Traction: larger is better?

[Vitaver]

Where the rubber hits the road is where traction takes place. There are at least 7 variables as an amateur I can identify: thread design, tire material composition, tire design, tire 3 dimensions (OD, ID, (wall as OD-ID) width, heat-cold effect on it, speed rating, tire pressure, etc. Now, keeping the 'mission' in mind plus the weather/road conditions, choosing the right tire for the job appears a daunting proposition.

At the most basic, it would appear that traction will depend in big part on pressure (weight) divided by the surface of contact with the road. Too large an area (duallys as opposed to just two per axle) would spread that weight on a larger surface and while making more area contact, the pressure per sq inch is lower: lower traction? On the other extreme, if we replace the tires with bicycle tires (if that was possible), too little surface, and extreme pressure pers sq inch would also mean less traction.

What is the answer to this puzzle? We need excellent traction towing with performance to spare as stuff happens.

[CapriRacer]

There is a technology triangle for tread rubber involving traction, treadwear and rolling resistance. Change one and you affect the others. Put another way, you can not get the best of any one property without sacrificing at least one of the others.

And of all the things that affects traction, this is by far the largest.

If we are talking tow vehicles - basically pickup trucks - and mostly LT tires at that, then there is enough weight that dry traction is rarely an issue.

Also, every vehicle manufacturer puts their vehicle through rigorous handling tests to make sure the vehicle behaves relatively benignly - and that includes pickup trucks. I've seen fully loaded one ton pickups smoking their tires when performing these tests.

[OTRA15]

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[The Sounds of Silence]

[Countryboy59]

Originally Posted by Vitaver

Where the rubber hits the road is where traction takes place. There are at least 7 variables as an amateur I can identify: thread design, tire material composition, tire design, tire 3 dimensions (OD, ID, (wall as OD-ID) width, heat-cold effect on it, speed rating, tire pressure, etc. Now, keeping the 'mission' in mind plus the weather/road conditions, choosing the right tire for the job appears a daunting proposition.

At the most basic, it would appear that traction will depend in big part on pressure (weight) divided by the surface of contact with the road. Too large an area (duallys as opposed to just two per axle) would spread that weight on a larger surface and while making more area contact, the pressure per sq inch is lower: lower traction? On the other extreme, if we replace the tires with bicycle tires (if that was possible), too little surface, and extreme pressure pers sq inch would also mean less traction.

What is the answer to this puzzle? We need excellent traction towing with performance to spare as stuff happens.

Spreading weight over more contact patches does not decrease total normal force. Normal force x Coefficient of friction = lateral force.

Don't overthink it.

[mykytiukr]

The best combination would be the tire size that originally came on the vehicle with a fairly aggressive tread and proper inflation for the weight being carried by the tire. No "all season" tires!!! You may gain a wee bit more traction by going one or two sizes narrower but check the weight rating. Any wider and things can get dangerous real quick!!! The more aggressive the tread the better the traction on snow. Ice? It doesn't matter. Also the more aggressive the more noise they make. A softer compound will make a difference too if you can find a choice. Siping makes very little if any difference so don't pay any more for that.

[dcasr]

Originally Posted by CapriRacer

...If we are talking tow vehicles - basically pickup trucks - and mostly LT tires at that, then there is enough weight that dry traction is rarely an issue.....

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With dry traction I agree. My last three TV have been shift on the fly 4wd because when you run into a poor traction situation, rain, snow, sand, etc., I shift into 4wd and slow down. With 4wd option your front tires not only have braking effect on the tires, but the steering is assisted by the motive force available. I've towed with 4wd since 1986 and would never go back to 2wd. The OP is right to be concerned about the traction effect of various types of tires, amount of rubber on the road, etc. Although 4wd does not improve braking performance necessarily, it does double the motive force and spread it out over two additional tires when traction is reduced due to rain, snow or sand/grit on the road.

[MelGoddard]

Originally Posted by mykytiukr

The best combination would be the tire size that originally came on the vehicle with a fairly aggressive tread and proper inflation for the weight being carried by the tire. No "all season" tires!!! You may gain a wee bit more traction by going one or two sizes narrower but check the weight rating. Any wider and things can get dangerous real quick!!! The more aggressive the tread the better the traction on snow. Ice? It doesn't matter. Also the more aggressive the more noise they make. A softer compound will make a difference too if you can find a choice. Siping makes very little if any difference so don't pay any more for that.

