Wheel nut torque to wide versus thin tyres

[RRT]

www.aulro.com/afvb/l319-discovery-3-and-4-a/263845-i-bought-torque-wrench-6.html (http://www.aulro.com/afvb/l319-discovery-3-and-4-a/263845-i-bought-torque-wrench-6.html)

This picture and explanation (from here: Dynamics - Pressure (http://www.batesville.k12.in.us/physics/phynet/mechanics/newton2/Pressure.html)) using knives is pretty good for pressure / force relationship.


https://farm1.staticflickr.com/929/28856563147_a406d15064.jpg (https://flic.kr/p/KXXqSP)

David


Was looking up wheel nut torque and whether my ryobi 18v rattle is a worthwhile investment - too powerful at 160Nm it seems ahaa ahhha ha

But in the discussion is something many have alluded to re the choice of tyres, thin give more pressure to terra firma this would seem to prove. Therefore I would surmise to cut through loose surfaces down to the base rock so to speak and gain greater traction the thins win!!! Still must say the fatty ones do look tough - even if they may look tuff stuck in the mud!

MMMMM

Arty

[roverrescue]

Tall and thin profile tyres also have the advantage in soft surfaces in that their surface area is long with a narrow width. Therefore less resistance against the leading edge moving forward.
Newer vehicles compensate for their fat tyres with lots more power. Current SUV type Fourbies get away with fat tyres (which look sexy) by having a zillion kilowatts.

WRT to your 18V rattler, just buy a torque extension bar in the range you need for your wheel nuts, spin em off at full noise, apply using the torque bar

Kincrome - Torque Extension Bar Set 10 Piece 1/2" Square Drive | Sockets, Socket Sets & Acces (174) - Kincrome Australia Pty Ltd (https://www.kincrome.com.au/torque-ext-set-10pce)

S

[AK83]

which Ryobi gun do you have(or are you looking to buy one)?

I have the 181W model .. works OK, nowhere near as strong as say a Makita(or other high quality, super expensive brand/models), but for us mere mortals .. strong enough.
The 181W does up to 360Nm, but remember they have various speeds, which then lower the total torque they apply.

eg. can't remember the exact specs, but at speed 3 mine supposedly does 360N, speed 2 about 200-ish, and at speed 1 around 100-ish too. Can't remember, manual and box got recycled ages ago!

Also got a torque tube set too a while back .. not so much for the wheel nuts, but it's handy to have for them too.
So what I do is leave the 110Nm torque tube on the extending bar I have in the D1 for the wheel nuts. Without any extension tube, it's a pain to use extension bar as a wheel brace due to it's closeness to the tyre.
So given that I need an extension bar, may as well use a torque tube.
They work good, you can easily feel when they start to flex .. easy peasy stuff.
They're quite accurate too, used my torque wrench to estimate how tight they get(and it will vary, as you need to include human error) but between 100 and 120Nm is what I seem to get from the 110Nm tube.

The Kingchrome torque tube set was wayyyy too exxy as an investment, I found a set(of 4) at Nightgales(in Laverton, if you don't know them) about $70 or so.

As for the investment value .. probably high. I've used mine for much more than just auto stuff ... always use it to undo wheel nuts, use it on low speed to do them up after all nuts have been started on their threads.
Recently tho, I'm building my shed, which involves "half a million" nuts and bolts, way too many of these for the footings with long threads. Couldn't imagine having to do them the old way, with a ratcheting wrench.
I reckon the speed savings using the impact wrench over doign them manually will save me at least an hour or so ... just on the footings nuts and dynabolts(about 24 all up).
The box of nuts and bolts I need for the frame are both marked 220 and 240 respectively, makes about 400+ all up for all of the columns and beams and gables and stuff.
Having to do them all by hand(even tho they're short) is going to be a pain. rattle gun and the 3/8's cordless wrench I also have will save me hours of tedium.

investment value .. IMO .. very high.

[twr7cx]

There’s a bazillion articles and arguments on fat versus thin tyres. Sometimes it also depends on what you can access. For example in 33” I have the choice of my currently 285/75R16 (fatties) or 255/85R16 (thinnies) but the type range and availability in one is far broader and superior to the other that it’s not the size determining my choice.

Personally, I’d not use the rattle gun for torquing up the wheel nuts - they’re find for undoing. A torque wrench set to 140NM rather.

