Lots of very complicated answers here, and a few strait to the point ones too. I can only speak from experience and i think the tyres in Aus are poo (ducks for cover). I had an EA Falcon when I lived in Cairns and even at 30-40kmh without power being put in the car would slide around bends in the wet, the car was that old and past it, it was the only time I could get the wheels to spin:biggrin: Now back to the Zed, the HICAS was dismissed out of hand early in this thread and unfarely I think. If you think about how old these cars are and the way the rear stearing works its not hard to figure out that not maintained it can be deadly. The stearing arm pushes on a ball joint (which alot of the time you can't see if its worn until you take the arm off), which in turn moves the hub and turns the wheel, now if the bushes are old and have play in them and the outer ball joint is hanging out, and they do often, then the rear wheels will stear at will. If you hit a puddle at speed with one wheel it will cause drag and turn that wheel, if you hit a pot hole or bump it will turn that wheel, if you floor the load pedal it will steer you from the rear to the right. Once changed for new ones and set up right the Zed handles like a dream and you will be able to power around bends with confidence.
Not really. Force = area * pressure Force is the weight of the car and constant Pressure is assumed the same => area is the same Bit confusing but many years of 4WD driving has taught me a bit about tyre pressures and footprints.
LD of C = longitudinal distance of contact. Your term, not mine(and I suggest you get the old text book out, rather than quote figures as factual, when you now admit them to be guesstimates). If you're a student of Physics, I'm surprised you are unfamiliar with the concept of tyre contact areas of different sizes, having different load per square inch rates(try supporting 1 tonne on a square centimeter, as opposed a square meter, and then tell me which one will be punched into the ground). That is what I refer to as "downforce" (static weight) on a tyre/snowshoe etc.
YES! Racecar builders from bye-gone years, knew only too well, the error of "wider is always better" when applied to tyres and cornering forces(if this was not the case, then every car fitted with wider rear tyres, would understeer like a bastard, due to the rear wheels overpowering the attempt to change direction with the narrower fronts). There is always a point at which wider becomes worse, as traction decreases due to less "weight per square inch" on the rear tyres.:zlove::zlove:
i didnt know everyone had this problem....i thought it was only me due to my snow tyres that came from japan on it.......as i had 18" bbs with really good tyres on a V8 soarer and once they were stolen then i put some stockies with snow tyres and you couldnt plant it as it would slide, not as fun as the zeds...... its actually cool when it slides as it feels really powerful, and the guy next to you is like
Another thought - don't underestimate tyres in this equation. My Zed came with really nice looking tyres, good tread depth, known brand etc - Only thing was, I could light them up easily enough in the dry, let alone in the wet. They were crap. (Mind you, psychologically the car felt all powerful ) Due to some other issue the tyres were replaced (firestone's with silica in my case), and the difference is huge. Now the cornering ability is sssoooooo much better. It can still slide, it just takes much more to do it, and it much more controllable. Cheers, Simon.
up to speed im still coming up to speed on this one, in a short answer , will wider tyres provide a higher level of grip on the street?
Maybe I'm gonna look into it in much more depth then we will all know I know my theory is correct, but I'm sure there is much more influencing grip than just friction. Drive around on you space savers, that is always interesting
Tyre compound, tyre profile, tyre width, tyre flex, tyre pressure, wheel diameter, road surface, road camber, road contamination (oil/rubber and even the road paint), RWKW, driver ability, dodgey/worn suspension components, suspension adjustments, wheel allignments, depth of the water you are driving through (1 mm or 3 inches), speed, and shite loads more variables. If your car is not well maintained, then it will be harder to drive in the wet than it need be. Every Zed will be different.
