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    My misconceptions about WHY wider tires = better grip.

    The idea of wider tires having better grip always seems so obvious to me. So simple: A wider tire has a larger footprint (what the pros call contact area), therefore it has better grip. Intuitively this makes so much sense.

    However, I recently saw on a forum a post that seems to prove me dead wrong. Two arguments were put forth:

    1. Wider tires do NOT have larger contact area. "The narrower tyre has a longer, thinner contact patch. The fatter tyre has a shorter, wider contact patch, but the area is the same on both." (Reference URL to come.)

    2. If Frictional Force = Coefficient of Friction x Vertical Force, then why does contact area matter at all?
    ("Contact area" is not in the equation to determine friction, aka grip.)

    1 is fact, so no question there. 2 proves to be problematic. It sort of pushes me "over the edge" into the abyss of confusion. Smiley So if contact area doesn't matter, as so obviously shown in the equation, then a Turbo with skinny tire has as much grip as my big, fat, expensive Pilot Sport?

    So these are 2 questions I thought the amateurs among us might want to ponder. And the pros might feel free to explain.
    I found an article that I think provides some sort of answer. But before I post it, let me make sure I understand what hysteresis is. Smiley

    (BTW, mod please consider unlocking the thread below. Same pictures but topic has nothing to do with the GT3 per se; more about a recent thread on wings of various 911's, and MMD's extreme distaste for wings. You wouldn't lock all threads that have the some pics of, say, the new Turbo, right? Smiley)
    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    It has a lot to do with the surface the tire is contacting.  Have you ever noticed how a dually pickup can't gain any traction in a muddy field while an ordinary pickup can?  It seems to me the dually's tires spread out the load so much that the treads of the tires can't dig into the soil as easily.

    Let's move to dry asphalt. That's a different situation entirely.   The advanced tire compounds used in modern tires are part of the explanation.  They work better with more contact area and low loading as opposed to less contact area and high loading.  The latest dragsters have the widest tires you ever saw.  So do the formula one cars.  While I can't explain the physics of it all, those guys have been experimenting with tire widths and tire treads and tire compounds for many, many years.  If the skinny tire did a better job, the wide tire would have disappeared long ago.  I think it's called "evolution".


    --

    2008 GT3

     


    Re: My misconceptions about WHY wider tires = better grip.

    I think the contact area is more dependent on tire pressure than on tire size?


    Re: My misconceptions about WHY wider tires = better grip.

    LOL Cannga, once again, a nice technical subject!
    I thought I'd type a story about p=F/A, Ffriction = coefficient of friction time Fnormal, and things like that, but I couldn't figure it out myself :P

    I'm going to believe Greentree, sounds like a reasonable story, and it stops me from getting frustrated because I can't figure out another reasoning :)

    -Joost-

     


    --

    Porsche, seperates LeMans from LeBoys

    Re: My misconceptions about WHY wider tires = better grip.

    Greentree:

    It has a lot to do with the surface the tire is contacting.  Have you ever noticed how a dually pickup can't gain any traction in a muddy field while an ordinary pickup can?  It seems to me the dually's tires spread out the load so much that the treads of the tires can't dig into the soil as easily.

    Let's move to dry asphalt. That's a different situation entirely.   The advanced tire compounds used in modern tires are part of the explanation.  They work better with more contact area and low loading as opposed to less contact area and high loading.  The latest dragsters have the widest tires you ever saw.  So do the formula one cars.  While I can't explain the physics of it all, those guys have been experimenting with tire widths and tire treads and tire compounds for many, many years.  If the skinny tire did a better job, the wide tire would have disappeared long ago.  I think it's called "evolution".


    Joost and Greentree,

    Thanks for participating in the guess work. BTW, the more I read, the more I realize I am running into a big time ambush, and even professionals write paper over this puzzle. A lot of the info I read is way above my head, so any expert here please correct as needed. You won't hurt my ego; just be gentle. Smiley

    First, let's set the table. The conditions here are: same compound, same load, same pressure, same construction; the only difference being one is skinny, one fat, within reason.

