sandtire.htm
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Various notes about sand tires
FROM: g_buster@hotmail.com
SUBJECT: Re: tire width and sand
DATE: Mon, 01 Feb 1999 21:57:13 GMT
ORGANIZATION: Deja News - The Leader in Internet Discussion
NEWSGROUPS: rec.autos.4x4
Couldn't resist jumping in here....with my .02. Having spent many years
exploring the deserts of Arabia, we found the Michlin sand tires (marketed in
the MidEast and Africa) to be the best. Toyo, Yokohama, Goodyear,
Hankook, Firestone all make good sand tires for this market. All are
tall, and have a tread like an agricultural-flotation tire. In
particular, I liked the Michlin XS 11:00-16 the best on my Blazer.
It was 38" tall, steel-belted, and I aired down to 6 psi with it.
The others are all bias-nylon and typically 33-9:00x16, 6 or 8 ply.
The Yokohama's were 34-9:00x16. The only other 11x16 was made by
Goodyear in a 36-11:00x16, 8-ply bias, and was unavailable after the Gulf War.
There was an amazing 44-11:00x16 8-ply Nylon sand tire made by
Goodyear of England, which sold for about $800 each. 38s were all
I could slip under my K5. Steve, now in NC.
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FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: tire width and sand
DATE: Tue, 02 Feb 99 18:53:43 GMT
ORGANIZATION: A1 Internet news-server
NEWSGROUPS: rec.autos.4x4
In article <7957vm$k22$1@nnrp1.dejanews.com>, g_buster@hotmail.com wrote:
>Couldn't resist jumping in here....with my .02. Having spent many years
>exploring the deserts of Arabia, we found the Michlin sand tires (marketed
in
>the MidEast and Africa) to be the best. Toyo, Yokohama, Goodyear,
>Hankook, Firestone all make good sand tires for this market. All are
>tall, and have a tread like an agricultural-flotation tire. In
>particular, I liked the Michlin XS 11:00-16 the best on my Blazer.
>
>It was 38" tall, steel-belted, and I aired down to 6 psi with it.
>The others are all bias-nylon and typically 33-9:00x16, 6 or 8 ply.
>The Yokohama's were 34-9:00x16. The only other 11x16 was made by
>Goodyear in a 36-11:00x16, 8-ply bias, and was unavailable after the Gulf
War.
>There was an amazing 44-11:00x16 8-ply Nylon sand tire made by
>Goodyear of England, which sold for about $800 each. 38s were all
>I could slip under my K5. Steve, now in NC.
Thank you for this voice of rationality, proven in hostile environments,
instead of yuppie-driven beaches....;-))
Btw, the original poster was also located in Australia....you don't want to
have a very unusual tire size with you if you start travelling long
distances, since there is no chance of getting exotic replacements in a
bush town.
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: g_buster@hotmail.com
SUBJECT: Re: tire width and sand
DATE: Tue, 02 Feb 1999 16:37:48 GMT
ORGANIZATION: Deja News - The Leader in Internet Discussion
NEWSGROUPS: rec.autos.4x4
In article <796s1v$be5$13@news.a1.nl>,
w.j.markerink@a1.nl (Willem-Jan Markerink) wrote:
snip....
> you don't want to
> have a very unusual tire size with you if you start travelling long
> distances, since there is no chance of getting exotic replacements in a
> bush town. Bye,
> Willem-Jan Markerink
yes indeed...this matter is important. On long trips into the Empty Quarter,
we were 4 or 5 days drive from a track. Then possibly another
days drive to a bedoin area. Tire irons, hot patches, air compressor, were all
needed. The Michilin XS radial
was the toughest of the lot, with the Yokohama close behind. Ordinary
steel wheels are preferred because they can be hammered back into
shape in the bush. Steve now in NC
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FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: tire width and sand
DATE: Wed, 03 Feb 99 19:29:46 GMT
ORGANIZATION: A1 Internet news-server
NEWSGROUPS: rec.autos.4x4
In article <7979kq$b3a$1@nnrp1.dejanews.com>, g_buster@hotmail.com wrote:
>In article <796s1v$be5$13@news.a1.nl>,
> w.j.markerink@a1.nl (Willem-Jan Markerink) wrote:
>
>snip....
>> you don't want to
>> have a very unusual tire size with you if you start travelling long
>> distances, since there is no chance of getting exotic replacements in a
>> bush town. Bye,
>> Willem-Jan Markerink
>
>yes indeed...this matter is important. On long trips into the Empty
Quarter,
>we were 4 or 5 days drive from a track. Then possibly another
>days drive to a bedoin area. Tire irons, hot patches, air compressor, were
all
>needed. The Michilin XS radial
>was the toughest of the lot, with the Yokohama close behind. Ordinary
>steel wheels are preferred because they can be hammered back into
>shape in the bush. Steve now in NC
I have seen alloys crack with a flat tire, after being pushed over a hump
into a garage....8-))
Chasing another set of 16x8" OEM Toyota rims as we speak!....:-))
Lovely 8mm thick steel, not the crappy 5mm you get with Mangels....
FROM: "Randall J.Thomas"
SUBJECT: Re: tire width and sand
DATE: Mon, 01 Feb 1999 23:14:39 -0600
ORGANIZATION: Performance Unlimited 4-Wheel & Off Road Center
NEWSGROUPS: rec.autos.4x4
I run 22" wide x 33" and 35" tall paddles on the front and back of my '67
Bronco, and they are very easy to move along the sand, moreso than the taller
tires, however, the taller tires (38" hawg radials) do seem to be more 'sure
footed' with less slippage on the sand. Nearly every stock and modified dune
buggy runs the 15-20 wide models with similar ease as an all terrain. One
important note is the longer tire (acting like a cat track) doesn't 'build up'
a wider birm in front of the tire, and rolls over already 'compressed' ground,
if not spun. The wider tire has the ability to move and push against more earth
at one time, being a favorite choice in acceleration situations. Wider tires
seem to be a bit more difficulat to initially 'get going' than taller ones, with
longer tread contact patches
The longer the tread becomes on the ground increases surface area more than
going wider, due to the fact the increased length is already multiplying the
higher percentage rate of overall width already present.
