[The_K_Man]

The MYTH Of Wider Tire Contact Patch Being of Greater Size: Dispelled!

So I took it upon myself to magnify and measure the tire contact patch areas in square inches, as illustrated on page 291 of 'Automotive Engineering' edited by David A. Crolla, copyright 2009 Elsevier Publishing.

Now: the popular (mis)conception is that that a wider wheel/tire will produce a larger contact patch than that of a narrower wheel/tire combination, given the same make and model of tire applied to the same vehicle.

Well, what is really happening is that the orientation of that patch changes, from longitudinal to lateral(side to side) not the area. Exactly what you don't want, unless you plan to drive the car sideways at least fifty percent of the time! I believe the term for that is 'drifting'.

Anywho, the results of my measurements are (hopefully) attached: In case you have difficulty reading the area(sq. in):

Upper set of tires (L) 8.51 sq. in (R) 8.46 sq. in

Lower set of tires (L) 9.1 sq. in (R) 8.34 sq. in

Again, my measurement tool in PowerPoint is approximate, but the point has been made: given two sizes of the same tire model on the same vehicle, with appropriate cold air pressures applied, only the orientation of the contact patch changes, and actually the patch from the wider tire is slightly smaller.

When it comes to my preference for narrower, smaller diameter wheels wrapped in narrower, higher profile rubber... I REST MY CASE: The contact patches of the tires on a motor vehicle should be oriented longitudinally, parallel to the direction said vehicle is intended to travel in.

This will enhance - or at least preserve and maintain - sufficient self-aligning torque - or return from turns, as well as resist tramlining(following ruts and other road imperfections) and make driving a more relaxing and pleasant experience.

 

[DARKART]

Yes, narrower, higher profile tires will be more forgiving over road imperfections providing a more pleasant ride, but people want the looks of the large wheel, small tire.

 

[jackpine]

There's an additional problem with wider tires - they increase the likelyhood of hydroplaning on wet roads, which is something you never want to experience in a turn!

- Jack

 

[The_K_Man]

Unfortunately, we now live in a culture driven by appearances over technical common sense, which also makes the engineers’ job tougher when designing new cars, etc.

When you see a 2010 Civic coming down the road with 300mm wide tires on 22” rims, negatively cambered to fit under the fenders, something’s wrong…. !

 

[midnight witch]

Again, my measurement tool in PowerPoint is approximate

lol

pizza cutters are great for ride comfort, wider tires with low profile sidewalls are better for handling. not sure what you've proven here, but good job, we're all very proud of you.

 

[capkirk123]

Yeah, people haven’t spent the past 60 years trying to get the widest tires possible for their super cars and race cars because it looks nice. Also, at the same tire pressure, two tires will have the same contact patch size (assuming similar tire stiffness). The tire will deform until the pressure on the inside is equal to the pressure on the outside.

 

[The_K_Man]

lol

pizza cutters are great for ride comfort, wider tires with low profile sidewalls are better for handling. not sure what you've proven here, but good job, we're all very proud
of you.

Come come, differing viewpoints, be tolerant.

Yeah, people haven’t spent the past 60 years trying to get the widest tires possible for their super cars and race cars because it looks nice. Also, at the same tire pressure, two tires will have the same contact patch size (assuming similar tire stiffness). The tire will deform until the pressure on the inside is equal to the pressure on the outside.

Au contraire …

Even a casual read-through of search results for why some folks prefer low profile tires will reveal ‘looks’ as the number one reason for adopting them. Performance/ handling a not too distant second.

I, too, am concerned with looks: therefore I try to keep the wheels clean from road grime and brake dust, etc. But never never never would I even think of changing the size of my wheels or rims for the sake of how they appear to others around me.

That combination of wheels, tires, and cold pressures listed on the vehicle door frame, inside the fuel lid, drivers manual, etc. was arrived at by studies, design, engineering, and endless testing.

So who do I think I am deciding I want to plus-size the wheel & tire size and proportions from what Honda’s(or Ford’s or Mercedes) engineers determined to be the best combination of ride, comfort, handling, fuel economy, and yes, appearance? Some cocky arrogant know-it-all, to put it mildly?

