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Old 12-14-2009, 09:08 PM   #21 (permalink)
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Variable pressure = something more to go wrong, waste fuel, and weigh more.
True but... I'd rather have variable tire pressure than A/C or Bluetooth, or an automatic, or an ICE, or 8 way electric adjust seats, or cruise control...

OK, I thought about it for longer than an nanosecond... it's a silly idea. Need lower pressure, Get out and let some air out.

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Old 12-14-2009, 09:10 PM   #22 (permalink)
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True but... I'd rather have variable tire pressure than A/C or Bluetooth, or an automatic, or an ICE, or 8 way electric adjust seats, or cruise control...
There's no "I'd rather have" in the marketing scheme of the publicly traded auto manufacturers... only "Here's what you need, here's how much more you're going to pay for it."
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Old 12-14-2009, 09:14 PM   #23 (permalink)
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I know. *sigh* I'm just living in my little dream world here...Ya gotta have dreams.
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Old 12-14-2009, 09:24 PM   #24 (permalink)
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"Here's what you need, here's how much more you're going to pay for it."
There's why your market share is down another couple of percentage points this year :-)

You know, I just realized something: 1) US automakers' market share is down to about 50%; 2) By definition, half the population has below-average intelligence. You suppose there's a connection :-)
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Old 12-14-2009, 10:39 PM   #25 (permalink)
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You know, I just realized something: 1) US automakers' market share is down to about 50%; 2) By definition, half the population has below-average intelligence. You suppose there's a connection :-)
Have a similar theory about political affiliation but I'm too smart to elaborate.
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Old 12-14-2009, 11:37 PM   #26 (permalink)
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Have a similar theory about political affiliation but I'm too smart to elaborate.
...ah, a member of the Astute Party?
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Old 12-14-2009, 11:42 PM   #27 (permalink)
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Did someone just take high school physics? Yes the contact patch affects grip, because the rubber and the road aren't two perfectly smooth surfaces. The rubber conforms to the bumps in the pavement, and the more bumps the more grip.

If bigger contact patch = same grip, why do lawyers love staggered tire sizes?

http://www.modified.com/projectcars/...t_2/index.html

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Old 12-15-2009, 12:23 AM   #28 (permalink)
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Did someone just take high school physics? Yes the contact patch affects grip, because the rubber and the road aren't two perfectly smooth surfaces. The rubber conforms to the bumps in the pavement, and the more bumps the more grip.
Perhaps someone should take high school physics. More bumps do not equal more grip. If this were so, drag racers, NASCAR racers, IRL racers, Formula 1 racers, etc., would want bumpy race surfaces. The very opposite is true. They put smooth grippy tires on smooth track surfaces. The reason street tires are not smooth like race tires, is that they have to be able to displace water.
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Old 12-15-2009, 12:40 AM   #29 (permalink)
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Pretty sure the "bumps" are teensy, at which point the rubber displaces around them, causing "traction". Ice is smooth, nope we don't want that.
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Old 12-15-2009, 03:51 AM   #30 (permalink)
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All of these thing depend upon the rubber formulation, temperature, speed, application, road surface. Here I am talking about passenger tires on asphalt / concrete in normal driving conditions.

My intention is to find and present specific information regarding the relationship between traction and inflation pressure. Whenever this is discussed some people express extreme reserve at inflating to max sidewall and hysteria at inflating somewhat past max sidewall claiming all kinds of calamity and no proof of it. I think these people are misinformed. The AutoSpeed article is interesting, if incomplete, but generally sound, and gave me somewhere to start learning more. The study I posted shows a small reduction in braking distance between low and max sidewall.

My personal opinion on this, at this time, is that up to a point, and generally speaking, higher inflation pressure gives better FE (undisputed) and gives better or the same traction (unknown but suspected) up to and a bit above max sidewall to a point I don't know what that point is but I have a hunch it's somewhere around the point at which 90% of the reduction rolling resistance from slightly higher inflation has been achieved. This is not an extreme pressure. If I had tires that were sold as low RR, I might even just leave them at max sidewall but really, I would only run lower pressures if ride were my priority. Otherwise all other safety/traction,handling issues are better at max sidewall.

One of the biggest and most common dangers is actually underinflation which can lead to blowouts from temperature build up. Higher inflation pressures (not extreme pressures) reduce the possibility of blow out by reducing heat build up.

It is not my intention to give advise, just present information I have found and my opinion on it. My opinion is based on what I have read and some of it is extrapolated from that information. I am willing to change my opinion if I find credible evidence.


From what I have found so far, max sidewall reduces...
1) risk of rollover
2) failure from overheating*
3) stopping distances
4) hydroplaning
5) slipping in snow* (depending on conditions, sometimes lower is better)
6) body lean in cornering

* edited to increase clarity

The only disadvantage to max sidewall I can think of is ride quality.

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contact patch, inflation, max sidewall, tires, traction

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