10" wide, 6" long = 60 SqIn.
+ 1" wider (10x7) = 66 SqIn. +1" longer (11x6) = 70"
In fear of repeating this again, here are the comparisons between two of my
favorites used when at the dunes...
The paddles are awesome, throw sand in 100 foot roosters and all that, *but* the
extremely aired down Hawgs at 2.5 psi out shine the paddles in ridiculous
fashion. Why? The super wide paddles actually have less of a contact patch than
the 38" Radial Hawgs. The aired down paddles Contact Patch is 22" wide x 8" long
(176 square inches on the ground per tire). The awesome and super flexible hawgs
at 2.5 psi lengthen out to an amazing 28.7" long x 11.9" wide (341.53 Square
Inches). Nearly *twice* as much as the mean looking paddles... One would assume
the superwide paddles would kick behind, and they do in acceleration, but the
taller (and still somewhat wide, but narrower in comparison) Hawgs do very well
'just driving'.
--
Randall J.Thomas
President - A.A.T. Advanced Automotive Technologies Corporation
Owner - Performance Unlimited 4-Wheel & Off-Road Center
RETAIL STORE: 766 Grand Avenue, Hartford, WI 53027
CORPORATE OFFICES: 522 McKinley Avenue, Hartford, WI 53027
PHONE NUMBER: (414)673-4077 FAX (414-673-4077 (Auto server)
----------------------------------------------------------------------
E-Mail Address: perfman@nconnect.net
Performance Unlimited Off-Road Center Web Site
http://www.performanceunlimited.com
P.Y.T. Offroaders Association 4x4 Club Web Site
http://www.pyt.org
From: "Bragg, Ian"
To: "'80_series@sgiblab.sgi.com'" <80_series@sgiblab.sgi.com>
Subject: RE: [80] 33x9.50s on an OME suspension[CHAT]
Date sent: Sun, 13 Jun 1999 01:26:20 +0800
Send reply to: 80_series@sgiblab.sgi.com
Craig,
I don't know that narrow tyres are preferred. Certainly split rims (ie.
narrow rims) are more convenient if you're going to have multiple flats.
'All' government and Land Council (Aboriginal) vehicles have skinnies
because they buy DX's. Also, it's not all that long ago that skinnies were
in the majority on new vehicles. There is also the thought that it's city
based folk doing their "trip of a lifetime" on wornout wide rubber that
suffer the most punctures.
My experience is that tubed (split rims) tyres are more sensitive (self
destruct) to low pressure than tubeless tyres.
Ian B
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: what can/can't AWD do?
DATE: Sat, 09 Jun 01 14:05:49 GMT
NEWSGROUPS: rec.autos.4x4
In article ,
Erik <++kickinit@home.com> wrote:
>Holy SHIT!
>
>Unless sand is wholly different in the Sahara than in the US, narrow
>tires are the WORST tires imaginable for deep, loose sand.
Tall & narrow....not only narrow.
As in 'same contact patch'.
>Every observation I've made and every report, article, or book I've
>read that talks about driving on sand states that FLOTATION is the key
>to success.
A contact patch of 25cm wide x 50cm long gives the same floation as 50cm
wide x 25cm long, but the latter will have heaps more rolling resistance,
be it snow or sand (the only difference being that you don't air down in
snow if you can reach the hard surface underneath).
>A fat tire will float, due to it's large contact patch (NO MATTER ITS
>FUCKING SHAPE), whereas a skinny tire will SINK!
Shape is everthing....try rolling a military track crosswise, if it
technically could....it would dig itself in by sheer rolling resistance in
no time.
>Once you bury that skinny tire, you hit the chassis or suspension, and
>once you do that, your ride is OVER.
Amazing that so many folks return from the Sahara, isn't it?
>Please, this is senseless. You can't possibly justify your position.
>Your logic is inherently flawed. Stop it!!
I'll stop if no Sahara traveller with skinny tires returns.
FROM: Seth Dillon
SUBJECT: Re: what can/can't AWD do?
DATE: Sat, 09 Jun 2001 11:28:52 -0400
ORGANIZATION: MindSpring Enterprises
NEWSGROUPS: rec.autos.4x4
I think you guys are arguing apples and oranges here. While I have not
been to the sahara I did spend a bit of time in Saudia Arabia a few
years ago. In addition I have read many accounts of the LRDG and SAS.
Much of the area is not like your typical Hollywood portrayal with deep
rolling dunes of bottomless sand (Rat Patrol et al). It is flat dry
rocky barren ground. Some soft areas exist but these are usually
avoided. The Calenseco (excuse me if I misspelled it) sand sea has the
tall dunes which most of think of when we think of the desert but this
area was and as far as I know usually avoided by desert travelers. For
this type of terrain tall & skinny would be better.
As far as the beach goes, the more floation the better no matter how you
get it be it tall, wide, or tall and wide getting on top of the sand and
staying there is the name of the game.
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: what can/can't AWD do?
DATE: Sat, 09 Jun 01 17:12:56 GMT
NEWSGROUPS: rec.autos.4x4
In article <3B2240B4.19F8@mindspring.com>,
Seth Dillon wrote:
>I think you guys are arguing apples and oranges here. While I have not
>been to the sahara I did spend a bit of time in Saudia Arabia a few
>years ago. In addition I have read many accounts of the LRDG and SAS.
>Much of the area is not like your typical Hollywood portrayal with deep
>rolling dunes of bottomless sand (Rat Patrol et al). It is flat dry
>rocky barren ground. Some soft areas exist but these are usually
>avoided. The Calenseco (excuse me if I misspelled it) sand sea has the
>tall dunes which most of think of when we think of the desert but this
>area was and as far as I know usually avoided by desert travelers. For
>this type of terrain tall & skinny would be better.
