Tyre pressures for wet mud

I spent yesterday afternoon on a cave rescue in a field in the middle of the
White Peak. It got progressively wetter as the afternoon wore on and as it
went dark, just as we were packing up, it started to **** down.

At the cave entrance, about a quarter mile across a sheep-grazed field, we
had a variety of vehicles - the police had a couple of Rav 4's, and a 4 x 4
Merc. Sprinter van, the fire service had a 110, the police surgeon had a
RangeRover Sport, DCRO had their (2WD) Iveco rescue van, I had my 90 and the
DCRO first responders had a Subaru estate. Apart from the Michelin X tyres on
my 90 and a set of MT's on the Fire Service 110, everyone else was on road
tyres.

Getting out of the field turned into a right mudbath. Even the farmer's
tractor was having problems by the time we got the last vehicle off the
field. The field was actually pretty flat, but just a few very gentle dips
and hummocks was enough to completely strand most of the vehicles once the
surface had been broken.

I only got stuck once and for a very short period, while attempting to get to
the Rangerover to pull it out. Oh for a winch! Three men pushing for 20 feet
was enough though.

Last night, I completely forgot that one way of increasing traction would
have been to let the tyres on the vehicles down. Stupid, really, but there it
is. I don't have a compressor on the 90 (yet!) but both DCRO and the Fire
service carry bottled air, so re-inflating should not have been too much of
an issue.

So, to the questions:

How much difference does letting the tyres down make under these
circumstances? Does it really work, or is this just an old wive's tale?

Would it help with both road tyres and things with hunkier tread, or is it a
waste of time on road tyres?

What sort of minimum pressure is advisable?

Can one get away with it on tubeless tyres, or should one only try this on
tubes?

What else does one need to know about this technique?

We have a team de-brief on Wednesday night. It would be quite nice to have a
few ideas before then - any comments welcome.

Nick.

Nick Williams <[email protected]> uttered summat worrerz
funny about:
> I spent yesterday afternoon on a cave rescue in a field in the middle
> of the White Peak. It got progressively wetter as the afternoon wore
> on and as it went dark, just as we were packing up, it started to
> **** down.
>
> At the cave entrance, about a quarter mile across a sheep-grazed
> field, we had a variety of vehicles - the police had a couple of Rav
> 4's, and a 4 x 4 Merc. Sprinter van, the fire service had a 110, the
> police surgeon had a RangeRover Sport, DCRO had their (2WD) Iveco
> rescue van, I had my 90 and the DCRO first responders had a Subaru
> estate. Apart from the Michelin X tyres on my 90 and a set of MT's on
> the Fire Service 110, everyone else was on road tyres.
>
> Getting out of the field turned into a right mudbath. Even the
> farmer's tractor was having problems by the time we got the last
> vehicle off the field. The field was actually pretty flat, but just a
> few very gentle dips and hummocks was enough to completely strand
> most of the vehicles once the surface had been broken.
>
> I only got stuck once and for a very short period, while attempting
> to get to the Rangerover to pull it out. Oh for a winch! Three men
> pushing for 20 feet was enough though.
>
> Last night, I completely forgot that one way of increasing traction
> would have been to let the tyres on the vehicles down. Stupid,
> really, but there it is. I don't have a compressor on the 90 (yet!)
> but both DCRO and the Fire service carry bottled air, so re-inflating
> should not have been too much of an issue.
>
> So, to the questions:
>
> How much difference does letting the tyres down make under these
> circumstances? Does it really work, or is this just an old wive's
> tale?
>
> Would it help with both road tyres and things with hunkier tread, or
> is it a waste of time on road tyres?
>
> What sort of minimum pressure is advisable?
>
> Can one get away with it on tubeless tyres, or should one only try
> this on tubes?
>
> What else does one need to know about this technique?
>
> We have a team de-brief on Wednesday night. It would be quite nice to
> have a few ideas before then - any comments welcome.
>
> Nick.

It would give you a wider footprint which may or may not add to your
problems dependant upon the type of surface.

On some ground you ideally want to cut through the top slop to reach the
harder surface below for which narrow tyres will be better and also offer
less resistance to forwards motion. However it you have no firm lower
surface as it sounds here then you may gain the edge having lower pressures
to give a wider footprint to prevent cutting into the surface and bogging
down to the axles.

