johnc Posted November 28, 2006 Share Posted November 28, 2006 Wider tires do provide more lateral and longitudinal grip then narrow tires. Why and how they do is up for debate and I have yet to read a convincing arguement for one point of view over another. I tend to lean towards the argument that: When a tire starts to breakaway and slide, that actually starts at the rear of the contact patch and propogates forward. With a properly inflated, properly cambered wider tire that propogation progresses more slowly due to the greater frontal area (propogation line) of the contact patch area beaking away. The breakaway shear forces are spread along a larger area and are less concentracted then if the contact patch was narrower. Quote Link to comment Share on other sites More sharing options...
Guest magnadyne Posted November 28, 2006 Share Posted November 28, 2006 Wider tires do provide more lateral and longitudinal grip then narrow tires. Why and how they do is up for debate and I have yet to read a convincing arguement for one point of view over another. Read the thread, I have explained why and how It almost sounds like you are describing a slip angle, and that is how a tire turns, but not entirely how it grips. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted November 28, 2006 Share Posted November 28, 2006 If I'm understanding this correctly, folks are relating "grip" to something different than "friction". I'm a bit confused here (nothing new) but, without "friction" can there be "grip"? If grip is indeed induced by friction, then it seems obvious (to me) there there will be parasitic power loss caused by added friction (grip) of larger tires. But then... I'm probably the "baldest tire" of this group... slippage of the old brain cogs, ya' know. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 28, 2006 Share Posted November 28, 2006 It almost sounds like you are describing a slip angle, and that is how a tire turns, but not entirely how it grips. What I described above regarding the contact patch is the transition from grip to slide. Its how the contact patch is losing grip. The most heavily loaded part of the contact patch is just ahead of the trailing edge and that's the part that starts "letting go" of the pavement first as the tire reaches its grip limit. Where this process starts is typically at the point where the linear portion of the slip curve starts to flatten out and the contact patch has lost all grip and is sliding where the slip curve starts downward. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted November 28, 2006 Share Posted November 28, 2006 magnadyne, With all due respect, it sounds to me like johnc has done a lot more reading on this topic than you. Your comment about increasing normal force (weight/aerodynamics) is true, up to a point. Milliken & Milliken have several examples of tyre load sensitivity charts, which is what you are talking about. When you add loading via weight, you increase not only the force the tyre can generate, but you increase the amount of force that is required to achieve a given acceleration. The problem is that the force required increases at a linear rate, but the increased force generated (as per tyre's load sensitivity) is not-linear, and has limitations. I dislike talking about `grip' as well. What we are talking about is the ability of a tyre to exert a force on the car's suspension components to produce an acceleration. Dave Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 28, 2006 Author Share Posted November 28, 2006 Thanks for all the info guys but I think Johnc has it. Seems like no one realy knows. I am not asking about grip. I realize that there simply is more grip and I am not concerned why. I assume it probably has to do with a larger contact area having more ridges and such that will adhere to the road -> higher mu. I was simply talking about friction only. I was wondering if friction is affected. The only variable was tire width, thus weight does not change nor tire compound. Quote Link to comment Share on other sites More sharing options...
Guest magnadyne Posted November 28, 2006 Share Posted November 28, 2006 My suggestion would be to pick up a book. As stated above, it is not as simple as it may seem. I tried to dumb it down to make a simple explination of it, but it isn't possible without leaving out details that others find important. Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted November 29, 2006 Share Posted November 29, 2006 It is my belief that the tire grip (or friction) is not very dependent on the width of the tire (or tread). One reason to run wide tires on race cars is due to heat dissapation. When tires get overly hot, they tend to lose grip. Wide tires have more surface area exposed to the air than narrow tires. In road racing, it is very easy to overheat tires, which is one reason why wide tires perform better when road racing. Wide tires also change the "feel' of the car, compared to narrow tires, with quicker steering response. My own experience with wide tires is that they pick up more nails than narrow tires. Quote Link to comment Share on other sites More sharing options...