If there were no vast differences between 'rally-raid/rock' type of tires
and dedicated sand tires, you could have a point.
But the most dedicated sand tires are pretty bad on sharp rocks, because
they are so damn soft and flexible (and that's also why they wear down like
an eraser-gum on hard pavement)
>As far as the beach goes, the more floation the better no matter how you
>get it be it tall, wide, or tall and wide getting on top of the sand and
>staying there is the name of the game.
Getting on top is much easier with a tall tire, just as it is much easier
for a tracked vehicle to climb on top of obstacles. While just a wider
track doesn't make that more easy....
Snakes and caterpillars move lengthwise too....;))
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: Seth Dillon
SUBJECT: Re: what can/can't AWD do?
DATE: Sat, 09 Jun 2001 23:38:27 -0400
ORGANIZATION: MindSpring Enterprises
NEWSGROUPS: rec.autos.4x4
Willem-Jan Markerink wrote:
>
> In article <3B2240B4.19F8@mindspring.com>,
> Seth Dillon wrote:
> >I think you guys are arguing apples and oranges here. While I have not
> >been to the sahara I did spend a bit of time in Saudia Arabia a few
> >years ago. In addition I have read many accounts of the LRDG and SAS.
> >Much of the area is not like your typical Hollywood portrayal with deep
> >rolling dunes of bottomless sand (Rat Patrol et al). It is flat dry
> >rocky barren ground. Some soft areas exist but these are usually
> >avoided. The Calenseco (excuse me if I misspelled it) sand sea has the
> >tall dunes which most of think of when we think of the desert but this
> >area was and as far as I know usually avoided by desert travelers. For
> >this type of terrain tall & skinny would be better.
>
> If there were no vast differences between 'rally-raid/rock' type of tires
> and dedicated sand tires, you could have a point.
> But the most dedicated sand tires are pretty bad on sharp rocks, because
> they are so damn soft and flexible (and that's also why they wear down like
> an eraser-gum on hard pavement)
>
> >As far as the beach goes, the more floation the better no matter how you
> >get it be it tall, wide, or tall and wide getting on top of the sand and
> >staying there is the name of the game.
>
> Getting on top is much easier with a tall tire, just as it is much easier
> for a tracked vehicle to climb on top of obstacles. While just a wider
> track doesn't make that more easy....
>
> Snakes and caterpillars move lengthwise too....;))
Ahh, but in the american desert a member of the rattlesnake family, the
sidewinder, moves....sideways.
I understand what you are trying to say, that in sand one must maximize
contact patch and I agree, to a point. Increasing height is indeed one
way to accomplish this however there is a point where due to vehicle
constraints you can only go so far, after that point the only way to
increase contact patch is by increasing width. For me 33" dia is the
maximum practical diameter I can fit on my Jeep. These tires are
available in either a 9.5" or a 12.5" width. If I follow your argument
correctly, you are stating that the 9.5" wide tire will perform better
in sand than the 12.5" tire, and with that I must disagree.
Of course there are many factors which contribute to performance of a
certain tire in sand. Among these are interior tread pattern, shoulder
pattern, sidewall flex, tread flex, rubber compound, etc. IMNSO I
believe that a radial carcassed, non steel belted, two ply sidewall tire
with a tread similiar to that of an aircraft tire with a very rounded
shoulder would be about the best design for a soft (beach) sand tire.
-Seth
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: what can/can't AWD do?
DATE: Sun, 10 Jun 01 12:08:09 GMT
NEWSGROUPS: rec.autos.4x4
In article <3B22EBB3.4631@mindspring.com>,
Seth Dillon wrote:
>Willem-Jan Markerink wrote:
>>
>> In article <3B2240B4.19F8@mindspring.com>,
>> Seth Dillon wrote:
>> >I think you guys are arguing apples and oranges here. While I have not
>> >been to the sahara I did spend a bit of time in Saudia Arabia a few
>> >years ago. In addition I have read many accounts of the LRDG and SAS.
>> >Much of the area is not like your typical Hollywood portrayal with deep
>> >rolling dunes of bottomless sand (Rat Patrol et al). It is flat dry
>> >rocky barren ground. Some soft areas exist but these are usually
>> >avoided. The Calenseco (excuse me if I misspelled it) sand sea has the
>> >tall dunes which most of think of when we think of the desert but this
>> >area was and as far as I know usually avoided by desert travelers. For
>> >this type of terrain tall & skinny would be better.
>>
>> If there were no vast differences between 'rally-raid/rock' type of
tires
>> and dedicated sand tires, you could have a point.
>> But the most dedicated sand tires are pretty bad on sharp rocks, because
>> they are so damn soft and flexible (and that's also why they wear down
like
>> an eraser-gum on hard pavement)
>>
>> >As far as the beach goes, the more floation the better no matter how
you
>> >get it be it tall, wide, or tall and wide getting on top of the sand
and
>> >staying there is the name of the game.
>>
>> Getting on top is much easier with a tall tire, just as it is much
easier
>> for a tracked vehicle to climb on top of obstacles. While just a wider
>> track doesn't make that more easy....
>>
>> Snakes and caterpillars move lengthwise too....;))
>
>Ahh, but in the american desert a member of the rattlesnake family, the
>sidewinder, moves....sideways.
>
>I understand what you are trying to say, that in sand one must maximize
>contact patch and I agree, to a point. Increasing height is indeed one
>way to accomplish this however there is a point where due to vehicle
>constraints you can only go so far, after that point the only way to
>increase contact patch is by increasing width. For me 33" dia is the
>maximum practical diameter I can fit on my Jeep. These tires are
>available in either a 9.5" or a 12.5" width. If I follow your argument
>correctly, you are stating that the 9.5" wide tire will perform better
>in sand than the 12.5" tire, and with that I must disagree.