[goingbush]

interesting, I recently changed from Kumho MT to a slightly skinnier profile road pattern AT tyres for my Electric Series in the interests of getting less rolling resistance and a quieter ride.

From Kumho 225/75r16 MT to Evergreen ERS89 215/85r16

No difference noted in kwh/km after a few hundred km , but I tell you what - they are noticeably better off road esp in mud, I always knew skinnier was better but I thought the more aggressive tread of MT's played more of a part. I won't be wasting $$ on MT's again.

[NPG]

Unlike pressure, friction does not depend on the contact surface area but on the coefficient of friction between the 2 surfaces and the force exerted downwards. Traction on the other hand refers to the grip of the tyre with the road surface, where 2 more factors are involved - the adhesion forces (i.e. the bonding between the rubber and the road surface) and the mechanical interlocking as the tyre deforms against the road surface. All things being equal, as the contact surface area increases, so do adhesion and mechanical interlocking, meaning that the wider the tyres, the better the grip (and unfortunately the higher the fuel consumption).

[RRT]

Purchased this second hand a while ago and Ryobi reckons its 160Nm which exceeds the 140Nm Land Rover recommend but well within the ball park allowing for boasting by the company.Will need to be sure they at least do 140 so will have to get this checked insitu.

As I am looking at having a set of HT on the D2 for daily driving and having just lucked a set of 5 * 265 75 16's Bridgstone Dueller AT's at roughly 80% for $115 will not worry too much about muddies yet (just had hell getting these fitted as the front alloys bonded nicely to hubs, no way could it have done on the side of the road!!!!) and have 235 80's on the TDi 300, both nominally 32's but these are an inch wider and a hell of a lot more rubber on road versus the space of 235 muddy.

At first view it looked the tyres would rub but even on full lock nothing, nice!

But in looking to change over the wheels for off road purposes, the idea of changing 25 wheel nuts by hand seems over the top, hence the buying of a rattle gun as well as for screw in tent pegs. The shop used the makita but will loosen these off and rattle them to my max so to speak.

Have never seen those bars before, do they have some form of ratchet or slip disc?

The need for horsepower, well, lets say a standard Td5 should have 335's standard then shouldn't they?


Arty

[RRT]

Unlike pressure, friction does not depend on the contact surface area but on the coefficient of friction between the 2 surfaces and the force exerted downwards. Traction on the other hand refers to the grip of the tyre with the road surface, where 2 more factors are involved - the adhesion forces (i.e. the bonding between the rubber and the road surface) and the mechanical interlocking as the tyre deforms against the road surface. All things being equal, as the contact surface area increases, so do adhesion and mechanical interlocking, meaning that the wider the tyres, the better the grip (and unfortunately the higher the fuel consumption).

Absolutely but as any F1 driver will tell you, the force of the tyre into the tarmac makes all the difference hence all the down force of the wings etc. The use of different compounds is a variable as of course is width. But ultimately it is the force down that makes the difference. No conclusion of course which is best just that all factors are important and I think as Goingbush says the variables are many and which is best is not necessarily looking at one area of the equation in the simple scenario such as wider is better grip which does not take into account how hard the thin tyre is being pushed into the surface and therefore requiring more pressure to elicit sideways movement or loss of grip against a wide tyre with very little pressure on the surface that could easily (relatively of course) lose grip.

Maybe if you have wider tyres, just load up with more kilos LOL

[RRT]

Sorry for the spelling joke, it is Tuesday

[AK83]

.....

Have never seen those bars before, do they have some form of ratchet or slip disc?

....

The torque tubes?
If so, no. They just twist as you use them(both tight and loosen).
Each tube is successively thinner/thicker .. thin = low torque, thick = higher torque.
On my set, min is 90Nm.
You can tighten more, as it twists .. or flexes, it still tightens.
So that is, if I use the 90 to do the ~100 that the wheel nuts need, I can keep going past it's twist point.
The idea is that you tighten(using the tube) and then you feel it twist more than tighten.
Kind'a hard to describe, but makes sense in use. That is, you feel it(ie. some human error is going to be involved)

Can't remember the exact wheel nut torque, but I think it's 100Nm, so I chose the 110 tube to keep in the car with the extending ratchet.
Idea of this is I can't see much difference between 100 and 110.
But if the nuts tighten over time, if I have the 90 tube, it may not be strong enough of the nuts have tightened to say 160Nm, or as you sometimes enocounter .. the wheel changing monkey at the tyre store used the dugga-dugga gun at 1000Nm or something (not uncommon).
I still usually have a normal extension in my socket set, but a PITA to get too in the tool box.