zedevan Posted November 29, 2006 Share Posted November 29, 2006 Wide tires have more surface area exposed to the air than narrow tires my thought would be they only have the same surface per area, so therefore cooling would be the same? therefore this woudln't affect anything? except that since the force was spread over a larger area it woudlnt be working as hard so it woudlnt get as hot? my thoughts regarding this question (just been thinking about it since being told that friction isn't dependant on surface area and wondering why running wider tyres would help) is that while friction isn't dependant on the surface area in that basic equation, the normal force is. as in the pressure (force/area) is less with a larger area, and hence the normal force per cm^2 is less, therefore it requires a larger force to make it spin...(although the higher the normal force the better the friction so ?) And that somewhere down the line they are going to say that f=mN is the basic equation, now though it out the window and use this one (what ever it might be) as that is something they seem to like doing Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted November 29, 2006 Share Posted November 29, 2006 If tires lose grip when they get hot, then why to Indy car racers wiggle the steering wheel while awaiting the checkered flag and why to drag racers do burn-outs? Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted November 29, 2006 Share Posted November 29, 2006 "...friction isn't dependant on surface area..." I take everything I hear with a grain of salt. I question everything I think, say or do. I do the same with what others think, say, do... or write. Just because something is "written" doesn't make it 100 percent accurate in every situation. And, if you're wondering, yes... I'm pulling this from my butt. I often find that my butt is more accurate than the written word. Conversley, I often find that my butt is full of... For me, the jury is still deliberating. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted November 29, 2006 Share Posted November 29, 2006 A lot of this has to do with the contact patch of a narrow tire being equal to the contact patch of a wider tire. I'm not sure if that's true. Things I do know.... Rubber's coeffeicent of friction increases as the pressure decreases. Rubber is kind of like velco, it hooks into the other surface. It requires extra force to seperate the two. So IF the wider tire has a greater contact patch for a given vehicle weight, the wider tire has a higher friction and the more contact gives more velco to rip apart. Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 29, 2006 Author Share Posted November 29, 2006 A lot of this has to do with the contact patch of a narrow tire being equal to the contact patch of a wider tire. I'm not sure if that's true. Things I do know.... Rubber's coeffeicent of friction increases as the pressure decreases. Rubber is kind of like velco, it hooks into the other surface. It requires extra force to seperate the two. So IF the wider tire has a greater contact patch for a given vehicle weight, the wider tire has a higher friction and the more contact gives more velco to rip apart. Ding ding ding. You win. I can buy that, atleast for now. Quote Link to comment Share on other sites More sharing options...
Duke Posted November 29, 2006 Share Posted November 29, 2006 The topic of grip and friction is a tricky one. Tire compound, as you know, is created primarily from two materials, styrene and butadiene. Because the styrene molecule has a vinyl group with a double bond, it can polymerize. It is used as a monomer to make plastics such as polystyrene, ABS, styrene-butadiene (SBS) rubber, styrene-butadiene latex, and unsaturated polyesters. All are created from petroleum. Polyester and Kevlar is used to give the tire strength. How these factors affect traction and grip is obvious to anyone who has ever received a shock walking across carpeting. The polyester in the carpeting and the latex in your shoes interact to create an electrostatic charge that builds current in the body giving you a shock when you touch metal. The same principal is at work on the road where petroleum products from the tarmac (a negative charge) and the reciprocating tire compound (generating a strong positive charge simliar to a spinning planetoid.) are attracted to each other pulling the soft rubber compound by electrostatic attraction into the surface defects of the tarmac. Losing adhesion is therefore called breakaway because these smaller rubber nodes are sheared by the lateral forces and immediately lose charge thus destabilizing the attraction forces between the tire and the road surface. So why, as JohnC postulated, do wider tires have more grip? As you have already no doubt surmised, the larger tire acts as a larger electromagnet generating a larger positive charge. This in turns creates a larger field of attraction with the road surface. You can see in the diagram below how the concentrated compound in the tread are would focus the positive charge through centrifugal force tossing positively charged electrons aginst the road surface thus creating the grip. By carefully hollowing out the chafer area and installing #9 resistors you can significantly stabilize the electrostatic characteristics of the tire and thus maximise these grip creating qualities. Every racecar driver knows this secret...except for GT drivers who discount the adverse effect that rain has in dispersing the attraction field. They, of course, are ignoring the mighty #9 at their own peril. Hope this helps. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted November 29, 2006 Share Posted November 29, 2006 Finally. Someone understands me! I installed slip-rings on the inner shell of my wheels, with brushes directly from my battery to induce the attraction. Unfortunately, the polarity was reversed, and well, you know the end of that story. (it had the same dire consequences as the helium in the tires). Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 29, 2006 Share Posted November 29, 2006 Damn. Wish I hadn't taken so many drugs back in the hippie days. This thread seems to be causing me flashbacks. Cathodic traction. Damn. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted November 29, 2006 Share Posted November 29, 2006 I understand the basic concept of electrostatic attraction... we've all rubbed baloons and stuck them to our hair, right? I just don't see how this could help or harm traction on a 2500+ pound car. This rings my BS bell... no offense intended;) Quote Link to comment Share on other sites More sharing options...
Dtsnlvrs Posted November 29, 2006 Share Posted November 29, 2006 Gription, Stickyness, Friction (lateral of course)...whatever...I just know they get sticky and I dont loose the ass of the car... Quote Link to comment Share on other sites More sharing options...
Duke Posted November 30, 2006 Share Posted November 30, 2006 It's a good approach Blueovalz, but try flipping the slip rings around and re-installing them. I also have luck rubbing the the slip-ring against a cat before installation. Or try the Chafer modification mentioned in my last post. Good Luck. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 30, 2006 Administrators Share Posted November 30, 2006 By carefully hollowing out the chafer area and installing #9 resistors... Quote Link to comment Share on other sites More sharing options...
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