If you are talking about BFG here, then you have a pretty nasty
size/construction in case of this 9.5"....for whatever reason, anyone who
uses that tire anything but a light Suzuki (read: Cruisers of 2 ton and
more) has cursed it for it's
The added problem of tall & wide is that you can often fit a taller tire,
or a wider tire, but not taller and wider (putting gearing aside for the
moment). Now add the US-market, which does not offer any decent
*narrow* size taller than 33" (effectively 32" for most!), and you've got
your choices severely limited.
Note that a 7.50x16 is effectively 31" tall, equal to most US 32" types.
8.25x16 is effectively 33", awfully close to most US 35" types....and above
that, there is not much thread-pattern choice in the US, serving sand and
mud crowd equally, while 9.00x16 and 11.00x16 is still supplied as a
dedicated sand tire by Michelin.
>Of course there are many factors which contribute to performance of a
>certain tire in sand. Among these are interior tread pattern, shoulder
>pattern, sidewall flex, tread flex, rubber compound, etc. IMNSO I
>believe that a radial carcassed, non steel belted, two ply sidewall tire
>with a tread similiar to that of an aircraft tire with a very rounded
>shoulder would be about the best design for a soft (beach) sand tire.
I believe one of the tricks is a set of ridges on the shoulder, that give
the tire an almost square shape at low pressure, while still protecting the
flank....or at least are optimized in the context of equal ground pressure
all around....
Plus indeed thread-flex, optimized for the same, as well as climbing on top
of that ridge of sand that forms in front of the tire.
Here is another thought: given the same low pressure, and the same height,
a narrow tire will deflate better than a wide tire (compare with
superwide F1 tires, who run very low pressures; the wider, the less
pressure you need). To get equal deflation in terms of length of contact
patch (which is directly related to rolling resistance and tracking
performance), you must deflate the wide tire more than the narrow tire,
which increases the danger of a bead popping.
While that might inconvenient in the typical USA-application, it's
downright deadly in the Sahara if it occurs too often.
And if sand tires were so easy to make, Michelin would never have succeeded
to ask an arm and a leg for these tires....8-))
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: Erik <++kickinit@home.com>
SUBJECT: Re: what can/can't AWD do?
DATE: Mon, 11 Jun 2001 00:51:26 GMT
ORGANIZATION: Excite@Home - The Leader in Broadband http://home.com/faster
NEWSGROUPS: rec.autos.4x4
>Tall & narrow....not only narrow.
>As in 'same contact patch'.
NO! With a tall AND WIDE tire, you get a much larger contact patch
than an equally tall, narrow tire. You can't argue this point.
>Shape is everthing....try rolling a military track crosswise, if it
>technically could....it would dig itself in by sheer rolling resistance in
>no time.
With this logic, you've breeched the bounds of the physics applied to
OUR situation. Of course you can't push a track sideways, but no TIRE
will ever assume the extreme shape of a sideways track. You're
analogy in non-applicable even though it makes sense.
Due to the inherent shape of 4x4 rim, no narrow (and yes tall) tire
can stretch itself out long enough to form a contact patch proprtional
to a snake's belly. Again, your snake analogy makes sense, but it's
non-applicable due to the physical limitations of our situation.
You can only fit so many tire sizes under a typical 4x4, and based on
these limitations, you have to choose which tire will work best in
sand.
What you need is surface area. What you need is super low pressure.
Did you know that the PSI within a tire actually equals the PSI
applied to the ground surface by that tire? Calculate it...
So, with a TALL and WIDE tire, you can run tire pressures as low as
5psi without much problem. This creates a huge contact patch, large
enough to float a 2.5 ton 4x4 on top of loose sand.
A tall narrow tire can't achieve this. Yes, maybe a tractor tire can,
but you can't fit 'em under a 4x4.
>Amazing that so many folks return from the Sahara, isn't it?
I suppose so. But I question if these folks are actually traversing
deep, loose sand or wether they're sticking to developed trails that
have only a thin veneer of loose sand. A tall tire would work better
in this situation because it'd sink through the loose stuff and grip
the hard stuff. But this is a TOTALLY DIFFERENT situation than
crossing loose sand several feet thick.
Every dune buggy should be equipped with motorcycle tires if you were
right.
>I'll stop if no Sahara traveller with skinny tires returns.
No, you'll stop when you realize you're going about this the wrong
way.
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: what can/can't AWD do?
DATE: Mon, 11 Jun 01 18:43:47 GMT
NEWSGROUPS: rec.autos.4x4
In article <9m38itkdbaai30r42g211anvtr709iaai0@4ax.com>,
Erik <++kickinit@home.com> wrote:
>
>>Tall & narrow....not only narrow.
>>As in 'same contact patch'.
>
>NO! With a tall AND WIDE tire, you get a much larger contact patch
>than an equally tall, narrow tire. You can't argue this point.
But also more rolling resistance....tall is pure gain physically speaking,
wide is a compromise.
>>Shape is everthing....try rolling a military track crosswise, if it
>>technically could....it would dig itself in by sheer rolling resistance
in
>>no time.
>
>With this logic, you've breeched the bounds of the physics applied to
>OUR situation. Of course you can't push a track sideways,
I didn't say push, I said roll, as if it could roll around its other axis
(it can't of course).
>but no TIRE
>will ever assume the extreme shape of a sideways track. You're
>analogy in non-applicable even though it makes sense.
Analogies that are 1:1 applicable are not analogies, but examples.
>Due to the inherent shape of 4x4 rim, no narrow (and yes tall) tire
>can stretch itself out long enough to form a contact patch proprtional
>to a snake's belly. Again, your snake analogy makes sense, but it's
>non-applicable due to the physical limitations of our situation.
The extreme ends of an analogy work very nicely to explain the limitations
on either end, and their interaction.
>You can only fit so many tire sizes under a typical 4x4, and based on
>these limitations, you have to choose which tire will work best in
>sand.