In fact, if I were not amidst the personal economic circumstances I presently find myself in, I would definitely shell out some dough for a set of wheels and tires of Honda OEM size for a 2010 LX, for my 2010 EX. Slightly narrower 60-series 215s, for stronger self-aligning torque from turns, plus a bonus of a slightly smoother, quieter ride - taller sidewalls be damned!

Also, at the same tire pressure, two tires will have the same contact patch size (assuming similar tire stiffness).

Correct, with a caveat: That contact patch, as illustrated in my excerpt
from that text, will have changed orientation in the lower profile examples,
to a patch perpendicular to the direction of vehicular travel.

Which to me doesn’t make sense. In the long run, the contact patch should parallel, dynamically, the direction of travel, for maximum stability and concentration of vehicle weight down through any inclement road conditions.

Such can be achieved with any profile of tire down to 60-series sidewall to tread aspect ratio - the threshold of what I would consider ‘low profile’ tires.

Lower than that: 55series and lower, more aggressive doses of assistive alignment angles, such as Caster and/or SAI(steering axis inclination, or ‘kingpin angle’ for old timers) would be required to help center the steer tires from turns. Or, slightly reduced or variable power steering assist that becomes less assistive at higher speeds, progressively, IE over 30mph.

It’s just simply easier to engineer a suspension around narrower, higher profile tires, that meets the needs of ordinary drivers, but still acceptable for weekend F1 fantasy drivers… !

 

[midnight witch]

Come come, differing viewpoints, be tolerant.

no

you type a lot without saying anything.

 

[The_K_Man]

no

you type a lot without saying anything.

How does the above comment contribute to, or advance, the conversation?

 

[midnight witch]

How does the above comment contribute to, or advance, the conversation?

was it supposed to?

if you can prove that your tall, skinny tires are better than wider low-profile ones objectively, this might be an interesting thread, but instead you're basically making things up.

are they better for your use case? sure. are they better for people who want to take a corner without the sidewall folding over and the tires howling in protest? not a chance. this is always going to be subjective without actual empirical evidence, and using the measurement tool in powerpoint sure as hell doesn't count.

 

[The_K_Man]

was it supposed to?

if you can prove that your tall, skinny tires are better than wider low-profile ones objectively, this
might be an interesting thread, but instead you're basically making things up.

are they better for your use case? sure. are they better for people who want to take a corner
without the sidewall folding over and the tires howling in protest? not a chance. this is always
going to be subjective without actual empirical evidence, and using the measurement tool in
powerpoint sure as hell doesn't count.

Objectively: It's right in my first post: The narrower tire contact patch is parallel to the direction of travel. That is ideal.

And I never said that narrow high profiles were ideal in every theater of use. Ideal for the 95 percent of people who never compete on a race circuit. Ideal for those who just drive to work, the supermarket, church, school, and on vacation. Not so ideal for those who drive competitively, as in NASCAR, F1, or IndyCar.

Midnight: I used to drive like one of those whose driving style might benefit from superwide low profile rubber:

- Maintaining at least 10mph above posted speed limit on all kinds of roads, most of the time.

- Taking turns at 5-10mph over posted speed limit, and having to brake check frequently to avoid rear-ending the driver in front of me.

-Etc.

I'm not longer that driver. I stay in the outermost(North America: right hand) lane on highways, and cruise at, or just below, posted speed limit. And seldom do other drivers get annoyed with me - they have anywhere from 1 to 4 lanes to my left to pass me in! I end up applying my brakes far less than I would have just a few years ago, and ironically spend less time standing and waiting at red lights. Also, doing 55 in a 55mph zone gives on-rampers more margin to merge onto the freeway in front of me, without me having to slow down to accommodate them.

The way everyone should drive!

And narrow "pizza cutters" as you critique such tires, are more than adequate for such ordinary driving.

 

[midnight witch]

Objectively: It's right in my first post: The narrower tire contact patch is parallel to the direction of travel. That is ideal.

blah blah blah who cares

hey real quick, it that's ideal, why is that narrow tire contact patch so terrible on a drag strip? that's "parallel to the direction of travel", right?

also, what happens to that narrow contact patch when you turn?