I'd think if Farmer giles tractor with no doubt heavy aggricultural tyres on
was having problems then in your cirs it may have made little difference.

This is one of those questions that you could give to 20 different people in
a sound proof booth and they all come out with differing answers none of
which will be wrong but all of which will be opinion.

Having bottled air is fine but have they the correct valves? Worth checking
before deflating.

Depending on the distance from the road / firm ground then consider multiple
long tow ropes, shackles and leaving one of the vehicles closer to the dry
area as a contingency. Especially if it starts to pee down. Who ever is in
command of the RVP needs to build this in to the plan I'd say. Being on a
big flat surface which is slightly undulating is often worse than good old
hills which despite offering different problems tend to drain well to
somewhere or other... though if your in the hole ;-)

Also consider having enough waffle boards to build a temporary road for the
largest vehicles, drive forward to end... pick up ones at back place in
front... drive forwards , pick up ones at back etc etc. May look like a
circus act / reinactment of stone henge in the making but if it save someone
putting there back out it's worth it.

Lee

--
www.lrproject.com
Reaching the parts other Landrover restorers can't reach - JLo makes new
home in the USA.
Percy IIa - two Engines to the mile, awaits a new chassis.
Morph - He's "living the dream".

On 2006-03-26, Nick Williams <[email protected]> wrote:

> Last night, I completely forgot that one way of increasing traction would
> have been to let the tyres on the vehicles down. Stupid, really, but there it
> is. I don't have a compressor on the 90 (yet!) but both DCRO and the Fire
> service carry bottled air, so re-inflating should not have been too much of
> an issue.

I've seen the technique mentioned in a few off-roading books, also
used on modded trucks with fat tyres for off-roading nuts in snowy
countries. Also some trucks, the Humvee (proper one) have tyre
inflation and deflation devices built in so the tyres can be deflated
and re-inflated to gain traction. Never needed to try it myself yet
but I reckon it's worth a crack. On the fat-tyred snow trucks the
tyres were tubeless but apparently you can go to lower pressures with
tubes as the bead can slip on the lower pressures which would break
the seal with tubeless. Bear in mind that letting your tyres down
reduces ground clearance.

One technique I have tried, picked up from this very boutique, is
driving with the brakes on. The idea is to even up the resistance
across the axles to stop one wheel soaking up all the power by
spinning, I've used it to reverse out of a stuck situation where I
couldn't move at all, and to get out of a cross-axle situation. Keep
the revs up with one foot and with the other, either bosh up and down
on the brake quickly as if you were cadence braking, or try pushing
down on the brake slowly, keeping the revs up. I found the former
easier than the latter.

--
Blast off and strike the evil Bydo empire!

In message <[email protected]>
Nick Williams <[email protected]> wrote:

> I spent yesterday afternoon on a cave rescue in a field in the middle of the
> White Peak. It got progressively wetter as the afternoon wore on and as it
> went dark, just as we were packing up, it started to **** down.
>
> At the cave entrance, about a quarter mile across a sheep-grazed field, we
> had a variety of vehicles - the police had a couple of Rav 4's, and a 4 x 4
> Merc. Sprinter van, the fire service had a 110, the police surgeon had a
> RangeRover Sport, DCRO had their (2WD) Iveco rescue van, I had my 90 and the
> DCRO first responders had a Subaru estate. Apart from the Michelin X tyres on
> my 90 and a set of MT's on the Fire Service 110, everyone else was on road
> tyres.
>
> Getting out of the field turned into a right mudbath. Even the farmer's
> tractor was having problems by the time we got the last vehicle off the
> field. The field was actually pretty flat, but just a few very gentle dips
> and hummocks was enough to completely strand most of the vehicles once the
> surface had been broken.
>
> I only got stuck once and for a very short period, while attempting to get to
> the Rangerover to pull it out. Oh for a winch! Three men pushing for 20 feet
> was enough though.
>
> Last night, I completely forgot that one way of increasing traction would
> have been to let the tyres on the vehicles down. Stupid, really, but there it
> is. I don't have a compressor on the 90 (yet!) but both DCRO and the Fire
> service carry bottled air, so re-inflating should not have been too much of
> an issue.
>
> So, to the questions:
>
> How much difference does letting the tyres down make under these
> circumstances? Does it really work, or is this just an old wive's tale?
>
> Would it help with both road tyres and things with hunkier tread, or is it a
> waste of time on road tyres?
>
> What sort of minimum pressure is advisable?
>
> Can one get away with it on tubeless tyres, or should one only try this on
> tubes?
>
> What else does one need to know about this technique?
>
> We have a team de-brief on Wednesday night. It would be quite nice to have a
> few ideas before then - any comments welcome.
>
> Nick.
>

Always an embarassing one that! Flat field, water and no go.....