[V8Ian]

Correct torque for a D2 is 120Nm.

[Bigbjorn]

Sorry for the spelling joke, it is Tuesday

In Southern Racer English they are "tars". Refer Smokey Yunick autobiography.

[trout1105]

As I have NEVER used a torque wrench on a wheel stud I wouldn't have a clue what the tension setting is on ANY of the 4WD I have owned, All I have ever done is to use a breaker bar and tighten until I hear the wheel nut "Creak" then drive for about an hour and retighten.
I have NEVER lost a wheel or stripped/broken a wheel stud using this method over the last 4 decades driving roughly 40,000k's a year.
I bought an 18v rattle gun a few years back and found it to be invaluable when changing wheels because it takes 80% of the work out of the job.
I use it to remove the wheel studs and also put the studs back on (Loosely) then I do the breaker bar trick[thumbsupbig]

[AK83]

Correct torque for a D2 is 120Nm.

Just checked RAVE, listed under suspension in the torque settings.

is 140Nm! :eek2:

[ChookD2]

I understand the OP was about wheel nut torque and yes most alloy wheels are done to 140Nm. I also found the fat vs thin discussion interesting.
After a bit of a poke around I found this.... Ground Pressure (https://en.wikipedia.org/wiki/Ground_pressure)
I knew tanks had a low pressure (overall) but the table in this article is intersting.

M1 Abrams Tank - 15 psi
1993 Toyota 4Runner/Hilux Surf - 25 psi (I need to wash my hands now)
Mountain Bike - 40 psi
Stiletto Heel - 471 psi

This got the cogs turning and came up with the following:

We all tend to lower our tyre (internal) pressure in certain off road situations. Therefore, when lowering this pressure and lengthening our tread contact area with the ground we also lower our ground pressure due to this larger contact area. With that in mind we know that lowering tyre pressure on sand is a good thing (lower ground pressure) but may not be absolutely necessary in some situations.

Have I got that right?

[AK83]

....

Have I got that right?

I don't think that's quite right.
Not pretending to fully understand the numbers, but ground pressure alone can't be used to calculate overall grip for a set of specific conditions.
Gives you an idea of how to compare one set of conditions to another tho.

eg. say we have a vehicle .. even the dreaded Surf! [biggrin] ... and say we're on sand.

Their theory says that your tyre pressures is a good approximation of the ground pressure your car exerts on the ground.
They start driving over the sand with tyres at 40psi. They're not getting good grip, so stop and lower tyres to 15psi.
The important point to be mindful of in the variance in those figures is the "per square inch" part.
Vehicle weight doesn't change, so obviously the only change is the area of contact patch.

Sounds obvious of course, and stuff that we all know either through experience or observation or theory or whatever ... but maybe not enough to conceptualise visualise the actual change happening.

We know that friction is always related to surface area for given conditions as well. That is, the more surface area, the more friction .. friction = grip.

So even in mud, slush, gloop .. surface area = grip. So over the top of it you still have some grip .. just not enough to overcome the weight of the vehicle.
The theory is that the taller skinnier tyres in deep muddy slop are supposed to cut their way through to firmer ground, and that may well be spot on, but there's no guarantee that you will reach this firmer deep section either.
That is, you're more likely to bottom out more so than break through to firmer ground. So, you want more grip(ie. surface area) to begin with hoping to get through over the soft sloppy part before it digs in too far.
Technically, a fully deflated tyre will give the most grip, as it will have deformed as far as it can. This then provides the most surface area on the surface that is causing the grip issue.
Obvious alert!!! yeah, tyres spin off rim .. etc. tyre damage, etc... so the perfect off road tyre/rim set up would be run flat tyre designs.

Have you ever heard of the dreadnought wheel? used a lot in WWI in the sloppy/muddy Euroean battlefields. Basically run flat wheel design.
If you have the inclination, do a search for Big Lizzie, huge tractor in the Wimmera(Vic) that cleared thousands of acres of sandy land. Used those dreadnought type wheels very successfully.

