Announcement

Collapse
No announcement yet.

Tire width & contact patch discussion

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Tire width & contact patch discussion

    Originally posted by beitodesstrafe
    fatter tire gives ya more rubber on the road... it's better for traction in good conditions...
    I will politely disagree with this, it's physics. Given that the weight of the vehicle remains the same, and the tires are inflated to a proper pressure, the contact area with the road will remain the same. You can think about it like this...the contact area on each tire will be wider, with a wider tire, however the contact area on each tire in the direction of front to rear is less.

    Or if you reduce tire pressure, you will get "more rubber on the road" however at any given tire pressure, comparing a wide tire to a narrow one, the total area in contact remains the same

    A narrow tire has more contact in the direction of front to rear, but less side to side (or width)

    Now I’m not saying there is no advantage to a wider tire…
    2006 G6 GT Liquid Silver Sedan with leather package, Monsoon sound w/6 CD, 17" alloy rims, standard sunroof, Dr Speed CAB, GM strut bar...

  • #2
    I'm sorry, I'm not an expert at physics, but I really don't think that your numbers are adding up here.

    There is a lot more involved than what you have stated, and a wider tire does give you more of a contact patch. The weight of the car is not the only number you need to figure that out. You need the width of the car, the width of the tires, the firmness and height of the sidewalls of the tires, etc.. More contact with the surface of the road = more traction.

    The only reason that wider tires have issues in the snow or rain is that the wider tire has more trouble actually making contact with the road, as it needs to push the snow/rain out of the way.

    sigpic
    Mobil 1 | Doctorspeed Stage 3 & 4 CAI | CRABS | Sacchi S45 245 Black 18" Rims | 6000k HID Headlights + Fogs | GT-R Exhaust | 20% Tint | Pioneer AppRadio 2

    Comment


    • #3
      Originally posted by TLS2000
      I'm sorry, I'm not an expert at physics, but I really don't think that your numbers are adding up here.

      There is a lot more involved than what you have stated, and a wider tire does give you more of a contact patch. The weight of the car is not the only number you need to figure that out. You need the width of the car, the width of the tires, the firmness and height of the sidewalls of the tires, etc.. More contact with the surface of the road = more traction.

      The only reason that wider tires have issues in the snow or rain is that the wider tire has more trouble actually making contact with the road, as it needs to push the snow/rain out of the way.
      I'm not an expert either, however I don't see the width of the car as a factor at all. It could be 12 foot wide, you still have the weight of the car
      spread over 4 wheels. Now the firmness of the sidewalls, maybe, the height is also meaningless, but I suspect you mean the height has something to do with the firmness.

      Again, let's keep it simple...given the weight of the car stays the same, and you inflate the tires to the proper pressure...the weight is still distributed to each tire the same whether the car has wide or narrow tires

      2006 G6 GT Liquid Silver Sedan with leather package, Monsoon sound w/6 CD, 17" alloy rims, standard sunroof, Dr Speed CAB, GM strut bar...

      Comment


      • #4
        so you're sayin' a corvette with 245s will handle and ride just as well as one with 325s?
        -Mike #1

        ||2006 GTP Coupe - Gone but not forgotten||

        'Black cars denote an aggressive personality or someone who's an outsider or rebel.'

        Current Ride: 2009 White Hot Pontiac G8 GT with Onyx/Red Interior

        Comment


        • #5
          Originally posted by 06_G6_GT
          I'm not an expert either, however I don't see the width of the car as a factor at all. It could be 12 foot wide, you still have the weight of the car
          spread over 4 wheels. Now the firmness of the sidewalls, maybe, the height is also meaningless, but I suspect you mean the height has something to do with the firmness.

          Again, let's keep it simple...given the weight of the car stays the same, and you inflate the tires to the proper pressure...the weight is still distributed to each tire the same whether the car has wide or narrow tires

          You are confusing contact patch with weight distibution. A wider tire (with the same pressure that you previously mentioned) will at all times have a larger contact patch. However since the same weight is still being put in the contact patch of the tire you may have less tractive force, since each square inch of the contact patch doesn't have as much weight on it. This chances the dynamics of the vehicle though, and is a much more indepth conversation than I feel like getting into right now.