>
>What you need is surface area.
But given that surface area, physics indicates a preference for long/tall
instead of wide. If tall is at its limit, then wide is the next preference,
but it's not as pure gain as taller.
>What you need is super low pressure.
>Did you know that the PSI within a tire actually equals the PSI
>applied to the ground surface by that tire? Calculate it...
Well, yes and no....yes, of course it does, action is reaction....but no,
of course it can't, otherwise the center of the contact patch would have
the exact same pressure as the last mm that touches the
earth/road/sand....and of course that is a gliding scale, from max to 0.
One of my theories is that a long contact patch has a more equal pressure
distribution than a wide contact patch, *especially* at very low
pressures....at some point, the air pressure will be so low that the rubber
flank itself carries the vehicle, with much more pressure on the sides than
in the center....
>So, with a TALL and WIDE tire, you can run tire pressures as low as
>5psi without much problem. This creates a huge contact patch, large
>enough to float a 2.5 ton 4x4 on top of loose sand.
>
>A tall narrow tire can't achieve this. Yes, maybe a tractor tire can,
>but you can't fit 'em under a 4x4.
Btw tractor tires: I am currently pondering about the orientation of
directional tractor tires, those with the 'V' profile....should the point
of the V be directed forwards or backwards (measured at the contact patch).
Something tells me that the V pointed backwards will clear the voids more
easily of mud, but also digs easier, while the V pointed forward will
'cling' to the surface better.
Not sure though about dynamics & stability onroad, at higher speed,
accelerating and braking.
>>Amazing that so many folks return from the Sahara, isn't it?
>
>I suppose so. But I question if these folks are actually traversing
>deep, loose sand or wether they're sticking to developed trails that
>have only a thin veneer of loose sand.
There are no trails in area's where dunes are traveling in meters pro
week....8-))
>A tall tire would work better
>in this situation because it'd sink through the loose stuff and grip
>the hard stuff. But this is a TOTALLY DIFFERENT situation than
>crossing loose sand several feet thick.
Also consider that, while a tall tire sinks, it immediately starts
increasing its contact patch much better than a wide tire does, for the
same amount of 'sink'.
>Every dune buggy should be equipped with motorcycle tires if you were
>right.
Every dune buggy should be equipped with twin golf-cart tires if you were
right....;))
>>I'll stop if no Sahara traveller with skinny tires returns.
>
>No, you'll stop when you realize you're going about this the wrong
>way.
Those who wander are not necessarily lost....;))
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: Erik <++kickinit@home.com>
SUBJECT: Re: what can/can't AWD do?
DATE: Tue, 12 Jun 2001 02:14:26 GMT
ORGANIZATION: Excite@Home - The Leader in Broadband http://home.com/faster
NEWSGROUPS: rec.autos.4x4
On Mon, 11 Jun 01 18:43:47 GMT, w.j.markerink@a1.nl (Willem-Jan
Markerink) wrote:
>I didn't say push, I said roll, as if it could roll around its other axis
>(it can't of course).
Wait a second...
Yes, a sideways track would have more rolling resistance than a proper
one, but the magnitude of this resistance is negligible in almost any
situation concerning simple success in deep sand. The track would
still FLOATand provide traction. Whether it's facing the sand
squarely or not doesn't matter. It's CONTACT PATCH is what matters.
Sure, maybe you couldn't reach 40 mph with this track compared to a
proper one, but we're not interested in that situation.
>The extreme ends of an analogy work very nicely to explain the limitations
>on either end, and their interaction.
Of course you're right, but your mixing theory, which isn't altogether
valid, with practicality. We're not looking for the academic
ramblings of a self-righteous post-doc, but rather the no-nonsense
explanations of a seasoned veteran. I'm not a seasoned veteran, but I
play one on TV....
>But given that surface area, physics indicates a preference for long/tall
>instead of wide. If tall is at its limit, then wide is the next preference,
>but it's not as pure gain as taller.
YES! I think we're getting somewhere.
>Well, yes and no....yes, of course it does, action is reaction....but no,
>of course it can't, otherwise the center of the contact patch would have
>the exact same pressure as the last mm that touches the
>earth/road/sand....and of course that is a gliding scale, from max to 0.
Sorry, AVERAGE pressure. And I'm impressed... many people don't make
the connection between tire PSI and ground PSI.
>One of my theories is that a long contact patch has a more equal pressure
>distribution than a wide contact patch, *especially* at very low
>pressures....at some point, the air pressure will be so low that the rubber
>flank itself carries the vehicle, with much more pressure on the sides than
>in the center....
Makes sense, for a very tall tire compared to a short wide one. But
wouldn't that tall tire be even better if it was wide too?
>Also consider that, while a tall tire sinks, it immediately starts
>increasing its contact patch much better than a wide tire does, for the
>same amount of 'sink'.
Okay... but now that sunk tire has incredible "rolling resistence" to
overcome. It has to trench its way through the sand to continue. And
that won't happen. A narrow tire isn't better in sand. It is
elsewhere, like on snow, but not sand.
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: what can/can't AWD do?
DATE: Tue, 12 Jun 01 19:02:02 GMT
NEWSGROUPS: rec.autos.4x4
In article <4iuaitc3mqgdpkkil2d68ghje36ujs5rt0@4ax.com>,
Erik <++kickinit@home.com> wrote:
>On Mon, 11 Jun 01 18:43:47 GMT, w.j.markerink@a1.nl (Willem-Jan
>Markerink) wrote:
>
>>I didn't say push, I said roll, as if it could roll around its other axis
>>(it can't of course).
>
>Wait a second...
>Yes, a sideways track would have more rolling resistance than a proper
>one, but the magnitude of this resistance is negligible in almost any
>situation concerning simple success in deep sand. The track would
>still FLOATand provide traction. Whether it's facing the sand
>squarely or not doesn't matter. It's CONTACT PATCH is what matters.