Lowering the tyre pressure would help if the ground was all soft,
but knowing the area you were in I'd venture that it was clay-ish
soil on rock with a nice coating of Peak Park Special greasy grass,
in which case lowering tyre pressures won't make a lot of odds.

This is one case where tyre choice can make a significant difference,
something with a failry open block tread like Pirelli's are very
effective, or if damaging the surface is not an issue then Michellin
OR's are good as they are very good at removing the surface (without
truning into slicks) and gripping on the sub-surface.

Alxe diff locks are the best solution in these circumstances, but
for a once-in-not-very-often senario thats' probably over-kill.
You can use a little pressure on the brake pedal to make a
"temporary" axle diff lock, but it doesn't always work on that
sort of surface.

If you have sufficient people on hand to push then thats the
easiest (if embarrassing) solution - winches are all well and
good but, in these circumstances, a lot of faffing about compared
to a couple of minutes cringing.

Just my 2p

Richard

--
www.beamends-lrspares.co.uk [email protected]
Running a business in a Microsoft free environment - it can be done
Powered by Risc-OS - you won't get a virus from us!!
Boycott the Yorkshire Dales - No Play, No Pay

It usually helps. FYI the minimum pressure for ARC CCV trials is 12psi,
from memory. Anything much lower and you run the risk of the tyre and
tube slipping on the rim, which neatly cuts the valve off which gives
you 0 psi!

Gordon

On Mon, 27 Mar 2006 09:54:44 +0100, beamendsltd wrote
(in article <aaac11e4e%[email protected]>):


>
> Always an embarassing one that! Flat field, water and no go.....
>
> Lowering the tyre pressure would help if the ground was all soft,
> but knowing the area you were in I'd venture that it was clay-ish
> soil on rock with a nice coating of Peak Park Special greasy grass,
> in which case lowering tyre pressures won't make a lot of odds.
>
> This is one case where tyre choice can make a significant difference,
> something with a failry open block tread like Pirelli's are very
> effective, or if damaging the surface is not an issue then Michellin
> OR's are good as they are very good at removing the surface (without
> truning into slicks) and gripping on the sub-surface.
>
> Alxe diff locks are the best solution in these circumstances, but
> for a once-in-not-very-often senario thats' probably over-kill.
> You can use a little pressure on the brake pedal to make a
> "temporary" axle diff lock, but it doesn't always work on that
> sort of surface.
>
> If you have sufficient people on hand to push then thats the
> easiest (if embarrassing) solution - winches are all well and
> good but, in these circumstances, a lot of faffing about compared
> to a couple of minutes cringing.

Amen to that - I've long been a proponent of the theory that these things are
often better managed with lots of manpower and some common sense rather than
a more technological solution!

Thanks Richard, useful comments (and the rest of you, as well!)

Someone from Australia (thanks Ron) has sent me an e-mail response which
refers to 'Stuan deflators' which I presume are a handy widget which lets the
air out to a pre-determined pressure. Are these available in the UK, and if
so how much and where?

Nick.