    The second paragraph brings up advanced tire compound; excellent point and actually surprisingly close to where the answer is. But, I don't think it answers my question: Given that they are made of the same advanced compound, and given that they are used on the same asphalt surface, why would the fat tire has better grip, since F(f)=MuF(n), therefore friction would be the same between the 2?

    Joost,
    That formula is at the heart of this question, that is, since A=F/P, contact area would be same between the 2 tires, since load and pressure are given to be the same.

    BTW, I am not trying to increase suspense at all. I am stalling for time as I continue with my web research. Smiley


    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    Cann, the p in this formula is the pressure that is put on the tire by the weight of the car, not the same as the pressure in the tyre.

    I think the solution lies in the fact that a bigger tire with the same tyre pressue deforms more under the same force. So, if the same car, with bigger tyres, the deformation of the tyre will be bigger. So, the contact area will be bigger, due to the fact that it's wider AND the fact that the tyre deforms more under the same weight. Now, when the force applied by the tyre to the road stays equal, and the contact area is bigger, than the maximum F(friction) that can be delivered by the wider tyres is bigger. Is this a solution?

    PS, I really like discussions of this type. Too bad we can't have them in a pub with a pint ...


    --

    Porsche, seperates LeMans from LeBoys

    Re: My misconceptions about WHY wider tires = better grip.

    Eunice:

    I think the contact area is more dependent on tire pressure than on tire size?

    Hi Eunice, you are correct the contact area is definitely more dependent on tire pressure than tire size. In fact the premise of this thread is that contact area is in fact unrelated to tire width (assuming load, pressure, construction to be equal or at least similar).

    I am still reading Smiley but the shapes of those 2 contact areas give a hint as to how the experts will try to explain this. It has to do with the following characters of the fat tire, that has the short wide patch:
    a. Deals with heat issue better. The wheel with the long thin patch gets hotter than the one with the short wide patch (At any given moment, a larger percentage of the tire is in contact with the road, if I understand what I am reading correctly. Smiley I am finding myself having to read what these guys write 3-4 times before anything sinks in. Plus a couple of aspirin's afterwards. Smiley).
    b. Better grip -- related to slip angle behavior. The long thin patch behaves differently from the short wide patch. Basically, the long thin patch has less max grip. Note how interesting this argument is: Even though areas are the same, the shape of the contact patch dictates grip!

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

    (URL reference coming)

     

    contact patch

     

    Imagine driving on to a glass road and looking up underneath your tyres. This is the example contact patch (in red) for the situation I explained above. The narrower tyre has a longer, thinner contact patch. The fatter tyre has a shorter, wider contact patch, but the area is the same on both.

    And there is your 'eureka' moment. Overall, the area of your contact patch has remained more or less the same. But by putting wider tyres on, the shape of the contact patch has changed. Actually, the contact patch is really a squashed oval rather than a rectangle, but for the sake of simplicity on this site, I've illustrated it as a rectangle - it makes the concept a little easier to understand. So has the penny dropped? I'll assume it has. So now you understand that it makes no difference to the contact patch, this leads us on nicely to the sticky topic of grip.

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

     


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    Thank you very much cannga for these insights.

    Do I understand it correctly that tire width controls the width of the contact area but reduces the length so the total area stays the same?

    Tire pressure influences the total area then? And what about tire size (radius)?


    Re: My misconceptions about WHY wider tires = better grip.

    Check this article for a more "scientific" approach to tire width, tire pressure and contact area: Fact or Friction 


    --

    987 Boxster S, Arctic Silver, H&R Monotube Coil-Overs and Anti Roll Bars, Strut Brace, FVD Stage 1, Sachs Racing Clutch and Single-Mass Flywheel, Recaro Racing Shells, PSE.

    997 Carrera 4S, Guards Red, Bilstein PSS10 Damptronic, H&R Anti Roll Bars, IPD Plenum, Dension Gateway 500, PSE.


    Re: My misconceptions about WHY wider tires = better grip.

    bluelines:

    Check this article for a more "scientific" approach to tire width, tire pressure and contact area: Fact or Friction 

     Wow, thanks!