>Sure, maybe you couldn't reach 40 mph with this track compared to a
>proper one, but we're not interested in that situation.
The key factor of difference is the radius with which it rolls through the
sand....perhaps you need an even more extreme example: a pencil of infinite
length, but very small diameter....contact patch is equal, rolling
resistance (or: eagerness to dig in) isn't.
>>The extreme ends of an analogy work very nicely to explain the
limitations
>>on either end, and their interaction.
>
>Of course you're right, but your mixing theory, which isn't altogether
>valid, with practicality. We're not looking for the academic
>ramblings of a self-righteous post-doc, but rather the no-nonsense
>explanations of a seasoned veteran. I'm not a seasoned veteran, but I
>play one on TV....
>
>>But given that surface area, physics indicates a preference for long/tall
>>instead of wide. If tall is at its limit, then wide is the next
preference,
>>but it's not as pure gain as taller.
>
>YES! I think we're getting somewhere.
>
>>Well, yes and no....yes, of course it does, action is reaction....but no,
>>of course it can't, otherwise the center of the contact patch would have
>>the exact same pressure as the last mm that touches the
>>earth/road/sand....and of course that is a gliding scale, from max to 0.
>
>Sorry, AVERAGE pressure. And I'm impressed... many people don't make
>the connection between tire PSI and ground PSI.
See the related F1-example I used in one of my previous postings....they
run on relatively low pressures....;))
>>One of my theories is that a long contact patch has a more equal pressure
>>distribution than a wide contact patch, *especially* at very low
>>pressures....at some point, the air pressure will be so low that the
rubber
>>flank itself carries the vehicle, with much more pressure on the sides
than
>>in the center....
>
>Makes sense, for a very tall tire compared to a short wide one. But
>wouldn't that tall tire be even better if it was wide too?
But can you predict it's 'digging' eagerness, with uneven pressure
distribution left/center/right, vs uneven distribution
front/center/right?....;))
Many many moons ago, I read an article about the dynamics of a tire rolling
through sand....I believe it pointed out a higher pressure at front and
rear of the contact patch, lower pressure in the center, with the optimum
at a given ratio, at a given pressure, more than just being equal (at
probably a higher pressure).
Add to this the fact that a track once driven on, and backed up on, becomes
more solid, because the sand clings together (doesn't work on all types of
sand I believe) and on which the tires won't dig in as easily the next time
(which is also the reason one should back up exactly as one drove into the
obstacle/tough spot)....now extrapolate that to the 'micro' concept, within
a contact patch....higher pressure up front, lower one follows, finished by
higher pressure....with the sand inbetween not able to 'get out' (all this
is totally reverse to a high pressure contact patch, with the maximum in
the center, lower at both front and rear....
>>Also consider that, while a tall tire sinks, it immediately starts
>>increasing its contact patch much better than a wide tire does, for the
>>same amount of 'sink'.
>
>Okay... but now that sunk tire has incredible "rolling resistence" to
>overcome.
But a wide tire has more of that....;))
>It has to trench its way through the sand to continue.
Not much different than a tracked vehicle sinking in....but much different
than a tracked vehicle sinking in with the imaginary other rolling
axis....or even the pencil-analogy, if you want it more extreme.
> And
>that won't happen. A narrow tire isn't better in sand. It is
>elsewhere, like on snow, but not sand.
Don't make the mistake to compare full pressure (snow) with low
pressure....quite a difference in digging behaviour....;))
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: "Mike Locke"
SUBJECT: Re: Tire inflation decided by chalk?
DATE: Fri, 3 Aug 2001 08:46:37 -0700
ORGANIZATION: http://extra.newsguy.com
NEWSGROUPS: rec.autos.4x4
Maximum Frog wrote in message
news:Uuv97.95$sm4.9592@nntp.csufresno.edu...
> My door sticker says to run 35 psi in all tires on my '95 Bronc..I've been
> doing this for about a year, checking tires at every fillup..and I notice
> clean, slightly smooth spots on the outside and inside of the tread,
> indicating underinflated tires.
>
> The stock tires were 265/75/r15 and the ones now are 31"..I dont really
know
> what sort of difference this is but is it enough to run higher PSI, and
how
> do I figure out what is proper?
>
> Someone said something about chalk on the wheel? ..but never finished.
Tire inflation pressure (for a fixed loading) is primarily a function of the
width of the tire and any contouring that the tire mfg may have put on the
tread rubber. It is a very weak function of the tire diameter, so that any
reasonable change of that dimension will have essentially no influence on
the correct tire inflation pressure.
Correct tire inflation pressures vary with operating speeds also. Depending
on the weight of the tread area of the tire, the spinning of the tire at
high speeds (70mph+) will distort the tire the similar to overinflation
(above 100MPH, most tires will expand enough to throw the speedometer
noticeably off). OTOH, at high speeds higher inflation pressures are needed
to prevent tire overheating. If your tires are designed such that they must
be overinflated to not overheat at your usual 80MPH driving speed, then you
cannot possibly get uniform tread wear. Likewise if the tire is designed
such that they run properly at 80MPH (with uniform tread wear), but you do
all your driving in town with a lower inflation pressure, then you will not
be able to get uniform tread wear.
--
S'later, Mike Locke lockem@scrserv.com
FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Tire inflation decided by chalk?
DATE: Fri, 03 Aug 01 19:44:42 GMT
NEWSGROUPS: rec.autos.4x4
In article <9kegac0j7l@enews3.newsguy.com>,
"Mike Locke" wrote:
>
>Tire inflation pressure (for a fixed loading) is primarily a function of
the
>width of the tire and any contouring that the tire mfg may have put on the
>tread rubber. It is a very weak function of the tire diameter, so that
any
>reasonable change of that dimension will have essentially no influence on
>the correct tire inflation pressure.
Hmmm....maybe this is also one of the physical arguments why a tall/narrow
tire can perform better in sand than a low/wide tire, given the same
contact patch.