About "Aggressive noise";

I used 'General 'AT' s on the 4-Runner; good tire, lasted long, growled like a tiger on the road.
My wife's Camry has unknown snow tires that growl on the road.
I recently installed B.F. Goodrich 'All Terrain' T/A on the Ford.
I'm pleasantly surprised at how quiet they are.

[MelGoddard]

Originally Posted by dcasr

____________________

with dry traction i agree. My last three tv have been shift on the fly 4wd because when you run into a poor traction situation, rain, snow, sand, etc., i shift into 4wd and slow down. With 4wd option your front tires not only have braking effect on the tires, but the steering is assisted by the motive force available. I've towed with 4wd since 1986 and would never go back to 2wd. The op is right to be concerned about the traction effect of various types of tires, amount of rubber on the road, etc. Although 4wd does not improve braking performance necessarily, it does double the motive force and spread it out over two additional tires when traction is reduced due to rain, snow or sand/grit on the road.

ditto!:d

[Lumatic]

I'm not a formula guy, but I know a fatter tire is more prone to hydroplaning and sucks in snow.

[Boxite]

Tread material and tread design have importance which is difficult for the average motorist to evaluate. I once had a set of Bridgestones that acted like they were on grease anytime it rained. The exact same tire size in MIchelins were fine.

There are, emblazoned upon the tire sidewall, some guidelines established by Federal Standards for WEAR, TEMPERATURE, and TRACTION. Those standards should be comparable between similar tire designs (i.e. street-tread, off-road, M/S, etc.)

https://tireguides.com/TireTips/TireDocument/3

and

https://crashstats.nhtsa.dot.gov/Api...ication/807805

[tjdonahoe]

Most of my tires are an all season on our vehicles and they do fine..

[streaminwild]

Common sense is not so common anymore. Easy does it is better than stompin on the gas, in most cases. You be amazed what I can do with a 1 wheel drive truck. I also know it's limitations...that's where common sense kicks in. Those lego leveling blocks can do more than level your trailer. A few years back, the cool thing to do was install single wide tires instead of duallys.... then it rained...not cool.

[Scorge-ION]

OK, back to high school physics, Newtonian static friction. Sure, tires aren’t exactly Newtonian but they’re close enough to start.
Newton’s law of friction states that the force required to slide two surfaces past each other depends only on the coefficient of friction between them and the normal force holding them together. The size of the contact patch is irrelevant. In the case of tires, we simply have the coefficient of friction between the tire and the pavement and the normal force – weight – holding them together. Full stop.
Sure, the tire is rolling. However, that tiny contact patch of rubber that kisses the pavement is not sliding unless you’re out of control or spinning your wheels.
So, with a coefficient of friction = ½, we can accelerate a passenger car or truck at a maximum of ½ G (gravity); racing tires can actually generate more than 1 G but they pay for it in fast wear.
Which brings us to the concept of the tire’s traction circle: Ideally, the tire will generate the same acceleration sideways (cornering) as it does in braking and acceleration.
In actual fact, the circle is an oval or ellipse. Drag racing tires are designed for traction while accelerating. Tires used in other pavement motor sports usually have more traction for cornering.
All of this assumes dry pavement. Things change when you interpose water, ice or any other stuff.
As has been pointed out, wide tires hydroplane easier than narrow. Same goes for soft snow: it’s easier for a narrow tire to cut down to the pavement. Enter tread design. Tread gives water and snow a place to go to get out of the way. Race cars usually use slicks on dry pavement.
Ice is different, depending on lots of factors. Ice melts under pressure, forming a water layer to be dissipated. In very cold conditions, a tire can get very good traction. Melting ice is the worst.
OK, now I’ll introduce the related concept of slip angle. The tire has not broken traction but is crawling sideways so it’s not moving in the same direction as it’s pointed. Lots of things factor into this:
1. Tire air pressure
2. Tire rubber compound
3. Tire construction: sidewalls, tread, tread depth, etc.
4. Tread
5. Aspect ratio
6. Too many factors for this space

So a side wind is pushing your vehicle sideways. It’s no where near ultimate traction limits. The tires are just crawling sideways. What to do? Do anything that reduces the sideways deflection of the contact patch in relation to the metal wheel. Try lower aspect ratio tires, tread with more rubber and less air space. Add more sidewalls (duals) for more stiffness.
Of course, most changes will compromise some other performance aspect: ride, wear, predictability, etc.


Now, the question “why do we want excellent brakes?” Most people answer, “to stop fast” but that’s wrong. We want better brakes so we can go faster.


