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01-20-2017, 01:05 PM | #23 | |
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What you're saying is that the contact patch would just be longer, and more narrow, due to the same load just being distributed differently?
Here is a more technical rebuttle I found, but now were just above my head: Quote:
Last edited by bNks334; 01-20-2017 at 01:13 PM.. |
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02-10-2017, 04:26 PM | #24 | |
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02-10-2017, 07:10 PM | #25 | |
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Not saying your lying, cause I've heard this before, but I definitely notice a difference with acceleration between my summer and winter tires. |
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02-11-2017, 10:45 AM | #26 | |
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Wider tires do provide more grip but not to the degree and not via the mechanisms that most people think. He's correct on his principles of contact patch size. If pressure is equal between two sets of tires of different widths, the static patch will be the same size. But that's just static. Tires become extremely complex in a dynamic state almost to a point where you can't say anything too general without experimental data from the tires in question. |
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02-11-2017, 06:15 PM | #27 |
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There is a lot of theory in this thread.
Let me give you my own real word experience. As I mentioned earlier our 135i is my work car and the car I am using for this comparison is a 2001 Holden Monaro, similar to pontiac GTO. The car is lowered on coilovers and set up more for circuit rather than drag racing. The rear shock absorbers are double adjustable for compression and rebound. On Mickey Thompson 245/40/18 drag radials full power can not be applied off the line. With Mickey Thompson 265/40/18 drag radials full power launches have resulted in several 1.52 second 60' times. Reducing the compression on the rear shocks I have launched gently on Kumho 275/30/19 street tyres and so far run a best of 1.67 second 60' times which is quicker than I have been able to launch the much stickier 245/40/18 drag radials. There is no substitute for taking it to the track and experimenting. By the way 135i suspension is a lot better than the car I run down the strip. |
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02-15-2017, 09:56 PM | #28 | |
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Drives: 2008 BMW 135i (E88 N54 6AT)
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Wow, I was following this thread actively for the first week but I just checked back and it's still going! Thanks everyone for all the answers - esp to WDE82, Vigilante375, kirill1221 & Ginger_Extract which were all along the lines of 'stop relying on the computer and learn to drive you bloody idiot.'
I'm loving WDE82's response, I think it sums the answer up perfectly: Quote:
Now, this conversation has veered towards tires, I’ll weigh in with some science that lays very strong credence to WDE82’s claim that “Tires have adhesion properties as well, not just traditional frictional. They're very complex.” Not only is the contact area between the tire and the road dependant only on the weight of the car and the pressure of the tire, not the width of the tire (ie. A wider tire will just have a wider, shorter contact patch and a narrower tire will have a longer, narrower contact area); but the amount of friction you have between your car and the road doesn’t change depending on your contact area. Theoretically, it doesn’t matter if you have 145/45R18’s at 42PSI or 285/30R18’s at 18PSI – your friction is determined by the ‘stickiness’ of the rubber, not by the size or shape of the contact patch. The two laws of friction are 1) The friction between two surfaces is proportional to the force pressing one to the other. And 2) The friction is independent of the contact area. Furthermore, (on wet roads) you can sometimes get more grip with a smaller contact area because it’s easier to get the water out of the way and thus less likely to aquaplane. The standard friction equation Ff = μN says the only way you can get more grip is to get sticker tires (or a heavier car). Now, you might be saying “That’s BS”. But if you google “does contact patch affect friction”, you’ll find plenty of articles saying it’s not. The science checks out. The reason performance tires are bigger and wider (so they say) is because they wear quicker, so it’s helpful to have more rubber to wear away. But, it is BS - to an extent - and it's easy to test: if you let your tires down to 18 psi then do a few timed laps, or measure your breaking distances, then repeat for 30 psi and 45 psi, you’ll find it does make a big difference. Why? Well, in the real world, your grip and handling is affected by much more than just the amount of friction between your tires and the road beneath them. As WDE82 said: "They're very complex.” |
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02-16-2017, 08:49 AM | #29 | ||
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Question: Will lowering psi, therefore, softening the sidewall, increase the effective contact patch area? I would say, yes. It is so counter-intuitive to think that the resulting increased surface area, and compliance under load, wouldn't lead to increased friction... At the very least, the tire would heat up faster; therefore, improving the amount of chemical adhesion to the pavement. As I posted earlier, wouldn't distributing the applied "force," or load, differently have an effect on the friction coefficient? Quote:
This thread is geared toward people drag racing. Traditionally, people drag racing run very soft, sticky, and fat tires coupled with very a very soft and compliant suspension (to absorb the initial load of launching). I take my car to road courses, so I am personally ok with running wider tires with stiff sidewalls to gain cornering ability and agility at the loss of a bit of traction under dynamic loading situations. Last edited by bNks334; 02-16-2017 at 09:09 AM.. |
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02-16-2017, 09:02 PM | #30 | ||
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