    The experimental data clearly shows that simplified models do not work in this case. Smiley


    Re: My misconceptions about WHY wider tires = better grip.

    I tried to find the data from Avon Tyres that is mentioned in the fact or friction article, but no luck so far. Does anyone have a link? 


    Re: My misconceptions about WHY wider tires = better grip.

    Bluelines, thanks. Yes I know and that's what I would call a 5-aspirin article right there. I hope by now everyone is googling like crazy -- that is the spirit of this thread.

    I hope everyone is also reading up on slip angle. If you like to understand your car's handling, you'll read up on slip angle.

    The contact area puzzle is building. In some way it doesn't surprise me. As in all things brought to an expert level, there would be some basic rules, and there would be myriads of exceptions that the experts debate. (Pushing amateurs like me deeper into the abyss of confusion. LOL)
    I do think he has a point because real contact patch area is discussed as being a percentage of theoretical and there are myriads of other factors that come into play, besides A=F/P, such as side wall and tire compound stiffness. As an example, just think of a run flat tire which keeps a good shape when flat.
    Anyway, the HUGE difficulty for me is how to understand at an amateur level, without being grossly wrong.

    But... note also, assuming you find a satisfactory solution to the contact patch area, you still haven't answered the second question central to this thread, that is: Since F(friction) = Friction Coefficient x F(normal), why would contact area matter at all?

    I think (or rather, someone wrote) that the answer is in the shape of the contact patch, all else being similar or equal. More to come!

     


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    cannga:

    But... note also, assuming you find a satisfactory solution to the contact patch area, you still haven't answered the second question central to this thread, that is: Since F(friction) = Friction Coefficient x F(normal), why would contact area matter at all?

     

     From your formula, it doesn't matter at all.

    But a small patch would get extremely hot and therefore the friction coefficient would change (also think of tire wear)?


    Re: My misconceptions about WHY wider tires = better grip.

    Eunice:

    Thank you very much cannga for these insights.

    1. Do I understand it correctly that tire width controls the width of the contact area but reduces the length so the total area stays the same?

    2. Tire pressure influences the total area then?

    3. And what about tire size (radius)?

    Eunice, thanks. Please don't use the word insight -- it embarrasses me. I am actually reading as I type the answer Smiley. I could be wrong. 

    1. Yes, within reasons, I think the basic idea is that wider tire has a wider contact patch, but the patch is shorter, such that the total area stays more or less the same.

    2. Definitely tire pressure influences total area. Deflation = more contact area. Assuming again, tires of similar construction; I don't imagine Run Flat Tire changes as much as normal tire for example.

    3. Hmm, don't know about this one. Anyone?

    >>>>>>>>>>>

    http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=10

    The shape of a tire's contact patch or "footprint" greatly influences its performance and is dependent on its profile or "aspect ratio". Low profile tires (most performance tires) have a short and wide contact patch that is effective in converting the driver's input into very responsive handling, cornering stability and traction...especially on dry roads.

    High profile tires (light truck and most passenger tires) have a long and narrow contact patch which helps to provide predictable handling, a smooth ride and especially good traction in snow.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    You questioned something I thought I knew for sure, and you have been right on that. I would call that an insight. 

    But I really would love to have access to that Avon data!


    Re: My misconceptions about WHY wider tires = better grip.

     A paper about the subject with pictures of a tire test machine and some charts:

    http://www.millikenresearch.com/TTC_SAE_paper.pdf


    Re: My misconceptions about WHY wider tires = better grip.

    Eunice:

     A paper about the subject with pictures of a tire test machine and some charts:

    http://www.millikenresearch.com/TTC_SAE_paper.pdf

     

    Now you've found the mother load.  The Millikens know just about everything and anything having to do with tire characteristics as they relate to vehicle dynamics.

    Also, if friction is proportional only to normal force, how can any tire generate more than 1g of traction without aerodynamic downforce?

    Give up?

    Modern tires are viscous/soft enough to mold themselves into the micro-structure of the pavement and provide sort of a gear-like interface with the road surface.  It's very tricky to make this happen at optimum levels and taken to extremes, some of the "gear teeth" break off, causing rapid wear (track "marbles").