          I just looked up bridgestonetire.com.

          A 205/50-17 has a tread width of 7.7". A 225/45-17 has a tread width of 8.5" (a 10% increase).

          You diagram is just wrong. The width changes when you put a wider tire on, but the fore/aft doesn't.
          04 CTS-V......like a G6, but with an extra 200hp, a proper transmission, and it is correct wheel drive:
          Self described crotchety old man!

          Comment


          • #6
            No, as I said in my first post,

            All I am saying is that wider tires do not provide "more rubber to the road"
            Only a different contact pattern

            Given the same car and weight, each tire supports the same amount of weight, and given that the tires are inflated to the recommended pressure, they have the same contact "area"...whether the tires are wide or narrow...

            I am "not" saying wider tires do not provide an advantage

            How can wider tires have more contact area, when the weight on that tire is the same?

            I'm not trying to be argumentive, but all I'm saying is the contact area changes by size not "area" (lets say 7" wide x 1" for a wide tire and 5" wide x 1.4" for a narrow tire) both equal 7 square inches of contact. Because the weight hasn't changed...this is physics... it's unchangable

            How can a car that weights the same provide more "contact area" with a wider tire when the weight remains the same?


            >>so you're sayin' a corvette with 245s will handle and ride just as well as one with 325s?

            Again I am not talking about handling and ride...only area of contact

            Wider tires do provide better handling due to a wider stance, not "area of contact"
            2006 G6 GT Liquid Silver Sedan with leather package, Monsoon sound w/6 CD, 17" alloy rims, standard sunroof, Dr Speed CAB, GM strut bar...

            Comment


            • #7
              i don't see how they could have the same size contact patch? place a toilet paper tube next to a papertowel tube and try and tell me that they have the same contact patch (assuming for the example that they have identical inner and outter diameters like comparable tires). the diameters are the same, the pressures are the same (atmospheric in this case), the only difference is the width, but the wider tube certainly has a larger contact patch.

              i understand what you are saying about the weight and how a wider tire will have more area to disperse the weight without distorting as much as the more narrow tire, but i don't think that it makes enough of a difference to make the contact areas the same size. i guess you could even say both paper tubes have the same amount of weight on them, since 0 is an amount (allowing for gravity and their own weight of course).

              i do agree with both of you on one thing....i'm no physics major either

              Comment


              • #8
                06_G6_GT is right.

                The width of the tire has nothing to do with the area of the contact patch. Putting wider tires on a car will not give you a bigger footprint and vice versa. And no, you will not get more friction or traction either. Wider tires simply change the shape of the contact patch.

                Even if you have a bigger footprint, traction will still remain the same. More rubber on the road does not give you better traction. Friction depends only on two things. The pressure between the two surfaces and the co-efficient of friction between the two materials. The area of contact has no effect on friction. So how do you get more friction? By getting a tire with a different (softer, stickier) rubber compound, and not by simply getting a wider tire.

                Is a wider tire better than a narrower tire? Not always, otherwise all cars will come with tires as wide as possible. Wider tires change only the shape (not the size) of the footprint. But this is important because the shape affects the cars dynamic balance, lateral acceleration, and handling. Yes, there are definite advantages to using wider tires, but like everything in life, there are also trade-offs. You don't get something for nothing.

                Comment


                • #9
                  after doing more searching pretty much everything i found seems to agree with 06_G6_GT.

                  i found this mazda article to have a good explanation:
                  http://www.mazda6tech.com/index.php?opt ... &Itemid=50

                  it still seems odd to me, but i can't argue with physics lol.

                  Comment


                  • #10
                    I got to thinking more about it. Though it seems wrong the contact patch does just change shape with a wider tire.
                    04 CTS-V......like a G6, but with an extra 200hp, a proper transmission, and it is correct wheel drive:
                    Self described crotchety old man!

                    Comment


                    • #11
                      Originally posted by mrslcom
                      06_G6_GT is right.