"Nick Williams" <[email protected]> wrote in message
news:[email protected]...
> I spent yesterday afternoon on a cave rescue in a field in the middle of
the
> White Peak. It got progressively wetter as the afternoon wore on and as it
> went dark, just as we were packing up, it started to **** down.
>
> At the cave entrance, about a quarter mile across a sheep-grazed field, we
> had a variety of vehicles - the police had a couple of Rav 4's, and a 4 x
4
> Merc. Sprinter van, the fire service had a 110, the police surgeon had a
> RangeRover Sport, DCRO had their (2WD) Iveco rescue van, I had my 90 and
the
> DCRO first responders had a Subaru estate. Apart from the Michelin X tyres
on
> my 90 and a set of MT's on the Fire Service 110, everyone else was on road
> tyres.
>
> Getting out of the field turned into a right mudbath. Even the farmer's
> tractor was having problems by the time we got the last vehicle off the
> field. The field was actually pretty flat, but just a few very gentle dips
> and hummocks was enough to completely strand most of the vehicles once the
> surface had been broken.
>
> I only got stuck once and for a very short period, while attempting to get
to
> the Rangerover to pull it out. Oh for a winch! Three men pushing for 20
feet
> was enough though.
>
> Last night, I completely forgot that one way of increasing traction would
> have been to let the tyres on the vehicles down. Stupid, really, but there
it
> is. I don't have a compressor on the 90 (yet!) but both DCRO and the Fire
> service carry bottled air, so re-inflating should not have been too much
of
> an issue.
>
> So, to the questions:
>
> How much difference does letting the tyres down make under these
> circumstances? Does it really work, or is this just an old wive's tale?
>
> Would it help with both road tyres and things with hunkier tread, or is it
a
> waste of time on road tyres?
>
> What sort of minimum pressure is advisable?
>
> Can one get away with it on tubeless tyres, or should one only try this on
> tubes?
>
> What else does one need to know about this technique?
>
> We have a team de-brief on Wednesday night. It would be quite nice to have
a
> few ideas before then - any comments welcome.
>
> Nick.
>

In my experience of being bogged far too often for my own good,
dropping tyre pressures dont do squiddly dit. In mud the tyre
tread pattern is the major factor, does the mud drop out of the
tread as you move forward? Road tyres dont do that, they just
fill up with mud and slide all over the place. Dropping tyre pressure
only increases the likelyhood of the tread retaining the mud, it
also reduces the approach angle of the tyre over the surface which
makes it harder for the tyre to keep on top and rolling forward.

In fact I'd say that in most situations dropping tyre pressures is
a waste of time and effort, even on sand where the larger the
diameter (to reduce approach angle) of the tyre is far more
important than the spread of the tyre by a couple of mm.

On 2006-03-27, Nick Williams <[email protected]> wrote:

> Someone from Australia (thanks Ron) has sent me an e-mail response which
> refers to 'Stuan deflators' which I presume are a handy widget which lets the
> air out to a pre-determined pressure. Are these available in the UK, and if
> so how much and where?

Quick google search for "Staun Deflator UK" will give you links.
Their main website is at http://www.staunproducts.com/ and you can
order from them.

--
Blast off and strike the evil Bydo empire!

On 2006-03-27, Roger <[email protected]> wrote:

> Dropping tyre pressure only increases the likelyhood of the tread
> retaining the mud,

Alternatively, it makes the tyre flex at more acute angles at the
point at which the tyre leaves contact with the ground, so helping it
get rid of mud.

> it also reduces the approach angle of the tyre
> over the surface which makes it harder for the tyre to keep on top
> and rolling forward.

Alternatively, it allows the tyre to "step" over the edge of an
obstacle, particularly useful when rock crawling which is why rock
crawlers use low pressures, as well as those who drive in the desert
and on beaches, snow, mud etc.

> In fact I'd say that in most situations dropping tyre pressures is
> a waste of time and effort, even on sand where the larger the
> diameter (to reduce approach angle) of the tyre is far more
> important than the spread of the tyre by a couple of mm.

Alternatively, the tyre becomes concave not convex so doesn't push the
sand away but compacts it underneath, and the reduction in pressure
increases the footprint of the tyre by a very significant amount as
it's both wider by a few centimetres when flat, and the contact point
is longer by a few centimetres too. A larger diameter tyre has a
larger contact footprint than a smaller diameter tyre, unless you let
the smaller tyre down.

So either one of us is talking out of our hats, or you've not been
letting your tyres down enough ;-)

--
Blast off and strike the evil Bydo empire!

Roger wrote:

>
> "Nick Williams" <[email protected]> wrote in message
> news:[email protected]...
>> I spent yesterday afternoon on a cave rescue in a field in the middle of
> the
>> White Peak. It got progressively wetter as the afternoon wore on and as
>> it went dark, just as we were packing up, it started to **** down.
>>
>> At the cave entrance, about a quarter mile across a sheep-grazed field,
>> we had a variety of vehicles - the police had a couple of Rav 4's, and a
>> 4 x
> 4
>> Merc. Sprinter van, the fire service had a 110, the police surgeon had a
>> RangeRover Sport, DCRO had their (2WD) Iveco rescue van, I had my 90 and
> the
>> DCRO first responders had a Subaru estate. Apart from the Michelin X
>> tyres
> on
>> my 90 and a set of MT's on the Fire Service 110, everyone else was on
>> road tyres.
>>
>> Getting out of the field turned into a right mudbath. Even the farmer's
>> tractor was having problems by the time we got the last vehicle off the
>> field. The field was actually pretty flat, but just a few very gentle
>> dips and hummocks was enough to completely strand most of the vehicles
>> once the surface had been broken.
>>
>> I only got stuck once and for a very short period, while attempting to
>> get
> to
>> the Rangerover to pull it out. Oh for a winch! Three men pushing for 20
> feet
>> was enough though.
>>
>> Last night, I completely forgot that one way of increasing traction would
>> have been to let the tyres on the vehicles down. Stupid, really, but
>> there
> it
>> is. I don't have a compressor on the 90 (yet!) but both DCRO and the Fire
>> service carry bottled air, so re-inflating should not have been too much
> of
>> an issue.
>>
>> So, to the questions:
>>
>> How much difference does letting the tyres down make under these
>> circumstances? Does it really work, or is this just an old wive's tale?
>>
>> Would it help with both road tyres and things with hunkier tread, or is
>> it
> a
>> waste of time on road tyres?
>>
>> What sort of minimum pressure is advisable?
>>
>> Can one get away with it on tubeless tyres, or should one only try this
>> on tubes?
>>
>> What else does one need to know about this technique?
>>
>> We have a team de-brief on Wednesday night. It would be quite nice to
>> have
> a
>> few ideas before then - any comments welcome.
>>
>> Nick.
>>
>
> In my experience of being bogged far too often for my own good,
> dropping tyre pressures dont do squiddly dit. In mud the tyre
> tread pattern is the major factor, does the mud drop out of the
> tread as you move forward? Road tyres dont do that, they just
> fill up with mud and slide all over the place. Dropping tyre pressure
> only increases the likelyhood of the tread retaining the mud, it
> also reduces the approach angle of the tyre over the surface which
> makes it harder for the tyre to keep on top and rolling forward.
>
> In fact I'd say that in most situations dropping tyre pressures is
> a waste of time and effort, even on sand where the larger the
> diameter (to reduce approach angle) of the tyre is far more
> important than the spread of the tyre by a couple of mm.

I have relatively little experience of mud, but I would be inclined to agree
with you, although where dropping the pressure makes the difference between
going over the top and digging in it will work, and I have experienced
this.

But I do have about two years of full time desert work, and I can assure you
that in sand tyre pressure is by far the most important factor, more
important than tyre size or type or tread type or even 2wd or 4wd. And
pressures have to be well down - 12-15psi tops.
JD

In message <[email protected]>, Ian Rawlings
<[email protected]> writes
>On 2006-03-27, Roger <[email protected]> wrote:
>
>> Dropping tyre pressure only increases the likelyhood of the tread
>> retaining the mud,
>
>Alternatively, it makes the tyre flex at more acute angles at the
>point at which the tyre leaves contact with the ground, so helping it
>get rid of mud.
>
>> it also reduces the approach angle of the tyre
>> over the surface which makes it harder for the tyre to keep on top
>> and rolling forward.
>
>Alternatively, it allows the tyre to "step" over the edge of an
>obstacle, particularly useful when rock crawling which is why rock
>crawlers use low pressures, as well as those who drive in the desert
>and on beaches, snow, mud etc.
>
>> In fact I'd say that in most situations dropping tyre pressures is
>> a waste of time and effort, even on sand where the larger the
>> diameter (to reduce approach angle) of the tyre is far more
>> important than the spread of the tyre by a couple of mm.
>
>Alternatively, the tyre becomes concave not convex so doesn't push the
>sand away but compacts it underneath, and the reduction in pressure
>increases the footprint of the tyre by a very significant amount as
>it's both wider by a few centimetres when flat, and the contact point
>is longer by a few centimetres too. A larger diameter tyre has a
>larger contact footprint than a smaller diameter tyre, unless you let
>the smaller tyre down.
>
>So either one of us is talking out of our hats, or you've not been
>letting your tyres down enough ;-)
>
Or both of you.

Sand, rocks, snow irrelevant in this discussion as the OP was concerned
solely with trying to get of a fairly flat very wet grassy, quickly
becoming muddy field.