    --

    Mike

    2005 Carrera GT - Signal Yellow

    2008 Tesla Roadster - Thunder Gray

    1972 BMW 3.0 CSi - Nachtblau

    2009 Bentley Arnage T - Black Saphire


    Re: My misconceptions about WHY wider tires = better grip.

    W8MM:

    Now you've found the mother load.  The Millikens know just about everything and anything having to do with tire characteristics as they relate to vehicle dynamics.

     

    Here's a web crib from Karl Ludvigsen about the family patriarch:

    "Meeting Bill, you might think you were encountering a dry-as-dust New Englander, a down-easter who might be a town clerk or head librarian. Five and a half feet tall, he's no heavier than the 130 pounds he weighed in high school. And his engaging politeness knows no bounds. "I never could manage to get through a door after him," said a friend. "He always opened the door for others and went through after them."

    But looks do deceive. For Bill Milliken the right word is dynamic. Nothing static ever interested Bill. Driving a car in a straight line wasn't for him. Milliken wanted to know what happened in a turn, why it happened and what could be done about it. As both driver and pilot he was driven to understand the subtleties of control in dynamic maneuvers. Teaming with knowledgeable colleagues, Bill built the foundations of our knowledge of how and why cars and airplanes handle as they do.

    How seriously is Milliken's work taken? When Ferrari's racing department conducted an audit recently it rounded up 14 copies of his Race Car Vehicle Dynamics, written with his son Doug. When major race teams simulate lap times to plan their race strategy they use a computer program developed by Bill's Milliken Research Associates. Decades of Bill's inputs and analyses have provided the basis for GM's understanding of vehicle dynamics. Major racing organizations and companies like DaimlerChrysler pay five-figure sums for his analytical programs."


    --

    Mike

    2005 Carrera GT - Signal Yellow

    2008 Tesla Roadster - Thunder Gray

    1972 BMW 3.0 CSi - Nachtblau

    2009 Bentley Arnage T - Black Saphire


    Re: My misconceptions about WHY wider tires = better grip.

    bluelines:

    Check this article for a more "scientific" approach to tire width, tire pressure and contact area: Fact or Friction 

    The premise they start with is a fallacy. It's true that P = F / A. But A in this case is predefined by F and many other factors, such as tire compound and tire temp.

    Whoever thinks, within reason, that a narrow tire has the same grip as a wide tire may be a buyer for a bridge I have for sale in the AZ desert. Should  a 917k be shodded with bycicle tires? :) 

    However wider beyond a certain width adds no value and may cause harm. Weissach picks tire width carefully and their choices work well for street driving. I always frown at the amateur engineering of tires/wheels/suspensions often done without proper analysis and testing and think that the OEM product is quite good.


    --

    _________________________________________________________ 

    A. Dias --- 997.2S (ordered). Previous cars: Corvette C6,  996 C4.


    Re: My misconceptions about WHY wider tires = better grip.

    Intuitionally, wider tires provide more lateral grip even the contact patch remain the same.

    Also, some downsides of using too wide tires are

    1) added unsprung weight

    2) If you lose grip, it takes longer to recover grip.

    3) expensive to buy.  may need to modify fenders.

    So choose your tires wisely,don't go crazy on wide tires if you don't really need them. 

     


    Re: My misconceptions about WHY wider tires = better grip.

    I really think tire compound is a big part of the answer.  Consider an Indy car of the 1950's.  Those tires were pretty narrow!  You wonder how they could corner at all.  It seems to me that the rubber they were using at the time dictated that particular profile or we'd still be using it today.

    There is also the possibility that the drivers of that time wanted wider tires, but the technology required to build them just wasn't there.


    --

    2008 GT3

     


    Re: My misconceptions about WHY wider tires = better grip.

    If one considers tires of the same diameter, a wider tire will have more of its total external surface area not in contact with the pavement.  The total exposed cooling area relative to the heat of slip friction will allow better heat ejection and allow a softer, stickier compound  -- all things being otherwise equal.