                      The width of the tire has nothing to do with the area of the contact patch. Putting wider tires on a car will not give you a bigger footprint and vice versa. And no, you will not get more friction or traction either. Wider tires simply change the shape of the contact patch.

                      Even if you have a bigger footprint, traction will still remain the same. More rubber on the road does not give you better traction. Friction depends only on two things. The pressure between the two surfaces and the co-efficient of friction between the two material. The area of contact has no effect on friction. So how do you get more friction? By getting a tire with a different rubber compound, not by getting a wider tire.

                      Is wider tire better than a narrower tire? No, otherwise all cars will come with tires as wide as possible. Wider tires change only the shape (not the size) of the footprint. But this is important because the shape affects the cars dynamic balance, lateral acceleration, and handling. Yes, there are definite advantages to using wider tires, but like everything in life, there are also trade-offs. You don't get something for nothing.
                      Sounds like someone smarter than me...it's been an interesting thread, always good to challenge the gray matter :smoke:
                      2006 G6 GT Liquid Silver Sedan with leather package, Monsoon sound w/6 CD, 17" alloy rims, standard sunroof, Dr Speed CAB, GM strut bar...

                      Comment


                      • #12
                        Good discussion. Not sure I know who is right though. lol

                        I'll keep reading.
                        2006 GTP Coupe: Leather, Zinik wheels, GM Strut Bar, DoctorSpeed CAB, Custom Dual Magnaflow's / Resonator Exhaust

                        Comment


                        • #13
                          I believe all the facts about just changing the size of the contact patch are correct for a vehicle sitting still.

                          However, as stated friction is due to pressure between the two surfaces. while accelerating there is an increased load on the tires creating more pressure on them and this causes them to change their shape. If your tire is not wide enough you cannot get the appropriate contact patch because the torque applied to this wheel will be greater than friction and cause the wheel to spin. While under load with a wider tire that has been compressed creating a larger contact patch which allows traction to become greater than torque
                          BMG Cofounder who happens to be a Petrolsexual
                          ^ The Man
                          v The Legend

                          Comment


                          • #14
                            This may shed some light on the subject:



                            An excerpt from the above:
                            If you were looking up at a car through a glass road, you could measure the size of the contact patch. You would multiply the length of the contact patch by its width to get the area, then add up area for all four tires to get the total area of the contact patch.
                            For your 2-ton (4,000 lb) car, you will find that the area of the contact patch is about equal to the weight of the car divided by the tire pressure. In this case 4,000 pounds divided by 30 pounds per square inch equals 133 square inches. That may seem like a lot, but your car's tires are probably about 7 inches wide. That means that the contact patch for each tire will be about 4.75 inches long.

                            If I'm reading the article correctly it looks like it does not increase the area of the patch if you go with wider tires. It simply changes the shape to a wider individual footprint for each wheel, but the overall contact patch will remain the same.

                            Like several others have said in this thread, I admit that I always thought that wider tires put more rubber on the road. Live and learn!
                            SOLD * 2006 G6 GTP 6MT * SOLD
                            Crimson Red W/Taupe 2-Tone Leather; DoctorSpeed Stage 4 CAB, Custom Dual Muffler Exhaust ;"JAKED" Lower Grille, GM Strut Bar, Aftermarket Spoiler, White Faced Gauges, Painted Interior Parts, Window Tints, Mostly debadged.
                            CURRENT: 2007 Acura TL Type-S 286 HP 6MT
                            Moroccan Red Pearl /Taupe Leather Sports Seats; Tints: 15% rears, 50% fronts;Axis Hiro 18X8.5 hyper silver wheels w/Yokohama Advan S.4. 245/40/18 UHPAS Tires; Color-Matched Splash Guards

                            Comment


                            • #15
                              yea and if you think about it too, back in the 50s and 60s a lot of sports and muscle cars had very thin tires. They looked pretty stupid, but they still hauled.
                              -Mike #1

                              ||2006 GTP Coupe - Gone but not forgotten||

                              'Black cars denote an aggressive personality or someone who's an outsider or rebel.'

                              Current Ride: 2009 White Hot Pontiac G8 GT with Onyx/Red Interior

                              Comment

                              Working...
                              X