 

[The_K_Man]

hey real quick, it that's ideal, why is that narrow tire contact patch so terrible on a drag strip? that's "parallel to the direction of travel", right?

also, what happens to that narrow contact patch when you turn?

Read the second paragraph in post #11 before you start spuyten duyvil: I did say there were exceptions

 

[jackpine]

hey real quick, it that's ideal, why is that narrow tire contact patch so terrible on a drag strip? that's "parallel to the direction of travel", right?

also, what happens to that narrow contact patch when you turn?

Witch - what tires are you talking about? The rear powered slicks (that push the vehicle straight ahead) or the front skinny ones that are responsible for steering (control)?

- Jack

 

[capkirk123]

I mean, an Acura TL weighs about the same as a V6 Accord, and the TL gets 235s while the Accord gets 205s. Honda clearly has no problem with putting wider tires on the Accord platform, the Accord gets skinnier tires to make it ride smoother, the TL gets wider tires to make it handle better.

 

[The_K_Man]

I mean, an Acura TL weighs about the same as a V6 Accord, and the TL gets 235s while the Accord gets 205s. Honda clearly has no problem with putting wider tires on the Accord platform, the Accord gets skinnier tires to make it ride smoother, the TL gets wider tires to make it handle better.

"handle better" is subjective.

Safer? To me, not. Such hair-trigger, highly responsive steering can quickly get one into trouble as far as I'm concerned.

 

[DARKART]

"handle better" is subjective.

Safer? To me, not. Such hair-trigger, highly responsive steering can quickly get one into trouble as far as I'm concerned.

For someone not really attentive to driving.

Handling is quantifiable; more control in steering and turns, skidpad, etc. Cruising down the freeway on a marshmallow suspension with little to no steering input is not “handling”. If you want that, there are better examples than an Accord.

 

[jackpine]

I generally find, in discussions like these, that looking at extremes helps clarify things.

If wider tires are good, why don't we have street tires with 3 ft wide treads on them? Sure, they'd be more expensive, and the vehicles would have to be modified structurally to mount them, but hey, if wider improves handling/performance/looks, go for it, right?

Or, if narrower tires are better, why not mount tires that have the aspect ratio of wagon wheels? We'd get used to them in time and we could surely stiffen the sidewalls enough to make them a reality.

The reality is that tire design is a compromise between looks/dry pavement performance/wet pavement performance/wear, and so on. Slick, wide tires offer best traction on dry roads, but lose all traction with just a little bit of water on the road. Narrow, highly grooved tires offer great traction in wet conditions, but don't have as much grip on dry roads due to the lack of rubber contact. And, off-road tires give you good traction in mud and snow, but they are noisy and uncomfortable on the highway, plus they don't wear well and probably hurt your gas mileage.

So, tire engineers and vehicle engineers have to work together to produce a combination that will cover ALL conditions adequately that the vehicle is likely to encounter, even though none of these conditions is handled perfectly. Somewhere in all this, "looks" come into the equation too, and satisfying looks probably hurts the other conditions somewhat too.

As K_Man hinted at, what you get from the factory is likely the best compromise, unless you use your vehicle in extreme conditions.

- Jack

 

[The_K_Man]

For someone not really attentive to driving.

Handling is quantifiable; more control in steering and
turns,skidpad, etc. Cruising down the freeway on a
marshmallow suspension with little to no steering input
is not “handling”. If you want that, there are better
examples than an Accord.

If you want ‘quantifiable’ I can give you quantifiable.

I am “quantifiably” ADHD, so perhaps I’m not adequately explaining what I prefer here.

1) Return-from-turns, self-aligning torque: As the textbook from which I captured those contact patches from stated, narrower wheel & tire combinations possess higher levels of self-aligning torque than do wider combos. And I prefer more of that than I do steering than borders on F1 sensitive.