    On the other hand, the wider one makes a tire on a given vehicle, the more difficult it is to keep the entire width of the tire face in intimate contact with the road.  Roll of the chassis can promote lifting part of the contact patch off the road.  Suspension design then becomes more critical and a point of diminishing returns can be reached as one increases section width without improving this aspect of the suspension geometry.

    Tires also have their own spring constants (they compress when loaded) and can significantly contribute to overall suspension characteristics.  In fact, the tires can contribute as much as 0.5 degree/g of roll compliance on some stiffly sprung race cars and overwhelm the roll characteristics of the chassis springs and anti-roll bars.

    The whole subject can be a can of worms and finding optimums is difficult for even the best chassis engineers.  This is why Porsche insists on controlling tire design ("N" ratings) for fitments to their cars.  They can do all sorts of trick chassis design that can then be undone by unplanned changes in the tires.


    --

    Mike

    2005 Carrera GT - Signal Yellow

    2008 Tesla Roadster - Thunder Gray

    1972 BMW 3.0 CSi - Nachtblau

    2009 Bentley Arnage T - Black Saphire


    Re: My misconceptions about WHY wider tires = better grip.

    How would a narrower tire have a longer contact patch? Same exact size tires height wise one wide, one narrower have the same exact length wise contact patch, no? The only way I could see it having a longer contact patch is because more pressure on a narrower tire would cause more deformation but less tire pressure on the wider tire would create the same thing?????????

     


    --

    08 PORSCHE Turbo Cabriolet, 06 Ferrari F430,  04 Durango HEMI,  04 Harley Davidson Screamin Eagle,  93 Harley Davidson Nostalgia


    Re: My misconceptions about WHY wider tires = better grip.

    Thanks everyone for the contribution and excellent posts. I hope after this thread you'll think twice every time you see a fat tire! Smiley
    Since some very knowledgeable person  has started to mention the word "slip" (slip friction) already, and I know the (possible - LOL) answer to the riddle will partly involve slip angle behavior with different shapes of the contact patch, if you are not familiar with the concept you might want to do a quick google, or wikipedia  wikipeda-slip angle
    Slip angle is an essential concept to understanding car's behavior in corner so please trust me you want to read about it if you're not already familiar Smiley. Below is one of my favorite sites for basic level information.

    (In fact if you look at the highlighted sentence in the last paragraph of the quote, you'll see how I got involved with this headache.  Smiley Author made a statement linking wider tire = larger contact patch, that made me ask "why so," and upon further examination and challenge, may or may NOT be true!)

    >>>>>>>>>>>>>
    http://www.autozine.org/technical_school/handling/tech_handling_4.htm#Neutral:

    Neutral / Understeer / Oversteer

      We often hear these 3 terms in car magazines. I think few people would argue if I say they are the most important elements in the study of handling.

      What is understeer ? Basically, if you turn the steering wheel and find the car steers less than you expect, the car is understeering. This is not because your subjective judgement goes wrong, in fact any car must have some degree of non-neutral steering due to the weight distribution, suspension design, tyre used, lateral acceleration and road conditions. Further more, a car could understeer in this corner and then oversteer in that corner. The whole picture is very complicated, so I'll spend more paragraphs to discuss this topic.

      What do we need ?

      It seems that neutral steer must be more desirable than understeer and oversteer, but in fact it is not.

      In fact, when running in straight line, we want a little bit understeer to make the car stable. When the car is subjected to side force, probably due to cross wind or the road's irregularities, understeer could resist the force and avoid the car to be steered automatically, therefore the driver need not to correct the steering frequently.

      When the car is entering a corner, we also need a light understeer to provide the stability while the driver is easing off the brakes and building up cornering force. In mid corner, we need neutral steer. In the exit phase, a slight oversteer will be welcomed as it helps tightening the path. However, the degree of oversteer must be progressive and easily controllable by applying and easing throttle. We call this "Power Oversteer". Without power oversteer, we have to ease the throttle (thus loss time) or the car will run out of the corner.

