Why is smaller better

Sorry Troll 81 your father is right, the wider the footprint the better the tyre "floats" over the sand as the load is spread over a wider area. The skinny tyres (sometimes called chees cutters) have a small footprint and thus the load per square centimetre/foot is greater so places a greater force on the sand and hence more prone to sinking into the sand and leads to greater force required to drive. Keep the skinny tyres for mud.

"The width of the tyre has no relationship to the contact area with the sand or road."
" Now for a skinny tyre to flatten to such an area requires much more bending of the tyre than a wide one (this causes heat and an increase in pressure - this is the reason that race cars use fat tyres - to keep the heat down)."

"skinny are better."

Tim I do not know how much sand driving you do but around Beachport/Robe we have plenty of sand and if you are crazy enough to go go into the dunes with skinny tyres then expect to make your vehicle work harder as when you stop the footprint created will be smaller and as previously explained there will be a greater tendency to sink into the sand. As for racing cars using wider tyres to keep heat down I think in my opinion you need to pay closer attention to the commentators on car racing broadcasts in that the cars need heat in the tyres to make the tyres sticky as they use a totally different compound and these cars often start with as low as 10psi in the tyres because they do heat up from the flexing of the side walls.

I have tried skinny tyres and wide tyres in sand and I would definitely use the wider tyres in sand at all times in preference to skinny tyres.

TROLL

The theories go either way, however letting your tyres down is all about increasing the track of the the tyre in other words it has nothing to do with the width. In super soft sand it is alot harder for a motor to rotate a large or wide tyre as opposed to a thinner tyre. For example talk to the rangers on Fraser island, one had a hilux that he ran fats on but his cruiser (company car) had skinnys. The hilux he said was always struggling, changed the tyres over that is put skinnys 23575R16 on the hilux, it was then unstoppable easy to drive and better fuel economy. Traction means everything with tyres, good traction means your 4wd is going forward. The army still uses skinny tyres for their rovers, they also have placards that state what tyre pressure to run in sand mud etc. I remember our old rovers always went better and drove alott easier with skinnys rather than fats. We run 23585R16 on the cruiser td 100 series and they work a treat. I have never seen someone driving in sand with skinnys and low tyre pressure bogged.

Thanks for the responses so far and it looks like skinny is better then for Sand and Beach work

Quite a perplexing subject this one... Everyone seems to have either a theory or an experience which leads them one way or the other... Myself, I have only had beach experience with two vehicles, my Triton and my old Rocky... With both vehicles, I had a second set of wheels wearing 31/10.5-15's... In both instances, IMO, they both performed better on the wider tyres. Both engines ran cooler in the soft stuff on wider tyres which leads me to believe that the wider tyres were easier to push around in the sand. For the record, I was running 12psi on both vehicles and in both sets of tyres.

Hi guys just my 2 bobs worth ive been going to Fraser and Double Island for 30 years, driving 4x4 for 25 up the beach when you had to make your own tracks when nothing was boarded for easier driving. in my experience it what you feel comfortable driving on I run skinny tyres for years on landcriuser Ute and even a couple of trips with tyres that had 12 ply walls that where nearly bald and have never been bogged I still have the old girl. I just bought a 100 series cruiser wagon and it has the large Bridgestone’s on it and used it to tow a camper trailer up to Double Island this year. my thoughts are that tyre pressure and engine speed is more important than size my advice is if you go sand driving try to go with someone experienced and listen to their advice you will learn more in one lesson than going a dozen times on your own .every time I go I am still learning .one thing on the 100 series take the spare off and put it in the back as it acts like a plough in the soft sand dags

Maybe one of those monthly 4X4 magazines could arrange a test?

Yes a wide tyre is no better on sand that a narrower tyre (of the same diameter). Its the length of the footprint that is paramount, not the width. This is what you are doing when letting your tyres down, lengthening the footprint. So a larger diameter tyre is the go for sand - doesn’t matter much about the width (but as some have pointed out you maybe worse off the wider you go as you are creating more work)- it has been an old wives tale (sorry ladies) for generations that wide tyres are better on sand - probably because it seems to make sense but in reality it not true. The dead giveaway is that even people with “fat” tyres still need to let their tyres down on sand…so where is the advantage? Simple - there is none.