While on that topic, I also prefer steering with, perhaps, more weight off center than the average driver today might be used to. Combined with a tendency to center faster than some drivers might be used to. And there are a variety of ways to achieve that:

a) Cold tire pressure: The lower, or closer to recommended on the door frame, the heavier the steering will feel, all other things equal. The higher the tire pressure, particularly in combination with wider wheel/tires, the less that self-centering force will be, and lighter will be the steering overall. Again - this is all in that textbook I quoted, in my initial post.

b) Minus-sizing the wheels & tires - from a wider tire with larger diameter rim to a narrower tire with smaller diameter rim. This is what I wanted to do, above, assuming my finances improve: Putting Honda’s OEM wheels & tire size from a 2010 LX onto my 2010 EX. I was told on these boards some time ago that fitment wouldn’t be a problem.

c) Alignment angles: Increase centering forces(such as Caster) as much as possible within spec range. This one is tough, because on most modern passenger vehicles caster angle is manufactured in, and not directly adjustable.

d) Modify the Power steering: Find a way to reduce, slightly at that, the amount of hydraulic or electric assist, particularly at speeds over 30mph. Again, not always easy on modern vehicles with everything designed in.


2) “marshmallow”/cushy ride and “no steering input” or feedback. Hardly! If I wanted that I wouldn’t even think of buying an Accord, from any decade! My 2010 EX rides just firmly, just comfortably enough, as long as my cold tire pressures drift no more than 2-3psi north of the 32psi listed on its door frame placard. Plus I can feel the road enough through the steering wheel and all wheels for that matter.

I only wish that when designing the higher trim EX & up, Honda hadn’t ‘gone for broke’ by putting wide 50-series low profile tires on it. Perhaps 55-series on a slightly wider 16” wheel would have been the sweetspot. I think they went with the 55R17s as much for ‘premium look’ as for handling in my car’s case.

I hope the above clears up both what I am advocating: a return to more sensible wheel & tire size and proportions, and, my personal preferences.

 

[capkirk123]

If you want ‘quantifiable’ I can give you quantifiable.

I am “quantifiably” ADHD, so perhaps I’m not adequately explaining what I prefer here.

1) Return-from-turns, self-aligning torque: As the textbook from which I captured those contact patches from stated, narrower wheel & tire combinations possess higher levels of self-aligning torque than do wider combos. And I prefer more of that than I do steering than borders on F1 sensitive.

While on that topic, I also prefer steering with, perhaps, more weight off center than the average driver today might be used to. Combined with a tendency to center faster than some drivers might be used to. And there are a variety of ways to achieve that:

a) Cold tire pressure: The lower, or closer to recommended on the door frame, the heavier the steering will feel, all other things equal. The higher the tire pressure, particularly in combination with wider wheel/tires, the less that self-centering force will be, and lighter will be the steering overall. Again - this is all in that textbook I quoted, in my initial post.

b) Minus-sizing the wheels & tires - from a wider tire with larger diameter rim to a narrower tire with smaller diameter rim. This is what I wanted to do, above, assuming my finances improve: Putting Honda’s OEM wheels & tire size from a 2010 LX onto my 2010 EX. I was told on these boards some time ago that fitment wouldn’t be a problem.

c) Alignment angles: Increase centering forces(such as Caster) as much as possible within spec range. This one is tough, because on most modern passenger vehicles caster angle is manufactured in, and not directly adjustable.

d) Modify the Power steering: Find a way to reduce, slightly at that, the amount of hydraulic or electric assist, particularly at speeds over 30mph. Again, not always easy on modern vehicles with everything designed in.


2) “marshmallow”/cushy ride and “no steering input” or feedback. Hardly! If I wanted that I wouldn’t even think of buying an Accord, from any decade! My 2010 EX rides just firmly, just comfortably enough, as long as my cold tire pressures drift no more than 2-3psi north of the 32psi listed on its door frame placard. Plus I can feel the road enough through the steering wheel and all wheels for that matter.

I only wish that when designing the higher trim EX & up, Honda hadn’t ‘gone for broke’ by putting wide 50-series low profile tires on it. Perhaps 55-series on a slightly wider 16” wheel would have been the sweetspot. I think they went with the 55R17s as much for ‘premium look’ as for handling in my car’s case.

I hope the above clears up both what I am advocating: a return to more sensible wheel & tire size and proportions, and, my personal preferences.

Yes, it’s personal preference. You want to mount a skinnier tire, satisfied that it’ll be safe because low trim levels of the Accord platform come with skinnier tires. I want to mount a wider tire, satisfied that it’ll be safe because higher trim levels of the Accord platform (the Acura TL) come with wider tires.