      However, I must make clear that what I say "slight understeer / oversteer" is usually deemed to be "near neutral steer" by most car magazines. This is because in reality there are too many cars running on severe understeer thus they used to them. In other words, if a car magazine said the Porsche 996 has mild understeer, it probably equals to "medium understeer" in our sense.

      Basic Concept : Slip Angle

      Before going on our study, we must understand the concept of slip angle first.

      When a car enters a corner, all the tyres are turned with respect to the ground. Due to the elasticity of the pneumatic tyre, the tread in the contact patch will resist the turning action because there is friction generated between the rubber and the road surface. As a result, the treads on the contact patch will be distorted, whose direction always lags behind the direction of the wheel ( See figure in below ). We call the angular difference between the treads and the wheel's direction as Slip Angle.

    Note : the car is turning left

      In which direction the wheel is running ? It is the direction of the tread, not the direciton of the wheel. I am not saying the tread has any ability to force the wheel to travel in its direction. On the contrary, the tread is only a sign showing how an arbitrary point on the tyre surface travels. If the arbitrary point travels in that direction, so does the wheel which is the summation of thousands of those points.

      Now you must think the existence of slip angle must reduce the car's steering angle thus leads to understeer. In fact, it is not so if everything else are perfect. Because both the front and rear tyres have more or less the same slip angles, they counter each other thus the resulting steering angle remains unaltered.

      However, if the front and rear wheels have different slip angles, then we get understeer and oversteer :
       

        Understeer : Front Slip Angle > Rear Slip Angle

        Oversteer   : Front Slip Angle < Rear Slip Angle

        Neutral steer : Front Slip Angle = Rear Slip Angle

     

    .......

    New Trend for RWD cars

    In the past 2 decades, we saw car makers gradually increases understeer in RWD cars, making them more "secure" to drive. Porsche 996 is a good example. Its predecessor 911 used to offer hell a lot of oversteer, now the 996 becomes a very civilised GT.

    This is partly due to the market orientation ( it seems the wealthy customers tend to love secure rather than excitement), partly due to the use of wider tyres. In the past 2 decades, tyres of sports cars had been widened for about 50%, in addition to the growth in diameter, the contact patch area had been largely increased. Of course this is intended to increase the grip. However, increased contact patch area means every square inches of the contact patch carries less cornering force, so the tread distort less and the slip angle is reduced.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

    cannga:
    Eunice:

    Thank you very much cannga for these insights.

    1. Do I understand it correctly that tire width controls the width of the contact area but reduces the length so the total area stays the same?

    2. Tire pressure influences the total area then?

    3. And what about tire size (radius)?

    Eunice, thanks. Please don't use the word insight -- it embarrasses me. I am actually reading as I type the answer Smiley. I could be wrong. 

    1. Yes, within reasons, I think the basic idea is that wider tire has a wider contact patch, but the patch is shorter, such that the total area stays more or less the same.

    2. Definitely tire pressure influences total area. Deflation = more contact area. Assuming again, tires of similar construction; I don't imagine Run Flat Tire changes as much as normal tire for example.

    3. Hmm, don't know about this one. Anyone?

    >>>>>>>>>>>

    http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=10

    The shape of a tire's contact patch or "footprint" greatly influences its performance and is dependent on its profile or "aspect ratio". Low profile tires (most performance tires) have a short and wide contact patch that is effective in converting the driver's input into very responsive handling, cornering stability and traction...especially on dry roads.

    High profile tires (light truck and most passenger tires) have a long and narrow contact patch which helps to provide predictable handling, a smooth ride and especially good traction in snow.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

     

    High profile, narrower tires have better traction in snow because they make more contact w/ the road during snow, it's easier for them to go through the snow to reach the pavement, where as the wide tire sits more on top of the snow because of it's greater surface area which distributes more weight hence less contact w/ the pavement.. But you cant use that situation as it applies to dry pavement driving.  

    --

    08 PORSCHE Turbo Cabriolet, 06 Ferrari F430,  04 Durango HEMI,  04 Harley Davidson Screamin Eagle,  93 Harley Davidson Nostalgia


    Re: My misconceptions about WHY wider tires = better grip.