My theory….
Drive forces are front to rear so this is where you need to get the contact area happening – ie you need to create a long enough contact area so that the sand to which the drive forces are being applied does not slip on itself, thereby causing you to stop. Length is required so that the frictional forces of the sand are combined in the direction to which the force is being applied. The “threshold” contact area (which will vary for weight of car and sand conditions) required is easily reached (in most normal circumstances) by letting your tyres down, even with your standard, what some call “skinny”, tyres.

I notice some people state – “but I put on wider tyres and they were better” – maybe they were but it wasn’t because they were wider – keep in mind a tyre has a number of characteristics – width is only one of them….why are you assuming it’s the width that is giving the advantage on sand? Maybe the wide tyre was a slightly larger diameter, maybe it flattens more front to rear that the older tyre you had?

There are advantages and disadvantages of replacing your standard tyres with something a bit wider but don’t do it expecting it to be better in sand just because they are wider. You maybe disappointed.
Cheers
Greg
Sandgroper

Have a look in last months 4x4 monthly magazine and they have done a test using ink on the tread pattern then rolling accross paper at different pressures quit interesting. Also did testing on sand (beaches etc) Regards Steve M

Geeezzz, lots of theories arn't there ! Ok, here is mine and it works.

The ideal footprint is like a catterpilar or, if you like the tracks on a bulldozer - long and thin. Wide tyres push loose sand in front like a snowplow and create far to much drag. So the best tyres are thin but with a long footprint. Best way to get a long footprint is to use the highest tyre that you can so it's rolling footprint is as long as possible. Go have a look at any photos, videos etc. of the type of wheels that the early pioneer dessert travelers used - tall and narrow. The wheels on some of Tom Kruze's trucks appear to be over waist high and look at the conditions that he got through before he even had 4wd ! Wide tyres are great for distributing load but you do not want that big wave of loose sand in front of them sucking away your horsepower. Some trucks have so much spare horsepower that they can use wide tyres and getaway with it. If you don't have mega hp avaiable then go for the higest tyres you can.

Its not all about covering the ground.

Skinnys work because they have a longer footprint , so the build up of sand in front of the tyre is less , therefore doesn't take as much power to push through it.

Not a huge problem for modern vehicles.

It was for older vehicles.

The old 800cc Zuk my Dad had was unstopable on the beach the skinny tyres , it wouldn't move when larger tyres were fitted.

This discussion has produced many thoughts and opinions on what is best and reference has been made to 2358516r tyres, these would not be classed as thin, thin would be 175. The first figure I understand represents the width so 235's I do not class as thin. The other reference to elongating the footprint seems misplaced. Have a look at your tyre when it is flat, which way does the tyre get bigger on the ground, across the width (vehicle sideways) or length (front to back) by the greatest amount? My understanding is that the sidewalls are softer construction to allow flexing whilst the actual tread area is firmer so any reference to tyre footprint/area not being related to tyre width does not appear correct.

In theory a round object eg tyre sitting on a flat surface will have a certain contact area that relates to the width of the tyre so a tyre 175mm wide will have an area of 175 x 10mm = 1,750sqmm( using a fixed 10mm front to back contact length) whilst a tyre 235mm wide will have 235 x 10 = 2,350 sqmm contact.

This issue of fitting a larger diameter tyre to the vehicle is not possible in most instances. How do you fit a 17inch diameter wheel under a vehicle that is factory fitted 15inch wheel arch. You don not without some major modifications, so to increase the footprint you made the tyre wider (from 175 to 235).

As with all discussions on this forum there is always going to be a difference of opinion and to each their own, so if you beleive skinny tyres are the go so be it, I know what my vehicle can and cannot do and I will stick with what I know until there is factual data to prove me wrong.

Cheers

Watching the recent Dakar Rally, I noticed the Mitsubishis & Touregs were running comparatively narrow tyres (compared to say a 31x10.5). Now some of the sand situations they were in was VERY soft- even heaps softer to the drifts on Stockton and Fraser.
I think the techos associated with those teams would have a fair idea!!

Smaller is way better, just ask my wife, she alway's tell's me, "It's not the size that count's, it's the way you use it"...

Here's a link which explains how tyre pressures work.