The big problem as has been identified is that road tyre treads fill up
with mud and become like slicks. In fields usually the further down you
go the harder it gets, unless you have failed to look ahead and driven
into a bog, so narrower tyres will probably do better than wider ones.

Top gear did a test awhile back with various 4x4s as supplied from the
showroom. Of course the shiny ones came along with road tyres and were
useless, whereas a Series LR with nice knobbly 750x16s won hands down.

The lesson for the OP's team is simple - if your work requires you to
go off the tarmac then make sure you are properly equipped.
--
hugh
Reply to address is valid at the time of posting

On or around 27 Mar 2006 00:06:12 -0800, "gordon" <[email protected]>
enlightened us thusly:

>It usually helps. FYI the minimum pressure for ARC CCV trials is 12psi,
>from memory. Anything much lower and you run the risk of the tyre and
>tube slipping on the rim, which neatly cuts the valve off which gives
>you 0 psi!

bearing in mind that on newer vehicles the tyres are just as likely to be
tubeless, which can get unseated with the same effect.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Once, when the secrets of science were the jealously guarded property of
a small priesthood, the common man had no hope of mastering their arcane
complexities. Years of study in musty classrooms were prerequisite to
obtaining even a dim, incoherent knowledge of science.
Today, all that has changed: a dim, incoherent knowledge of science is
available to anyone. - Tom Weller, Science Made Stupid, 1986

On or around Sun, 26 Mar 2006 21:30:23 +0100, Nick Williams
<[email protected]> enlightened us thusly:

>Getting out of the field turned into a right mudbath. Even the farmer's
>tractor was having problems by the time we got the last vehicle off the
>field. The field was actually pretty flat, but just a few very gentle dips
>and hummocks was enough to completely strand most of the vehicles once the
>surface had been broken.

Had this once at Margam park watching the rally. many cars all parked in
field, during the stage, mucho ****ingdownrain, later all cars stuck in
field. Amused by one bloke in a ford ranger pickup trying to tow something
like a fiesta and getting stuck himself.

After a bit of amusement and a bit of pushing of other things and so forth,
I got into the 4x4 sierra with fast road-pattern tyres, and drove straight
across and out the gate, almost took out a bystander when the front wheels
suddenly gripped and proved to be at an angle to the direction of travel
mind.

How? viscous couplings in the rear and centre diffs. It's unbelievably
good on slippery stuff. Obviously, as an off-roader it'd be hopeless, with
ground clearance of about 4" and not much suspension travel at all. But on
flat slippery (or even steep slippery, such as icy roads) I've not found
much to beat it.

And the good news is that the bloke in the garage has almost finished the
work on it for the MOT, so it'll be on the road again soon. Bugger, forgot
to phone the insurance idiots. Bloody Firebond. They've been told, at
least 4 times, that the motor has been off the road, not in use, and as such
has no MOT, that it's being repaired and MOTed and when that's done I shall
tell them the MOT number and the MOT mileage figure as requested, and take
the 6 photos they want to prove the condition for the agreed value bit. I
can't take the bloody pictures when it's not here, FFS!

But that doesn't stop them sending letters about every 2 days wanting to
know where the rest of the info and pictures are.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Once, when the secrets of science were the jealously guarded property of
a small priesthood, the common man had no hope of mastering their arcane
complexities. Years of study in musty classrooms were prerequisite to
obtaining even a dim, incoherent knowledge of science.
Today, all that has changed: a dim, incoherent knowledge of science is
available to anyone. - Tom Weller, Science Made Stupid, 1986

On or around Mon, 27 Mar 2006 22:17:25 +1100, JD <[email protected]>
enlightened us thusly:

>Roger wrote:
>
>>
>> In fact I'd say that in most situations dropping tyre pressures is
>> a waste of time and effort, even on sand where the larger the
>> diameter (to reduce approach angle) of the tyre is far more
>> important than the spread of the tyre by a couple of mm.

The trials boys wouldn't agree - they typically go as low as about 8psi and
get a lot more grip on some surfaces. Mind, they also have bolts or screws
in the rim to secure the tyre on the bead, quite often.

Lowering pressure, in the OP's circumstance, would almost certainly have
made sod-all difference unless the mud was both deep and soft. On hard
stony slippery terrain it make some difference and on very soft going it
gives you a bit more flotation effect.