So the measure of a tow vehicle and trailer’s performance is, “how well does it stop?” and “how stable is it in side winds?”
The first question gives the answer to why I like Airstreams. Airstreams have those neat independent suspensions that everybody loves to hate to replace. Compare the Henschen axles to the common tandem axles with leaf springs and a “weight equalizing” toggle between. Many have brakes on both axles but the brakes on the front axle are nearly useless because the torques applied by the brakes tend to lift the front axle off the ground. Even if it’s not off the ground, the reduced weight on the tire also reduces its traction. (Duh!) I’ve even had the spring on the front axle over-center and leave it high! If you adjust the brake controller so the front axle never locks up, the trailer will never brake its own weight and always depend on the tow vehicle’s brakes. Airstreams have no such problem.
I’ll introduce another concept here: roll steer. When the vehicle’s body rolls as when cornering or blown sideways, or going over rolling pavement, the leaf spring-suspended trailer’s springs will steer it. When the wind blows it sideways, the springs and axles steer it to follow the wind, exacerbating the movement.
I won’t even get into a rant about how primitive it is to use springs to steer the wheels of a vehicle!


- Dave, the Scourge of the ION

[xrvr]

T.he best tire worn too low is dangerous. Don't wear them down to the wear indicators. Replace them sooner, please.

[CapriRacer]

Originally Posted by Scorge-ION

OK, back to high school physics, Newtonian static friction. Sure, tires aren’t exactly Newtonian but they’re close enough to start. ........

Unfortunately, they don't teach in high school that tires don't behave according to *Newtonian Physics*.

Originally Posted by Scorge-ION

..... Newton’s law of friction states that the force required to slide two surfaces past each other depends only on the coefficient of friction between them and the normal force holding them together. ......

It's Amonton's Laws of Friction - and those require some conditions that don't apply to tires - the biggest of which is that road surfaces are textured. The rubber in the tire penetrates the surface and the maximum traction occurs when the tire is sliding 10% to 15% - meaning rubber is being ripped off the surface of the tread. Even at low levels of traction, some rubber is being removed.

So:

Originally Posted by Scorge-ION

..... The size of the contact patch is irrelevant. ....

is NOT correct.

The size of the contact patch IS relevant, but the tread compound plays a larger role than any other single item.

And just for the record, the size of the footprint can NOT be determined by knowing the load on the tire and the pressure.

https://en.wikipedia.org/wiki/Contact_patch

That's why racing tires are wide. That provides a larger contact patch than a skinny tire - and therefore, more traction.

OK, I'm going to stop there and wait for rebuttals before moving on. This concept is important enough that we need to get it right before we start to talk about wet traction and snow traction

[Countryboy59]

Originally Posted by CapriRacer

Unfortunately, they don't teach in high school that tires don't behave according to *Newtonian Physics*.

[/SIZE]

It's Amonton's Laws of Friction - and those require some conditions that don't apply to tires - the biggest of which is that road surfaces are textured. The rubber in the tire penetrates the surface and the maximum traction occurs when the tire is sliding 10% to 15% - meaning rubber is being ripped off the surface of the tread. Even at low levels of traction, some rubber is being removed.

So: [/SIZE] is NOT correct.

The size of the contact patch IS relevant, but the tread compound plays a larger role than any other single item.

And just for the record, the size of the footprint can NOT be determined by knowing the load on the tire and the pressure.

https://en.wikipedia.org/wiki/Contact_patch

That's why racing tires are wide. That provides a larger contact patch than a skinny tire - and therefore, more traction.

OK, I'm going to stop there and wait for rebuttals before moving on. This concept is important enough that we need to get it right before we start to talk about wet traction and snow traction

Explains why stopping distance with ABS is sometimes longer than without.

[Vitaver]

Capriracer, please do talk about traction on different surfaces and conditions. This is very important topic.

A side comment can be the importance/selection, etc. of tires for the trailer as while it does not provide positive traction, the brakes do affect how that big thing flollowing us is braking, pushing us, sliding, etc. Of course i made up this 'positive traction' expression, I have no idea what it is the technical term for it.

Again, thank you for sharing his info which I am sure concern us all (or it should).

[Kent M]

Scorge-ION:

Yeah, I noticed the presence or absence of the "u".....

That's one of the best general knowledge explanations of that subject I've ever seen. Good job, and without a single equation or formula.....I couldn't have done that.


Kent
Houston