Tyre pressures

Tim
Maybe you do not understand
You are entitled to your opinion regarding skinny tyre perference over wide on sand but if you look at the link to the landrover site then you may be able to picture where the tyre width comes into the picture. Picture this, two tubes, same diameter but one is 100mm long and one is 50mm long, which one makes a larger impression when you push them both onto a soft surface, the 50mm long one or the 100mmm long one? This is the footprint/area. If you say the 50mm long one then you keep driving the skinny 175 tyres in soft sand with no solid base and see how deep the tyre sinks into the sand, in mud you want to get deeper to reach the firm base and to get traction.

Your "facts" have not proved a thing to support the arguement for skinny tyres at the same pressure as opposed to wide tyres at the same pressure on sand.

We will appear to remain with a difference of opinion regardless of the arguements. Cheers to you and enjoy the experience.

Good post on the age old question.
Having lived in Saudi for 2 years and seen many combinations i would like to add 2 cents worth.
1 Dedicated sand tyres are sold in Saudi and elsewhere. They are like an aircraft tyre. They have no tread except for a number of longitudenal lines, and they are V shaped, so that when fully inflated only about one inch contacts the road.
The theory is that the shape minimizes the frontal area, and the longitudinal (lateral? circumfrential?) lines stop the sand from moving out towards the sides.
Friends report these are the ducks guts on sand but diabolical on road.
They are quite high in profoile maybe over 100% , and are balloon tyres which are quite wide at their widest point say 10 ins on a narrow rim. One of friends got them on a Patrol but we had rain one day in Riyadh and they were totally undrivable, so he swapped them..
2 The next best were Michelin Saharas. Obvious usage from the name. These had a round profile with rounded tread blocks, like an AT but everything is round. They are still sold mainly in truck sizes I believe. They are still pretty bad on road.
They are usally in narrow sizes like 205R16.
Personally I used 205R16 Continental HT tyres on 6 inch riims on my Range Rover in the Sahara with good results.
I think there are several elements that make a good sand tyre ..
1 Fine tread with deep water grooves
2 Round shoulders
3 Flexible sidewalls. the 15 inch widies usually have very much thinner sidewalls Than LT 16 inch tyres, and in the US and elsewhere are called amazingly enough "Floatation tyres"
4 also the tyre width vs the rim width is important. Generally I noticed a tyre on the narrowist sensible rim was best as it allowed the sidewalls to bulge better.

So there is no one answer but a good compromise is a HT with round shoulders and deep rain grooves. Narrow is probably better but its more the relationships above that matter.
Wide 15 inch tyres may be good DESPITE their width not because of it, because of other factors such as rounded shoulders,flexible sidewalls that are intrinsic in the floataion design and a wide tyre vs the rim size..
NOW I will get flames from those with muddies that glide over sand.
BUT I have been there and done that in the Sahara, which makes Big Red look like a Molehill. What a disappointment it was!
regards Philip A

Our 'entertainment' on Fraser is to sit on the patio of an afternoon and watch the vehicles get 'bogged' as they come up from the beach into Happy Valley. It appears to be of little consequence what size, make or model or what tyre pressures or types of tyres less than 20% get through without some sort of problems. Even some of the Kingfiser 4 x 4 tour buses with their BIG oversize singles have two or three goes when it has been very dry. My mate with his Hilux on skinnys (and years of experience) and me in my Pajero with wide tyres (265x70x16) have no trouble at all and we are using that track up to six times a day. I use 4wd at all times once I leave Rainbow Beach but the Hilux does it frequently in 2wd. (He doesn't want to wear out the front diff!!!)
What we have noticed is that some drivers will race in at speed but in top gear and then have to 'grab' for a downstick when only partway through. That loss of momentum brings on the grief. Much better to go in fairly hard in 2nd and have the constant power up the sleeve. I grew up on the Darling Downs so black soil and mud are more my scene but watching the locals can be beneficial. When in Rome!!!

Kevin J

Thanks for all the input guys.....was a good read

Greetings Earthlings, (dags666 your spot on)
Just to add more fuel to the fire, the father in law has been going to Fraser for over 30 yrs in an old landrover 2A, on skinny nearly bald tyre and has never been bogged once. He actually used to drive around the guys who were bogged and have a good chuckle to himself. We are about to inherit this old girl and we wont change the tyres.
It's not all about tyre/tyre pressures, although that is a big part. Common sense and willingness to listen to those who have been there and done it will also go a long way. :)

Spak

All you people that have ideas about a tyre getting wider when you reduce pressure had better get out to your vehicle and take a ruler and some chalk.