But you do have to let a lot of air out.

>I have relatively little experience of mud, but I would be inclined to agree
>with you, although where dropping the pressure makes the difference between
>going over the top and digging in it will work, and I have experienced
>this.
>
>But I do have about two years of full time desert work, and I can assure you
>that in sand tyre pressure is by far the most important factor, more
>important than tyre size or type or tread type or even 2wd or 4wd. And
>pressures have to be well down - 12-15psi tops.
>JD

--
Austin Shackles. www.ddol-las.net my opinions are just that
"Festina Lente" (Hasten slowly) Suetonius (c.70-c.140) Augustus, 25

On 2006-03-27, hugh <hugh@[127.0.0.1]> wrote:

> Or both of you.

Yeah I know, don't worry, I've done enough off-roading to know that
there's so many variables that hard-and-fast rules don't tend to
exist, pretty much the same as the rest of life: it's all shades of
gray, not black and white.

--
Blast off and strike the evil Bydo empire!

Austin Shackles wrote:
> On or around Sun, 26 Mar 2006 21:30:23 +0100, Nick Williams
> <[email protected]> enlightened us thusly:
>
>> Getting out of the field turned into a right mudbath. Even the
>> farmer's tractor was having problems by the time we got the last
>> vehicle off the field. The field was actually pretty flat, but just
>> a few very gentle dips and hummocks was enough to completely strand
>> most of the vehicles once the surface had been broken.
>
> Had this once at Margam park watching the rally. many cars all
> parked in field, during the stage, mucho ****ingdownrain, later all
> cars stuck in field. Amused by one bloke in a ford ranger pickup
> trying to tow something like a fiesta and getting stuck himself.
>
> After a bit of amusement and a bit of pushing of other things and so
> forth, I got into the 4x4 sierra with fast road-pattern tyres, and
> drove straight across and out the gate, almost took out a bystander
> when the front wheels suddenly gripped and proved to be at an angle
> to the direction of travel mind.
>
> How? viscous couplings in the rear and centre diffs. It's
> unbelievably good on slippery stuff. Obviously, as an off-roader
> it'd be hopeless, with ground clearance of about 4" and not much
> suspension travel at all. But on flat slippery (or even steep
> slippery, such as icy roads) I've not found much to beat it.
>
> And the good news is that the bloke in the garage has almost finished
> the work on it for the MOT, so it'll be on the road again soon.
> Bugger, forgot to phone the insurance idiots. Bloody Firebond.
> They've been told, at least 4 times, that the motor has been off the
> road, not in use, and as such has no MOT, that it's being repaired
> and MOTed and when that's done I shall tell them the MOT number and
> the MOT mileage figure as requested, and take the 6 photos they want
> to prove the condition for the agreed value bit. I can't take the
> bloody pictures when it's not here, FFS!
>
> But that doesn't stop them sending letters about every 2 days wanting
> to know where the rest of the info and pictures are.

And there was I thinking it was only Adrian Fux who got their knickers all twisted
and did that sort of thing!
--
"He who says it cannot be done is advised not to interrupt her doing
it."

If at first you don't succeed,
maybe skydiving's not for you!

On or around Mon, 27 Mar 2006 19:15:43 GMT, "GbH"
<[email protected]> enlightened us thusly:

>Austin Shackles wrote:
[Firebond]
>
>And there was I thinking it was only Adrian Fux who got their knickers all twisted
>and did that sort of thing!

I expect they're all reselling the same policy
--
Austin Shackles. www.ddol-las.net my opinions are just that
Appearances: You don't really need make-up. Celebrate your authentic
face by frightening people in the street.
from the Little Book of Complete B***ocks by Alistair Beaton.

On Mon, 27 Mar 2006 20:53:36 +0100, Austin Shackles
<[email protected]> wrote:

>On or around Mon, 27 Mar 2006 19:15:43 GMT, "GbH"
><[email protected]> enlightened us thusly:
>
>>Austin Shackles wrote:
>[Firebond]
>>
>>And there was I thinking it was only Adrian Fux who got their knickers all twisted
>>and did that sort of thing!
>
>I expect they're all reselling the same policy

Yep, Sureterm cancelled the policy on my S2, despite me telling them
that I'd need a feckin long lens and x-ray vision to photograph the
damned thing. Got cross and went to firebond.

They did exactly the same!

--
Tim Hobbs