Since a wide tire must start of with a lower pressure than a narrow one
(regardless of height, within limits), a narrow tire can be aired down
further in an absolute sense, while not getting into bead-risking low
pressures as a wide tire would, given the same relative pressure drop.
This same relative pressure drop (with absolute limits) also shows that the
argument 'but a tall *and* wide tire is even better!' also has it's
limits....it's not without compromise either, in this context....to expand
the footprint length-wise (in favor of tracking stability) you *want* to
air down, even if the footprint of that tall+wide tire was already better
than either narrow/tall or wide/low....
My apologies for causing cracking brains on the other side....:))
>Correct tire inflation pressures vary with operating speeds also.
Depending
>on the weight of the tread area of the tire, the spinning of the tire at
>high speeds (70mph+) will distort the tire the similar to overinflation
>(above 100MPH, most tires will expand enough to throw the speedometer
>noticeably off).
I recently saw a note about high-speed/power (street) motorbike tires,
which are claimed to have slip up to 6%....
Your speedo note suggests an error in the other direction though....:))
> OTOH, at high speeds higher inflation pressures are needed
>to prevent tire overheating. If your tires are designed such that they
must
>be overinflated to not overheat at your usual 80MPH driving speed, then
you
>cannot possibly get uniform tread wear. Likewise if the tire is designed
>such that they run properly at 80MPH (with uniform tread wear), but you do
>all your driving in town with a lower inflation pressure, then you will
not
>be able to get uniform tread wear.
Note that there are also pressure-tests based on heat/pressure-build
up....I vaguely recall something like 4psi....once a tire pressure
increases more than this between cold/idle and warm/highspeed, you need
more pressure.
OTOH, there are not many people who will even think of running for example
a BFG at 80psi, not even with this argument....:))
--
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
[note: 'a-one' & 'en-el'!]
FROM: "Mike Locke"
SUBJECT: Re: Tire inflation decided by chalk?
DATE: Wed, 8 Aug 2001 23:51:42 -0700
ORGANIZATION: http://extra.newsguy.com
NEWSGROUPS: rec.autos.4x4
Willem-Jan Markerink wrote in message
news:9keuro$48pvb$1@ID-34205.news.dfncis.de...
> In article <9kegac0j7l@enews3.newsguy.com>,
> "Mike Locke" wrote:
> >
> >Correct tire inflation pressures vary with operating speeds also.
> Depending
> >on the weight of the tread area of the tire, the spinning of the tire at
> >high speeds (70mph+) will distort the tire the similar to overinflation
> >(above 100MPH, most tires will expand enough to throw the speedometer
> >noticeably off).
>
> I recently saw a note about high-speed/power (street) motorbike tires,
> which are claimed to have slip up to 6%....
> Your speedo note suggests an error in the other direction though....:))
Rounded motorcycle or bicycle tires are not comparable to flat tread
automotive/truck tires. One extremely peculiar characteristic of a round
profile tire that is significantly narrower than the overall wheel diameter
is that the contact patch size *and shape* is almost completely independent
of the tire width. This is very counter-intuitive, but it is derived from
physics and stands up to actual measurements. Of course, wide tires usually
have lower inflation pressures, creating a limit on the range of the
comparisons, since the contact patch dimensions are strongly affected by the
inflation pressure.
My 1964 Jag E-type owner's manual comes with a "speed correction table" of
factors for wheel expansion. I'm sure it is not accurate for modern tires,
but at 100+ MPH it is a significant factor. Dragster tires increase in
diameter obviously and visibly as the machine accelerates.
>
> > OTOH, at high speeds higher inflation pressures are needed
> >to prevent tire overheating. If your tires are designed such that they
> must
> >be overinflated to not overheat at your usual 80MPH driving speed, then
> you
> >cannot possibly get uniform tread wear. Likewise if the tire is designed
> >such that they run properly at 80MPH (with uniform tread wear), but you
do
> >all your driving in town with a lower inflation pressure, then you will
> not
> >be able to get uniform tread wear.
>
> Note that there are also pressure-tests based on heat/pressure-build
> up....I vaguely recall something like 4psi....once a tire pressure
> increases more than this between cold/idle and warm/highspeed, you need
> more pressure.
> OTOH, there are not many people who will even think of running for example
> a BFG at 80psi, not even with this argument....:))
I regularly run 90psi in my Bridgestones and that's not very close to the
115psi max. My rims limit the pressure to 95psi.
--
S'later, Mike Locke
2000 Dodge/Cummins 2500 Q-cab 4x4 6spd long bed
245 70R19.5 (G) wheels
From: Michael (sgone@snowy.com)
Subject: Re: 9.00x16 tyres on a Defender
View this article only
Newsgroups: alt.fan.landrover
Date: 2000/04/18
On Sun, 16 Apr 2000 09:45:15 +0100, John wrote:
>It looks as though you do not really know why you are doing this! Just
>for looks?? You have large diameter tyres for ground clearance and
>gearing, wide tyres for floatation. You do not say why you are looking
>at them.
>
>Also they put a lot more strain on the axles and gearbox, personally
>if you are going to use them heavily, uprated half shafts and 4 pin
>diffs are needed.
>
>john 110 on 35/12.5/15, Salisbury axles both ends
>
Hmmm.. thanks for your input, John, but actually, I *do* know exactly
*why* I am opting for taller tyres. I just don't know what I need to
do to my vehicle to fit them!
I agree with your comments on the transmission strain (I mentioned
that snag in my original post), and yes, I intend uprating the diffs
and half-shafts. I am also aware of the problems with handling, the
extra unsprung mass, and the increased purchase price...
But larger diameter tyres:
* offer much better flotation (see footnote).
* Wear out more slowly (other things being equal)
* Offer better ground clearance
* Dissipate heat more effectively
* Travel over uneven ground more easily (don't snag on obstacles)
* Build up less of a "front" of sand or mud as you drive - this is a
real problem for wide tyres.