Put the side of the ruller up against the tread of the tyre where it touches the ground and chalk a line out on the pavement at rt angles to the vehicle. Make a chalk mark in the front and at the rear of the tyre. Measure the distance between the chalk marks. Note also that any bulging of the side wall does NOT touch the ground - it is a bulge only !!

Now reduce the tyre pressure and do it all again.
1. The fore and aft 'footprint will be a lot longer
2. The side wall bulge will be bigger but it will still NOT TOUCH THE GROUND !

Next, make a chalk on the side wall down to the ground and mark the ground as well. Roll the truck forward one revolution of the wheel and mark the ground where the chalk mark on the side wall almost touches the ground.
Measure and record the distance between the chalk marks on the ground.

Now do it all again at a different tyre pressure and report back here.

Untill you have done this or already know that the answer to the original question is NARROW tyres are best in sand you need not make any more comments as you are only repeating what a friend of a friend has told you. Wide tyres only work well when you have mega amounts of spare horsepower available to overcome the snowplowing effect of wide tyres.

Sand is not always the worst problem either. Gravel beaches consisting of almost round stones about 5 mm dia are far worse then fine sand beaches. Even the slightest wheel spin will have you sitting on the chassis rails in seconds. Very low speed without throwing any material out from behind the wheels is the only way to make progress.

Get read - so many theories, so little time !

I don't think anyone has mentioned the most important fact. Big 4wds look "better" with wider tyres.

They just look odd with skinny pizza cutters !!

Even my RAV looks the part with wider tyres (and goes pretty good in the sand with wider tyres as well)

RD

Some key principles being missed here. The air in a tyre at no matter what pressure is designed to keep the general shape of the tyre and comfort of the ride. The pressure (PSI) is a measurement of the exertion of pressure against a known area CONTAINED within that tyre and is irrelevant to mass of vehicle through tyre onto land surface - take your tyre off and measure PSI then put it back on the vehicle and measure - very minor change only caused from part of the tyre being lessened (compressed) in size by the mass of the vehicle. Pressure in tyre does not equate to pressure on road - A tyre with 50 psi in it exerts the same pressure/weight downwards as the same tyre with 15 psi it except for the weight/volume of air between the two pressure differences - which is minimal.

Now - tyres dont need air in them (be a bad ride but...) - but a solid tyre with load bearing area on a road of a set width/length exerts so much force to the ground (depending on mass it is supporting) per given area and wider longer bearing area (like when tyre deflated) exerts less for the same given area and mass. This is why whether fat or skinny tyres when you let them down you are increasing the load bearing area with the same fixed vehicle mass - end result better floatation as less force downward per given area.

Re comment above about sidewalls not touching - have a look out the window next time in soft sand - the sidewalls do touch the sand surface, giving load bearing capability and greater surface area in touch with road/sand (as well as more friction - hence motor power being required to overcome that portion of overall resistance), but in most cases the "overall" gain is bigger than the extra resistance, and why most vehicles perform better with tyres deflated.

Now it has become obvious why your tag is Troll, you have created a post for today that has had the most views, responses and posts and yet there is still no definitive answer just a lot of conjecture from all sorts.

End result, know your vehicle, its limitations and enjoy the off road driving whether it be toyota, ford, nissan, mitsu or lady Niva.

Ah! A great debate. Love it.
Just 2 points.
1. I am happy that skinny tyres (say 7inch) are better than 10 or 11 inch tyres in sand.

2. But most of us have on set of tyres, which are a compromise to meet our various driving needs. My tyres are 265mm (about 10.5 inches ) wide. I don't and won't change them when I go to Fraser. So I have to adjust my tyre pressure and driving style to get the best out of them.

So while it is a good theoretical debate. In practice, few of us do a lot of sand driving (compared to the amount of black top driving). We have the tyres we have. so the variables available are in other things, rather than tyre size.

Good discussion all the same.

I've been doing a few formula calculations and came to this conclusion. If you've got the background then it may make sense.

tp=h1/2DIVIDED BY 100XacPisquared-circum>235,159*AB+iced coffee

The conclusion - WHO GIVES!!!!!!

P.s. I like beer

D-Jack

D-JACK,You should have posted that on Friday(phunny).