    STRADALE:

    How would a narrower tire have a longer contact patch? Same exact size tires height wise one wide, one narrower have the same exact length wise contact patch, no? The only way I could see it having a longer contact patch is because more pressure on a narrower tire would cause more deformation but less tire pressure on the wider tire would create the same thing?????????

    Read the Fact or Friction article for the long answer.

    The short answer is that the wider tire does not deform as much as the narrower tire (same load and pressure), resulting in a shorter contact patch and the same area.

    But this is can not really be applied to reality, in fact depending on pressure and load, sometimes the wider tire has indeed the bigger contact area, sometimes it's the opposite!


    Re: My misconceptions about WHY wider tires = better grip.

    Eunice:
    STRADALE:

    How would a narrower tire have a longer contact patch? Same exact size tires height wise one wide, one narrower have the same exact length wise contact patch, no? The only way I could see it having a longer contact patch is because more pressure on a narrower tire would cause more deformation but less tire pressure on the wider tire would create the same thing?????????

    Read the Fact or Friction article for the long answer.

    The short answer is that the wider tire does not deform as much as the narrower tire (same load and pressure), resulting in a shorter contact patch and the same area.

    But this is can not really be applied to reality, in fact depending on pressure and load, sometimes the wider tire has indeed the bigger contact area, sometimes it's the opposite!

     

    Yeah, I get that part about it not deforming as much, that's what I mentioned above but if it's only based on that, then it's a false premise since you normally wouldn't have the same pressure narrow vs wide tire in the first place??? yes, no???

    But if narrower tires have a larger contact patch, they should switch these front tires to the rear:

    32048.jpg

    And they didnt tell these guys:

    4.jpg


    --

    08 PORSCHE Turbo Cabriolet, 06 Ferrari F430,  04 Durango HEMI,  04 Harley Davidson Screamin Eagle,  93 Harley Davidson Nostalgia


    Re: My misconceptions about WHY wider tires = better grip.

    Tire width does not mean lower pressure, that depends on the tire construction itself.

    Let's compile a pro/con list for wider tires:

    Pro:

    • Better heat dissipation (=less wear)
    • Reduced deformation (=less wear)
    • More rubber (=better longevity)

    Con:

    • More unsprung mass
    • Flat surface needed
    • Do not sink in and only use surface grip (bad wet/gravel/snow)
    • Body roll can lift part of the tire
    • More wear due to stearing alone (bad for front tires)
    • It's harder to build a tire that distributes the load evenly across the whole width.

    Did I make mistakes? Can you think of anything else?

    In the early days of racing, tires were small, my bet is the main reason was the last one (harder to build). 

    tn_M09 Porsche Formula One.jpg


    Re: My misconceptions about WHY wider tires = better grip.

    Gregg, there are 3 parameters involved:

    1. Tire width
    2. Lateral grip (note I didn't say straight line traction)
    3. Contact patch

    Based on practical experience, we know that 1 leads to 2. That's partly why F1 cars, and sports cars, have wide tires. More lateral grip = better handling (faster) in corners. This is NOT in dispute.

    The central question of the thread is (assuming similar load, construction, pressure, etc.) does 1 lead to 3?
    And if not, then why does 1 lead to 2?

    BTW, I saw a very interesting post attempting to explain why although drag car and F1 cars both have huge rear tire, the reasons are different, or at least the reasons are emphasized on different aspects. In the F1, it's more handling, in the drag car, it might (Ha ha -  with so many sharp people on this thread, I have to be extra extra careful with everything I write on the topic. Smiley I feel like I am sitting next to my lawyer. Smiley) be related to heat management leading to better straight line traction. It will become clear in a few posts. I think.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )


    Re: My misconceptions about WHY wider tires = better grip.

     Tire width is of course a tradeoff along compound characteristics and temp behavior. Those who look at this lienarly I challenge them to fit a bicycle tire on a 917... :)


    --

    _________________________________________________________ 

    A. Dias --- 997.2S (ordered). Previous cars: Corvette C6,  996 C4.


     
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