Regards,
Michael...
Footnote:
Actually all tyres, no matter how wide, narrow, big or small diameter,
offer almost the same contact area on a flat road, at any given
pressure!
A weight of 500kg (5000 newtons of downward force) on a tyre at 100kPa
(1 Bar) will spread the tyre over an area of 0.002 square metres (if I
have my arithmetic right). It doesn't matter what dimensions the tyre
starts with, it will distort until there is sufficient ground
supporting it.
The advantage of bigger tyres (wider OR taller), is that they can be
run at lower pressures. The increased distortion (leading to a bigger
"footprint") takes place over a bigger area, and therefore doesn't
damage the tyre.
Of course the picture changes somewhat if a tyre digs into soft
ground. Under these circumstances a large diameter tyre will have a
clear advantage over a small tyre, no matter how wide the small tyre
is. The small tyre has a very steep "hill" to climb to get out of the
hole, compared to the large tyre.
Hope this was of interest to someone!
http://www.d-90.com/faq/Tire/TireSize.html
From: Alan E. Foster[SMTP:alan.foster@vt.edu]
Sent: Tuesday, February 15, 2000 7:23 PM
Subject: [D90] michelin XZLs
I spoke with a customer service rep from Michelin today ... fairly informative. The short of it is:
The XZL is for sale in the USA (apparently the XL is not) ... therefore, distributors can get them.
I'm still waiting to hear back from the local dist. to see what their prices are, but here are the
order numbers she cited me (since most tire shops have never heard of this tire):
8.25x16 = 46526
9.00x16 = 99806
I'm interested to see what kinds of prices you guys might get around the country (anyone else wanna
make some phone calls to the local tire shop?), just to see what the avg. asking price is ... I
didn't mean to steal this one out from under SG, but if I can save a bunch of cash on a potentially
cool tire (still want something ~34x9.50x16 ... interco needs to make a radial, darn it!)
-Alan
http://www.d-90.com/faq/Tire/TireSize.html
From: Clarke Williams[SMTP:clarkewilliams@halcyon.com]
Sent: Thursday, August 24, 2000 4:48 PM
Subject: RE: [D90] Michelin XZL Tires and cooling
Chris,
The XL (old XCL) is a multi-purpose directional tread tire designed mostly for rock and mud. The XL
(aka XCL) also works well on pavement (lowest rolling resistance of ANY tire manufactured -- M.I.T.
won a solar-powered car distance contest using these tires), if aired up to moderately high
pressures (45 psig or so).
The XML is a purpose-built mud tire. Very deep treads. Non-directional.
XZL is designed as a multi-purpose non-directional tire for rock, mud, and sand. It replaces the
older XS sand tire and supercedes the XL tires, too. The XL tires are continuing in production but
I expect will be phased out in a few years. They continue because the XL/XCL is a standard military
tire for something like 40 countries as well as NATO.
The XS was considered for years to be the best sand tire available for desert crossings. Testing by
Michelin in the Sahara and Saudi deserts showed that the XZL actually had better sand performance,
in large part because of reduced rolling resistance (narrower section). This testing was conducted
in the late 1980's. Thus the XS tires were discontinued.
The rubber compound of all X-series tires is fairly hard. The XZL and XL tires have decent snow and
rain performance only if kept aired up. The XML tires have superb mud traction but the very deep
lugs are somewhat fragile in rocks. All of the X-series tires have very large lugs and clean
themselves of mud quickly.
XL tires, although directional, will work adequately in reverse rotation so one could, conceivably,
get away with a single spare. I always carried two spares when I was running XCLs. In two sets of
6 tires I had a single tire failure and that was a faulty carcass (bubbles in sidewall that I
stupidly ignored).
Clarke
From: "Tom Gill"
To:
Subject: sand tyers
Date: Fri, 19 Aug 2005 09:44:52 +0930
From my experience with a lot of off road driving with work, split rim type
tyres, narrow and tall, perform best in super soft sand. In really soft
sand, the tires will sink in regardless of their footprint or deflation.
Narrower tires need less power to push through the soft sand (think of
ploughing you hand through sand versus one finger). Also the taller tire
means that when the sand firms up, it is easier for the tire to crawl out of
the rutt as the exit angle is slacker.
http://forum.buschtaxi.org/viewtopic.php?t=19144
xxxxxxxxxxxxxxxxxxxxxxxxx
Timo
Verfasst am: So Jun 29, 2008 13:58 Antworten mit Zitat Report Post
Anmeldungsdatum: 08.06.2001 Beiträge: 1510 Wohnort: Trier
Liebe Freunde des niedrigen Luftdrucks!
Vor einigen Tagen habe ich bei ebay die OffRoad 10/1988 ersteigert (wegen FJ62 Test) und in dem
schon damals von OffRoad veröffentlichten Reifen-Journal ein kleines Schmankerl entdeckt:
Leider ist es ja, jedenfalls soweit ich das mitbekommen habe, auf keinem bisherigen btt dazu
gekommen, die Reifenaufstandsfläche bei verschiedenen Luftdrücken zu messen.
Nun, in diesem besagten Heft ist ein kleines Bildchen, auf dem die Reifenaufstandsfläche eines
Michelin XSF bei verschieden Drücken abgebildet ist:
4,0 bar = 645 cm2
??? bar = 1250 cm2
??? bar = 1677 cm2
0.4 bar = 2320 cm2
Leider fehlt die Angabe zur Reifengröße (7.50R16?) und die Angabe des Luftdrucks bei den 2
mittleren Werten... Dennoch ganz interessant, wie ich finde.
PS: den BFG AT gab es 1988 auch in 255/85R16...
_________________
ABSOLUT. LC HJ60 - when in doubt, floor it !
&
LC 78 - der RAMBLER - when you're ready to get serious !
If you have any question, remark, comment, want to share some
philosophy or just want to express your opinion about these pages,
feel free to send email to:
w.j.markerink @ a1.nl
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