A serious answer Hi Many of the "smart-ass" posts here about the driver and any wet weather driving have some truth in them. My solution - i had 71/2" rims and matching Kumho tyres on the back and had managed to excite quite a few drivers around me with my ability to control a wild (to them) fishtail in the wet. I changed to 91/2" rims and the widest Toyo Proxes tyres ($600 something each) that would fit. Now the other drivers don't even notice that I have slid sideways into the space between them and the car in front. Summary 1) the best quality rubber you can get 2) the widest rim / amount of rubber combination that the car will take 3) some wet weather driving skill regards Terry
haven't had a chance to read all the replies yet. but I'll chime in anyways. When I first got my car it had 3 different brand tyres on it. and the rear tyres had different treads & were barely legal. (not that having different treads is legal) I would slide out wet or dry if I gave it a bit. I could slide out when accellerating in a straight line! Then one day I got off my lazy ass and took it to get some new tyres (and brakes while i was there). Went all out and got 4 new Bridgestone Potenzas! Now it only loses traction in the dry at like 6000RPM. and I haven't tried very hard.. but haven't gone sideways in the wet yet. Definately lost traction several times but never control. You can barely feel the loss of traction.
The LAWS of friction A few years ago I was studying engineering and came across the "laws of friction" in a book called "Applied Engineering Mechanics" by Watkins Jensen and Chenoweth. The first thing is that they are split into two categories Dry surfaces, and wet surfaces. Just covering the first three for each. Dry surfaces. 1. The friction force is dependant on the kinds of materials and the degree of rooghness of the two surfaces in contact. 2 The maximum friction force which can be developed is dependant upon the normal pressure between the contacting surfaces and is proportional to it 3. The friction force is not dependant upon the areas of the surfaces in contact. Wet surfaces 1. The friction force is not dependent on the kinds of materials nor on the degree of roughness of the contacting surfaces. 2. The friction force is not dependent upon the normal pessure between the contacting surfaces. 3. The friction force is dependent upon the areas of the surfaces in contact. Essentially what this means for wet weather driving is that traction is dependant on keeping your tyres on the road ie not aqua planing. To do that the only thing to do is drive very carefully around corners at low speed. I have had my NA two seater for three years have done 50,000 km in it and have not lost it once
Beware of theory Watchout, theory in textbooks is not engineering. It is maths and science full of simplifications and assumptions. Useful for torturing uni students with and ok for curiosities sake. Engineers think of real situations, which is where they quickly learn to go talk to the operators who in this case are drivers, mechanics etc. They mightnt understand quite why but they will have a good feel for what works and what doesnt in the real world. PS if you can prove me wrong patent your accurate and proven multivariate complex dynamic model and sell it to tyre companies for lots of money!:biggrin:
i think youre trying to make this too complicated.. the car is a constant weight, change the tyre widths and you change the surface area that the weight is distributed over- lower pressure on the contact areas yeah? Combine that with water on the surface and you're more likely to aquaplane seems pretty straight forward?? i did physics at uni too.. and those arguments about the normal force not changing doesnt really seem compelling... Cruiser that i think that text seems to sum it up pretty well
Wider tires are marginally better if you are driving around corners fast? Interesting conversation! It is great to hear the conflicting points on this one. Also Here is a good article ripped from mazda6tech that mainly talks about side wall deformation in relation to wider tyres. The sidewall of the tire must bend a little to create the contact patch. As seen in the diagram, this happens less on the wider tire. Because the sidewall has less bend, less of the car's weight is being supported by the sidewall. Instead, it is being supported by the tire's air pressure, which is constant among the entire contact patch. Since the even distribution of weight among the tire's surface will allow the tire to function better, the wider contact patch has more overall grip. Why is this important? Because sidewall deformation robs traction, overheats tires, and causes them to wear unevenly! In some cases, lateral stability might be so good that the tire pressure need not be as high. If we can lower the tire pressure without worrying about the sidewall deforming, then we can increase the contact patch! Just remember that for good lateral grip (cornering), preventing the sidewall from deforming is the greatest priority. Worry about that first- don't get hung up on wide tire sizes that, in the end, make only marginal improvements. http://www.mazda6tech.com/index.php?option=com_content&task=view&id=20&Itemid=50
Experimental evidence that wider tires are better: In the dry only http://www.motorauthority.com/news/safety/are-wide-tires-better-than-narrow/
