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05-06-2021, 07:41 AM | #16 | |
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Re: Another Tire Pressure Question! Front-Rear Considerations
It is my impression that lower rear tire pressures will cause the rear to swing out further and that's a bad thing. - BUT - I suspect this phenomenon depends on the particular maneuver. I don't think contact patch size enters into the equation when we are talking about transient responses.
Frankly, I don't think cars as old as yours matter so much about precise inflation pressures. The bushings are probably loose and that likely has more effect that small changes in inflation pressure. The only thing would be the direction. Going towards more oversteer is likely to lead to more issues. |
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05-06-2021, 04:12 PM | #17 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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2. Worn Bushings - I know what I'll hear even from taking an 80,000mile car to even three of my most trusted local mechanics: "Come back when you're over 150,000mi!" What are signs of advanced wear in bushings - from a behind the wheel perspective? |
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05-07-2021, 07:03 AM | #18 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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05-07-2021, 08:40 AM | #19 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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I just found this, Capri: https://www.rimex.com/images/TyreSen...n-pressure.pdf What does it mean? If I set my tire pressures to 32psi on a given morning, is their actual pressure lower than what's indicated on the gauge? By the reasoning and examples in this article, I should, depending on morning ambient temperature, be setting my tires to between 34-36psi(via gauge) to get true 32psi. What?! |
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05-08-2021, 07:41 AM | #20 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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The first concerns "Cold Pressure". They define it differently than all the tire manufacturers define it. "Cold pressure" is the pressure in a tire when the tire hasn't been operated for some time - that is "cold". The fact that if you set the cold pressures when the ambient temperature is - say - 50° F, then later measure the pressure when the ambient temperature is 90° F, you get a different pressure reading - is just an unfortunate fact of Physics. Rimex is trying claim that their device works off a different law of Physics - that the proper pressure in a tire is defined as occurring at a particular set of temperature and atmospherically pressure conditions - which oddly enough are different that STP (Standard Temperature and Pressure) as defined in Chemistry. That is incorrect - and I suspect they are deliberately doing this incorrectly because their device would require more complication to do correctly. So while there is a lot of correct physics in the article, their starting premise is incorrect. |
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05-08-2021, 12:23 PM | #21 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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I think the premise is that if you want, IE: 32psi when you are driving, the gauge will indicate a compensating pressure based on current ambient F/C. IE: With an outside ambient of F°40, the gauge will recommend 28-30psi. About 5-10 minutes of driving, and your tires will peak out around your goal - 32psi. Something which I suspect is more important for competition, not every day street driving. Let me know if I'm on the right path with that, or totally out to lunch, lol! I'm simpler than that: I use a gauge that indicates actual PSI, and adjust my tires to desired pressure cold - just before sunup, car not driven since yesterday. That's my definition of 'cold' pressures. |
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05-09-2021, 07:36 AM | #22 | |
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Re: Another Tire Pressure Question! Front-Rear Considerations
One of the things that has always bothered me about "Hot Pressures" is that if you start at 40°F, you get a different operating temperature than if you start at 90°F (with the same "cold" inflation pressure". So I can see why some would want to use a standard temperature and pressure reference when setting pressures.
But the problem is everyone focuses in on the air chamber pressure/temperature, when it's the temperature at the edge of the belt that is the important temperature. This is something that could be determined, but I don't think anyone has sat down and done the homework to actually quantify how this actually works. |
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05-10-2021, 05:57 AM | #23 | ||
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Re: Another Tire Pressure Question! Front-Rear Considerations
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I'm sure it take longer for a tire to heat up when driving during lower ambient temperatures. I guess that's a factor these temperature-compensating gauges takes into consideration when it reads you a pressure. Confusing as heck to me! I just make sure my tires read, in my specific case, 32psi first thing in the morning, be it 20°F or 80F outside. |
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front , pressure , rear , tire |
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