I just did some quick math.
Going by the theory in the link you posted(tyre pressure is approximation of ground pressure)
A low to medium weight vehicle or about 2t(~4K lbs) with 40psi tyres, has about 1 sheet of A4 papers worth of contact area on the ground.
Drop the tyres to 15psi, and that changes the contact area to 2.84 sheets of the same paper.
Actual numbers are 266 sqin at 15psi, 100 sqin at 40psi. Close to 3x the area difference between tyre and ground.

[NPG]

So, you want more grip(ie. surface area) to begin with hoping to get through over the soft sloppy part before it digs in too far.

That's precisely why wide tyres are better because the force of friction remains the same while they provide more traction due to the larger contact surface (and therefore more surface adhesion and mechanical interlocking) and because there's less chance of sinking due to the reduced pressure exerted on the ground by the wheels.

Another important factor when wheels are sunk below the surface is that the rolling resistance shoots up. Therefore more torque will need to be applied to the wheels to overcome this resistance in order to initiate forward or reverse motion. But as more torque is applied to the wheels, there is a good chance that the force will be far greater than the force of static friction that is keeping the wheels pinned to the ground. If this happens, grip will be lost and the applied torque will be wasted in spinning and sinking the wheels even further instead of moving the vehicle.

[AK83]

.....

Another important factor when wheels are sunk below the surface is that the rolling resistance shoots up. Therefore more torque will need to be applied to the wheels to overcome this resistance in order to initiate forward or reverse motion. But as more torque is applied to the wheels, there is a good chance that the force will be far greater than the force of static friction that is keeping the wheels pinned to the ground. If this happens, grip will be lost and the applied torque will be wasted in spinning and sinking the wheels even further instead of moving the vehicle.

This is why it's a balance consideration.

Wide tyres on rocks .. almost certainly better. tyres don't dig in and create the additional force to overcome.
Taller skinnier tyres in sand .. almost certainly better once aired down .. More track like, forward/rearward spread when aired down.

This is why you read some folks claim taller skinner tyres are better .. they probably do more sand type driving.

Been there too.
I rarely venture out into the more rocky country, and prefer the central desert areas(even here in western Vic).
I recently changed from 255/70's to 245/75's simply due to my preferred use.
I still do go out to say Vic High Country, and maybe the 255's would give me an extra percentage of grip, but my balance preference is for tall/skinny.

But someone that does more rocky country off roading would be better served with wider fatter tyres .. etc, etc.

[RRT]

Good points as the variance is pretty much on what you want the tyre to have.

On sand you want for want of a better term buoyancy the tyre to stay on top of the surface rather than a high pressure with it cutting through to the under surface where as on silt or dust or shale or mud you want them pushing or cutting down to bedrock for grip and forward movement being key.

Maybe therefore taking pressures down on the loose stuff such as up in the high country is wrong as it decreases the pressure per sqcm and a modicum of sacred height!

Rocks on the other hand, just like with big hands all the easier to grip you with, the extra friction of greater surface area versus the tighter grip of a smaller footprint exerting greater pressure per sqcm, ahhh but which is better? is it not the one where there is less chance of wheel spin due to the tyre having traction but until there is conclusive proof,

Both fat and thin are still the best!!!!


Arty

[RRT]

Actually just had another thought - does the lower pressure tyre exhibit more squirm in the north south direction as well as east west? That is does the deformation of the tyre perpendicular to direction - understanding of course the belts within would keep this moderate - occur and assist in traction in certain circumstances and possibly in others detract?

Still think rubber is the best compound to have hitting the dirt


Arty

[trout1105]

Skinny tyres tend to do far more damage to tracks than wider tyres especially when the useless bastards don't air down.[bigsad]
There is also the advantage with wider tyres being able to take a heavier load[thumbsupbig]
Don't get me wrong in Some situations a skinny tyre is better than a wide one But overall wider tyres tend to be a better choice.
I run 245/70/16's on my D2a which are neither a skinny or a wide tyre and they do everything I ask from them However on the beach the 265/75/16's I have fitted to my Navara and my 79 series seem to do the job much easier.
As Most of my off road work is either on the beach or on rocky limestone tracks carrying/towing heavy loads I find the wider/taller tyres perform the best for me in these conditions.