Avis MiniMoke once to go shooting. That worked a Treat. Took awhile to clean out the Goose feathers and 12 guage shells. Bloke at Avis gave me some nasty looks on return. Bottom line is, I reckon once the Diff Housings are embedded, Your Gone.
Regards
Greg
AnswerID: 346292

Follow Up By: Member - Greg H (NT) - Wednesday, Jan 28, 2009 at 22:17

Wednesday, Jan 28, 2009 at 22:17
I was gone!!!
Hi lift jack, doors, boards, tyres, rims, winching and a lot sweat, we eventually got it out.

Greg
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FollowupID: 614452

Reply By: Member - Russnic [NZ] - Wednesday, Jan 28, 2009 at 13:29

Wednesday, Jan 28, 2009 at 13:29
Hi Greg
Once the diffs try to push mud aside unsuccessfully you are about stuffed no matter what the tyre pressure is. Where I live and farm in NZ I have got bogged a time or five. Frankly I don't think there is any definitive answer, if it works it is good driving if it doesn't ,think why did I put myself in this position anyway.
With a lifetime of 4WD starting with a series 1 Landrover through to a 08 V8 Troopy I still don't know the correct answer, I did know more than the National Service driving instructor back when I was 19, who insisted that a Series 1 could not be in 4WD when you pulled the ratio lever back into low ratio. It would not be in 4WD because the yellow knob popped up. After I drove the remaining convoy through the swamp after the first three had got bogged, he admitted I was right, those old girls could go a lot of places in Low Ratio 3rd, speed to torque ratio seemed to be ideal.
I do know that driving on steep slippery hills skinny tyres at pressure bite more and resist sliding sideways down into the gully, providing you keep a bit of power on.
I had never deliberately aired down in the past but in saying that would run Landcruiser tyre pressure lower on gravel, embedded rock roads so as to give a better ride.
Never to late to learn though, recently I went to drive out to a back corner in Jap import SWB, just got off the hard and thought, Uh Oh. wrong way, lost traction, the Wife gave me a barrel, why did you go that way and stalked off to get a tractor.
I could get some movement rocking, thought I should put into effect what I had read on this forum, dropped tyre pressure until the tyres were bagging out, drove out without any drama, turned round and drove back through where I had been bogged to get back on the hard.
Met the good wife out at the road after a 5k walk to get the tractor.
She is now even more convinced I am mad touring outback deserts for fun!
Not that I would admit she might be right!.
AnswerID: 346327

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